fix(ui): make download file deletion explicit in task dialog (#1622) (#1638)

Replace server startup panics with returned errors, print actionable CLI
messages with exit status 1, and clarify the API token flags.

Add regressions for missing web authentication credentials.

Fixes GopeedLab/gopeed#1614

.github/workflows/build.yml

@@ -106,17 +106,32 @@ jobs:
           if ("${{ matrix.arch }}" -eq "amd64") {
               # for amd64
               $release = "build\windows\x64\runner\Release\"
-              $mingw = "C:\Program Files\Git\mingw64\bin"
-              cp $mingw\libstdc++-6.dll $release
-              cp $mingw\libgcc_s_seh-1.dll $release
+              # Use the same toolchain as cgo instead of Git's bundled DLLs.
+              $cc = (Get-Command -Name (go env CC) -CommandType Application -ErrorAction Stop | Select-Object -First 1).Source
+              foreach ($dll in @("libstdc++-6.dll", "libgcc_s_seh-1.dll", "libwinpthread-1.dll")) {
+                  $runtimePath = [string](& $cc "-print-file-name=$dll")
+                  if ($LASTEXITCODE -ne 0 -or [string]::IsNullOrWhiteSpace($runtimePath)) {
+                      throw "Failed to locate $dll using $cc"
+                  }
+                  $runtimePath = $runtimePath.Trim()
+                  # Some MinGW distributions keep runtime DLLs beside gcc.exe.
+                  if ($runtimePath -eq $dll) {
+                      $runtimePath = Join-Path (Split-Path -Parent $cc) $dll
+                  }
+                  if (!(Test-Path -LiteralPath $runtimePath -PathType Leaf)) {
+                      throw "MinGW runtime $dll was not found by $cc (reported path: $runtimePath)"
+                  }
+                  Write-Host "Copying MinGW runtime: $runtimePath"
+                  Copy-Item -LiteralPath $runtimePath -Destination $release
+              }
           } else {
               # for ARM64
               $release = "build\windows\arm64\runner\Release\"
               $mingw = "$env:CLANGARM64_ROOT\aarch64-w64-mingw32\bin"
               cp $mingw\libc++.dll $release
               cp $mingw\libunwind.dll $release
+              cp $mingw\libwinpthread-1.dll $release
           }
-          cp $mingw\libwinpthread-1.dll $release
           cp $system\msvcp140.dll $release
           cp $system\vcruntime140.dll $release
           cp $system\vcruntime140_1.dll $release

.github/workflows/test.yml

@@ -69,6 +69,49 @@ jobs:
         with:
           files: ./coverage.txt
           token: ${{ secrets.CODECOV_UPLOAD_TOKEN }}
+  test-flutter-category:
+    # The settings editor and the backend have to read an extension list the
+    # same way, so both sides run the shared rule table. The Go side is covered
+    # by the test job above, this runs the ui side of it.
+    name: Test shared category rules
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: subosito/flutter-action@v2
+        with:
+          flutter-version: ${{ env.FLUTTER_VERSION }}
+      - name: Run the shared category rule table on the ui side
+        working-directory: ui/flutter
+        run: |
+          flutter pub get
+          flutter gen-l10n
+          flutter test test/api/downloader_config_test.dart
+  test-flutter-task-context-menu:
+    name: Test task context menus and text inputs
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    env:
+      CHROME_EXECUTABLE: /usr/bin/google-chrome
+    steps:
+      - uses: actions/checkout@v3
+      - uses: subosito/flutter-action@v2
+        with:
+          flutter-version: ${{ env.FLUTTER_VERSION }}
+      - name: Prepare Flutter tests
+        working-directory: ui/flutter
+        run: |
+          flutter pub get
+          flutter gen-l10n
+      - name: Test task menu actions and native input policy
+        working-directory: ui/flutter
+        run: |
+          flutter test --no-pub test/features/tasks/presentation/widgets/task_context_menu_test.dart test/shared/widgets/app_text_field_test.dart
+          flutter test --no-pub test/widget_test.dart --plain-name 'task context menu exposes'
+      - name: Test browser menu cancellation and input policy
+        working-directory: ui/flutter
+        run: |
+          "$CHROME_EXECUTABLE" --version
+          flutter test --no-pub --platform chrome test/features/tasks/presentation/widgets/task_context_menu_test.dart test/shared/widgets/app_text_field_test.dart
   test-webview-integration:
     name: Test webview integration (${{ matrix.name }})
     strategy:

README.md

@@ -20,7 +20,7 @@ Beyond core download management, Gopeed offers browser integration, JavaScript e
 
 Visit ✈ [Official Website](https://gopeed.com)
 
-![Application screenshot](_docs/img/ui-concept-en.png)
+![Application screenshot](_docs/img/ui-concept-en.webp)
 
 ## ✨ Features
 
@@ -63,7 +63,7 @@ Connect Gopeed to an AI agent and manage downloads with natural language. For ex
 
 Gopeed 2.0.0 is currently in public beta, introducing a redesigned interface, a native communication architecture that connects desktop and mobile clients directly to the Go core through FFI, a more consistent cross-platform experience, improved task management, more flexible API support, and MCP-based AI agent integration. Some features may still be incomplete or unstable, so please try it and report any issues you encounter.
 
-- [Download Gopeed 2.0.0 Beta 2](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.2)
+- [Download Gopeed 2.0.0 Beta 3](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.3)
 
 Once the features and stability meet our release standards, we will publish the official Gopeed 2.0.0 release. Beta users will be able to upgrade directly to the final release, while existing stable users will not be automatically moved onto the beta channel.
 

README_ja-JP.md

@@ -20,7 +20,7 @@ Gopeed（**Go Speed** の略）は、Go と Flutter で開発された高速で
 
 ✈ [公式サイト](https://gopeed.com)
 
-![アプリのスクリーンショット](_docs/img/ui-concept-en.png)
+![アプリのスクリーンショット](_docs/img/ui-concept-en.webp)
 
 ## ✨ 主な機能
 
@@ -63,7 +63,7 @@ Gopeed を AI Agent と連携すると、自然言語でダウンロードを管
 
 Gopeed 2.0.0 は現在パブリックベータ版です。刷新されたインターフェース、デスクトップおよびモバイルから FFI で Go コアへ直接接続するネイティブ通信アーキテクチャ、より統一されたクロスプラットフォーム体験、強化されたタスク管理、より柔軟な API、MCP による AI Agent 連携機能を導入しています。一部の機能はまだ不完全または不安定な場合がありますので、ぜひお試しいただき、問題があればフィードバックをお寄せください。
 
-- [Gopeed 2.0.0 Beta 2 をダウンロード](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.2)
+- [Gopeed 2.0.0 Beta 3 をダウンロード](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.3)
 
 機能と安定性が正式リリースの基準に達した時点で、Gopeed 2.0.0 正式版を公開します。ベータ版のユーザーは正式版へ直接アップデートできます。既存の安定版ユーザーが自動的にベータチャンネルへ移行することはありません。
 

README_vi-VN.md

@@ -20,7 +20,7 @@ Ngoài việc quản lý tải xuống hằng ngày, Gopeed còn hỗ trợ tíc
 
 Truy cập ✈ [Trang web chính thức](https://gopeed.com)
 
-![Ảnh chụp màn hình ứng dụng](_docs/img/ui-concept-en.png)
+![Ảnh chụp màn hình ứng dụng](_docs/img/ui-concept-en.webp)
 
 ## ✨ Tính năng chính
 
@@ -63,7 +63,7 @@ Sau khi kết nối Gopeed với AI Agent, bạn có thể quản lý tải xu
 
 Gopeed 2.0.0 hiện đang trong giai đoạn beta công khai, với giao diện được thiết kế lại, kiến trúc giao tiếp native kết nối trực tiếp ứng dụng desktop và di động với lõi Go qua FFI, trải nghiệm đa nền tảng nhất quán hơn, khả năng quản lý tác vụ được cải thiện, API linh hoạt hơn và khả năng tích hợp AI Agent qua MCP. Một số tính năng có thể vẫn chưa hoàn thiện hoặc chưa ổn định, vì vậy hãy dùng thử và gửi phản hồi nếu bạn gặp vấn đề.
 
-- [Tải Gopeed 2.0.0 Beta 2](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.2)
+- [Tải Gopeed 2.0.0 Beta 3](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.3)
 
 Khi các tính năng và độ ổn định đáp ứng tiêu chuẩn phát hành, chúng tôi sẽ phát hành Gopeed 2.0.0 chính thức. Người dùng bản beta có thể nâng cấp trực tiếp lên bản chính thức, trong khi người dùng bản ổn định hiện tại sẽ không tự động được chuyển sang kênh beta.
 

README_zh-CN.md

@@ -20,7 +20,7 @@ Gopeed（全称 **Go Speed**，也叫“够快下载器”）是一款使用 Go
 
 访问 ✈ [官方网站](https://gopeed.com)
 
-![应用截图](_docs/img/ui-concept-zh-CN.png)
+![应用截图](_docs/img/ui-concept-zh-CN.webp)
 
 ## ✨ 主要特性
 
@@ -63,7 +63,7 @@ Gopeed（全称 **Go Speed**，也叫“够快下载器”）是一款使用 Go
 
 Gopeed 2.0.0 目前处于公开 Beta 测试阶段，引入了全新界面、通过 FFI 直连 Go 核心的原生通信架构、更一致的跨平台体验、更完善的任务管理、更灵活的 API，以及用于 AI Agent 接入的 MCP 能力。部分功能仍可能不够完善或稳定，欢迎提前体验并向我们反馈问题。
 
-- [下载 Gopeed 2.0.0 Beta 2](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.2)
+- [下载 Gopeed 2.0.0 Beta 3](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.3)
 
 当功能完整度和稳定性达到正式发布标准后，我们会发布 Gopeed 2.0.0 正式版。已安装 Beta 版本的用户可以直接升级到最终正式版，现有稳定版用户则不会被自动切换到 Beta 渠道。
 

README_zh-TW.md

@@ -20,7 +20,7 @@ Gopeed（**Go Speed** 的縮寫）是一款以 Go 與 Flutter 開發的高速、
 
 瀏覽 ✈ [官方網站](https://gopeed.com)
 
-![應用程式截圖](_docs/img/ui-concept-en.png)
+![應用程式截圖](_docs/img/ui-concept-en.webp)
 
 ## ✨ 主要功能
 
@@ -63,7 +63,7 @@ Gopeed（**Go Speed** 的縮寫）是一款以 Go 與 Flutter 開發的高速、
 
 Gopeed 2.0.0 目前處於公開 Beta 測試階段，引入了全新介面、透過 FFI 直連 Go 核心的原生通訊架構、更一致的跨平台體驗、更完善的任務管理、更靈活的 API，以及透過 MCP 串接 AI Agent 的能力。部分功能仍可能不夠完善或穩定，歡迎搶先體驗並向我們回報問題。
 
-- [下載 Gopeed 2.0.0 Beta 2](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.2)
+- [下載 Gopeed 2.0.0 Beta 3](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.3)
 
 當功能完整度與穩定性達到正式發布標準後，我們會發布 Gopeed 2.0.0 正式版。已安裝 Beta 版本的使用者可以直接升級至最終正式版，現有穩定版使用者則不會被自動切換至 Beta 頻道。
 

_docs/task-batch-api.md

@@ -0,0 +1,52 @@
+# Batch task creation
+
+`POST /api/v1/tasks/batch` accepts ordinary and grouped batches:
+
+```json
+{
+  "group": true,
+  "groupName": "album",
+  "opts": {"path": "/downloads"},
+  "reqs": [
+    {"rid": "resolved-resource-id", "opts": {"selectFiles": [1]}},
+    {"req": {"url": "https://example.com/cover.jpg"}}
+  ]
+}
+```
+
+Each member accepts `rid` or `req`. A nonempty `rid` takes priority and creates a
+task from the cached resolve result. A member's `opts`, when present, replaces
+batch `opts` as a whole; omitted fields do not inherit individual batch values.
+Members without `opts` use batch `opts`. BT file selections use the indexes from
+the resolve result. Requests without `rid` continue to work.
+
+For groups, batch `opts.path` selects the parent directory. Members inheriting
+batch options, or with an empty path, use the reserved group directory. Explicit
+relative member paths are resolved under that directory; do not prefix them with
+the batch parent path. For example, parent `downloads` and member path `nested`
+place the member in `downloads/<group name>/nested`. Absolute paths under the
+parent directory preserve their relative structure within the group. In ordinary
+batches, an empty member path uses the configured default download directory.
+
+All members are attempted. If at least one task is persisted, the response is
+successful and contains the created task IDs. A task that fails to start after
+being persisted is included; use the existing task controls to retry it.
+Successful tasks are kept when other members fail. If every member fails, the
+API returns an error and removes any newly reserved empty group and directory.
+
+Both ordinary and grouped batches now return an object in `data`:
+
+```json
+{"code": 0, "msg": "", "data": {"taskIds": ["task-1", "task-2"], "parentId": "group-id"}}
+```
+
+Ordinary batches omit `parentId`. **This replaces the former array response for
+ordinary batches.** The outer `code`/`msg`/`data` envelope is unchanged. Clients
+must read `data.taskIds`; there are no per-member results. A successful response
+completes the batch, including partial success, so clients must not automatically
+resubmit missing members.
+
+With `group: true`, the server generates the group ID and reserves its directory.
+Creation does not accept a client group ID or append to an existing group. Group
+metadata remains available through the existing task list and detail responses;
+`parentId` identifies membership for group operations.

cmd/api/main.go

@@ -1,6 +1,9 @@
 package main
 
 import (
+	"fmt"
+	"os"
+
 	"github.com/GopeedLab/gopeed/cmd"
 	"github.com/GopeedLab/gopeed/pkg/rest/model"
 )
@@ -13,5 +16,8 @@ func main() {
 		Storage:   model.StorageBolt,
 		WebEnable: true,
 	}
-	cmd.Start(cfg)
+	if err := cmd.Start(cfg); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 }

cmd/extmock/main.go

@@ -166,7 +166,7 @@ func runResolve(args []string) error {
 	result, err := d.Resolve(&base.Request{
 		URL:    url,
 		Labels: map[string]string(labels),
-	}, nil)
+	})
 	if err != nil {
 		return err
 	}
@@ -250,7 +250,7 @@ func runDownload(args []string) error {
 	result, err := d.Resolve(&base.Request{
 		URL:    url,
 		Labels: map[string]string(labels),
-	}, nil)
+	})
 	if err != nil {
 		return err
 	}

cmd/gopeed/flags.go

@@ -7,9 +7,11 @@ import (
 )
 
 type args struct {
-	url         string
-	connections *int
-	dir         *string
+	url          string
+	connections  *int
+	dir          *string
+	checksum     *string
+	checksumAlgo *string
 }
 
 func parse() *args {
@@ -20,6 +22,8 @@ func parse() *args {
 	var args args
 	args.connections = flag.Int("C", 16, "Concurrent connections.")
 	args.dir = flag.String("D", dir, "Store directory.")
+	args.checksum = flag.String("checksum", "", "Expected checksum hash (hex encoded).")
+	args.checksumAlgo = flag.String("checksum-algo", "md5", "Checksum algorithm: md5, sha1, or sha256.")
 	flag.Parse()
 	t := flag.Args()
 	if len(t) > 0 {

cmd/gopeed/main.go

@@ -19,6 +19,18 @@ func main() {
 
 	var wg sync.WaitGroup
 	wg.Add(1)
+	var checksumOpt *http.ChecksumOption
+	if args.checksum != nil && *args.checksum != "" {
+		algo := "md5"
+		if args.checksumAlgo != nil && *args.checksumAlgo != "" {
+			algo = *args.checksumAlgo
+		}
+		checksumOpt = &http.ChecksumOption{
+			Algorithm: algo,
+			Expected:  *args.checksum,
+		}
+	}
+
 	_, err := download.Boot().
 		URL(args.url).
 		Listener(func(event *download.Event) {
@@ -43,8 +55,11 @@ func main() {
 			}
 		}).
 		Create(&base.Options{
-			Path:  *args.dir,
-			Extra: http.OptsExtra{Connections: *args.connections},
+			Path: *args.dir,
+			Extra: http.OptsExtra{
+				Connections: *args.connections,
+				Checksum:    checksumOpt,
+			},
 		})
 	if err != nil {
 		panic(err)

cmd/server.go

@@ -16,17 +16,18 @@ import (
 //go:embed banner.txt
 var banner string
 
-func Start(cfg *model.StartConfig) {
-	fmt.Println(banner)
+func Start(cfg *model.StartConfig) error {
 	srv, listener, err := rest.BuildServer(cfg)
 	if err != nil {
-		panic(err)
+		return err
 	}
+	fmt.Println(banner)
 	downloadCfg, err := rest.Downloader.GetConfig()
 	if err != nil {
-		panic(err)
+		listener.Close()
+		return err
 	}
-	if downloadCfg.FirstLoad {
+	if rest.Downloader.IsFirstLoad() {
 		// Set default download config
 		if cfg.DownloadConfig != nil {
 			cfg.DownloadConfig.Merge(downloadCfg)
@@ -51,13 +52,20 @@ func Start(cfg *model.StartConfig) {
 				rest.Downloader.PutConfig(downloadCfg)
 			}
 		}
+
+		// The default download dir is resolved only after the core starts, so
+		// seed the built-in categories now that the dir is known. Init is
+		// idempotent and leaves an existing category list untouched.
+		downloadCfg.Init()
+		rest.Downloader.PutConfig(downloadCfg)
 	}
 	watchExit()
 
 	fmt.Printf("Server start success on http://%s\n", listener.Addr().String())
 	if err := srv.Serve(listener); err != nil && err != http.ErrServerClosed {
-		panic(err)
+		return err
 	}
+	return nil
 }
 
 func watchExit() {

cmd/server_test.go

@@ -0,0 +1,35 @@
+package cmd
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/pkg/rest/model"
+)
+
+func TestStartInvalidWebAPITokenReturnsError(t *testing.T) {
+	tests := []struct {
+		name    string
+		webAuth *model.WebAuth
+	}{
+		{name: "no credentials"},
+		{name: "missing username", webAuth: &model.WebAuth{Password: "secret"}},
+		{name: "missing password", webAuth: &model.WebAuth{Username: "gopeed"}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := Start(&model.StartConfig{
+				WebEnable: true,
+				ApiToken:  "test-token",
+				WebAuth:   tt.webAuth,
+			})
+			if err == nil {
+				t.Fatal("Start() error = nil, want web authentication validation error")
+			}
+			if !strings.Contains(err.Error(), "web authentication username and password are required") {
+				t.Fatalf("Start() error = %q, want missing web authentication credentials", err)
+			}
+		})
+	}
+}

cmd/web/flags.go

@@ -52,8 +52,8 @@ func loadCliArgs() *args {
 	flag.StringVar(cfg.Username, "username", "gopeed", "Web Authentication Username")
 	cfg.Password = flag.String("p", "", "Web Authentication Password, if no password is set, web authentication will not be enabled")
 	flag.StringVar(cfg.Password, "password", "", "Web Authentication Password, if no password is set, web authentication will not be enabled")
-	cfg.ApiToken = flag.String("T", "", "API token, it must be configured when using HTTP API in the case of enabling web authentication")
-	flag.StringVar(cfg.ApiToken, "api-token", "", "API token, it must be configured when using HTTP API in the case of enabling web authentication")
+	cfg.ApiToken = flag.String("T", "", "API token (requires web authentication with username and password)")
+	flag.StringVar(cfg.ApiToken, "api-token", "", "API token (requires web authentication with username and password)")
 	flag.BoolVar(&cfg.MCPEnable, "mcp-enable", false, "Enable MCP endpoint")
 	cfg.TempDir = flag.String("temp-dir", "", "Temporary directory (defaults to the OS temporary directory)")
 	cfg.StorageDir = flag.String("d", "", "Storage directory")

cmd/web/main.go

@@ -62,7 +62,10 @@ func main() {
 		WebFS:             sub,
 		WebAuth:           webAuth,
 	}
-	cmd.Start(cfg)
+	if err := cmd.Start(cfg); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 }
 
 func isNotBlank(str *string) bool {

go.mod

@@ -10,11 +10,13 @@ require (
 	github.com/bodgit/sevenzip v1.6.1
 	github.com/dop251/goja v0.0.0-20260106131823-651366fbe6e3
 	github.com/dop251/goja_nodejs v0.0.0-20240728170619-29b559befffc
+	github.com/fclairamb/ftpserverlib v0.31.0
 	github.com/go-git/go-git/v5 v5.8.1
 	github.com/google/jsonschema-go v0.4.3
 	github.com/gorilla/handlers v1.5.1
 	github.com/gorilla/mux v1.8.0
 	github.com/imroc/req/v3 v3.52.2
+	github.com/jlaffaye/ftp v0.2.4
 	github.com/matoous/go-nanoid/v2 v2.0.0
 	github.com/mattn/go-ieproxy v0.0.12
 	github.com/mholt/archives v0.1.5
@@ -23,6 +25,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/rs/dnscache v0.0.0-20230804202142-fc85eb664529
 	github.com/rs/zerolog v1.31.0
+	github.com/spf13/afero v1.15.0
 	github.com/tetratelabs/wazero v1.12.0
 	github.com/xiaoqidun/setft v0.0.0-20220310121541-be86327699ad
 	go.etcd.io/bbolt v1.4.3
@@ -59,13 +62,13 @@ require (
 	github.com/segmentio/asm v1.1.3 // indirect
 	github.com/segmentio/encoding v0.5.4 // indirect
 	github.com/sorairolake/lzip-go v0.3.8 // indirect
-	github.com/spf13/afero v1.15.0 // indirect
 	github.com/ulikunitz/xz v0.5.15 // indirect
 	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.uber.org/automaxprocs v1.6.0 // indirect
 	go.uber.org/mock v0.5.1 // indirect
 	go4.org v0.0.0-20230225012048-214862532bf5 // indirect
+	golang.org/x/mod v0.33.0
 	golang.org/x/oauth2 v0.35.0 // indirect
 	golang.org/x/sync v0.20.0 // indirect
 )
@@ -156,7 +159,6 @@ require (
 	go.opentelemetry.io/otel/metric v1.39.0 // indirect
 	go.opentelemetry.io/otel/trace v1.39.0 // indirect
 	golang.org/x/crypto v0.48.0 // indirect
-	golang.org/x/mod v0.33.0 // indirect
 	golang.org/x/net v0.50.0
 	golang.org/x/sys v0.44.0 // indirect
 	golang.org/x/text v0.34.0

go.sum

@@ -205,6 +205,8 @@ github.com/emirpasic/gods v1.18.1 h1:FXtiHYKDGKCW2KzwZKx0iC0PQmdlorYgdFG9jPXJ1Bc
 github.com/emirpasic/gods v1.18.1/go.mod h1:8tpGGwCnJ5H4r6BWwaV6OrWmMoPhUl5jm/FMNAnJvWQ=
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
+github.com/fclairamb/ftpserverlib v0.31.0 h1:ws4fLJvuU/mgg1uIgRjCJfc6CrFSgIBAOxVsnawXegE=
+github.com/fclairamb/ftpserverlib v0.31.0/go.mod h1:C5hUT0sd9P5XsHMxsmpcrT6wdZexu3qtUu1z0Ih6aG0=
 github.com/felixge/fgprof v0.9.5 h1:8+vR6yu2vvSKn08urWyEuxx75NWPEvybbkBirEpsbVY=
 github.com/felixge/fgprof v0.9.5/go.mod h1:yKl+ERSa++RYOs32d8K6WEXCB4uXdLls4ZaZPpayhMM=
 github.com/felixge/httpsnoop v1.0.1 h1:lvB5Jl89CsZtGIWuTcDM1E/vkVs49/Ml7JJe07l8SPQ=
@@ -347,6 +349,8 @@ github.com/imroc/req/v3 v3.52.2 h1:xJocr1aIv0a2K9knfBQ4JnZHk+kWTITdjf0mgDg229I=
 github.com/imroc/req/v3 v3.52.2/go.mod h1:dBGsDloOSZJcFs6PnTjZXYBJK70OXbZpizHBLNqcH2k=
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 h1:BQSFePA1RWJOlocH6Fxy8MmwDt+yVQYULKfN0RoTN8A=
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99/go.mod h1:1lJo3i6rXxKeerYnT8Nvf0QmHCRC1n8sfWVwXF2Frvo=
+github.com/jlaffaye/ftp v0.2.4 h1:JqI85DdkfZj8ntaHk8W9U2SC3jNfiPUU70+wtIWmlfE=
+github.com/jlaffaye/ftp v0.2.4/go.mod h1:Y1ZnkzxownGIuX7xQ1mQzzkZ21+DbjVIyeKL/V+IIz4=
 github.com/josharian/intern v1.0.0/go.mod h1:5DoeVV0s6jJacbCEi61lwdGj/aVlrQvzHFFd8Hwg//Y=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=
 github.com/json-iterator/go v1.1.9/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
@@ -527,6 +531,8 @@ github.com/rs/zerolog v1.31.0/go.mod h1:/7mN4D5sKwJLZQ2b/znpjC3/GQWY/xaDXUM0kKWR
 github.com/rwcarlsen/goexif v0.0.0-20190401172101-9e8deecbddbd/go.mod h1:hPqNNc0+uJM6H+SuU8sEs5K5IQeKccPqeSjfgcKGgPk=
 github.com/ryszard/goskiplist v0.0.0-20150312221310-2dfbae5fcf46 h1:GHRpF1pTW19a8tTFrMLUcfWwyC0pnifVo2ClaLq+hP8=
 github.com/ryszard/goskiplist v0.0.0-20150312221310-2dfbae5fcf46/go.mod h1:uAQ5PCi+MFsC7HjREoAz1BU+Mq60+05gifQSsHSDG/8=
+github.com/secsy/goftp v0.0.0-20200609142545-aa2de14babf4 h1:PT+ElG/UUFMfqy5HrxJxNzj3QBOf7dZwupeVC+mG1Lo=
+github.com/secsy/goftp v0.0.0-20200609142545-aa2de14babf4/go.mod h1:MnkX001NG75g3p8bhFycnyIjeQoOjGL6CEIsdE/nKSY=
 github.com/segmentio/asm v1.1.3 h1:WM03sfUOENvvKexOLp+pCqgb/WDjsi7EK8gIsICtzhc=
 github.com/segmentio/asm v1.1.3/go.mod h1:Ld3L4ZXGNcSLRg4JBsZ3//1+f/TjYl0Mzen/DQy1EJg=
 github.com/segmentio/encoding v0.5.4 h1:OW1VRern8Nw6ITAtwSZ7Idrl3MXCFwXHPgqESYfvNt0=
@@ -566,6 +572,8 @@ github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+github.com/stretchr/testify v1.12.1 h1:EuwCh5fleGS7H32xRwO3wRGT7DxrDhLAT6FF8MpWDWE=
+github.com/stretchr/testify v1.12.1/go.mod h1:MDEgiDPPsNp5cuIrHPPCyornHKgEVbtFUmoNlxoYthg=
 github.com/tetratelabs/wazero v1.12.0 h1:DuWcpNu/FzgEXgGBDp8J1Spc+CWOvvtvVyjKlaZopYU=
 github.com/tetratelabs/wazero v1.12.0/go.mod h1:LvKtzl2RqO4gyF27BiXU+nKAjcV8f38U+kP/q2vgxh0=
 github.com/tidwall/btree v1.8.1 h1:27ehoXvm5AG/g+1VxLS1SD3vRhp/H7LuEfwNvddEdmA=
@@ -612,6 +620,8 @@ go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
 go.uber.org/mock v0.5.1 h1:ASgazW/qBmR+A32MYFDB6E2POoTgOwT509VP0CT/fjs=
 go.uber.org/mock v0.5.1/go.mod h1:ge71pBPLYDk7QIi1LupWxdAykm7KIEFchiOqd6z7qMM=
+go.yaml.in/yaml/v3 v3.0.5 h1:N6y/pJk8buWs9NY5ERU2HSMfm+IuD/OtfdAnq6kESPw=
+go.yaml.in/yaml/v3 v3.0.5/go.mod h1:HVTZu1O7/Vkt2N+BFy8Zza+lnLsABggaTM2ZpNIGuKg=
 go4.org v0.0.0-20230225012048-214862532bf5 h1:nifaUDeh+rPaBCMPMQHZmvJf+QdpLFnuQPwx+LxVmtc=
 go4.org v0.0.0-20230225012048-214862532bf5/go.mod h1:F57wTi5Lrj6WLyswp5EYV1ncrEbFGHD4hhz6S1ZYeaU=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=

internal/controller/controller.go

@@ -3,6 +3,7 @@ package controller
 import (
 	"github.com/GopeedLab/gopeed/internal/tempfiles"
 	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/rs/zerolog"
 	"net/http"
 	"net/url"
 	"os"
@@ -15,6 +16,9 @@ type Controller struct {
 	TempDir           string
 	GetConfig         func(v any)
 	GetProxy          func(requestProxy *base.RequestProxy) func(*http.Request) (*url.URL, error)
+	// Logger is the downloader's core logger. It may be nil, in which case
+	// fetchers log nothing.
+	Logger *zerolog.Logger
 	FileController
 	//ContextDialer() (proxy.Dialer, error)
 }

internal/fetcher/fetcher.go

@@ -12,7 +12,7 @@ import (
 // Each download task will have a corresponding Fetcher instance for the management of the download task
 type Fetcher interface {
 	Setup(ctl *controller.Controller)
-	Resolve(req *base.Request, opts *base.Options) error
+	Resolve(req *base.Request) error
 	Start() error
 	// Patch modifies task-specific data based on the protocol.
 	// For HTTP: can modify Request info (URL, headers, etc.)

internal/fetcher/jobs.go

@@ -0,0 +1,72 @@
+package fetcher
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"time"
+)
+
+type TriggerSource string
+
+const (
+	TriggerScheduled TriggerSource = "scheduled"
+	TriggerManual    TriggerSource = "manual"
+)
+
+var ErrJobSkipped = errors.New("protocol job skipped")
+var ErrConfigChanged = errors.New("protocol configuration changed during execution")
+
+// ConfigState embeds the common backend-owned state section in a protocol config.
+// Public config PUTs always retain this section from the latest stored config.
+type ConfigState[T any] struct {
+	State T `json:"state"`
+}
+
+// ProtocolHost is scoped to one manager. UpdateState runs against the latest
+// config under Downloader's lock; callbacks must not perform network I/O.
+type ProtocolHost struct {
+	Read        func(any) error
+	UpdateState func(func(config, state json.RawMessage) (any, error)) error
+	Fetch       func(context.Context, string, int64, func([]byte) error) ([]byte, error)
+}
+
+func ReadConfig[T any](host ProtocolHost) (*T, error) {
+	var cfg T
+	if err := host.Read(&cfg); err != nil {
+		return nil, err
+	}
+	return &cfg, nil
+}
+
+// UpdateState gives the callback a detached config snapshot and mutable state.
+// Only the state is committed; edits to the config snapshot are discarded.
+func UpdateState[C, S any](host ProtocolHost, update func(*C, *S) error) error {
+	return host.UpdateState(func(rawConfig, rawState json.RawMessage) (any, error) {
+		var cfg C
+		var state S
+		if err := json.Unmarshal(rawConfig, &cfg); err != nil {
+			return nil, err
+		}
+		if err := json.Unmarshal(rawState, &state); err != nil {
+			return nil, err
+		}
+		if err := update(&cfg, &state); err != nil {
+			return nil, err
+		}
+		return &state, nil
+	})
+}
+
+type CronJob struct {
+	Name    string
+	Every   time.Duration
+	Timeout time.Duration
+	Run     func(context.Context, TriggerSource) error
+}
+type CronProvider interface{ CronJobs(ProtocolHost) []CronJob }
+
+// ConfigNormalizer is optional. It owns protocol validation and derived fields.
+type ConfigNormalizer interface {
+	NormalizeConfig(json.RawMessage) (any, error)
+}

internal/githubmirror/README.md

@@ -0,0 +1,73 @@
+# GitHub mirror execution
+
+This package owns GitHub URL rewriting and execution strategies. It depends only
+on the standard library and does not depend on Downloader, HTTP clients, Git, or
+storage. Downloader persists `Config` at its top-level `githubMirror` field;
+`pkg/base` preserves the existing configuration names through aliases.
+
+## Race: resource reads
+
+```go
+body, err := githubmirror.Race(ctx, cfg.GithubMirror, rawURL,
+    githubmirror.Options[[]byte]{
+        Kind:    githubmirror.Resource,
+        Timeout: 30 * time.Second,
+    },
+    func(ctx context.Context, candidate string) ([]byte, error) {
+        return fetchAndValidate(ctx, client, candidate)
+    },
+)
+```
+
+The callback owns HTTP requests, size limits, and content validation. The first
+completed valid result wins. Other operations are canceled and drained. There is
+no HEAD-probe assumption or client-specific HTTP behavior inside the executor.
+
+## Fallback: repository operations
+
+```go
+repo, err := githubmirror.Fallback(ctx, cfg.GithubMirror, officialURL,
+    githubmirror.Options[*git.Repository]{
+        Kind: githubmirror.Repository,
+    },
+    func(ctx context.Context, candidate string) (*git.Repository, error) {
+        // Use a clean temporary checkout for each attempt.
+        return clone(ctx, candidate)
+    },
+)
+```
+
+The official URL is attempted first; mirrors follow their configured order.
+jsDelivr is excluded for repositories. Stop on the first success. Perform
+persistent installation or other business state changes after success, rather
+than inside a potentially repeated attempt.
+
+## Results with resources
+
+For temporary files, set `Options[*Download].Discard` to remove the file. Return
+the partial `*Download` alongside errors, so cleanup also covers failed reads or
+validation. The executor discards every failure and every race loser exactly
+once. The caller owns and must track/release the winning result.
+
+- `Timeout == 0` uses 30 seconds per resource attempt and no overall deadline
+  for repository attempts; a negative timeout is invalid. Extension Git HTTP
+  transport limits connections/TLS handshakes to 10 seconds and resets a 60-second
+  read deadline as data arrives. Slow continuous transfers can finish, while
+  stalled sources fail and allow ordered fallback. Parent cancellation still applies.
+- Attempts must honor the supplied context; draining waits for them to return.
+- Attempt contexts are canceled after return, so callbacks must finish reading
+  HTTP bodies before returning. Returning a still-streaming response is unsupported.
+- Discard callbacks must accept zero values, must not panic, and run serially.
+- Parent cancellation wins over a result selected while the parent is canceled;
+  the selected result is then discarded as well.
+- Errors preserve their causes through wrapping/joining for `errors.Is`.
+- `github.com` and `raw.githubusercontent.com` expand into eligible mirrors.
+  jsDelivr is only eligible for raw source resources. `api.github.com` is never
+  mirrored and is rejected by the public mirror candidates API.
+- Client application update checks request the official GitHub API directly,
+  falling back to the independent Gopeed website API on request or validation
+  failure. Only package downloads obtain URLs from
+  `POST /api/v1/mirrors/github/candidates`. Candidate generation never performs
+  HTTP requests.
+- Disabled mirrors and other URLs execute only the original URL.
+- Config is a caller-owned immutable snapshot for the duration of a call.

internal/githubmirror/config.go

@@ -0,0 +1,90 @@
+// Package githubmirror rewrites GitHub URLs and executes mirrored operations.
+package githubmirror
+
+import (
+	"fmt"
+	"net/url"
+	"strings"
+)
+
+type Mirror struct {
+	Type      string `json:"type"`
+	URL       string `json:"url"`
+	IsBuiltIn bool   `json:"isBuiltIn"`
+	IsDeleted bool   `json:"isDeleted"`
+}
+type Config struct {
+	Enabled bool     `json:"enabled"`
+	Mirrors []Mirror `json:"mirrors"`
+}
+
+func DefaultConfig() *Config {
+	return &Config{Enabled: true, Mirrors: []Mirror{
+		{Type: "jsdelivr", URL: "https://fastly.jsdelivr.net/gh", IsBuiltIn: true},
+		{Type: "ghProxy", URL: "https://fastgit.cc", IsBuiltIn: true},
+		{Type: "ghProxy", URL: "https://gh-proxy.com", IsBuiltIn: true},
+		{Type: "ghProxy", URL: "https://ghfast.top", IsBuiltIn: true},
+	}}
+}
+func (c *Config) Validate() error {
+	if len(c.Mirrors) > 32 {
+		return fmt.Errorf("too many GitHub mirrors")
+	}
+	for _, mirror := range c.Mirrors {
+		u, err := url.Parse(mirror.URL)
+		if err != nil || u == nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" || u.User != nil || u.RawQuery != "" || u.Fragment != "" {
+			return fmt.Errorf("invalid GitHub mirror URL")
+		}
+		if mirror.Type != "jsdelivr" && mirror.Type != "ghProxy" {
+			return fmt.Errorf("invalid GitHub mirror type: %s", mirror.Type)
+		}
+	}
+	return nil
+}
+
+// Kind describes what a candidate endpoint must support.
+type Kind uint8
+
+const (
+	Resource Kind = iota
+	Repository
+)
+
+// Candidates preserves the official URL first. jsDelivr is only eligible for
+// raw source resources; Git operations use mirrors supporting Git Smart HTTP.
+// GitHub API URLs are never mirrored.
+func Candidates(c *Config, raw string, kind Kind) []string {
+	result := []string{raw}
+	u, err := url.Parse(raw)
+	if err != nil || c == nil || !c.Enabled || u.User != nil || (u.Scheme != "https" && u.Scheme != "http") {
+		return result
+	}
+	if u.Host != "github.com" && u.Host != "raw.githubusercontent.com" {
+		return result
+	}
+	seen := map[string]bool{raw: true}
+	for _, mirror := range c.Mirrors {
+		if mirror.IsDeleted {
+			continue
+		}
+		var candidate string
+		switch mirror.Type {
+		case "ghProxy":
+			candidate = strings.TrimRight(mirror.URL, "/") + "/" + raw
+		case "jsdelivr":
+			if kind == Repository || u.Host != "raw.githubusercontent.com" {
+				continue
+			}
+			parts := strings.SplitN(strings.TrimPrefix(u.EscapedPath(), "/"), "/", 4)
+			if len(parts) != 4 {
+				continue
+			}
+			candidate = strings.TrimRight(mirror.URL, "/") + "/" + parts[0] + "/" + parts[1] + "@" + parts[2] + "/" + parts[3]
+		}
+		if candidate != "" && !seen[candidate] {
+			result = append(result, candidate)
+			seen[candidate] = true
+		}
+	}
+	return result
+}

internal/githubmirror/config_test.go

@@ -0,0 +1,38 @@
+package githubmirror
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestMirrorCandidates(t *testing.T) {
+	cfg := &Config{Enabled: true, Mirrors: []Mirror{
+		{Type: "jsdelivr", URL: "https://cdn.example/gh/"},
+		{Type: "ghProxy", URL: "https://mirror.example/"},
+		{Type: "ghProxy", URL: "https://deleted.example", IsDeleted: true},
+	}}
+	source := "https://raw.githubusercontent.com/owner/repo/main/a.txt"
+	want := []string{source, "https://cdn.example/gh/owner/repo@main/a.txt", "https://mirror.example/" + source}
+	if got := Candidates(cfg, source, Resource); !reflect.DeepEqual(got, want) {
+		t.Fatalf("got %v", got)
+	}
+	repo := "https://github.com/owner/repo.git"
+	if got := Candidates(cfg, repo, Repository); !reflect.DeepEqual(got, []string{repo, "https://mirror.example/" + repo}) {
+		t.Fatalf("git candidates %v", got)
+	}
+	for _, raw := range []string{"https://github.com.evil.example/a", "https://example.com/a", "https://user:[email protected]/a"} {
+		if got := Candidates(cfg, raw, Resource); !reflect.DeepEqual(got, []string{raw}) {
+			t.Fatalf("unexpected mirror: %v", got)
+		}
+	}
+	apiURL := "https://api.github.com/repos/GopeedLab/gopeed/releases?per_page=10"
+	for _, kind := range []Kind{Resource, Repository} {
+		if got := Candidates(cfg, apiURL, kind); !reflect.DeepEqual(got, []string{apiURL}) {
+			t.Fatalf("GitHub API must never use mirrors: %v", got)
+		}
+	}
+	cfg.Enabled = false
+	if got := Candidates(cfg, source, Resource); !reflect.DeepEqual(got, []string{source}) {
+		t.Fatalf("disabled mirror: %v", got)
+	}
+}

internal/githubmirror/execute.go

@@ -0,0 +1,160 @@
+package githubmirror
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+)
+
+// Options configures execution, not URL persistence. Discard releases results
+// from failed attempts and successful race losers, including partial results
+// returned together with an error. The caller owns the winning result.
+type Options[T any] struct {
+	Kind Kind
+	// Timeout limits each attempt. Zero uses 30 seconds for resources and no
+	// overall deadline for repositories, whose transport owns idle timeouts.
+	Timeout time.Duration
+	Discard func(T)
+}
+
+// Attempt must honor ctx and return a completed, validated result. Its context
+// is canceled after it returns, so live response streams must not be returned.
+// Return any partially acquired resources along with errors so Discard can
+// release them. Failed attempts must not mutate persistent business state.
+type Attempt[T any] func(context.Context, string) (T, error)
+
+const defaultTimeout = 30 * time.Second
+
+func prepare[T any](ctx context.Context, config *Config, raw string, options Options[T], attempt Attempt[T]) ([]string, time.Duration, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, 0, err
+	}
+	if raw == "" {
+		return nil, 0, errors.New("empty GitHub source URL")
+	}
+	if options.Kind != Resource && options.Kind != Repository {
+		return nil, 0, errors.New("invalid GitHub resource kind")
+	}
+	if options.Timeout < 0 {
+		return nil, 0, errors.New("invalid GitHub attempt timeout")
+	}
+	if attempt == nil {
+		return nil, 0, errors.New("GitHub mirror attempt is required")
+	}
+	if config != nil {
+		if err := config.Validate(); err != nil {
+			return nil, 0, err
+		}
+	}
+	timeout := options.Timeout
+	if timeout == 0 && options.Kind == Resource {
+		timeout = defaultTimeout
+	}
+	return Candidates(config, raw, options.Kind), timeout, nil
+}
+func invoke[T any](ctx context.Context, timeout time.Duration, candidate string, attempt Attempt[T]) (value T, err error) {
+	var cancel context.CancelFunc
+	if timeout > 0 {
+		ctx, cancel = context.WithTimeout(ctx, timeout)
+	} else {
+		ctx, cancel = context.WithCancel(ctx)
+	}
+	defer cancel()
+	defer func() {
+		if recovered := recover(); recovered != nil {
+			err = fmt.Errorf("GitHub mirror attempt panicked: %v", recovered)
+		}
+	}()
+	value, err = attempt(ctx, candidate)
+	if err == nil {
+		err = ctx.Err()
+	}
+	return
+}
+func discard[T any](options Options[T], value T) {
+	if options.Discard != nil {
+		options.Discard(value)
+	}
+}
+
+// Race executes the official URL and eligible mirrors concurrently. The first
+// completed successful result wins; losing attempts are canceled and drained
+// before return so no temporary files or other resources outlive the call.
+// HTTP status/content validation is the attempt's responsibility.
+func Race[T any](ctx context.Context, config *Config, raw string, options Options[T], attempt Attempt[T]) (T, error) {
+	var zero T
+	candidates, timeout, err := prepare(ctx, config, raw, options, attempt)
+	if err != nil {
+		return zero, err
+	}
+	raceCtx, cancel := context.WithCancel(ctx)
+	defer cancel()
+	type outcome struct {
+		index int
+		value T
+		err   error
+	}
+	outcomes := make(chan outcome, len(candidates))
+	for index, candidate := range candidates {
+		go func(index int, candidate string) {
+			value, err := invoke(raceCtx, timeout, candidate, attempt)
+			outcomes <- outcome{index, value, err}
+		}(index, candidate)
+	}
+	var winner T
+	won := false
+	failures := make([]error, len(candidates))
+	for range candidates {
+		outcome := <-outcomes
+		if !won && outcome.err == nil && ctx.Err() == nil {
+			winner = outcome.value
+			won = true
+			cancel()
+		} else {
+			discard(options, outcome.value)
+			if outcome.err != nil {
+				failures[outcome.index] = fmt.Errorf("GitHub source %d: %w", outcome.index+1, outcome.err)
+			}
+			if ctx.Err() != nil {
+				cancel()
+			}
+		}
+	}
+	if err := ctx.Err(); err != nil {
+		if won {
+			discard(options, winner)
+		}
+		return zero, err
+	}
+	if won {
+		return winner, nil
+	}
+	return zero, fmt.Errorf("all GitHub sources failed: %w", errors.Join(failures...))
+}
+
+// Fallback executes the official URL first, then eligible mirrors in their
+// configured order. It stops immediately on success and cleans every failure.
+func Fallback[T any](ctx context.Context, config *Config, raw string, options Options[T], attempt Attempt[T]) (T, error) {
+	var zero T
+	candidates, timeout, err := prepare(ctx, config, raw, options, attempt)
+	if err != nil {
+		return zero, err
+	}
+	failures := make([]error, 0, len(candidates))
+	for index, candidate := range candidates {
+		if err := ctx.Err(); err != nil {
+			return zero, err
+		}
+		value, err := invoke(ctx, timeout, candidate, attempt)
+		if err == nil && ctx.Err() == nil {
+			return value, nil
+		}
+		discard(options, value)
+		if parentErr := ctx.Err(); parentErr != nil {
+			return zero, parentErr
+		}
+		failures = append(failures, fmt.Errorf("GitHub source %d: %w", index+1, err))
+	}
+	return zero, fmt.Errorf("all GitHub sources failed: %w", errors.Join(failures...))
+}

internal/githubmirror/execute_test.go

@@ -0,0 +1,214 @@
+package githubmirror
+
+import (
+	"context"
+	"errors"
+	"reflect"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+const testSource = "https://github.com/owner/repo.git"
+
+func testConfig() *Config {
+	return &Config{Enabled: true, Mirrors: []Mirror{
+		{Type: "ghProxy", URL: "https://first.example"},
+		{Type: "ghProxy", URL: "https://second.example"},
+	}}
+}
+func TestRaceWinsAndDrainsOwnedResults(t *testing.T) {
+	config := testConfig()
+	candidates := Candidates(config, testSource, Resource)
+	var started sync.WaitGroup
+	started.Add(len(candidates))
+	discarded := []string{}
+	winner, err := Race(context.Background(), config, testSource, Options[string]{
+		Discard: func(value string) { discarded = append(discarded, value) },
+	}, func(ctx context.Context, address string) (string, error) {
+		started.Done()
+		started.Wait()
+		switch address {
+		case candidates[0]:
+			return address, errors.New("official offline")
+		case candidates[1]:
+			return address, nil
+		default:
+			<-ctx.Done()
+			return address, ctx.Err()
+		}
+	})
+	if err != nil || winner != candidates[1] {
+		t.Fatalf("winner=%s err=%v", winner, err)
+	}
+	if len(discarded) != 2 || !contains(discarded, candidates[0]) || !contains(discarded, candidates[2]) {
+		t.Fatalf("discarded %v", discarded)
+	}
+}
+func contains(values []string, value string) bool {
+	for _, item := range values {
+		if item == value {
+			return true
+		}
+	}
+	return false
+}
+func TestRaceCleansSimultaneousSuccessfulLosers(t *testing.T) {
+	config := testConfig()
+	var started sync.WaitGroup
+	started.Add(3)
+	cleaned := []string{}
+	winner, err := Race(context.Background(), config, testSource, Options[string]{Discard: func(value string) { cleaned = append(cleaned, value) }}, func(_ context.Context, address string) (string, error) {
+		started.Done()
+		started.Wait()
+		return address, nil
+	})
+	if err != nil || winner == "" || len(cleaned) != 2 || contains(cleaned, winner) {
+		t.Fatalf("winner=%s discarded=%v err=%v", winner, cleaned, err)
+	}
+}
+func TestRaceParentCancellationCleansWinnerToo(t *testing.T) {
+	config := testConfig()
+	config.Mirrors = config.Mirrors[:1]
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	cleaned := []string{}
+	winner, err := Race(ctx, config, testSource, Options[string]{Discard: func(value string) { cleaned = append(cleaned, value) }}, func(ctx context.Context, address string) (string, error) {
+		if address == testSource {
+			return address, nil
+		}
+		<-ctx.Done()
+		cancel()
+		return address, ctx.Err()
+	})
+	if !errors.Is(err, context.Canceled) || winner != "" || len(cleaned) != 2 || !contains(cleaned, testSource) {
+		t.Fatalf("winner=%s cleanup=%v err=%v", winner, cleaned, err)
+	}
+}
+func TestRaceTimeoutAndErrorAggregation(t *testing.T) {
+	expected := errors.New("offline")
+	config := testConfig()
+	config.Mirrors = config.Mirrors[:1]
+	discarded := 0
+	_, err := Race(context.Background(), config, testSource, Options[string]{Timeout: 10 * time.Millisecond, Discard: func(string) { discarded++ }}, func(ctx context.Context, address string) (string, error) {
+		if address == testSource {
+			return address, expected
+		}
+		<-ctx.Done()
+		return address, ctx.Err()
+	})
+	if !errors.Is(err, expected) || !errors.Is(err, context.DeadlineExceeded) || discarded != 2 {
+		t.Fatalf("discarded=%d err=%v", discarded, err)
+	}
+}
+func TestFallbackPreservesOrderAndStopsOnSuccess(t *testing.T) {
+	config := testConfig()
+	candidates := Candidates(config, testSource, Repository)
+	tried := []string{}
+	cleaned := []string{}
+	winner, err := Fallback(context.Background(), config, testSource, Options[string]{Kind: Repository, Discard: func(value string) { cleaned = append(cleaned, value) }}, func(_ context.Context, address string) (string, error) {
+		tried = append(tried, address)
+		if address == candidates[1] {
+			return address, nil
+		}
+		return address, errors.New("offline")
+	})
+	if err != nil || winner != candidates[1] || !reflect.DeepEqual(tried, candidates[:2]) || !reflect.DeepEqual(cleaned, candidates[:1]) {
+		t.Fatalf("winner=%s tried=%v discarded=%v err=%v", winner, tried, cleaned, err)
+	}
+	tried = nil
+	_, err = Fallback(context.Background(), config, testSource, Options[string]{Kind: Repository}, func(_ context.Context, address string) (string, error) {
+		tried = append(tried, address)
+		return address, nil
+	})
+	if err != nil || !reflect.DeepEqual(tried, candidates[:1]) {
+		t.Fatalf("tried=%v err=%v", tried, err)
+	}
+}
+func TestFallbackTimeoutContinuesWithFreshContext(t *testing.T) {
+	discarded := []string{}
+	winner, err := Fallback(context.Background(), testConfig(), testSource, Options[string]{Kind: Repository, Timeout: 10 * time.Millisecond, Discard: func(value string) { discarded = append(discarded, value) }}, func(ctx context.Context, address string) (string, error) {
+		if address == testSource {
+			<-ctx.Done()
+			return address, ctx.Err()
+		}
+		if err := ctx.Err(); err != nil {
+			return address, err
+		}
+		return address, nil
+	})
+	if err != nil || !strings.HasPrefix(winner, "https://first.example/") || !reflect.DeepEqual(discarded, []string{testSource}) {
+		t.Fatalf("winner=%s cleanup=%v err=%v", winner, discarded, err)
+	}
+}
+func TestFallbackCancellationStopsBeforeNextMirror(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	calls := 0
+	cleaned := 0
+	_, err := Fallback(ctx, testConfig(), testSource, Options[string]{Kind: Repository, Discard: func(string) { cleaned++ }}, func(ctx context.Context, address string) (string, error) {
+		calls++
+		cancel()
+		return address, ctx.Err()
+	})
+	if !errors.Is(err, context.Canceled) || calls != 1 || cleaned != 1 {
+		t.Fatalf("calls=%d discarded=%d err=%v", calls, cleaned, err)
+	}
+}
+func TestExecutorsDoNotStartInvalidOrCanceledRequests(t *testing.T) {
+	canceled, cancel := context.WithCancel(context.Background())
+	cancel()
+	for _, test := range []struct {
+		ctx     context.Context
+		config  *Config
+		options Options[string]
+		attempt Attempt[string]
+	}{
+		{ctx: canceled, options: Options[string]{}, attempt: func(context.Context, string) (string, error) { t.Fatal("called after cancellation"); return "", nil }},
+		{ctx: context.Background(), options: Options[string]{Kind: 99}, attempt: func(context.Context, string) (string, error) { t.Fatal("invalid kind"); return "", nil }},
+		{ctx: context.Background(), options: Options[string]{Timeout: -time.Second}, attempt: func(context.Context, string) (string, error) { t.Fatal("invalid timeout"); return "", nil }},
+		{ctx: context.Background(), options: Options[string]{}, attempt: nil},
+		{ctx: context.Background(), config: &Config{Mirrors: []Mirror{{Type: "invalid", URL: "https://mirror.example"}}}, attempt: func(context.Context, string) (string, error) { t.Fatal("invalid config"); return "", nil }},
+	} {
+		if _, err := Race(test.ctx, test.config, testSource, test.options, test.attempt); err == nil {
+			t.Fatal("invalid race accepted")
+		}
+		if _, err := Fallback(test.ctx, test.config, testSource, test.options, test.attempt); err == nil {
+			t.Fatal("invalid fallback accepted")
+		}
+	}
+}
+func TestAttemptPanicBecomesError(t *testing.T) {
+	attempt := func(context.Context, string) (string, error) { panic("broken operation") }
+	if _, err := Race(context.Background(), nil, testSource, Options[string]{}, attempt); err == nil || !strings.Contains(err.Error(), "broken operation") {
+		t.Fatal(err)
+	}
+	if _, err := Fallback(context.Background(), nil, testSource, Options[string]{}, attempt); err == nil || !strings.Contains(err.Error(), "broken operation") {
+		t.Fatal(err)
+	}
+}
+func TestNonGithubResourcesAndDisabledMirrorsUseOnlyOriginal(t *testing.T) {
+	for _, test := range []struct {
+		config *Config
+		raw    string
+	}{{testConfig(), "https://example.com/resource"}, {&Config{Enabled: false, Mirrors: testConfig().Mirrors}, testSource}} {
+		calls := 0
+		got, err := Race(context.Background(), test.config, test.raw, Options[string]{}, func(_ context.Context, address string) (string, error) { calls++; return address, nil })
+		if err != nil || got != test.raw || calls != 1 {
+			t.Fatalf("got=%s calls=%d err=%v", got, calls, err)
+		}
+	}
+}
+
+func TestRepositoryAttemptsHaveNoDefaultDeadline(t *testing.T) {
+	value, err := Fallback(context.Background(), nil, testSource, Options[string]{Kind: Repository}, func(ctx context.Context, raw string) (string, error) {
+		if _, ok := ctx.Deadline(); ok {
+			t.Fatal("repository attempt has a total deadline")
+		}
+		return raw, nil
+	})
+	if err != nil || value != testSource {
+		t.Fatalf("value=%s error=%v", value, err)
+	}
+}

internal/protocol/bt/config.go

@@ -1,12 +1,37 @@
 package bt
 
+import (
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+)
+
+type trackerSubscriptionStatus struct {
+	Success       bool      `json:"success"`
+	TrackerCount  int       `json:"trackerCount"`
+	LastFetchTime time.Time `json:"lastFetchTime"`
+}
+
+type state struct {
+	TrackerSubscriptionStatuses map[string]trackerSubscriptionStatus `json:"trackerSubscriptionStatuses"`
+	TrackerSources              map[string][]string                  `json:"trackerSources"`
+	LastTrackerUpdateTime       time.Time                            `json:"lastTrackerUpdateTime"`
+}
+
 type config struct {
-	ListenPort int      `json:"listenPort"`
-	Trackers   []string `json:"trackers"`
+	fetcher.ConfigState[state]
+	TrackerSubscribeURLs []string `json:"trackerSubscribeUrls"`
+	AutoUpdateTrackers   bool     `json:"autoUpdateTrackers"`
+	CustomTrackers       []string `json:"customTrackers"`
+	ListenPort           int      `json:"listenPort"`
 	// SeedKeep is always keep seeding after downloading is complete, unless manually stopped.
 	SeedKeep bool `json:"seedKeep"`
 	// SeedRatio is the ratio of uploaded data to downloaded data to seed.
 	SeedRatio float64 `json:"seedRatio"`
 	// SeedTime is the time in seconds to seed after downloading is complete.
 	SeedTime int64 `json:"seedTime"`
+	// DisableDHT and DisablePEX turn off DHT and PEX peer discovery. Like ListenPort,
+	// they are read when the shared client is built.
+	DisableDHT bool `json:"disableDht"`
+	DisablePEX bool `json:"disablePex"`
 }

internal/protocol/bt/download_test.go

@@ -0,0 +1,464 @@
+package bt
+
+import (
+	"encoding/json"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/controller"
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	btprotocol "github.com/GopeedLab/gopeed/pkg/protocol/bt"
+	"github.com/anacrolix/torrent"
+	pp "github.com/anacrolix/torrent/peer_protocol"
+	"golang.org/x/time/rate"
+)
+
+type btDownloadHarness struct {
+	*Fetcher
+	pendingRequests atomic.Int64
+}
+
+// These tests exercise the BT fetcher, native storage and real peer protocol.
+// All content is generated locally and served by a loopback seeder.
+func btDownloadFetcher(t *testing.T, f fetcher.Fetcher) *btDownloadHarness {
+	t.Helper()
+	if f == nil {
+		f = new(FetcherManager).Build()
+	}
+	ctl := controller.NewController()
+	ctl.GetConfig = func(v any) {
+		encoded, err := json.Marshal(new(FetcherManager).DefaultConfig())
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := json.Unmarshal(encoded, v); err != nil {
+			t.Fatal(err)
+		}
+	}
+	f.Setup(ctl)
+	t.Cleanup(func() {
+		if err := f.Close(); err != nil {
+			t.Error(err)
+		}
+		if err := closeClient(); err != nil {
+			t.Error(err)
+		}
+	})
+	h := &btDownloadHarness{Fetcher: f.(*Fetcher)}
+	// Keep the test client on loopback and observe real cancellation replies.
+	// Waiting for them avoids the pinned library's immediate cancel/resume
+	// request scheduling bug, without relying on arbitrary sleep durations.
+	cfg = torrent.TestingConfig(t)
+	cfg.DisableTrackers = false
+	cfg.Seed = true
+	cfg.DisableUTP = true
+	cfg.DisableIPv6 = true
+	cfg.DisableWebtorrent = true
+	cfg.KeepAliveTimeout = time.Minute
+	cfg.MaxAllocPeerRequestDataPerConn = 1 << 20
+	cfg.Callbacks.SentRequest = []func(torrent.PeerRequestEvent){func(torrent.PeerRequestEvent) {
+		h.pendingRequests.Add(1)
+	}}
+	cfg.Callbacks.ReadMessage = func(_ *torrent.PeerConn, msg *pp.Message) {
+		if !msg.Keepalive && (msg.Type == pp.Piece || msg.Type == pp.Reject) {
+			h.pendingRequests.Add(-1)
+		}
+	}
+	var err error
+	client, err = torrent.NewClient(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return h
+}
+
+func btResolve(t *testing.T, f *btDownloadHarness, source string) {
+	t.Helper()
+	if err := f.Resolve(&base.Request{URL: source}); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func btStart(t *testing.T, f *btDownloadHarness) {
+	t.Helper()
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func btAwaitDone(t *testing.T, f *btDownloadHarness) {
+	t.Helper()
+	done := make(chan error, 1)
+	go func() { done <- f.Wait() }()
+	timeout := time.NewTimer(20 * time.Second)
+	defer timeout.Stop()
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Fatalf("BT download failed: %v", err)
+		}
+		if !f.isDone() {
+			t.Fatal("Wait returned before selected files were verified")
+		}
+	case <-timeout.C:
+		var status strings.Builder
+		client.WriteStatus(&status)
+		t.Log(status.String())
+		t.Fatalf("BT download did not finish: progress=%v stats=%+v pieces=%+v peers=%+v", f.Progress(), f.torrent.Stats(), f.torrent.PieceStateRuns(), f.Stats().Runtime)
+	}
+}
+
+func btAwaitPartial(t *testing.T, f *btDownloadHarness) {
+	t.Helper()
+	timeout := time.NewTimer(15 * time.Second)
+	defer timeout.Stop()
+	ticker := time.NewTicker(20 * time.Millisecond)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			progress := f.Progress().TotalDownloaded()
+			if progress >= 32*1024 && progress < f.Meta().Res.Size {
+				return
+			}
+		case <-timeout.C:
+			t.Fatal("BT transfer did not reach partial progress")
+		}
+	}
+}
+
+func btPause(t *testing.T, f *btDownloadHarness) {
+	t.Helper()
+	if err := f.Pause(); err != nil {
+		t.Fatal(err)
+	}
+	timeout := time.NewTimer(5 * time.Second)
+	defer timeout.Stop()
+	ticker := time.NewTicker(10 * time.Millisecond)
+	defer ticker.Stop()
+	for {
+		if f.pendingRequests.Load() == 0 {
+			// The message callback runs under the client lock. Acquiring that
+			// lock ensures the final cancellation reply has finished processing.
+			client.Stats()
+			return
+		}
+		select {
+		case <-ticker.C:
+		case <-timeout.C:
+			t.Fatal("peer did not acknowledge cancelled requests")
+		}
+	}
+}
+
+func TestBTDownloadSources(t *testing.T) {
+	for _, kind := range []string{"magnet", "torrent", "file URI", "data URI"} {
+		t.Run(kind, func(t *testing.T) {
+			fixture := newBTFixture(t, map[string][]byte{"": btPayload(96*1024, kind)}, 0)
+			source := fixture.Magnet
+			switch kind {
+			case "torrent":
+				source = fixture.TorrentFile
+			case "file URI":
+				source = fixture.FileURI()
+			case "data URI":
+				source = fixture.DataURI
+			}
+			f := btDownloadFetcher(t, nil)
+			btResolve(t, f, source)
+			if f.Meta().Opts != nil {
+				t.Fatal("Resolve assigned download options")
+			}
+			f.storage.mu.RLock()
+			bound := f.storage.owner != nil
+			f.storage.mu.RUnlock()
+			if bound {
+				t.Fatal("Resolve bound download storage")
+			}
+			resolvedTorrent := f.torrent
+			dir := filepath.Join(t.TempDir(), "chosen-after-resolve")
+			f.Meta().Opts = &base.Options{Path: dir}
+			if _, err := os.Stat(dir); !os.IsNotExist(err) {
+				t.Fatalf("output directory exists before Start: %v", err)
+			}
+			btStart(t, f)
+			if f.torrent != resolvedTorrent {
+				t.Fatal("Start replaced the resolved torrent")
+			}
+			btAwaitDone(t, f)
+			fixture.AssertFiles(t, dir)
+		})
+	}
+}
+
+func TestBTDirectDownloadWithExtraTrackers(t *testing.T) {
+	for _, source := range []string{"request", "config", "subscription"} {
+		t.Run(source, func(t *testing.T) {
+			fixture := makeBTFixture(t, map[string][]byte{
+				"a.bin":        btPayload(20*1024, "direct-a"),
+				"nested/b.bin": btPayload(48*1024, "direct-b"),
+			}, 0, false, false)
+			magnet, err := url.Parse(fixture.Magnet)
+			if err != nil {
+				t.Fatal(err)
+			}
+			query := magnet.Query()
+			query.Del("tr")
+			query.Del("x.pe")
+			magnet.RawQuery = query.Encode()
+			req := &base.Request{URL: magnet.String()}
+			f := btDownloadFetcher(t, nil)
+			if source == "request" {
+				req.Extra = &btprotocol.ReqExtra{Trackers: []string{fixture.TrackerURL}}
+			} else {
+				backendConfig := new(FetcherManager).DefaultConfig().(*config)
+				if source == "config" {
+					backendConfig.CustomTrackers = []string{fixture.TrackerURL}
+				} else {
+					backendConfig.TrackerSubscribeURLs = []string{"https://subscription.example/list"}
+					backendConfig.State.TrackerSources[backendConfig.TrackerSubscribeURLs[0]] = []string{fixture.TrackerURL}
+				}
+				f.ctl.GetConfig = func(dst any) {
+					raw, err := json.Marshal(backendConfig)
+					if err != nil {
+						t.Error(err)
+						return
+					}
+					if err := json.Unmarshal(raw, dst); err != nil {
+						t.Error(err)
+					}
+				}
+			}
+			// CreateDirect supplies options before Downloader resolves the task.
+			dir := filepath.Join(t.TempDir(), "direct-download")
+			opts := &base.Options{Path: dir, SelectFiles: []int{}}
+			f.Meta().Opts = opts
+			resolved := make(chan error, 1)
+			go func() { resolved <- f.Resolve(req) }()
+			select {
+			case err := <-resolved:
+				if err != nil {
+					t.Fatal(err)
+				}
+			case <-time.After(5 * time.Second):
+				f.torrentDropFunc()
+				<-resolved
+				t.Fatal("direct magnet download did not obtain metadata from its extra tracker")
+			}
+			if f.Meta().Opts != opts || len(opts.SelectFiles) != len(fixture.Files) {
+				t.Fatal("resolution lost direct download options or did not select all files")
+			}
+			btStart(t, f)
+			btAwaitDone(t, f)
+			fixture.AssertFiles(t, dir)
+		})
+	}
+}
+
+func TestBTDownloadSelectedFiles(t *testing.T) {
+	fixture := newBTFixture(t, map[string][]byte{
+		"a.bin": btPayload(20*1024, "a"), "nested/b.bin": btPayload(48*1024, "b"),
+	}, 0)
+	f := btDownloadFetcher(t, nil)
+	dir := t.TempDir()
+	btResolve(t, f, fixture.Magnet)
+	selected := -1
+	for i, file := range f.Meta().Res.Files {
+		if file.Name == "b.bin" {
+			selected = i
+		}
+	}
+	if selected < 0 {
+		t.Fatal("selected file absent from metadata")
+	}
+	f.Meta().Opts = &base.Options{Path: dir}
+	if err := f.Patch(nil, &base.Options{SelectFiles: []int{selected}}); err != nil {
+		t.Fatal(err)
+	}
+	btStart(t, f)
+	btAwaitDone(t, f)
+	fixture.AssertFiles(t, dir, filepath.Join("bundle", "nested", "b.bin"))
+	if _, err := os.Stat(filepath.Join(dir, "bundle", "a.bin")); !os.IsNotExist(err) {
+		t.Fatalf("unselected output remains: %v", err)
+	}
+	if f.Meta().Res.Size != 48*1024 {
+		t.Fatal("selected resource size is incorrect")
+	}
+}
+
+func TestBTPauseAndResume(t *testing.T) {
+	fixture := newBTFixture(t, map[string][]byte{"": btPayload(512*1024, "pause")}, 64*1024)
+	f := btDownloadFetcher(t, nil)
+	dir := t.TempDir()
+	btResolve(t, f, fixture.Magnet)
+	f.Meta().Opts = &base.Options{Path: dir}
+	btStart(t, f)
+	btAwaitPartial(t, f)
+	btPause(t, f)
+	resolvedTorrent := f.torrent
+	fixture.Limiter.SetLimit(rate.Inf)
+	// Once cancelled requests have settled, no more data should arrive.
+	stats := f.torrent.Stats()
+	readWhilePaused := stats.BytesReadData.Int64()
+	time.Sleep(200 * time.Millisecond)
+	stats = f.torrent.Stats()
+	if stats.BytesReadData.Int64() != readWhilePaused || f.isDone() {
+		t.Fatal("data download continued while paused")
+	}
+	btStart(t, f)
+	if f.torrent != resolvedTorrent {
+		t.Fatal("resume replaced the resolved torrent")
+	}
+	btAwaitDone(t, f)
+	fixture.AssertFiles(t, dir)
+}
+
+type btFetcherCheckpoint struct {
+	Meta *fetcher.FetcherMeta `json:"meta"`
+	Data json.RawMessage      `json:"data"`
+}
+
+func btStore(t *testing.T, f *btDownloadHarness) []byte {
+	t.Helper()
+	data, err := new(FetcherManager).Store(f.Fetcher)
+	if err != nil {
+		t.Fatal(err)
+	}
+	encodedData, err := json.Marshal(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	encoded, err := json.Marshal(btFetcherCheckpoint{Meta: f.Meta(), Data: encodedData})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return encoded
+}
+
+func btRestore(t *testing.T, encoded []byte) *btDownloadHarness {
+	t.Helper()
+	var checkpoint btFetcherCheckpoint
+	if err := json.Unmarshal(encoded, &checkpoint); err != nil {
+		t.Fatal(err)
+	}
+	data, restore := new(FetcherManager).Restore()
+	if err := json.Unmarshal(checkpoint.Data, data); err != nil {
+		t.Fatal(err)
+	}
+	return btDownloadFetcher(t, restore(checkpoint.Meta, data))
+}
+
+func btCloseForRestart(t *testing.T, f *btDownloadHarness) {
+	t.Helper()
+	if err := f.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := new(FetcherManager).Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestBTColdStartResume(t *testing.T) {
+	for _, kind := range []string{"v1", "hybrid"} {
+		t.Run(kind, func(t *testing.T) {
+			var fixture *btFixture
+			if kind == "hybrid" {
+				fixture = newBTHybridFixture(t, btPayload(512*1024, "restart-hybrid"))
+				fixture.Limiter.SetLimit(64 * 1024)
+			} else {
+				fixture = newBTFixture(t, map[string][]byte{"": btPayload(512*1024, "restart")}, 64*1024)
+			}
+			f := btDownloadFetcher(t, nil)
+			dir := t.TempDir()
+			btResolve(t, f, fixture.Magnet)
+			f.Meta().Opts = &base.Options{Path: dir}
+			btStart(t, f)
+			btAwaitPartial(t, f)
+			btPause(t, f)
+			checkpoint := btStore(t, f)
+			hash := f.Meta().Res.Hash
+			btCloseForRestart(t, f)
+			seedStats := fixture.Torrent.Stats()
+			sentBeforeRestart := seedStats.BytesWrittenData.Int64()
+			restored := btRestore(t, checkpoint)
+			if restored.Meta().Opts.Path != dir || restored.Meta().Res.Hash != hash {
+				t.Fatal("download directory or hash was lost")
+			}
+			fixture.Limiter.SetLimit(rate.Inf)
+			btStart(t, restored)
+			btAwaitDone(t, restored)
+			fixture.AssertFiles(t, dir)
+			seedStats = fixture.Torrent.Stats()
+			if sent := seedStats.BytesWrittenData.Int64() - sentBeforeRestart; sent >= 512*1024 {
+				t.Fatalf("restart redownloaded the entire file: %d bytes", sent)
+			}
+		})
+	}
+}
+
+func TestBTDownloadHybrid(t *testing.T) {
+	fixture := newBTHybridFixture(t, btPayload(80*1024, "hybrid-v2"))
+	f := btDownloadFetcher(t, nil)
+	dir := t.TempDir()
+	btResolve(t, f, fixture.Magnet)
+	f.Meta().Opts = &base.Options{Path: dir}
+	btStart(t, f)
+	btAwaitDone(t, f)
+	fixture.AssertFiles(t, dir)
+}
+
+func TestBTRepairCorruptedExistingFile(t *testing.T) {
+	fixture := newBTFixture(t, map[string][]byte{"": btPayload(128*1024, "repair")}, 0)
+	dir := t.TempDir()
+	damaged := append([]byte(nil), fixture.Files["payload.bin"]...)
+	damaged[20000] ^= 0xff
+	if err := os.WriteFile(filepath.Join(dir, "payload.bin"), damaged, 0600); err != nil {
+		t.Fatal(err)
+	}
+	f := btDownloadFetcher(t, nil)
+	btResolve(t, f, fixture.Magnet)
+	f.Meta().Opts = &base.Options{Path: dir}
+	btStart(t, f)
+	btAwaitDone(t, f)
+	fixture.AssertFiles(t, dir)
+}
+
+func TestBTPatchSelectionWhilePaused(t *testing.T) {
+	fixture := newBTFixture(t, map[string][]byte{"a.bin": btPayload(256*1024, "patch-a"), "b.bin": btPayload(256*1024, "patch-b")}, 64*1024)
+	f := btDownloadFetcher(t, nil)
+	dir := t.TempDir()
+	btResolve(t, f, fixture.Magnet)
+	f.Meta().Opts = &base.Options{Path: dir, SelectFiles: []int{0}}
+	btStart(t, f)
+	btAwaitPartial(t, f)
+	btPause(t, f)
+	if err := f.Patch(nil, &base.Options{SelectFiles: []int{1}}); err != nil {
+		t.Fatal(err)
+	}
+	fixture.Limiter.SetLimit(rate.Inf)
+	btStart(t, f)
+	btAwaitDone(t, f)
+	fixture.AssertFiles(t, dir, filepath.Join("bundle", "b.bin"))
+	for _, suffix := range []string{"", ".part"} {
+		if _, err := os.Stat(filepath.Join(dir, "bundle", "a.bin") + suffix); !os.IsNotExist(err) {
+			t.Fatalf("unselected output remains: %v", err)
+		}
+	}
+}
+
+func TestBTDownloadMultiFileWithEmptyFile(t *testing.T) {
+	fixture := newBTFixture(t, map[string][]byte{"empty.txt": {}, "nested/data.bin": btPayload(48*1024, "empty-file")}, 0)
+	f := btDownloadFetcher(t, nil)
+	dir := t.TempDir()
+	btResolve(t, f, fixture.Magnet)
+	f.Meta().Opts = &base.Options{Path: dir}
+	btStart(t, f)
+	btAwaitDone(t, f)
+	fixture.AssertFiles(t, dir)
+}

internal/protocol/bt/fetcher.go

@@ -3,11 +3,13 @@ package bt
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net/url"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -33,6 +35,10 @@ var (
 )
 
 type Fetcher struct {
+	mu        sync.Mutex
+	closeOnce sync.Once
+	storage   *deferredFileStorage
+
 	ctl    *controller.Controller
 	config *config
 
@@ -61,22 +67,19 @@ func (f *Fetcher) Setup(ctl *controller.Controller) {
 	return
 }
 
+// initClient must be called with lock held.
 func (f *Fetcher) initClient() (err error) {
-	lock.Lock()
-	defer lock.Unlock()
-
 	if client != nil {
 		return
 	}
-	if closeCtx == nil {
-		closeCtx, closeFunc = context.WithCancel(context.Background())
-	}
 
 	cfg = torrent.NewDefaultClientConfig()
 	cfg.Seed = true
 	cfg.Bep20 = fmt.Sprintf("-GP%s-", parseBep20())
 	cfg.ExtendedHandshakeClientVersion = fmt.Sprintf("Gopeed %s", base.Version)
 	cfg.ListenPort = f.config.ListenPort
+	cfg.NoDHT = f.config.DisableDHT
+	cfg.DisablePEX = f.config.DisablePEX
 	cfg.HTTPProxy = f.ctl.GetProxy(f.meta.Req.Proxy)
 	dnsResolver := &DnsCacheResolver{RefreshTimeout: 5 * time.Minute}
 	cfg.TrackerDialContext = dnsResolver.DialContext
@@ -86,19 +89,34 @@ func (f *Fetcher) initClient() (err error) {
 	}
 
 	closeCtx, closeFunc = context.WithCancel(context.Background())
-	go func() {
-		dnsResolver.Run(closeCtx)
-	}()
+	// closeClient may reset closeCtx before the goroutine runs, so pass it as an argument.
+	go dnsResolver.Run(closeCtx)
 	return
 }
 
-func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
-	f.meta.Req = req
-	f.meta.Opts = opts
-	if f.meta.Opts == nil {
-		f.meta.Opts = &base.Options{}
+// addTorrentSpec holds lock from client initialization until the torrent is added,
+// so closeClient cannot close or reset the client in between.
+func (f *Fetcher) addTorrentSpec(spec *torrent.TorrentSpec) (*torrent.Torrent, bool, error) {
+	lock.Lock()
+	defer lock.Unlock()
+
+	if err := f.initClient(); err != nil {
+		return nil, false, err
 	}
-	if err := f.addTorrent(req, false); err != nil {
+	return client.AddTorrentSpec(spec)
+}
+
+func (f *Fetcher) Resolve(req *base.Request) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.torrent != nil {
+		f.safeDrop()
+		f.torrent = nil
+		f.storage = nil
+		f.torrentReady.Store(false)
+	}
+	f.meta.Req = req
+	if err := f.addTorrent(req); err != nil {
 		return err
 	}
 	f.updateRes()
@@ -106,12 +124,72 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 }
 
 func (f *Fetcher) Start() (err error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.meta.Opts == nil || f.meta.Opts.Path == "" {
+		return errors.New("download directory is required when starting a torrent")
+	}
+	if err := f.torrentDropCtx.Err(); err != nil {
+		return err
+	}
 	if !f.torrentReady.Load() {
-		if err = f.addTorrent(f.meta.Req, false); err != nil {
+		if err = f.addTorrent(f.meta.Req); err != nil {
 			return
 		}
 	}
 
+	path := f.meta.Opts.Path
+	if err := os.MkdirAll(path, 0755); err != nil {
+		return err
+	}
+	hashes, err := f.storage.bind(storage.NewFileClientOpts{
+		ClientBaseDir: path,
+		FilePathMaker: func(opts storage.FilePathMakerOpts) string {
+			_, name := torrentFileLayout(opts.Info, *opts.File)
+			return name
+		},
+	})
+	if err != nil {
+		return err
+	}
+	if hashes != nil {
+		// File storage infers completion from final file names and sizes. Verify
+		// before publishing that state, or peers can see an unverified file as
+		// complete and disconnect before a damaged piece is discovered.
+		// Late v2 hashes schedule their own initial checks through the library.
+		changes := f.torrent.SubscribePieceStateChanges()
+		defer changes.Close()
+		for i, known := range hashes {
+			if !known {
+				continue
+			}
+			if err := f.torrentDropCtx.Err(); err != nil {
+				return err
+			}
+			if err := f.torrent.Piece(i).VerifyDataContext(f.torrentDropCtx); err != nil {
+				return err
+			}
+			// VerifyDataContext can return while the result is still being
+			// written to storage. Wait for it before refreshing completion.
+			for {
+				state := f.torrent.Piece(i).State()
+				if !state.Hashing && !state.QueuedForHash && !state.Marking {
+					break
+				}
+				select {
+				case <-changes.Values:
+				case <-f.torrentDropCtx.Done():
+					return f.torrentDropCtx.Err()
+				case <-f.torrent.Closed():
+					return errors.New("torrent closed during verification")
+				}
+			}
+		}
+		for i := range hashes {
+			f.torrent.Piece(i).UpdateCompletion()
+		}
+	}
+
 	files := f.torrent.Files()
 	// If the user does not specify the file to download, all files will be downloaded by default
 	if f.data.Progress == nil {
@@ -132,21 +210,29 @@ func (f *Fetcher) Start() (err error) {
 		}
 	}
 	f.torrent.AllowDataDownload()
+	go f.doUpload(false)
 	return
 }
 
 func (f *Fetcher) Pause() (err error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.torrent == nil {
+		return nil
+	}
 	f.torrent.DisallowDataDownload()
 	return
 }
 
 func (f *Fetcher) Close() (err error) {
-	f.safeDrop()
-	f.torrentDropFunc()
-	f.uploadDoneCh <- nil
-	if len(client.Torrents()) == 0 {
-		err = closeClient()
-	}
+	f.closeOnce.Do(func() {
+		f.torrentDropFunc()
+		f.mu.Lock()
+		defer f.mu.Unlock()
+		f.safeDrop()
+		f.torrentReady.Store(false)
+		close(f.uploadDoneCh)
+	})
 	return nil
 }
 
@@ -164,6 +250,8 @@ func (f *Fetcher) Meta() *fetcher.FetcherMeta {
 }
 
 func (f *Fetcher) Stats() *fetcher.Stats {
+	f.mu.Lock()
+	defer f.mu.Unlock()
 	var stats torrent.TorrentStats
 	var pieceMap *base.PieceMap
 	pieceMapReady := false
@@ -370,48 +458,65 @@ func normalizeBTTransport(network string) string {
 }
 
 func (f *Fetcher) Progress() fetcher.Progress {
+	f.mu.Lock()
+	defer f.mu.Unlock()
 	if !f.torrentReady.Load() {
-		return f.data.Progress
+		return append(fetcher.Progress(nil), f.data.Progress...)
 	}
 	for i := range f.data.Progress {
 		selectIndex := f.meta.Opts.SelectFiles[i]
 		file := f.torrent.Files()[selectIndex]
 		f.data.Progress[i] = file.BytesCompleted()
 	}
-	return f.data.Progress
+	return append(fetcher.Progress(nil), f.data.Progress...)
 }
 
-func (f *Fetcher) Wait() (err error) {
+func (f *Fetcher) Wait() error {
+	f.mu.Lock()
+	var closed <-chan struct{}
+	if f.torrent != nil {
+		closed = f.torrent.Closed()
+	}
+	f.mu.Unlock()
+	ticker := time.NewTicker(time.Second)
+	defer ticker.Stop()
 	for {
 		select {
 		case <-f.torrentDropCtx.Done():
-			return
-		case <-time.After(time.Second):
-			if f.torrentReady.Load() && len(f.meta.Opts.SelectFiles) > 0 {
-				if f.isDone() {
-					// remove unselected files
-					for i, file := range f.torrent.Files() {
-						selected := false
-						for _, selectIndex := range f.meta.Opts.SelectFiles {
-							if i == selectIndex {
-								selected = true
-								break
-							}
-						}
-						if !selected {
-							root, name := torrentFileLayout(f.torrent.Info(), file.FileInfo())
-							if err := removeUnselectedFile(f.meta.Opts.Path, root, name); err != nil {
-								return err
-							}
-						}
-					}
-					return
-				}
+			return nil
+		case <-closed:
+			return nil
+		case <-ticker.C:
+			done, err := f.finishDownload()
+			if done || err != nil {
+				return err
 			}
 		}
 	}
 }
 
+func (f *Fetcher) finishDownload() (bool, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if !f.torrentReady.Load() || f.meta.Opts == nil || len(f.meta.Opts.SelectFiles) == 0 || !f.isDoneLocked() {
+		return false, nil
+	}
+	selected := make(map[int]bool, len(f.meta.Opts.SelectFiles))
+	for _, i := range f.meta.Opts.SelectFiles {
+		selected[i] = true
+	}
+	for i, file := range f.torrent.Files() {
+		if selected[i] {
+			continue
+		}
+		root, name := torrentFileLayout(f.torrent.Info(), file.FileInfo())
+		if err := removeUnselectedFile(f.meta.Opts.Path, root, name); err != nil {
+			return false, err
+		}
+	}
+	return true, nil
+}
+
 // Match the file storage layout, including its NoName convention for rootless
 // torrents. File.Path() always prepends BestName, even when storage omits it.
 func torrentFileLayout(info *metainfo.Info, file metainfo.FileInfo) (root, name string) {
@@ -469,13 +574,22 @@ func removeUnselectedFile(downloadDir, torrentRoot, torrentPath string) error {
 }
 
 func (f *Fetcher) isDone() bool {
-	if f.meta.Opts == nil {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return f.isDoneLocked()
+}
+
+func (f *Fetcher) isDoneLocked() bool {
+	if f.meta.Opts == nil || f.torrent == nil {
 		return false
 	}
-	for _, selectIndex := range f.meta.Opts.SelectFiles {
-		file := f.torrent.Files()[selectIndex]
-		if file.BytesCompleted() < file.Length() {
-			return false
+	for _, index := range f.meta.Opts.SelectFiles {
+		file := f.torrent.Files()[index]
+		for i := file.BeginPieceIndex(); i < file.EndPieceIndex(); i++ {
+			state := f.torrent.Piece(i).State()
+			if !state.Ok || !state.Complete || state.Hashing || state.QueuedForHash {
+				return false
+			}
 		}
 	}
 	return true
@@ -484,6 +598,11 @@ func (f *Fetcher) isDone() bool {
 // Patch modifies the BT task settings.
 // Invalid file indices are silently ignored.
 func (f *Fetcher) Patch(req *base.Request, opts *base.Options) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.meta.Opts == nil {
+		f.meta.Opts = &base.Options{}
+	}
 	if opts == nil {
 		return nil
 	}
@@ -540,9 +659,9 @@ func (f *Fetcher) updateRes() {
 		Files: make([]*base.FileInfo, len(f.torrent.Files())),
 		Hash:  f.torrent.InfoHash().String(),
 	}
-	// Directory torrent
-	if f.torrent.Info().Length == 0 {
-		res.Name = f.torrent.Name()
+	// Use the same root classification as storage (v2 single files have Length == 0).
+	if files := f.torrent.Files(); len(files) > 0 {
+		res.Name, _ = torrentFileLayout(f.torrent.Info(), files[0].FileInfo())
 	}
 	for i, file := range f.torrent.Files() {
 		res.Files[i] = &base.FileInfo{
@@ -559,61 +678,50 @@ func (f *Fetcher) updateRes() {
 }
 
 func (f *Fetcher) Upload() (err error) {
-	return f.addTorrent(f.meta.Req, true)
+	if err = f.Start(); err != nil {
+		return err
+	}
+	return nil
 }
 
 func (f *Fetcher) doUpload(fromUpload bool) {
 	if !f.torrentUpload.CompareAndSwap(false, true) {
 		return
 	}
-
-	// Check and update seed data
-	lastData := &fetcherData{
-		SeedBytes: f.data.SeedBytes,
-		SeedTime:  f.data.SeedTime,
-	}
-	var doneTime int64 = 0
+	f.mu.Lock()
+	initialBytes, initialTime := f.data.SeedBytes, f.data.SeedTime
+	torrentClosed := f.torrent.Closed()
+	f.mu.Unlock()
+	var doneTime int64
+	ticker := time.NewTicker(time.Second)
+	defer ticker.Stop()
 	for {
 		select {
 		case <-f.torrentDropCtx.Done():
 			return
-		case <-time.After(time.Second):
+		case <-torrentClosed:
+			return
+		case <-ticker.C:
+			f.mu.Lock()
 			if !f.torrentReady.Load() {
+				f.mu.Unlock()
 				continue
 			}
-
 			stats := f.torrentStats()
-			f.data.SeedBytes = lastData.SeedBytes + stats.BytesWrittenData.Int64()
-
-			// Check is download complete, if not don't check and stop seeding
-			if !fromUpload && !f.isDone() {
+			f.data.SeedBytes = initialBytes + stats.BytesWrittenData.Int64()
+			if !fromUpload && !f.isDoneLocked() {
+				f.mu.Unlock()
 				continue
 			}
 			if doneTime == 0 {
 				doneTime = time.Now().Unix()
 			}
-			f.data.SeedTime = lastData.SeedTime + time.Now().Unix() - doneTime
-
-			// If the seed forever is true, keep seeding
-			if f.config.SeedKeep {
-				continue
-			}
-
-			// If the seed ratio is reached, stop seeding
-			if f.config.SeedRatio > 0 {
-				seedRadio := f.seedRadio()
-				if seedRadio >= f.config.SeedRatio {
-					f.Close()
-					break
-				}
-			}
-
-			// If the seed time is reached, stop seeding
-			if f.config.SeedTime > 0 {
-				if f.data.SeedTime >= f.config.SeedTime {
-					f.Close()
-					break
-				}
+			f.data.SeedTime = initialTime + time.Now().Unix() - doneTime
+			stop := !f.config.SeedKeep && ((f.config.SeedRatio > 0 && f.seedRadio() >= f.config.SeedRatio) || (f.config.SeedTime > 0 && f.data.SeedTime >= f.config.SeedTime))
+			f.mu.Unlock()
+			if stop {
+				f.Close()
+				return
 			}
 		}
 	}
@@ -631,6 +739,8 @@ func (f *Fetcher) torrentStats() torrent.TorrentStats {
 }
 
 func (f *Fetcher) UploadedBytes() int64 {
+	f.mu.Lock()
+	defer f.mu.Unlock()
 	return f.data.SeedBytes
 }
 
@@ -639,13 +749,11 @@ func (f *Fetcher) WaitUpload() (err error) {
 	return nil
 }
 
-func (f *Fetcher) addTorrent(req *base.Request, fromUpload bool) (err error) {
+func (f *Fetcher) addTorrent(req *base.Request) (err error) {
+	f.ctl.GetConfig(&f.config)
 	if err = base.ParseReqExtra[bt.ReqExtra](req); err != nil {
 		return
 	}
-	if err = f.initClient(); err != nil {
-		return
-	}
 	schema := util.ParseSchema(req.URL)
 	privateTorrent := false
 	var spec *torrent.TorrentSpec
@@ -658,11 +766,16 @@ func (f *Fetcher) addTorrent(req *base.Request, fromUpload bool) (err error) {
 		var reader io.Reader
 		if schema == "FILE" {
 			fileUrl, _ := url.Parse(req.URL)
-			filePath := fileUrl.Path[1:]
+			filePath := fileUrl.Path
+			if runtime.GOOS == "windows" && len(filePath) > 2 && filePath[0] == '/' && filePath[2] == ':' {
+				filePath = filePath[1:]
+			}
+			filePath = filepath.FromSlash(filePath)
 			reader, err = os.Open(filePath)
 			if err != nil {
 				return
 			}
+			defer reader.(io.Closer).Close()
 		} else if schema == "DATA" {
 			_, data := util.ParseDataUri(req.URL)
 			reader = bytes.NewBuffer(data)
@@ -695,21 +808,6 @@ func (f *Fetcher) addTorrent(req *base.Request, fromUpload bool) (err error) {
 			return
 		}
 	}
-	spec.Storage = storage.NewFileOpts(storage.NewFileClientOpts{
-		ClientBaseDir: cfg.DataDir,
-		FilePathMaker: func(opts storage.FilePathMakerOpts) string {
-			_, name := torrentFileLayout(opts.Info, *opts.File)
-			return name
-		},
-		TorrentDirMaker: func(baseDir string, info *metainfo.Info, infoHash metainfo.Hash) string {
-			return f.meta.Opts.Path
-		},
-	})
-	f.torrent, _, err = client.AddTorrentSpec(spec)
-	if err != nil {
-		return
-	}
-
 	// Do not add external tracker to a private torrent.
 	if !privateTorrent {
 		// use map to deduplicate
@@ -722,23 +820,40 @@ func (f *Fetcher) addTorrent(req *base.Request, fromUpload bool) (err error) {
 				}
 			}
 		}
-		if len(f.config.Trackers) > 0 {
-			for _, tracker := range f.config.Trackers {
-				trackers[tracker] = true
-			}
+		for _, tracker := range f.config.effectiveTrackers() {
+			trackers[tracker] = true
 		}
 		if len(trackers) > 0 {
-			announceList := make([][]string, 0)
 			for tracker := range trackers {
-				announceList = append(announceList, []string{tracker})
+				spec.Trackers = append(spec.Trackers, []string{tracker})
 			}
-			f.torrent.AddTrackers(announceList)
 		}
 	}
-	<-f.torrent.GotInfo()
+	s := &deferredFileStorage{}
+	spec.Storage = s
+	var added bool
+	f.torrent, added, err = f.addTorrentSpec(spec)
+	if err != nil {
+		return err
+	}
+	if !added {
+		f.torrent = nil
+		return errors.New("torrent is already active")
+	}
+	f.storage = s
+	f.torrent.DisallowDataDownload()
+	// Extra trackers must be available while magnet metadata is still missing;
+	// they may be the only way to discover a peer that can provide it.
+	select {
+	case <-f.torrent.GotInfo():
+	case <-f.torrentDropCtx.Done():
+		f.safeDrop()
+		return f.torrentDropCtx.Err()
+	case <-f.torrent.Closed():
+		return errors.New("torrent closed during resolution")
+	}
 	f.torrentReady.Store(true)
 
-	go f.doUpload(fromUpload)
 	return
 }
 
@@ -834,17 +949,29 @@ func (fm *FetcherManager) AutoRename() bool {
 
 func (fm *FetcherManager) DefaultConfig() any {
 	return &config{
+		TrackerSubscribeURLs: append([]string{}, defaultTrackerSubscribeURLs...),
+		AutoUpdateTrackers:   true,
+		CustomTrackers:       []string{},
+		ConfigState: fetcher.ConfigState[state]{State: state{
+			TrackerSources:              map[string][]string{},
+			TrackerSubscriptionStatuses: map[string]trackerSubscriptionStatus{},
+		}},
 		ListenPort: 0,
-		Trackers:   []string{},
 		SeedKeep:   false,
 		SeedRatio:  1.0,
 		SeedTime:   120 * 60,
+		DisableDHT: false,
+		DisablePEX: false,
 	}
 }
 
 func (fm *FetcherManager) Store(f fetcher.Fetcher) (data any, err error) {
 	_f := f.(*Fetcher)
-	return _f.data, nil
+	_f.mu.Lock()
+	defer _f.mu.Unlock()
+	snapshot := *_f.data
+	snapshot.Progress = append(fetcher.Progress(nil), snapshot.Progress...)
+	return &snapshot, nil
 }
 
 func (fm *FetcherManager) Restore() (v any, f func(meta *fetcher.FetcherMeta, v any) fetcher.Fetcher) {

internal/protocol/bt/fetcher_test.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"sync"
 	"testing"
 
 	"github.com/GopeedLab/gopeed/internal/controller"
@@ -18,11 +19,11 @@ import (
 )
 
 func TestFetcher_Resolve_Torrent(t *testing.T) {
-	doResolve(t, buildFetcher())
+	doResolve(t, buildFetcher(t))
 }
 
 func TestFetcher_Resolve_DataUri_Torrent(t *testing.T) {
-	fetcher := buildFetcher()
+	fetcher := buildFetcher(t)
 	buf, err := os.ReadFile("./testdata/ubuntu-22.04-live-server-amd64.iso.torrent")
 	if err != nil {
 		t.Fatal(err)
@@ -31,7 +32,7 @@ func TestFetcher_Resolve_DataUri_Torrent(t *testing.T) {
 	dataUri := "data:application/x-bittorrent;base64," + base64.StdEncoding.EncodeToString(buf)
 	err = fetcher.Resolve(&base.Request{
 		URL: dataUri,
-	}, nil)
+	})
 	if err != nil {
 		panic(err)
 	}
@@ -53,7 +54,7 @@ func TestFetcher_Resolve_DataUri_Torrent(t *testing.T) {
 }
 
 func TestFetcher_Config(t *testing.T) {
-	doResolve(t, buildConfigFetcher(nil))
+	doResolve(t, buildConfigFetcher(t, nil))
 }
 
 func TestFetcher_ResolveWithProxy(t *testing.T) {
@@ -61,7 +62,7 @@ func TestFetcher_ResolveWithProxy(t *testing.T) {
 	proxyListener := test.StartSocks5Server(usr, pwd)
 	defer proxyListener.Close()
 
-	doResolve(t, buildConfigFetcher(&base.DownloaderProxyConfig{
+	doResolve(t, buildConfigFetcher(t, &base.DownloaderProxyConfig{
 		Enable: true,
 		System: false,
 		Scheme: "socks5",
@@ -71,6 +72,82 @@ func TestFetcher_ResolveWithProxy(t *testing.T) {
 	}))
 }
 
+func TestFetcher_CloseAfterInit(t *testing.T) {
+	if err := closeClient(); err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 100; i++ {
+		f := buildFetcher(t).(*Fetcher)
+		f.meta.Req = &base.Request{}
+		lock.Lock()
+		err := f.initClient()
+		lock.Unlock()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := closeClient(); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func TestFetcher_CloseWithoutClient(t *testing.T) {
+	if err := closeClient(); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("restored task", func(t *testing.T) {
+		_, build := new(FetcherManager).Restore()
+		f := build(&fetcher.FetcherMeta{
+			Req:  &base.Request{URL: "./testdata/test.torrent"},
+			Opts: &base.Options{},
+		}, &fetcherData{})
+		f.Setup(controller.NewController())
+		if err := f.Close(); err != nil {
+			t.Errorf("Close() got = %v, want nil", err)
+		}
+	})
+
+	t.Run("failed resolve", func(t *testing.T) {
+		f := buildFetcher(t)
+		if err := f.Resolve(&base.Request{URL: "./testdata/not-exist.torrent"}); err == nil {
+			t.Fatal("Resolve() got = nil, want error")
+		}
+		if err := f.Close(); err != nil {
+			t.Errorf("Close() got = %v, want nil", err)
+		}
+	})
+}
+
+func TestFetcher_ResolveWhileClientCloses(t *testing.T) {
+	if err := closeClient(); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { closeClient() })
+
+	var wg sync.WaitGroup
+	for _, u := range []string{"./testdata/test.torrent", "./testdata/ubuntu-22.04-live-server-amd64.iso.torrent"} {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for i := 0; i < 10; i++ {
+				f := buildFetcher(t)
+				// The other goroutine may close the client after the torrent was added.
+				if err := f.Resolve(&base.Request{URL: u}); err != nil && err.Error() != "torrent closed during resolution" {
+					t.Errorf("Resolve(%s) got = %v", u, err)
+					return
+				}
+				f.Close()
+				if err := closeClient(); err != nil {
+					t.Errorf("closeClient() got = %v", err)
+					return
+				}
+			}
+		}()
+	}
+	wg.Wait()
+}
+
 func doResolve(t *testing.T, fetcher fetcher.Fetcher) {
 	t.Run("Resolve Single File", func(t *testing.T) {
 		err := fetcher.Resolve(&base.Request{
@@ -81,7 +158,7 @@ func doResolve(t *testing.T, fetcher fetcher.Fetcher) {
 					"udp://tracker.bitsearch.to:1337/announce",
 				},
 			},
-		}, nil)
+		})
 		if err != nil {
 			panic(err)
 		}
@@ -111,7 +188,7 @@ func doResolve(t *testing.T, fetcher fetcher.Fetcher) {
 					"udp://tracker.bitsearch.to:1337/announce",
 				},
 			},
-		}, nil)
+		})
 		if err != nil {
 			panic(err)
 		}
@@ -145,7 +222,7 @@ func doResolve(t *testing.T, fetcher fetcher.Fetcher) {
 	t.Run("Resolve Unclean Torrent", func(t *testing.T) {
 		err := fetcher.Resolve(&base.Request{
 			URL: "./testdata/test.unclean.torrent",
-		}, nil)
+		})
 		if err != nil {
 			t.Errorf("Resolve Unclean Torrent Resolve() got = %v, want nil", err)
 		}
@@ -156,7 +233,7 @@ func doResolve(t *testing.T, fetcher fetcher.Fetcher) {
 		uri := "file:///" + file
 		err := fetcher.Resolve(&base.Request{
 			URL: uri,
-		}, nil)
+		})
 		if err != nil {
 			t.Errorf("Resolve file scheme Torrent Resolve() got = %v, want nil", err)
 		}
@@ -211,7 +288,7 @@ func TestFetcherManager_ParseName(t *testing.T) {
 	}
 }
 
-func buildFetcher() fetcher.Fetcher {
+func buildFetcher(t testing.TB) fetcher.Fetcher {
 	fb := new(FetcherManager)
 	fetcher := fb.Build()
 	newController := controller.NewController()
@@ -219,14 +296,15 @@ func buildFetcher() fetcher.Fetcher {
 		json.Unmarshal([]byte(test.ToJson(fb.DefaultConfig())), v)
 	}
 	fetcher.Setup(newController)
+	t.Cleanup(func() { fetcher.Close(); closeClient() })
 	return fetcher
 }
 
-func buildConfigFetcher(proxyConfig *base.DownloaderProxyConfig) fetcher.Fetcher {
+func buildConfigFetcher(t testing.TB, proxyConfig *base.DownloaderProxyConfig) fetcher.Fetcher {
 	fetcher := new(FetcherManager).Build()
 	newController := controller.NewController()
 	mockCfg := config{
-		Trackers: []string{
+		CustomTrackers: []string{
 			"udp://tracker.birkenwald.de:6969/announce",
 			"udp://tracker.bitsearch.to:1337/announce",
 		}}
@@ -237,29 +315,30 @@ func buildConfigFetcher(proxyConfig *base.DownloaderProxyConfig) fetcher.Fetcher
 		return proxyConfig.ToHandler()
 	}
 	fetcher.Setup(newController)
+	t.Cleanup(func() { fetcher.Close(); closeClient() })
 	return fetcher
 }
 
 // TestFetcher_Patch tests the Patch functionality for BT fetcher.
 // It tests modifying selected files after Resolve (without downloading).
 func TestFetcher_Patch(t *testing.T) {
-	f := buildFetcher()
+	f := buildFetcher(t)
 
 	// Resolve a multi-file torrent
 	err := f.Resolve(&base.Request{
 		URL: "./testdata/test.torrent",
-	}, nil)
+	})
 	if err != nil {
 		t.Fatalf("Resolve failed: %v", err)
 	}
 
-	// Verify initial state: 3 files, all selected by default
+	// Resolution describes files without choosing download options.
 	meta := f.Meta()
 	if len(meta.Res.Files) != 3 {
 		t.Fatalf("Expected 3 files, got %d", len(meta.Res.Files))
 	}
-	if len(meta.Opts.SelectFiles) != 3 {
-		t.Fatalf("Expected 3 selected files, got %d", len(meta.Opts.SelectFiles))
+	if meta.Opts != nil {
+		t.Fatal("Resolve should not assign download options")
 	}
 
 	// Total size of all files: 107484864
@@ -366,3 +445,52 @@ func TestFetcher_Patch(t *testing.T) {
 		}
 	})
 }
+
+func TestFetcher_PeerDiscoveryConfig(t *testing.T) {
+	tests := []struct {
+		name           string
+		stored         any
+		wantDisableDHT bool
+		wantDisablePEX bool
+	}{
+		{"default config", new(FetcherManager).DefaultConfig(), false, false},
+		{"stored config without the fields", map[string]any{"listenPort": 0, "seedRatio": 1.0}, false, false},
+		{"both disabled", map[string]any{"disableDht": true, "disablePex": true}, true, true},
+		{"only DHT disabled", map[string]any{"disableDht": true}, true, false},
+		{"only PEX disabled", map[string]any{"disablePex": true}, false, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f := buildFetcherWithConfig(tt.stored).(*Fetcher)
+			if f.config.DisableDHT != tt.wantDisableDHT || f.config.DisablePEX != tt.wantDisablePEX {
+				t.Errorf("config got DisableDHT = %v, DisablePEX = %v, want %v, %v", f.config.DisableDHT, f.config.DisablePEX, tt.wantDisableDHT, tt.wantDisablePEX)
+			}
+		})
+	}
+}
+
+func TestFetcher_PeerDiscoveryDisabledOnClient(t *testing.T) {
+	if err := closeClient(); err != nil {
+		t.Fatal(err)
+	}
+	f := buildFetcherWithConfig(map[string]any{"disableDht": true, "disablePex": true})
+	if err := f.Resolve(&base.Request{URL: "./testdata/test.torrent"}); err != nil {
+		t.Fatal(err)
+	}
+	if !cfg.NoDHT || !cfg.DisablePEX {
+		t.Errorf("client config got NoDHT = %v, DisablePEX = %v, want true", cfg.NoDHT, cfg.DisablePEX)
+	}
+	if n := len(client.DhtServers()); n != 0 {
+		t.Errorf("client got %d DHT servers, want 0", n)
+	}
+}
+
+func buildFetcherWithConfig(stored any) fetcher.Fetcher {
+	fetcher := new(FetcherManager).Build()
+	newController := controller.NewController()
+	newController.GetConfig = func(v any) {
+		json.Unmarshal([]byte(test.ToJson(stored)), v)
+	}
+	fetcher.Setup(newController)
+	return fetcher
+}

internal/protocol/bt/fixture_test.go

@@ -0,0 +1,212 @@
+package bt
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"encoding/binary"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/anacrolix/torrent"
+	"github.com/anacrolix/torrent/bencode"
+	"github.com/anacrolix/torrent/merkle"
+	"github.com/anacrolix/torrent/metainfo"
+	"golang.org/x/time/rate"
+)
+
+// btFixture serves generated, trackerless content over a real loopback TCP peer.
+// Its HTTP tracker exercises .torrent downloads; magnet links also carry the
+// explicit x.pe address.
+type btFixture struct {
+	MetaInfo    *metainfo.MetaInfo
+	Magnet      string
+	TorrentFile string
+	DataURI     string
+	TrackerURL  string
+	Files       map[string][]byte // Paths relative to the selected download directory.
+	Seeder      *torrent.Client
+	Torrent     *torrent.Torrent
+	Limiter     *rate.Limiter
+}
+
+func newBTFixture(t testing.TB, files map[string][]byte, bytesPerSecond int) *btFixture {
+	return makeBTFixture(t, files, bytesPerSecond, false, true)
+}
+
+func newBTHybridFixture(t testing.TB, payload []byte) *btFixture {
+	return makeBTFixture(t, map[string][]byte{"": payload}, 0, true, true)
+}
+
+func makeBTFixture(t testing.TB, files map[string][]byte, bytesPerSecond int, v2, private bool) *btFixture {
+	t.Helper()
+	source := t.TempDir()
+	name := "payload.bin"
+	if _, single := files[""]; !single {
+		name = "bundle"
+	}
+	root := filepath.Join(source, name)
+	expected := make(map[string][]byte, len(files))
+	for path, data := range files {
+		target := filepath.Join(root, filepath.FromSlash(path))
+		if err := os.MkdirAll(filepath.Dir(target), 0700); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(target, data, 0600); err != nil {
+			t.Fatal(err)
+		}
+		expected[filepath.Join(name, filepath.FromSlash(path))] = append([]byte(nil), data...)
+	}
+	info := metainfo.Info{PieceLength: 16 * 1024}
+	if err := info.BuildFromFilePath(root); err != nil {
+		t.Fatal(err)
+	}
+	var layers map[string]string
+	if v2 {
+		data := files[""]
+		h := merkle.NewHash()
+		h.Write(data)
+		root := h.Sum(nil)
+		var pieceHashes []byte
+		for off := 0; off < len(data); off += int(info.PieceLength) {
+			end := min(off+int(info.PieceLength), len(data))
+			ph := merkle.NewHash()
+			ph.Write(data[off:end])
+			pieceHashes = append(pieceHashes, ph.SumMinLength(nil, int(info.PieceLength))...)
+		}
+		info = metainfo.Info{Name: name, PieceLength: info.PieceLength, Length: int64(len(data)), Pieces: info.Pieces, MetaVersion: 2, FileTree: metainfo.FileTree{File: metainfo.FileTreeFile{Length: int64(len(data)), PiecesRoot: string(root)}}}
+		layers = map[string]string{string(root): string(pieceHashes)}
+	}
+	// Private torrents avoid public DHT discovery once metadata is available.
+	info.Private = &private
+	raw, err := bencode.Marshal(&info)
+	if err != nil {
+		t.Fatal(err)
+	}
+	mi := &metainfo.MetaInfo{InfoBytes: raw, PieceLayers: layers}
+	cfg := torrent.TestingConfig(t)
+	cfg.DataDir = source
+	cfg.Seed = true
+	cfg.DisableUTP = true
+	cfg.DisableIPv6 = true
+	cfg.DisableWebtorrent = true
+	cfg.KeepAliveTimeout = time.Minute
+	cfg.MaxAllocPeerRequestDataPerConn = 1 << 20
+	limiter := rate.NewLimiter(rate.Inf, 16*1024)
+	if bytesPerSecond > 0 {
+		limiter.SetLimit(rate.Limit(bytesPerSecond))
+	}
+	cfg.UploadRateLimiter = limiter
+	seed, err := torrent.NewClient(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { seed.Close() })
+	seeded, _, err := seed.AddTorrentSpec(torrent.TorrentSpecFromMetaInfo(mi))
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	if err := seeded.VerifyDataContext(ctx); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case <-seeded.Complete().On():
+	case <-ctx.Done():
+		t.Fatal("local seeder did not finish verification")
+	}
+	addr := seed.ListenAddrs()[0].String()
+	host, portString, err := net.SplitHostPort(addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resolved, err := net.ResolveTCPAddr("tcp4", net.JoinHostPort(host, portString))
+	if err != nil {
+		t.Fatal(err)
+	}
+	compact := make([]byte, 6)
+	copy(compact, resolved.IP.To4())
+	binary.BigEndian.PutUint16(compact[4:], uint16(resolved.Port))
+	tracker := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		response, err := bencode.Marshal(map[string]any{"interval": 3600, "peers": string(compact)})
+		if err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+		w.Write(response)
+	}))
+	t.Cleanup(tracker.Close)
+	// The pinned library has a hybrid tracker-dispatch assertion bug.
+	// Hybrid fixtures use their explicit loopback peer rather than a tracker.
+	if !v2 {
+		mi.Announce = tracker.URL
+	}
+	var encoded bytes.Buffer
+	if err := mi.Write(&encoded); err != nil {
+		t.Fatal(err)
+	}
+	torrentFile := filepath.Join(t.TempDir(), "fixture.torrent")
+	if err := os.WriteFile(torrentFile, encoded.Bytes(), 0600); err != nil {
+		t.Fatal(err)
+	}
+	m, err := mi.MagnetV2()
+	if err != nil {
+		t.Fatal(err)
+	}
+	magnet := m.String()
+	u, err := url.Parse(magnet)
+	if err != nil {
+		t.Fatal(err)
+	}
+	q := u.Query()
+	q.Add("x.pe", addr)
+	u.RawQuery = q.Encode()
+	return &btFixture{MetaInfo: mi, Magnet: u.String(), TorrentFile: torrentFile, DataURI: "data:application/x-bittorrent;base64," + base64.StdEncoding.EncodeToString(encoded.Bytes()), TrackerURL: tracker.URL, Files: expected, Seeder: seed, Torrent: seeded, Limiter: limiter}
+}
+
+func btPayload(size int, label string) []byte {
+	data := make([]byte, size)
+	for i := range data {
+		data[i] = byte((i*31 + i/251) % 251)
+	}
+	copy(data, label)
+	return data
+}
+
+func (f *btFixture) AssertFiles(t testing.TB, dir string, paths ...string) {
+	t.Helper()
+	if len(paths) == 0 {
+		for path := range f.Files {
+			paths = append(paths, path)
+		}
+	}
+	for _, path := range paths {
+		got, err := os.ReadFile(filepath.Join(dir, path))
+		if err != nil {
+			t.Fatal(err)
+		}
+		want, ok := f.Files[path]
+		if !ok {
+			t.Fatalf("unknown fixture file %q", path)
+		}
+		if !bytes.Equal(got, want) {
+			t.Fatalf("BT file %s differs: received %d bytes, want %d", path, len(got), len(want))
+		}
+	}
+}
+
+func (f *btFixture) FileURI() string {
+	path := filepath.ToSlash(f.TorrentFile)
+	if !strings.HasPrefix(path, "/") {
+		path = "/" + path
+	}
+	return (&url.URL{Scheme: "file", Path: path}).String()
+}

internal/protocol/bt/selection_test.go

@@ -17,25 +17,85 @@ import (
 	"github.com/anacrolix/torrent/storage"
 )
 
-func TestStartUsesSelectionSubmittedAfterResolve(t *testing.T) {
-	config := torrent.TestingConfig(t)
-	config.DataDir = t.TempDir()
-	config.DisableTCP = true
-	config.DisableUTP = true
-	c, err := torrent.NewClient(config)
+func TestStartDoesNotPublishUnverifiedCompletion(t *testing.T) {
+	cfg := torrent.TestingConfig(t)
+	cfg.DisableTCP = true
+	cfg.DisableUTP = true
+	c, err := torrent.NewClient(cfg)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer c.Close()
-	tor, err := c.AddTorrentFromFile("testdata/test.torrent")
+	payload := btPayload(32*1024, "unverified")
+	info := metainfo.Info{Name: "payload.bin", Length: int64(len(payload)), PieceLength: 16 * 1024}
+	for offset := 0; offset < len(payload); offset += int(info.PieceLength) {
+		hash := sha1.Sum(payload[offset : offset+int(info.PieceLength)])
+		info.Pieces = append(info.Pieces, hash[:]...)
+	}
+	raw, err := bencode.Marshal(info)
 	if err != nil {
 		t.Fatal(err)
 	}
-	f := &Fetcher{torrent: tor, meta: &fetcher.FetcherMeta{Opts: &base.Options{}}, data: &fetcherData{}}
+	store := &deferredFileStorage{}
+	spec := torrent.TorrentSpecFromMetaInfo(&metainfo.MetaInfo{InfoBytes: raw})
+	spec.Storage = store
+	tor, _, err := c.AddTorrentSpec(spec)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tor.DisallowDataDownload()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	f := &Fetcher{torrent: tor, storage: store, meta: &fetcher.FetcherMeta{}, data: &fetcherData{}, torrentDropCtx: ctx, torrentDropFunc: cancel, config: &config{SeedKeep: true}}
 	f.torrentReady.Store(true)
 	f.updateRes()
-	// Resolve initializes all files; creation replaces the selection before Start.
-	f.meta.Opts = &base.Options{SelectFiles: []int{2}}
+	dir := t.TempDir()
+	payload[20000] ^= 0xff
+	if err := os.WriteFile(filepath.Join(dir, info.Name), payload, 0600); err != nil {
+		t.Fatal(err)
+	}
+	f.meta.Opts = &base.Options{Path: dir}
+	// Retain the original event channel to detect even a transient completion.
+	// With no network transports, the damaged piece cannot have been repaired.
+	completed := tor.Complete().On()
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case <-completed:
+		t.Fatal("Start published completion before verifying the existing file")
+	default:
+	}
+}
+
+func TestStartUsesSelectionSubmittedAfterResolve(t *testing.T) {
+	cfg := torrent.TestingConfig(t)
+	cfg.DataDir = t.TempDir()
+	cfg.DisableTCP = true
+	cfg.DisableUTP = true
+	c, err := torrent.NewClient(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	store := &deferredFileStorage{}
+	mi, err := metainfo.LoadFromFile("testdata/test.torrent")
+	if err != nil {
+		t.Fatal(err)
+	}
+	spec := torrent.TorrentSpecFromMetaInfo(mi)
+	spec.Storage = store
+	tor, _, err := c.AddTorrentSpec(spec)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tor.DisallowDataDownload()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	f := &Fetcher{torrent: tor, storage: store, meta: &fetcher.FetcherMeta{}, data: &fetcherData{}, torrentDropCtx: ctx, torrentDropFunc: cancel, config: &config{SeedKeep: true}}
+	f.torrentReady.Store(true)
+	f.updateRes()
+	f.meta.Opts = &base.Options{Path: t.TempDir(), SelectFiles: []int{2}}
 	if err := f.Start(); err != nil {
 		t.Fatal(err)
 	}
@@ -83,10 +143,15 @@ func TestWaitCleansUnselectedFilesFromSharedPiece(t *testing.T) {
 				{Length: 4, Path: []string{"keep.txt"}},
 				{Length: 4, Path: []string{"nested", "skip.txt"}},
 			}}
-			store := storage.NewFileOpts(storage.NewFileClientOpts{
+			storageOpts := storage.NewFileClientOpts{
 				ClientBaseDir:   dir,
 				TorrentDirMaker: func(baseDir string, _ *metainfo.Info, _ metainfo.Hash) string { return baseDir },
-			})
+			}
+			// VerifyDataContext can return before storage finishes marking the piece
+			// complete. Disable automatic part-file promotion so it cannot rename
+			// the .part fixtures that this test creates to exercise cleanup.
+			storageOpts.UsePartFiles.Set(false)
+			store := storage.NewFileOpts(storageOpts)
 			defer store.Close()
 			config := torrent.TestingConfig(t)
 			config.DisableTCP = true

internal/protocol/bt/storage.go

@@ -0,0 +1,116 @@
+package bt
+
+import (
+	"context"
+	"errors"
+	"os"
+	"sync"
+
+	g "github.com/anacrolix/generics"
+	"github.com/anacrolix/torrent/metainfo"
+	"github.com/anacrolix/torrent/storage"
+)
+
+// deferredFileStorage lets metadata resolve without opening the user's files.
+// It binds once. After binding, pieces are supplied directly by file storage.
+type deferredFileStorage struct {
+	mu          sync.RWMutex
+	ctx         context.Context
+	info        *metainfo.Info
+	hash        metainfo.Hash
+	knownHashes []bool
+	owner       storage.ClientImplCloser
+	torrent     storage.TorrentImpl
+	closed      bool
+}
+
+func (s *deferredFileStorage) OpenTorrent(ctx context.Context, info *metainfo.Info, hash metainfo.Hash) (storage.TorrentImpl, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed || s.info != nil {
+		return storage.TorrentImpl{}, errors.New("torrent storage already opened or closed")
+	}
+	s.ctx, s.info, s.hash = ctx, info, hash
+	s.knownHashes = make([]bool, info.NumPieces())
+	return storage.TorrentImpl{
+		PieceWithHash: func(p metainfo.Piece, hash g.Option[[]byte]) storage.PieceImpl {
+			s.mu.Lock()
+			defer s.mu.Unlock()
+			if s.closed {
+				return metadataPiece{err: os.ErrClosed}
+			}
+			if s.owner == nil {
+				s.knownHashes[p.Index()] = hash.Ok
+				// A missing v2 hash must remain unknown until its arrival changes
+				// completion and updates the library's piece request priorities.
+				return metadataPiece{known: hash.Ok}
+			}
+			if s.torrent.PieceWithHash != nil {
+				return s.torrent.PieceWithHash(p, hash)
+			}
+			return s.torrent.Piece(p)
+		},
+		Close: s.Close,
+	}, nil
+}
+
+func (s *deferredFileStorage) bind(opts storage.NewFileClientOpts) ([]bool, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return nil, os.ErrClosed
+	}
+	if s.info == nil {
+		return nil, errors.New("torrent metadata is not ready")
+	}
+	if s.owner != nil {
+		return nil, nil
+	}
+	if opts.FilePathMaker == nil {
+		opts.FilePathMaker = func(o storage.FilePathMakerOpts) string { _, name := torrentFileLayout(o.Info, *o.File); return name }
+	}
+	owner := storage.NewFileOpts(opts)
+	t, err := owner.OpenTorrent(s.ctx, s.info, s.hash)
+	if err != nil {
+		owner.Close()
+		return nil, err
+	}
+	s.owner, s.torrent = owner, t
+	return append([]bool(nil), s.knownHashes...), nil
+}
+
+func (s *deferredFileStorage) Close() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return nil
+	}
+	s.closed = true
+	if s.owner == nil {
+		return nil
+	}
+	var err error
+	if s.torrent.Close != nil {
+		err = s.torrent.Close()
+	}
+	return errors.Join(err, s.owner.Close())
+}
+
+type metadataPiece struct {
+	known bool
+	err   error
+}
+
+func (p metadataPiece) Completion() storage.Completion {
+	return storage.Completion{Ok: p.known, Err: p.err}
+}
+func (p metadataPiece) ReadAt([]byte, int64) (int, error) {
+	return 0, errors.New("download storage is not initialized")
+}
+func (p metadataPiece) WriteAt([]byte, int64) (int, error) {
+	return 0, errors.New("download storage is not initialized")
+}
+func (p metadataPiece) MarkComplete() error { return errors.New("download storage is not initialized") }
+func (p metadataPiece) MarkNotComplete() error {
+	return errors.New("download storage is not initialized")
+}

internal/protocol/bt/trackers.go

@@ -0,0 +1,234 @@
+package bt
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/url"
+	"slices"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+)
+
+var defaultTrackerSubscribeURLs = []string{
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_all.txt",
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_all_http.txt",
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_all_https.txt",
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_all_ip.txt",
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_all_udp.txt",
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_all_ws.txt",
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_best.txt",
+	"https://raw.githubusercontent.com/ngosang/trackerslist/master/trackers_best_ip.txt",
+	"https://raw.githubusercontent.com/XIU2/TrackersListCollection/master/all.txt",
+	"https://raw.githubusercontent.com/XIU2/TrackersListCollection/master/best.txt",
+	"https://raw.githubusercontent.com/XIU2/TrackersListCollection/master/http.txt",
+}
+
+func validTracker(raw string) bool {
+	u, err := url.Parse(raw)
+	if err != nil || u.Hostname() == "" || u.User != nil {
+		return false
+	}
+	switch u.Scheme {
+	case "udp", "http", "https", "ws", "wss":
+		return true
+	}
+	return false
+}
+func uniqueTrackers(groups ...[]string) []string {
+	result := []string{}
+	seen := map[string]bool{}
+	for _, group := range groups {
+		for _, raw := range group {
+			value := strings.TrimSpace(raw)
+			if value != "" && !seen[value] {
+				seen[value] = true
+				result = append(result, value)
+			}
+		}
+	}
+	return result
+}
+
+// effectiveTrackers derives the client list without persisting duplicate lists.
+func (c *config) effectiveTrackers() []string {
+	groups := [][]string{c.CustomTrackers}
+	for _, source := range c.TrackerSubscribeURLs {
+		groups = append(groups, c.State.TrackerSources[source])
+	}
+	return uniqueTrackers(groups...)
+}
+func (fm *FetcherManager) NormalizeConfig(raw json.RawMessage) (any, error) {
+	c := fm.DefaultConfig().(*config)
+	if err := json.Unmarshal(raw, c); err != nil {
+		return nil, err
+	}
+	if c.ListenPort < 0 || c.ListenPort > 65535 || c.SeedRatio < 0 || c.SeedTime < 0 {
+		return nil, errors.New("invalid BT configuration")
+	}
+	if len(c.TrackerSubscribeURLs) > 64 {
+		return nil, errors.New("too many tracker subscriptions")
+	}
+	c.TrackerSubscribeURLs = uniqueTrackers(c.TrackerSubscribeURLs)
+	for _, source := range c.TrackerSubscribeURLs {
+		u, err := url.Parse(source)
+		if err != nil || u == nil || (u.Scheme != "https" && u.Scheme != "http") || u.Hostname() == "" || u.User != nil {
+			return nil, errors.New("invalid tracker subscription URL")
+		}
+	}
+	c.CustomTrackers = uniqueTrackers(c.CustomTrackers)
+	for _, tracker := range c.CustomTrackers {
+		if !validTracker(tracker) {
+			return nil, fmt.Errorf("invalid tracker URL: %s", tracker)
+		}
+	}
+	if c.State.TrackerSources == nil {
+		c.State.TrackerSources = map[string][]string{}
+	}
+	for source := range c.State.TrackerSources {
+		if !slices.Contains(c.TrackerSubscribeURLs, source) {
+			delete(c.State.TrackerSources, source)
+		}
+	}
+	if c.State.TrackerSubscriptionStatuses == nil {
+		c.State.TrackerSubscriptionStatuses = map[string]trackerSubscriptionStatus{}
+	}
+	for source := range c.State.TrackerSubscriptionStatuses {
+		if !slices.Contains(c.TrackerSubscribeURLs, source) {
+			delete(c.State.TrackerSubscriptionStatuses, source)
+		}
+	}
+	return c, nil
+}
+func (fm *FetcherManager) CronJobs(host fetcher.ProtocolHost) []fetcher.CronJob {
+	return []fetcher.CronJob{{
+		Name:    "update-trackers",
+		Every:   24 * time.Hour,
+		Timeout: 90 * time.Second,
+		Run: func(ctx context.Context, source fetcher.TriggerSource) error {
+			return fm.updateTrackers(ctx, host, source)
+		},
+	}}
+}
+func parseTrackers(data []byte) ([]string, error) {
+	scanner := bufio.NewScanner(bytes.NewReader(data))
+	scanner.Buffer(make([]byte, 4096), 64*1024)
+	result := []string{}
+	for scanner.Scan() {
+		line := strings.TrimSpace(strings.TrimPrefix(scanner.Text(), "\ufeff"))
+		if validTracker(line) {
+			result = append(result, line)
+		}
+		if len(result) > 20000 {
+			return nil, errors.New("too many trackers")
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+	if len(result) == 0 {
+		return nil, errors.New("subscription contains no valid trackers")
+	}
+	return uniqueTrackers(result), nil
+}
+func (fm *FetcherManager) updateTrackers(ctx context.Context, host fetcher.ProtocolHost, source fetcher.TriggerSource) error {
+	snapshot, err := fetcher.ReadConfig[config](host)
+	if err != nil {
+		return err
+	}
+	if (source == fetcher.TriggerScheduled && !snapshot.AutoUpdateTrackers) || len(snapshot.TrackerSubscribeURLs) == 0 {
+		return fetcher.ErrJobSkipped
+	}
+	fetched := map[string][]string{}
+	statuses := map[string]trackerSubscriptionStatus{}
+	var failures []error
+	var mu sync.Mutex
+	var wg sync.WaitGroup
+	slots := make(chan struct{}, 4)
+	for _, address := range snapshot.TrackerSubscribeURLs {
+		wg.Add(1)
+		go func(address string) {
+			defer wg.Done()
+			select {
+			case slots <- struct{}{}:
+				defer func() { <-slots }()
+			case <-ctx.Done():
+				return
+			}
+			data, err := host.Fetch(ctx, address, 2<<20, func(body []byte) error { _, err := parseTrackers(body); return err })
+			var trackers []string
+			if err == nil {
+				trackers, err = parseTrackers(data)
+			}
+			mu.Lock()
+			defer mu.Unlock()
+			statuses[address] = trackerSubscriptionStatus{Success: err == nil, TrackerCount: len(trackers), LastFetchTime: time.Now().UTC()}
+			if err != nil {
+				failures = append(failures, fmt.Errorf("subscription %s: %w", address, err))
+			} else {
+				fetched[address] = trackers
+			}
+		}(address)
+	}
+	wg.Wait()
+	if err := ctx.Err(); err != nil {
+		failures = append(failures, err)
+	}
+	if len(statuses) == 0 {
+		return errors.Join(failures...)
+	}
+	err = fetcher.UpdateState[config, state](host, func(current *config, state *state) error {
+		if !slices.Equal(current.TrackerSubscribeURLs, snapshot.TrackerSubscribeURLs) {
+			return fetcher.ErrConfigChanged
+		}
+		if state.TrackerSources == nil {
+			state.TrackerSources = map[string][]string{}
+		}
+		if state.TrackerSubscriptionStatuses == nil {
+			state.TrackerSubscriptionStatuses = map[string]trackerSubscriptionStatus{}
+		}
+		for address, status := range statuses {
+			state.TrackerSubscriptionStatuses[address] = status
+		}
+		for address, trackers := range fetched {
+			state.TrackerSources[address] = trackers
+		}
+		if len(failures) == 0 {
+			state.LastTrackerUpdateTime = time.Now().UTC()
+		}
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	current, err := fetcher.ReadConfig[config](host)
+	if err != nil {
+		return err
+	}
+	fm.applyTrackers(current.effectiveTrackers())
+	return errors.Join(failures...)
+}
+func (fm *FetcherManager) applyTrackers(trackers []string) {
+	lock.Lock()
+	defer lock.Unlock()
+	if client == nil {
+		return
+	}
+	announce := make([][]string, 0, len(trackers))
+	for _, tracker := range trackers {
+		announce = append(announce, []string{tracker})
+	}
+	for _, t := range client.Torrents() {
+		info := t.Info()
+		if info == nil || (info.Private != nil && *info.Private) {
+			continue
+		}
+		t.AddTrackers(announce)
+	}
+}

internal/protocol/bt/trackers_test.go

@@ -0,0 +1,217 @@
+package bt
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+)
+
+func trackerTestHost(t *testing.T, c *config, fetch func(context.Context, string, int64, func([]byte) error) ([]byte, error)) (fetcher.ProtocolHost, *sync.Mutex) {
+	t.Helper()
+	mu := &sync.Mutex{}
+	return fetcher.ProtocolHost{
+		Read: func(dst any) error {
+			mu.Lock()
+			defer mu.Unlock()
+			raw, err := json.Marshal(c)
+			if err != nil {
+				return err
+			}
+			return json.Unmarshal(raw, dst)
+		},
+		UpdateState: func(change func(config, state json.RawMessage) (any, error)) error {
+			mu.Lock()
+			defer mu.Unlock()
+			raw, _ := json.Marshal(c)
+			currentState, _ := json.Marshal(c.State)
+			next, err := change(raw, currentState)
+			if err != nil {
+				return err
+			}
+			raw, err = json.Marshal(next)
+			if err != nil {
+				return err
+			}
+			return json.Unmarshal(raw, &c.State)
+		},
+		Fetch: fetch,
+	}, mu
+}
+func TestTrackerRefreshPartialSuccessUsesLatestConfig(t *testing.T) {
+	fm := &FetcherManager{}
+	cfg := fm.DefaultConfig().(*config)
+	cfg.TrackerSubscribeURLs = []string{"https://a.example/list", "https://b.example/list"}
+	cfg.CustomTrackers = []string{"udp://custom.example:80/announce"}
+	cfg.State.TrackerSources = map[string][]string{cfg.TrackerSubscribeURLs[0]: {"udp://old.example:80/announce"}, cfg.TrackerSubscribeURLs[1]: {"udp://cached.example:80/announce"}}
+	host, mu := trackerTestHost(t, cfg, nil)
+	host.Fetch = func(ctx context.Context, address string, _ int64, validate func([]byte) error) ([]byte, error) {
+		if address == "https://b.example/list" {
+			return nil, errors.New("offline")
+		}
+		// Simulate a frontend update while the network request is in flight.
+		mu.Lock()
+		cfg.CustomTrackers = []string{"udp://new-custom.example:80/announce"}
+		mu.Unlock()
+		data := []byte("udp://fresh.example:80/announce\n# ignored\nudp://fresh.example:80/announce\n")
+		return data, validate(data)
+	}
+	err := fm.updateTrackers(context.Background(), host, fetcher.TriggerManual)
+	if err == nil {
+		t.Fatal("partial failure must be reported")
+	}
+	want := []string{"udp://new-custom.example:80/announce", "udp://fresh.example:80/announce", "udp://cached.example:80/announce"}
+	if !reflect.DeepEqual(cfg.effectiveTrackers(), want) {
+		t.Fatalf("got %v", cfg.effectiveTrackers())
+	}
+	success := cfg.State.TrackerSubscriptionStatuses["https://a.example/list"]
+	failure := cfg.State.TrackerSubscriptionStatuses["https://b.example/list"]
+	if !success.Success || success.TrackerCount != 1 || success.LastFetchTime.IsZero() || failure.Success || failure.TrackerCount != 0 || failure.LastFetchTime.IsZero() {
+		t.Fatalf("unexpected subscription statuses: %+v", cfg.State.TrackerSubscriptionStatuses)
+	}
+	if !cfg.State.LastTrackerUpdateTime.IsZero() {
+		t.Fatal("partial refresh marked fully successful")
+	}
+}
+func TestTrackerRefreshDiscardsChangedSubscriptions(t *testing.T) {
+	fm := &FetcherManager{}
+	cfg := fm.DefaultConfig().(*config)
+	cfg.TrackerSubscribeURLs = []string{"https://a.example/list"}
+	host, mu := trackerTestHost(t, cfg, nil)
+	host.Fetch = func(context.Context, string, int64, func([]byte) error) ([]byte, error) {
+		mu.Lock()
+		cfg.TrackerSubscribeURLs = []string{}
+		mu.Unlock()
+		return []byte("udp://fresh.example:80/announce"), nil
+	}
+	if err := fm.updateTrackers(context.Background(), host, fetcher.TriggerManual); !errors.Is(err, fetcher.ErrConfigChanged) {
+		t.Fatal(err)
+	}
+	if len(cfg.State.TrackerSources) != 0 {
+		t.Fatal("outdated source was committed")
+	}
+}
+func TestTrackerRefreshManualWorksWhenAutomaticDisabled(t *testing.T) {
+	fm := &FetcherManager{}
+	cfg := fm.DefaultConfig().(*config)
+	cfg.AutoUpdateTrackers = false
+	cfg.TrackerSubscribeURLs = []string{"https://a.example/list"}
+	calls := 0
+	host, _ := trackerTestHost(t, cfg, func(context.Context, string, int64, func([]byte) error) ([]byte, error) {
+		calls++
+		return []byte("udp://fresh.example:80/announce"), nil
+	})
+	if err := fm.updateTrackers(context.Background(), host, fetcher.TriggerScheduled); !errors.Is(err, fetcher.ErrJobSkipped) {
+		t.Fatal(err)
+	}
+	if calls != 0 {
+		t.Fatal("scheduled job fetched while disabled")
+	}
+	if err := fm.updateTrackers(context.Background(), host, fetcher.TriggerManual); err != nil {
+		t.Fatal(err)
+	}
+	if calls != 1 || cfg.State.LastTrackerUpdateTime.IsZero() {
+		t.Fatal("manual refresh did not succeed")
+	}
+}
+func TestTrackerConfigPreservesExplicitSettings(t *testing.T) {
+	value, err := (&FetcherManager{}).NormalizeConfig(json.RawMessage(`{
+		"listenPort":6881, "trackerSubscribeUrls":[], "autoUpdateTrackers":false,
+		"customTrackers":["udp://custom.example:80/announce"]
+	}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	cfg := value.(*config)
+	if cfg.AutoUpdateTrackers || len(cfg.TrackerSubscribeURLs) != 0 || cfg.ListenPort != 6881 {
+		t.Fatalf("%+v", cfg)
+	}
+	if !reflect.DeepEqual(cfg.effectiveTrackers(), cfg.CustomTrackers) {
+		t.Fatalf("derived trackers: %v", cfg.effectiveTrackers())
+	}
+}
+
+func TestParseTrackerList(t *testing.T) {
+	got, err := parseTrackers([]byte("\ufeffudp://tracker.example:80/announce\r\n\n<html>error</html>\nhttps://tracker.example/announce\n"))
+	if err != nil || len(got) != 2 {
+		t.Fatalf("%v %v", got, err)
+	}
+	if _, err := parseTrackers([]byte("<html>mirror error</html>")); err == nil {
+		t.Fatal("invalid mirror body accepted")
+	}
+}
+func TestTrackerDefaultsRegisterDailyJob(t *testing.T) {
+	jobs := (&FetcherManager{}).CronJobs(fetcher.ProtocolHost{})
+	if len(jobs) != 1 || jobs[0].Name != "update-trackers" || jobs[0].Every != 24*time.Hour {
+		t.Fatal(jobs)
+	}
+}
+
+func TestTrackerRefreshAllFailuresPersistStatusesAndKeepCache(t *testing.T) {
+	fm := &FetcherManager{}
+	cfg := fm.DefaultConfig().(*config)
+	address := "https://custom.example/trackers.txt"
+	cfg.TrackerSubscribeURLs = []string{address}
+	cfg.State.TrackerSources[address] = []string{"udp://cached.example:80/announce"}
+	cfg.State.TrackerSubscriptionStatuses[address] = trackerSubscriptionStatus{Success: true, TrackerCount: 1, LastFetchTime: time.Now().Add(-time.Hour)}
+	host, _ := trackerTestHost(t, cfg, func(context.Context, string, int64, func([]byte) error) ([]byte, error) {
+		return nil, errors.New("offline")
+	})
+	before := time.Now()
+	if err := fm.updateTrackers(context.Background(), host, fetcher.TriggerManual); err == nil {
+		t.Fatal("failure was not reported")
+	}
+	status, ok := cfg.State.TrackerSubscriptionStatuses[address]
+	if !ok || status.Success || status.TrackerCount != 0 || status.LastFetchTime.Before(before) {
+		t.Fatalf("failed fetch status not stored: %+v", status)
+	}
+	if !reflect.DeepEqual(cfg.State.TrackerSources[address], []string{"udp://cached.example:80/announce"}) {
+		t.Fatal("last good cache lost")
+	}
+	if !reflect.DeepEqual(cfg.effectiveTrackers(), cfg.State.TrackerSources[address]) {
+		t.Fatal("cached trackers not retained")
+	}
+}
+
+func TestTrackerConfigPrunesRemovedSubscriptions(t *testing.T) {
+	fm := &FetcherManager{}
+	cfg := fm.DefaultConfig().(*config)
+	address := "https://custom.example/trackers.txt"
+	cfg.TrackerSubscribeURLs = []string{}
+	cfg.State.TrackerSources[address] = []string{"udp://cached.example:80/announce"}
+	cfg.State.TrackerSubscriptionStatuses[address] = trackerSubscriptionStatus{Success: true, TrackerCount: 1, LastFetchTime: time.Now()}
+	raw, _ := json.Marshal(cfg)
+	value, err := fm.NormalizeConfig(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	next := value.(*config)
+	if len(next.State.TrackerSources) != 0 || len(next.State.TrackerSubscriptionStatuses) != 0 || len(next.effectiveTrackers()) != 0 {
+		t.Fatal("removed subscription still owns cached results")
+	}
+}
+
+func TestTrackerRefreshTimeoutPersistsCompletedAttemptStatus(t *testing.T) {
+	fm := &FetcherManager{}
+	cfg := fm.DefaultConfig().(*config)
+	address := "https://custom.example/trackers.txt"
+	cfg.TrackerSubscribeURLs = []string{address}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	host, _ := trackerTestHost(t, cfg, func(context.Context, string, int64, func([]byte) error) ([]byte, error) {
+		cancel()
+		return nil, context.DeadlineExceeded
+	})
+	if err := fm.updateTrackers(ctx, host, fetcher.TriggerManual); !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatal(err)
+	}
+	status, ok := cfg.State.TrackerSubscriptionStatuses[address]
+	if !ok || status.Success || status.TrackerCount != 0 || status.LastFetchTime.IsZero() {
+		t.Fatalf("timeout status lost: %+v", status)
+	}
+}

internal/protocol/ed2k/fetcher.go

@@ -67,17 +67,14 @@ func (f *Fetcher) Setup(ctl *controller.Controller) {
 	f.ctl.GetConfig(&f.config)
 }
 
-func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
+func (f *Fetcher) Resolve(req *base.Request) error {
 	link, err := parseLink(req.URL)
 	if err != nil {
 		return err
 	}
 
 	f.meta.Req = req
-	f.meta.Opts = opts
-	if f.meta.Opts == nil {
-		f.meta.Opts = &base.Options{}
-	}
+
 	f.meta.Res = buildResource(link)
 	return nil
 }

internal/protocol/ed2k/fetcher_test.go

@@ -13,7 +13,8 @@ func TestFetcher_Resolve(t *testing.T) {
 	f := (&FetcherManager{}).Build()
 	f.Setup(controller.NewController())
 
-	err := f.Resolve(&base.Request{URL: testLink}, &base.Options{Path: t.TempDir()})
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	err := f.Resolve(&base.Request{URL: testLink})
 	if err != nil {
 		t.Fatalf("Resolve() error = %v", err)
 	}

internal/protocol/ftp/conn.go

@@ -0,0 +1,404 @@
+package ftp
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/textproto"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/jlaffaye/ftp"
+	"golang.org/x/net/proxy"
+
+	pftp "github.com/GopeedLab/gopeed/pkg/protocol/ftp"
+)
+
+const (
+	connectTimeout = 15 * time.Second
+	readTimeout    = 15 * time.Second
+	quitTimeout    = 2 * time.Second
+)
+
+// target is a parsed FTP URL. It holds the password, so it must never be
+// formatted into an error or a log line.
+type target struct {
+	host    string // host name or IP, the TLS server name
+	addr    string // host:port
+	user    string
+	pass    string
+	path    string // path relative to the login directory, "" for the directory itself
+	tlsMode string
+}
+
+// parseTarget reads an ftp, ftps or ftpes URL. The path follows RFC 1738: it
+// is relative to the login directory, and an encoded leading slash
+// (ftp://host/%2Fpub) makes it absolute.
+func parseTarget(rawURL, optTLS string) (*target, error) {
+	u, err := url.Parse(rawURL)
+	if err != nil {
+		// url.Error repeats the whole URL, password included.
+		return nil, errors.New("ftp: invalid URL")
+	}
+	t := &target{}
+	switch strings.ToLower(u.Scheme) {
+	case "ftps":
+		t.tlsMode = pftp.TLSImplicit
+	case "ftpes":
+		t.tlsMode = pftp.TLSExplicit
+	case "ftp":
+		switch strings.ToLower(optTLS) {
+		case "", pftp.TLSNone:
+			t.tlsMode = pftp.TLSNone
+		case pftp.TLSExplicit:
+			t.tlsMode = pftp.TLSExplicit
+		case pftp.TLSImplicit:
+			t.tlsMode = pftp.TLSImplicit
+		default:
+			return nil, fmt.Errorf("ftp: unknown tls mode %q", optTLS)
+		}
+	default:
+		return nil, fmt.Errorf("ftp: unsupported scheme %q", u.Scheme)
+	}
+	t.host = u.Hostname()
+	if t.host == "" {
+		return nil, errors.New("ftp: URL has no host")
+	}
+	port := u.Port()
+	if port == "" {
+		port = "21"
+		if t.tlsMode == pftp.TLSImplicit {
+			port = "990"
+		}
+	}
+	t.addr = net.JoinHostPort(t.host, port)
+	if u.User != nil {
+		// Username and Password are already percent-decoded.
+		t.user = u.User.Username()
+		t.pass, _ = u.User.Password()
+	}
+	if t.user == "" {
+		t.user, t.pass = "anonymous", "anonymous@"
+	}
+	t.path = strings.TrimPrefix(u.Path, "/")
+	return t, nil
+}
+
+type dialContextFunc func(ctx context.Context, network, addr string) (net.Conn, error)
+
+// session is one logged-in control connection. It owns the network
+// connections it opens, so abort can unblock any read or write in progress.
+type session struct {
+	*ftp.ServerConn
+
+	ctrl     net.Conn // control connection as dialed, under any TLS layer
+	dataHost string   // where data connections go
+
+	mu     sync.Mutex
+	data   net.Conn // current data connection as dialed
+	closed bool
+	stop   func() bool
+}
+
+// deadline bounds the next control-connection exchange. The control
+// connection is idle during a transfer, so every exchange sets a new one.
+func (s *session) deadline() {
+	_ = s.ctrl.SetDeadline(time.Now().Add(readTimeout))
+}
+
+// clearDeadline lets the control connection stay idle through a transfer.
+func (s *session) clearDeadline() {
+	_ = s.ctrl.SetDeadline(time.Time{})
+}
+
+// abort closes every connection at once. Pending calls fail immediately.
+func (s *session) abort() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.closed = true
+	_ = s.ctrl.Close()
+	if s.data != nil {
+		_ = s.data.Close()
+	}
+}
+
+// quit logs out and waits, briefly, for the server to hang up. Servers that
+// cap logins count a session until they have seen it end, so the next login
+// would otherwise be refused.
+func (s *session) quit() {
+	if s.stop != nil {
+		s.stop()
+	}
+	_ = s.ctrl.SetDeadline(time.Now().Add(quitTimeout))
+	if s.ServerConn != nil {
+		_ = s.ServerConn.Quit()
+	}
+	s.abort()
+}
+
+func (s *session) setData(c net.Conn) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		_ = c.Close()
+		return net.ErrClosed
+	}
+	s.data = c
+	return nil
+}
+
+// ctrlConn is the control connection handed to the ftp library.
+type ctrlConn struct {
+	net.Conn
+}
+
+// RemoteAddr must be a *net.TCPAddr: the library asserts it. A connection
+// through a proxy may report something else, and its address is not used
+// for data connections anyway (see dialData).
+func (c ctrlConn) RemoteAddr() net.Addr {
+	if a, ok := c.Conn.RemoteAddr().(*net.TCPAddr); ok {
+		return a
+	}
+	return &net.TCPAddr{}
+}
+
+// Close is called by the library's Quit right after it sends QUIT. Reading
+// until the server hangs up (bounded by the deadline quit set) tells us the
+// server has ended the session.
+func (c ctrlConn) Close() error {
+	_, _ = io.Copy(io.Discard, c.Conn)
+	return c.Conn.Close()
+}
+
+// dial opens a control connection, upgrades it to TLS when asked, and logs in.
+//
+// The library is given a dial function for every connection. That is how
+// data connections go through the same proxy as the control connection, but
+// it also means the library does no TLS on them: with a dial function it
+// neither wraps an implicit-TLS control connection nor any data connection.
+// We do both here. Explicit TLS (AUTH TLS) is still done by the library, and
+// so are PBSZ and PROT P after login. For the same reason the library's
+// DialWithTimeout and DialWithContext would have no effect: connectTimeout
+// and ctx are applied to our own dials instead.
+func (f *Fetcher) dial(ctx context.Context, t *target) (*session, error) {
+	netDial, proxied, err := f.netDialer(t)
+	if err != nil {
+		return nil, err
+	}
+	var tlsConf *tls.Config
+	if t.tlsMode != pftp.TLSNone {
+		tlsConf = f.tlsConfig(t.host)
+	}
+
+	dialCtx, cancel := context.WithTimeout(ctx, connectTimeout)
+	defer cancel()
+	raw, err := netDial(dialCtx, "tcp", t.addr)
+	if err != nil {
+		return nil, err
+	}
+	ctrl := raw
+	if t.tlsMode == pftp.TLSImplicit {
+		tc := tls.Client(raw, tlsConf)
+		if err := tc.HandshakeContext(dialCtx); err != nil {
+			_ = raw.Close()
+			return nil, err
+		}
+		ctrl = tc
+	}
+
+	s := &session{ctrl: raw, dataHost: t.host}
+	if a, ok := raw.RemoteAddr().(*net.TCPAddr); ok && !proxied {
+		// Same IP as the control connection, as the library itself does,
+		// so a name with several addresses cannot send us elsewhere.
+		s.dataHost = a.IP.String()
+	}
+	s.stop = context.AfterFunc(ctx, s.abort)
+	s.deadline()
+
+	handedOut := false
+	opts := []ftp.DialOption{
+		ftp.DialWithShutTimeout(readTimeout),
+		ftp.DialWithDialFunc(func(network, addr string) (net.Conn, error) {
+			if !handedOut {
+				// Dial asks for the control connection first, once.
+				handedOut = true
+				return ctrlConn{ctrl}, nil
+			}
+			return s.dialData(ctx, netDial, tlsConf, addr)
+		}),
+	}
+	switch t.tlsMode {
+	case pftp.TLSImplicit:
+		opts = append(opts, ftp.DialWithTLS(tlsConf))
+	case pftp.TLSExplicit:
+		opts = append(opts, ftp.DialWithExplicitTLS(tlsConf))
+	}
+	c, err := ftp.Dial(t.addr, opts...)
+	if err != nil {
+		s.stop()
+		s.abort()
+		return nil, err
+	}
+	s.ServerConn = c
+	s.deadline()
+	if err := c.Login(t.user, t.pass); err != nil {
+		s.stop()
+		s.abort()
+		return nil, err
+	}
+	return s, nil
+}
+
+// dialData opens a passive data connection. The library takes the host from
+// the control connection's peer, which through a proxy is the proxy, so only
+// the port is used here.
+func (s *session) dialData(ctx context.Context, netDial dialContextFunc, tlsConf *tls.Config, addr string) (net.Conn, error) {
+	_, port, err := net.SplitHostPort(addr)
+	if err != nil {
+		return nil, err
+	}
+	dialCtx, cancel := context.WithTimeout(ctx, connectTimeout)
+	defer cancel()
+	raw, err := netDial(dialCtx, "tcp", net.JoinHostPort(s.dataHost, port))
+	if err != nil {
+		return nil, err
+	}
+	if err := s.setData(raw); err != nil {
+		return nil, err
+	}
+	if tlsConf != nil {
+		// The handshake runs on the first read, as in the library, because
+		// some servers only start it once the transfer command is answered.
+		return tls.Client(raw, tlsConf), nil
+	}
+	return raw, nil
+}
+
+// tlsConfig returns the TLS settings for one control connection and its data
+// connections. Certificates are verified unless the request sets
+// skipVerifyCert, as for HTTP.
+//
+// Each call gets its own one-entry session cache, so a data connection
+// resumes the TLS session of its own control connection. vsftpd
+// (require_ssl_reuse) only checks that some session was resumed, but ProFTPD's
+// mod_tls also checks that it is the control connection's; a cache shared by
+// several workers would hand a data connection another worker's session.
+// A cache in the manager's base config is kept as given.
+func (f *Fetcher) tlsConfig(host string) *tls.Config {
+	cfg := &tls.Config{}
+	if f.manager != nil && f.manager.baseTLS != nil {
+		cfg = f.manager.baseTLS.Clone()
+	}
+	cfg.ServerName = host
+	if f.meta.Req != nil && f.meta.Req.SkipVerifyCert {
+		cfg.InsecureSkipVerify = true
+	}
+	if cfg.ClientSessionCache == nil {
+		cfg.ClientSessionCache = tls.NewLRUClientSessionCache(1)
+	}
+	return cfg
+}
+
+// netDialer picks how to reach the server, from the same proxy settings the
+// HTTP protocol reads (the task's proxy, otherwise the global one).
+func (f *Fetcher) netDialer(t *target) (dialContextFunc, bool, error) {
+	direct := (&net.Dialer{Timeout: connectTimeout}).DialContext
+	pu, err := f.proxyURL(t)
+	if err != nil {
+		return nil, false, err
+	}
+	if pu == nil {
+		return direct, false, nil
+	}
+	switch strings.ToLower(pu.Scheme) {
+	case "socks5", "socks5h":
+		d, err := proxy.FromURL(pu, &net.Dialer{Timeout: connectTimeout})
+		if err != nil {
+			return nil, false, fmt.Errorf("ftp: socks5 proxy: %w", err)
+		}
+		if cd, ok := d.(proxy.ContextDialer); ok {
+			return cd.DialContext, true, nil
+		}
+		return func(_ context.Context, network, addr string) (net.Conn, error) {
+			return d.Dial(network, addr)
+		}, true, nil
+	default:
+		// An HTTP proxy is not used. Every passive data connection goes to
+		// a port the server picks, and HTTP proxies usually allow CONNECT to
+		// port 443 only, so the transfer would fail after the login worked.
+		f.warnOnce.Do(func() {
+			if l := f.logger(); l != nil {
+				l.Warn().Msgf("ftp: the %s proxy at %s cannot carry FTP data connections (HTTP proxy), connecting directly; use a SOCKS5 proxy for FTP", strings.ToLower(pu.Scheme), pu.Host)
+			}
+		})
+		return direct, false, nil
+	}
+}
+
+func (f *Fetcher) proxyURL(t *target) (*url.URL, error) {
+	if f.ctl == nil || f.ctl.GetProxy == nil {
+		return nil, nil
+	}
+	handler := f.ctl.GetProxy(f.meta.Req.Proxy)
+	if handler == nil {
+		return nil, nil
+	}
+	// The proxy chooser reads only the URL; the credentials stay out.
+	req := &http.Request{URL: &url.URL{Scheme: "ftp", Host: t.addr, Path: "/" + t.path}, Header: http.Header{}}
+	pu, err := handler(req)
+	if err != nil {
+		return nil, errors.New("ftp: cannot read the proxy settings")
+	}
+	return pu, nil
+}
+
+// isLoginRefusal tells a server that is full apart from bad credentials.
+// 421 always means "not now". 530 means a refused login; it is only a
+// capacity limit when these credentials have worked before. The library
+// drops the code when USER itself is refused, so a "too many" message counts
+// as well.
+func isLoginRefusal(err error, credentialsWorked bool) bool {
+	var te *textproto.Error
+	if errors.As(err, &te) {
+		switch te.Code {
+		case ftp.StatusNotAvailable:
+			return true
+		case ftp.StatusNotLoggedIn:
+			return credentialsWorked || strings.Contains(strings.ToLower(te.Msg), "too many")
+		}
+		return false
+	}
+	return strings.Contains(strings.ToLower(err.Error()), "too many")
+}
+
+// isPermanent reports errors a retry cannot fix: a 5xx reply and a
+// certificate that does not verify.
+func isPermanent(err error) bool {
+	var te *textproto.Error
+	if errors.As(err, &te) {
+		return te.Code >= 500
+	}
+	var verifyErr *tls.CertificateVerificationError
+	if errors.As(err, &verifyErr) {
+		return true
+	}
+	var recordErr tls.RecordHeaderError
+	if errors.As(err, &recordErr) {
+		return true
+	}
+	return errors.Is(err, errSizeChanged)
+}
+
+func replyCode(err error) int {
+	var te *textproto.Error
+	if errors.As(err, &te) {
+		return te.Code
+	}
+	return 0
+}

internal/protocol/ftp/download_test.go

@@ -0,0 +1,146 @@
+package ftp_test
+
+import (
+	"bytes"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/rs/zerolog"
+
+	"github.com/GopeedLab/gopeed/internal/logger"
+	iftp "github.com/GopeedLab/gopeed/internal/protocol/ftp"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/download"
+	pftp "github.com/GopeedLab/gopeed/pkg/protocol/ftp"
+)
+
+// syncBuffer is a log sink that the downloader's goroutines can share.
+type syncBuffer struct {
+	mu  sync.Mutex
+	buf bytes.Buffer
+}
+
+func (b *syncBuffer) Write(p []byte) (int, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.buf.Write(p)
+}
+
+func (b *syncBuffer) String() string {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.buf.String()
+}
+
+// taskEvents records the first done or error event of every task, so the
+// test never reads a task's status while the downloader writes it.
+type taskEvents struct {
+	mu    sync.Mutex
+	final map[string]download.EventKey
+}
+
+func (e *taskEvents) listen(ev *download.Event) {
+	if ev.Key != download.EventKeyDone && ev.Key != download.EventKeyError {
+		return
+	}
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	if _, seen := e.final[ev.Task.ID]; !seen {
+		e.final[ev.Task.ID] = ev.Key
+	}
+}
+
+func (e *taskEvents) wait(t *testing.T, id string) download.EventKey {
+	t.Helper()
+	deadline := time.Now().Add(60 * time.Second)
+	for time.Now().Before(deadline) {
+		e.mu.Lock()
+		key, ok := e.final[id]
+		e.mu.Unlock()
+		if ok {
+			return key
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	t.Fatalf("task %s did not finish", id)
+	return ""
+}
+
+// TestPasswordNeverLogged runs FTP tasks through the downloader with its core
+// logger captured: a success, a missing file and a wrong password, all behind
+// an HTTP proxy that FTP must skip with a warning.
+func TestPasswordNeverLogged(t *testing.T) {
+	srv := iftp.StartFTPServer(t, iftp.ServerOptions{User: "u", Pass: "p@ss"})
+	want := srv.WriteFile(t, "secret.bin", iftp.RandomBytes(300000, 21))
+
+	d := download.NewDownloader(&download.DownloaderConfig{Storage: download.NewMemStorage(), StorageDir: t.TempDir()})
+	logs := &syncBuffer{}
+	d.Logger = &logger.Logger{Logger: zerolog.New(logs)}
+	events := &taskEvents{final: map[string]download.EventKey{}}
+	d.Listener(events.listen)
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	// Close, not Clear: Clear resets the extension list without a lock while
+	// the last task's done hooks may still read it.
+	defer d.Close()
+	cfg, err := d.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	cfg.Proxy = &base.DownloaderProxyConfig{Enable: true, Scheme: "http", Host: "127.0.0.1:1", Usr: "proxyuser", Pwd: "proxysecret"}
+	if err := d.PutConfig(cfg); err != nil {
+		t.Fatal(err)
+	}
+
+	dir := t.TempDir()
+	create := func(rawURL string) string {
+		id, err := d.CreateDirect(&base.Request{URL: rawURL}, &base.Options{Path: dir, Extra: &pftp.OptsExtra{Connections: 2}})
+		if err != nil {
+			if strings.Contains(err.Error(), "p@ss") || strings.Contains(err.Error(), "p%40ss") {
+				t.Fatalf("the password leaked into an error: %v", err)
+			}
+			t.Fatal(err)
+		}
+		return id
+	}
+	root := "ftp://u:p%40ss@" + srv.Addr + "/"
+
+	okID := create(root + "secret.bin")
+	if key := events.wait(t, okID); key != download.EventKeyDone {
+		t.Fatalf("download ended with %q, logs:\n%s", key, logs.String())
+	}
+	ok := d.GetTask(okID)
+	if ok.Protocol != "ftp" {
+		t.Fatalf("protocol %q, want ftp", ok.Protocol)
+	}
+	if got := iftp.FileSHA256(t, ok.Meta.SingleFilepath()); got != want {
+		t.Fatalf("sha256 %s, want %s", got, want)
+	}
+	missingID := create(root + "missing.bin")
+	if key := events.wait(t, missingID); key != download.EventKeyError {
+		t.Fatalf("a missing file must fail, got %q", key)
+	}
+	wrongID := create("ftp://u:wr0ng%40pw@" + srv.Addr + "/secret.bin")
+	if key := events.wait(t, wrongID); key != download.EventKeyError {
+		t.Fatalf("a wrong password must fail, got %q", key)
+	}
+	missing, wrong := d.GetTask(missingID), d.GetTask(wrongID)
+	for _, task := range []*download.Task{ok, missing, wrong} {
+		if name := task.Name(); strings.Contains(name, "p@ss") || strings.Contains(name, "p%40ss") || strings.Contains(name, "wr0ng") {
+			t.Fatalf("task name %q shows the password", name)
+		}
+	}
+
+	out := logs.String()
+	if !strings.Contains(out, "task id") || !strings.Contains(out, "HTTP proxy") {
+		t.Fatalf("the captured log misses the expected lines, so it proves nothing:\n%s", out)
+	}
+	for _, secret := range []string{"p@ss", "p%40ss", "wr0ng", "proxysecret"} {
+		if strings.Contains(out, secret) {
+			t.Fatalf("%q appears in the log:\n%s", secret, out)
+		}
+	}
+}

internal/protocol/ftp/fetcher.go

@@ -0,0 +1,810 @@
+// Package ftp downloads files and directory trees over FTP, FTPS (implicit
+// TLS) and FTPES (explicit TLS, AUTH TLS).
+//
+// A file is split into segments of at least 1 MiB. Each segment is fetched on
+// its own login with REST and RETR, and its data connection is closed once
+// the segment's last byte has arrived. A server that refuses a login lowers
+// the task's connection ceiling to the logins that worked, and a server that
+// refuses REST gets one sequential stream per file.
+package ftp
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/jlaffaye/ftp"
+	"github.com/rs/zerolog"
+
+	"github.com/GopeedLab/gopeed/internal/controller"
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	pftp "github.com/GopeedLab/gopeed/pkg/protocol/ftp"
+)
+
+const (
+	// Many servers cap logins per user, so FTP starts lower than HTTP.
+	defaultConnections = 4
+	maxConnections     = 256
+	minSegmentSize     = 1 << 20
+	maxRetries         = 5
+	copyBufferSize     = 256 << 10
+)
+
+// retryDelay is the first wait before a retry. Later retries wait longer.
+var retryDelay = 500 * time.Millisecond
+
+var (
+	errSizeChanged     = errors.New("ftp: the remote file changed size since the task was resolved")
+	errShortTransfer   = errors.New("ftp: the transfer ended before the segment was complete")
+	errRestUnsupported = errors.New("ftp: the server does not support REST")
+	errDiskWrite       = errors.New("ftp: cannot write the downloaded data")
+)
+
+type config struct {
+	Connections int `json:"connections"`
+}
+
+// segment is a byte range of one file. End is inclusive, so an empty file
+// has End == Begin-1 and nothing to fetch.
+type segment struct {
+	File       int `json:",omitempty"` // index in Res.Files
+	Begin      int64
+	End        int64
+	Downloaded int64
+}
+
+func (s *segment) remain() int64 {
+	return s.End - s.Begin + 1 - s.Downloaded
+}
+
+// lane is one worker that logged in, shown as one connection in the stats.
+type lane struct {
+	downloaded int64
+	retryTimes int
+	failed     bool
+	completed  bool
+}
+
+// loginError marks a failure to connect or log in, as opposed to a failure
+// during a transfer.
+type loginError struct{ err error }
+
+func (e *loginError) Error() string { return e.err.Error() }
+func (e *loginError) Unwrap() error { return e.err }
+
+type Fetcher struct {
+	manager *FetcherManager
+	ctl     *controller.Controller
+	config  *config
+	meta    *fetcher.FetcherMeta
+	doneCh  chan error
+
+	warnOnce sync.Once
+	// loginOK is set once these credentials have logged in, after which a
+	// 530 on another login means the server is full.
+	loginOK atomic.Bool
+
+	// mu guards the download state below.
+	mu       sync.Mutex
+	segments []*segment
+	maxConns int
+	noRest   bool
+	lanes    []*lane
+	done     bool
+
+	// runMu serializes Start and Pause.
+	runMu   sync.Mutex
+	cancel  context.CancelFunc
+	runDone chan struct{}
+}
+
+func (f *Fetcher) Setup(ctl *controller.Controller) {
+	f.ctl = ctl
+	f.doneCh = make(chan error, 1)
+	if f.meta == nil {
+		f.meta = &fetcher.FetcherMeta{}
+	}
+	if ctl != nil && ctl.GetConfig != nil {
+		ctl.GetConfig(&f.config)
+	}
+	if f.config == nil {
+		f.config = &config{Connections: defaultConnections}
+	}
+}
+
+func (f *Fetcher) logger() *zerolog.Logger {
+	if f.ctl == nil {
+		return nil
+	}
+	return f.ctl.Logger
+}
+
+func (f *Fetcher) warn(format string, args ...any) {
+	if l := f.logger(); l != nil {
+		l.Warn().Msgf(format, args...)
+	}
+}
+
+func (f *Fetcher) initOptions() error {
+	if f.meta.Opts == nil {
+		f.meta.Opts = &base.Options{}
+	}
+	opts := f.meta.Opts
+	if err := base.ParseOptExtra[pftp.OptsExtra](opts); err != nil {
+		return err
+	}
+	if opts.Extra == nil {
+		opts.Extra = &pftp.OptsExtra{}
+	}
+	return nil
+}
+
+func (f *Fetcher) extra() *pftp.OptsExtra {
+	if f.meta.Opts != nil {
+		if e, ok := f.meta.Opts.Extra.(*pftp.OptsExtra); ok && e != nil {
+			return e
+		}
+	}
+	return &pftp.OptsExtra{}
+}
+
+// tlsMode is the request's "tls" field, empty when the request has none.
+func (f *Fetcher) tlsMode() string {
+	if f.meta.Req != nil {
+		if e, ok := f.meta.Req.Extra.(*pftp.ReqExtra); ok && e != nil {
+			return e.TLS
+		}
+	}
+	return ""
+}
+
+// connections is the number of parallel logins to use. The caller holds mu.
+func (f *Fetcher) connections() int {
+	if f.noRest {
+		return 1
+	}
+	n := f.extra().Connections
+	if n <= 0 && f.config != nil {
+		n = f.config.Connections
+	}
+	if n <= 0 {
+		n = defaultConnections
+	}
+	n = min(n, maxConnections)
+	if f.maxConns > 0 {
+		n = min(n, f.maxConns)
+	}
+	return n
+}
+
+func (f *Fetcher) Resolve(req *base.Request) error {
+	if err := base.ParseReqExtra[pftp.ReqExtra](req); err != nil {
+		return err
+	}
+	f.meta.Req = req
+	t, err := parseTarget(req.URL, f.tlsMode())
+	if err != nil {
+		return err
+	}
+	s, err := f.dial(context.Background(), t)
+	if err != nil {
+		return err
+	}
+	// quit, not abort: a server that caps logins must see this session end
+	// before the download's own logins arrive.
+	defer s.quit()
+	f.loginOK.Store(true)
+	res, err := f.resolveTarget(s, t)
+	if err != nil {
+		return err
+	}
+	f.meta.Res = res
+	f.mu.Lock()
+	f.segments = nil
+	f.done = false
+	f.mu.Unlock()
+	return nil
+}
+
+// selected returns the indexes of the files to download, in SelectFiles
+// order. The caller holds mu or owns the fetcher.
+func (f *Fetcher) selected() []int {
+	if f.meta == nil || f.meta.Res == nil {
+		return nil
+	}
+	if f.meta.Opts != nil && len(f.meta.Opts.SelectFiles) > 0 {
+		return f.meta.Opts.SelectFiles
+	}
+	all := make([]int, len(f.meta.Res.Files))
+	for i := range all {
+		all[i] = i
+	}
+	return all
+}
+
+// localPath is where a file lands: under the task path, with the file's
+// directories below the URL kept.
+func (f *Fetcher) localPath(index int) string {
+	if f.meta.Res.Name == "" {
+		return f.meta.SingleFilepath()
+	}
+	file := f.meta.Res.Files[index]
+	return path.Join(f.meta.FolderPath(), file.Path, file.Name)
+}
+
+// remotePath is the server path of a file. A single file uses the URL's own
+// path, which a local rename never touches.
+func (f *Fetcher) remotePath(t *target, index int) string {
+	if f.meta.Res.Name == "" {
+		return t.path
+	}
+	file := f.meta.Res.Files[index]
+	return path.Join(t.path, file.Path, file.Name)
+}
+
+// plan splits every selected file into segments of at least minSegmentSize,
+// one per connection at most. The caller holds mu.
+func (f *Fetcher) plan() {
+	conns := f.connections()
+	f.segments = nil
+	for _, index := range f.selected() {
+		size := f.meta.Res.Files[index].Size
+		n := int64(1)
+		if !f.noRest {
+			n = max(1, min(int64(conns), size/minSegmentSize))
+		}
+		for i := int64(0); i < n; i++ {
+			f.segments = append(f.segments, &segment{
+				File:  index,
+				Begin: i * size / n,
+				End:   (i+1)*size/n - 1,
+			})
+		}
+	}
+}
+
+// planSequential gives every unfinished file one segment from byte 0,
+// because without REST a transfer cannot start in the middle. The caller
+// holds mu.
+func (f *Fetcher) planSequential() {
+	complete := map[int]bool{}
+	for _, s := range f.segments {
+		if _, seen := complete[s.File]; !seen {
+			complete[s.File] = true
+		}
+		if s.remain() > 0 {
+			complete[s.File] = false
+		}
+	}
+	var out []*segment
+	for _, index := range f.selected() {
+		size := f.meta.Res.Files[index].Size
+		if complete[index] {
+			out = append(out, &segment{File: index, Begin: 0, End: size - 1, Downloaded: size})
+			continue
+		}
+		out = append(out, &segment{File: index, Begin: 0, End: size - 1})
+	}
+	f.segments = out
+	// Bytes counted by the old segments are fetched again.
+	f.lanes = nil
+}
+
+// openFiles opens every selected file for writing. A fresh plan creates and
+// sizes them; a resumed one keeps their content, and a file that has gone
+// missing starts over.
+func (f *Fetcher) openFiles(fresh bool) (map[int]*os.File, error) {
+	files := map[int]*os.File{}
+	closeAll := func() {
+		for _, file := range files {
+			_ = file.Close()
+		}
+	}
+	for _, index := range f.selected() {
+		name := f.localPath(index)
+		var (
+			file *os.File
+			err  error
+		)
+		_, statErr := os.Stat(name)
+		switch {
+		case fresh || os.IsNotExist(statErr):
+			file, err = f.ctl.Touch(name, f.meta.Res.Files[index].Size)
+			if err == nil && !fresh {
+				f.mu.Lock()
+				for _, s := range f.segments {
+					if s.File == index {
+						s.Downloaded = 0
+					}
+				}
+				f.mu.Unlock()
+			}
+		case statErr != nil:
+			err = statErr
+		default:
+			file, err = os.OpenFile(name, os.O_RDWR, 0)
+		}
+		if err != nil {
+			closeAll()
+			return nil, err
+		}
+		files[index] = file
+	}
+	return files, nil
+}
+
+func (f *Fetcher) Start() error {
+	f.runMu.Lock()
+	defer f.runMu.Unlock()
+	if f.runDone != nil {
+		select {
+		case <-f.runDone:
+		default:
+			return nil // already running
+		}
+	}
+	if err := f.initOptions(); err != nil {
+		return err
+	}
+	if err := base.ParseReqExtra[pftp.ReqExtra](f.meta.Req); err != nil {
+		return err
+	}
+	t, err := parseTarget(f.meta.Req.URL, f.tlsMode())
+	if err != nil {
+		return err
+	}
+
+	// A paused or failed run may have left a result nobody read.
+	select {
+	case <-f.doneCh:
+	default:
+	}
+
+	f.mu.Lock()
+	if f.done {
+		f.mu.Unlock()
+		f.doneCh <- nil
+		return nil
+	}
+	fresh := len(f.segments) == 0
+	if fresh {
+		f.plan()
+	} else if f.noRest {
+		f.planSequential()
+	}
+	f.mu.Unlock()
+
+	files, err := f.openFiles(fresh)
+	if err != nil {
+		return err
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	f.cancel = cancel
+	f.runDone = make(chan struct{})
+	go f.run(ctx, t, files, f.runDone)
+	return nil
+}
+
+func (f *Fetcher) run(ctx context.Context, t *target, files map[int]*os.File, done chan struct{}) {
+	defer close(done)
+	err := f.download(ctx, t, files)
+	for _, file := range files {
+		if cerr := file.Close(); cerr != nil && err == nil {
+			err = cerr
+		}
+	}
+	f.mu.Lock()
+	if err == nil {
+		f.done = true
+		for _, l := range f.lanes {
+			l.completed = true
+		}
+	}
+	f.mu.Unlock()
+	if err != nil && ctx.Err() != nil {
+		return // paused
+	}
+	select {
+	case f.doneCh <- err:
+	default:
+	}
+}
+
+func (f *Fetcher) download(ctx context.Context, t *target, files map[int]*os.File) error {
+	for {
+		err := f.runWorkers(ctx, t, files)
+		if !errors.Is(err, errRestUnsupported) {
+			return err
+		}
+		f.mu.Lock()
+		f.noRest = true
+		f.planSequential()
+		f.mu.Unlock()
+		f.warn("ftp: the server refused REST, so each file is downloaded in one stream")
+	}
+}
+
+// pool hands out the segments of one run to its workers. Every decision to
+// leave the run is taken under mu together with the queue it depends on, so
+// a segment put back can never be left without a worker.
+type pool struct {
+	mu      sync.Mutex
+	queue   []*segment
+	running int // workers still in the run
+}
+
+// take returns the next segment. A worker that finds the queue empty leaves
+// the run.
+func (p *pool) take() *segment {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if len(p.queue) == 0 {
+		p.running--
+		return nil
+	}
+	s := p.queue[0]
+	p.queue = p.queue[1:]
+	return s
+}
+
+func (p *pool) putBack(s *segment) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.queue = append([]*segment{s}, p.queue...)
+}
+
+// refused puts back the segment of a worker whose login the server turned
+// away. The worker leaves when another worker is still in the run to take
+// the segment, and left is the number of workers that remain; the last
+// worker stays and retries.
+func (p *pool) refused(s *segment) (leave bool, left int) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.queue = append([]*segment{s}, p.queue...)
+	if p.running > 1 {
+		p.running--
+		return true, p.running
+	}
+	return false, p.running
+}
+
+// leave takes a worker out of the run when it stops for any other reason.
+func (p *pool) leave() {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.running--
+}
+
+func (f *Fetcher) runWorkers(ctx context.Context, t *target, files map[int]*os.File) error {
+	runCtx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	f.mu.Lock()
+	p := &pool{}
+	for _, s := range f.segments {
+		if s.remain() > 0 {
+			p.queue = append(p.queue, s)
+		}
+	}
+	workers := min(f.connections(), len(p.queue))
+	f.mu.Unlock()
+	if workers == 0 {
+		return nil
+	}
+	p.running = workers
+
+	var (
+		wg       sync.WaitGroup
+		errMu    sync.Mutex
+		firstErr error
+	)
+	for id := 0; id < workers; id++ {
+		wg.Add(1)
+		go func(id int) {
+			defer wg.Done()
+			if err := f.worker(runCtx, t, files, p, id); err != nil {
+				errMu.Lock()
+				if firstErr == nil {
+					firstErr = err
+				}
+				errMu.Unlock()
+				cancel()
+			}
+		}(id)
+	}
+	wg.Wait()
+
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	if firstErr != nil {
+		return firstErr
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	for _, s := range f.segments {
+		if s.remain() > 0 {
+			return errors.New("ftp: the download stopped with data missing")
+		}
+	}
+	return nil
+}
+
+// worker fetches segments from the pool until it is empty. A worker whose
+// login the server refuses (421, or 530 once these credentials have worked)
+// hands its segment back and leaves while other workers remain, lowering the
+// task's ceiling to the workers left. This holds whether or not the worker
+// had logged in before: a slot can also go to another client mid-download.
+func (f *Fetcher) worker(ctx context.Context, t *target, files map[int]*os.File, p *pool, id int) error {
+	var ln *lane
+	f.mu.Lock()
+	if id < len(f.lanes) {
+		ln = f.lanes[id]
+	}
+	f.mu.Unlock()
+	onLogin := func() {
+		f.mu.Lock()
+		if ln == nil {
+			ln = &lane{}
+			f.lanes = append(f.lanes, ln)
+		}
+		f.mu.Unlock()
+	}
+
+	failures := 0
+	pendingRetries := 0
+	for {
+		seg := p.take()
+		if seg == nil {
+			return nil
+		}
+		err := f.fetchSegment(ctx, t, files, seg, &ln, onLogin)
+		if err == nil {
+			failures = 0
+			continue
+		}
+		if ctx.Err() != nil {
+			p.putBack(seg)
+			p.leave()
+			return nil
+		}
+
+		var le *loginError
+		if errors.As(err, &le) && isLoginRefusal(le.err, f.loginOK.Load()) {
+			if leave, left := p.refused(seg); leave {
+				f.lowerCeiling(left)
+				return nil
+			}
+			// The last worker: wait for a slot.
+		} else {
+			p.putBack(seg)
+			if errors.Is(err, errRestUnsupported) {
+				p.leave()
+				return err
+			}
+			if isPermanent(err) || errors.Is(err, errDiskWrite) {
+				f.markFailed(ln)
+				p.leave()
+				return err
+			}
+		}
+
+		failures++
+		f.mu.Lock()
+		if ln != nil {
+			ln.retryTimes += pendingRetries + 1
+			pendingRetries = 0
+		} else {
+			pendingRetries++
+		}
+		f.mu.Unlock()
+		if failures > maxRetries {
+			f.markFailed(ln)
+			p.leave()
+			return fmt.Errorf("ftp: giving up after %d retries: %w", maxRetries, err)
+		}
+		select {
+		case <-ctx.Done():
+			p.leave()
+			return nil
+		case <-time.After(retryDelay * time.Duration(failures)):
+		}
+	}
+}
+
+func (f *Fetcher) lowerCeiling(n int) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.maxConns == 0 || n < f.maxConns {
+		f.maxConns = n
+	}
+}
+
+func (f *Fetcher) markFailed(ln *lane) {
+	if ln == nil {
+		return
+	}
+	f.mu.Lock()
+	ln.failed = true
+	f.mu.Unlock()
+}
+
+// isRestRefused tells a REST the server does not implement. RETR itself
+// fails with 550 and the like, never with these codes.
+func isRestRefused(err error) bool {
+	switch replyCode(err) {
+	case ftp.StatusBadCommand, ftp.StatusBadArguments, ftp.StatusNotImplemented, ftp.StatusNotImplementedParameter:
+		return true
+	}
+	return false
+}
+
+// fetchSegment logs in, retrieves the segment from its first missing byte
+// and writes it in place. It stops reading at the segment's end and closes
+// the data connection; the server then reports the transfer aborted, which
+// is expected.
+func (f *Fetcher) fetchSegment(ctx context.Context, t *target, files map[int]*os.File, seg *segment, ln **lane, onLogin func()) error {
+	s, err := f.dial(ctx, t)
+	if err != nil {
+		return &loginError{err}
+	}
+	defer s.quit()
+	f.loginOK.Store(true)
+	onLogin()
+
+	remote := f.remotePath(t, seg.File)
+	f.mu.Lock()
+	noRest := f.noRest
+	wantSize := f.meta.Res.Files[seg.File].Size
+	if noRest {
+		seg.Downloaded = 0
+	}
+	pos := seg.Begin + seg.Downloaded
+	end := seg.End
+	f.mu.Unlock()
+
+	// A file that changed on the server would mix old and new bytes.
+	s.deadline()
+	if size, err := s.FileSize(remote); err == nil && size != wantSize {
+		return errSizeChanged
+	} else if err != nil && replyCode(err) == 0 {
+		return err
+	}
+
+	s.deadline()
+	var resp *ftp.Response
+	if noRest {
+		resp, err = s.Retr(remote)
+	} else {
+		resp, err = s.RetrFrom(remote, uint64(pos))
+	}
+	if err != nil {
+		if !noRest && pos > 0 && isRestRefused(err) {
+			return errRestUnsupported
+		}
+		return err
+	}
+	defer resp.Close()
+	s.clearDeadline()
+
+	file := files[seg.File]
+	buf := make([]byte, copyBufferSize)
+	for pos <= end {
+		n := int(min(int64(len(buf)), end-pos+1))
+		_ = resp.SetDeadline(time.Now().Add(readTimeout))
+		nr, rerr := resp.Read(buf[:n])
+		if nr > 0 {
+			if _, werr := file.WriteAt(buf[:nr], pos); werr != nil {
+				return fmt.Errorf("%w: %w", errDiskWrite, werr)
+			}
+			pos += int64(nr)
+			f.mu.Lock()
+			seg.Downloaded += int64(nr)
+			if *ln != nil {
+				(*ln).downloaded += int64(nr)
+			}
+			f.mu.Unlock()
+		}
+		if rerr != nil {
+			if pos > end {
+				break
+			}
+			if errors.Is(rerr, io.EOF) {
+				return errShortTransfer
+			}
+			return rerr
+		}
+	}
+	return nil
+}
+
+func (f *Fetcher) Patch(req *base.Request, opts *base.Options) error {
+	if req == nil {
+		return nil
+	}
+	if req.URL != "" {
+		f.meta.Req.URL = req.URL
+	}
+	if req.Labels != nil {
+		if f.meta.Req.Labels == nil {
+			f.meta.Req.Labels = make(map[string]string)
+		}
+		for k, v := range req.Labels {
+			f.meta.Req.Labels[k] = v
+		}
+	}
+	if req.Proxy != nil {
+		f.meta.Req.Proxy = req.Proxy
+	}
+	return nil
+}
+
+func (f *Fetcher) Pause() error {
+	f.runMu.Lock()
+	defer f.runMu.Unlock()
+	if f.cancel != nil {
+		f.cancel()
+	}
+	if f.runDone != nil {
+		<-f.runDone
+	}
+	return nil
+}
+
+func (f *Fetcher) Close() error {
+	return f.Pause()
+}
+
+func (f *Fetcher) Meta() *fetcher.FetcherMeta {
+	return f.meta
+}
+
+// Stats reports one connection per worker that logged in, in the HTTP
+// protocol's shape.
+func (f *Fetcher) Stats() *fetcher.Stats {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	var total int64
+	if n := int64(len(f.lanes)); n > 0 && f.meta != nil && f.meta.Res != nil && f.meta.Res.Size > 0 {
+		total = (f.meta.Res.Size + n - 1) / n
+	}
+	conns := make([]*pftp.StatsConnection, 0, len(f.lanes))
+	for _, l := range f.lanes {
+		conns = append(conns, &pftp.StatsConnection{
+			Downloaded: l.downloaded,
+			Total:      total,
+			Completed:  l.completed || (f.done && !l.failed),
+			Failed:     l.failed,
+			RetryTimes: l.retryTimes,
+		})
+	}
+	return &fetcher.Stats{Snapshot: &pftp.Stats{Connections: conns}}
+}
+
+// Progress returns the bytes downloaded of each selected file, in
+// SelectFiles order.
+func (f *Fetcher) Progress() fetcher.Progress {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	perFile := map[int]int64{}
+	for _, s := range f.segments {
+		perFile[s.File] += s.Downloaded
+	}
+	sel := f.selected()
+	p := make(fetcher.Progress, len(sel))
+	for i, index := range sel {
+		p[i] = perFile[index]
+	}
+	return p
+}
+
+func (f *Fetcher) Wait() error {
+	return <-f.doneCh
+}

internal/protocol/ftp/fetcher_manager.go

@@ -0,0 +1,109 @@
+package ftp
+
+import (
+	"crypto/tls"
+	"net/url"
+	"path"
+	"strings"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	pftp "github.com/GopeedLab/gopeed/pkg/protocol/ftp"
+)
+
+// fetcherData is what a task saves to resume later. Segments has the same
+// Begin, End and Downloaded fields every version writes; the other fields are
+// optional, so a save without them still restores.
+type fetcherData struct {
+	Segments []*segment
+	// MaxConns is the login ceiling the server enforced, 0 when none was hit.
+	MaxConns int `json:",omitempty"`
+	// NoRest records that the server refused REST, so the task downloads each
+	// file in one sequential stream.
+	NoRest bool `json:",omitempty"`
+}
+
+// FetcherManager handles ftp://, ftps:// (implicit TLS) and ftpes:// (explicit
+// TLS) URLs.
+type FetcherManager struct {
+	// baseTLS is the base for every TLS connection. Nil means the system
+	// roots; the package's tests set it to trust their own certificate. The
+	// task's skipVerifyCert still turns verification off.
+	baseTLS *tls.Config
+}
+
+func (fm *FetcherManager) Name() string {
+	return "ftp"
+}
+
+func (fm *FetcherManager) Filters() []*fetcher.SchemeFilter {
+	return []*fetcher.SchemeFilter{
+		{Type: fetcher.FilterTypeUrl, Pattern: "FTP"},
+		{Type: fetcher.FilterTypeUrl, Pattern: "FTPS"},
+		{Type: fetcher.FilterTypeUrl, Pattern: "FTPES"},
+	}
+}
+
+func (fm *FetcherManager) Build() fetcher.Fetcher {
+	return &Fetcher{manager: fm}
+}
+
+// ParseName names a task before it is resolved. It never includes the
+// userinfo of the URL.
+func (fm *FetcherManager) ParseName(u string) string {
+	parsed, err := url.Parse(u)
+	if err != nil {
+		return ""
+	}
+	name := path.Base(strings.TrimSuffix(parsed.Path, "/"))
+	if name == "" || name == "/" || name == "." {
+		name = parsed.Hostname()
+	}
+	return name
+}
+
+func (fm *FetcherManager) AutoRename() bool {
+	return true
+}
+
+func (fm *FetcherManager) DefaultConfig() any {
+	return &config{Connections: defaultConnections}
+}
+
+func (fm *FetcherManager) Store(f fetcher.Fetcher) (any, error) {
+	ff := f.(*Fetcher)
+	ff.mu.Lock()
+	defer ff.mu.Unlock()
+	segments := make([]*segment, len(ff.segments))
+	for i, s := range ff.segments {
+		c := *s
+		segments[i] = &c
+	}
+	return &fetcherData{
+		Segments: segments,
+		MaxConns: ff.maxConns,
+		NoRest:   ff.noRest,
+	}, nil
+}
+
+func (fm *FetcherManager) Restore() (v any, f func(meta *fetcher.FetcherMeta, v any) fetcher.Fetcher) {
+	return &fetcherData{}, func(meta *fetcher.FetcherMeta, v any) fetcher.Fetcher {
+		fd := v.(*fetcherData)
+		ff := fm.Build().(*Fetcher)
+		ff.meta = meta
+		if meta != nil && meta.Req != nil {
+			_ = base.ParseReqExtra[pftp.ReqExtra](meta.Req)
+		}
+		if meta != nil && meta.Opts != nil {
+			_ = base.ParseOptExtra[pftp.OptsExtra](meta.Opts)
+		}
+		ff.segments = fd.Segments
+		ff.maxConns = fd.MaxConns
+		ff.noRest = fd.NoRest
+		return ff
+	}
+}
+
+func (fm *FetcherManager) Close() error {
+	return nil
+}

internal/protocol/ftp/fetcher_test.go

@@ -0,0 +1,818 @@
+package ftp
+
+import (
+	"bytes"
+	"context"
+	"crypto/tls"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/armon/go-socks5"
+	"github.com/rs/zerolog"
+
+	"github.com/GopeedLab/gopeed/internal/controller"
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	pftp "github.com/GopeedLab/gopeed/pkg/protocol/ftp"
+)
+
+const mib = 1 << 20
+
+// testManager trusts the test server's certificate, the way an embedding
+// application could add private roots.
+func testManager(srv *FTPServer) *FetcherManager {
+	fm := &FetcherManager{}
+	if srv != nil {
+		fm.baseTLS = &tls.Config{RootCAs: srv.CA}
+	}
+	return fm
+}
+
+func testController(fm *FetcherManager) *controller.Controller {
+	ctl := controller.NewController()
+	ctl.GetConfig = func(v any) {
+		data, _ := json.Marshal(fm.DefaultConfig())
+		_ = json.Unmarshal(data, v)
+	}
+	return ctl
+}
+
+func buildFetcher(fm *FetcherManager) *Fetcher {
+	f := fm.Build().(*Fetcher)
+	f.Setup(testController(fm))
+	return f
+}
+
+func ftpURL(srv *FTPServer, scheme, userinfo, p string) string {
+	if userinfo != "" {
+		userinfo += "@"
+	}
+	return scheme + "://" + userinfo + srv.Addr + "/" + strings.TrimPrefix(p, "/")
+}
+
+// resolveOpts resolves req and then gives the fetcher its options, in the
+// order the downloader uses.
+func resolveOpts(f *Fetcher, req *base.Request, opts *base.Options) error {
+	if err := f.Resolve(req); err != nil {
+		return err
+	}
+	f.Meta().Opts = opts
+	return nil
+}
+
+func resolveTask(t *testing.T, f *Fetcher, rawURL string, extra *pftp.OptsExtra) {
+	t.Helper()
+	resolveRequest(t, f, &base.Request{URL: rawURL}, extra)
+}
+
+func resolveRequest(t *testing.T, f *Fetcher, req *base.Request, extra *pftp.OptsExtra) {
+	t.Helper()
+	opts := &base.Options{Path: t.TempDir()}
+	if extra != nil {
+		opts.Extra = extra
+	}
+	if err := resolveOpts(f, req, opts); err != nil {
+		t.Fatalf("resolve %s: %v", req.URL, err)
+	}
+}
+
+func waitFetcher(t *testing.T, f fetcher.Fetcher) error {
+	t.Helper()
+	done := make(chan error, 1)
+	go func() { done <- f.Wait() }()
+	select {
+	case err := <-done:
+		return err
+	case <-time.After(60 * time.Second):
+		t.Fatal("download did not finish in 60s")
+		return nil
+	}
+}
+
+func startAndWait(t *testing.T, f *Fetcher) {
+	t.Helper()
+	if err := f.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	if err := waitFetcher(t, f); err != nil {
+		t.Fatalf("download: %v", err)
+	}
+}
+
+func checkFile(t *testing.T, name, want string) {
+	t.Helper()
+	if got := FileSHA256(t, name); got != want {
+		t.Fatalf("%s: sha256 %s, want %s", name, got, want)
+	}
+}
+
+func ftpStats(t *testing.T, f *Fetcher) *pftp.Stats {
+	t.Helper()
+	stats, ok := f.Stats().Snapshot.(*pftp.Stats)
+	if !ok {
+		t.Fatalf("stats snapshot is %T, want *ftp.Stats", f.Stats().Snapshot)
+	}
+	return stats
+}
+
+func storeData(t *testing.T, fm *FetcherManager, f *Fetcher) []byte {
+	t.Helper()
+	data, err := fm.Store(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	blob, err := json.Marshal(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return blob
+}
+
+// restoreFetcher rebuilds a fetcher the way the downloader does after a
+// restart: the meta and the save blob both come back from JSON.
+func restoreFetcher(t *testing.T, fm *FetcherManager, meta *fetcher.FetcherMeta, blob []byte) *Fetcher {
+	t.Helper()
+	metaJSON, err := json.Marshal(meta)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var restoredMeta fetcher.FetcherMeta
+	if err := json.Unmarshal(metaJSON, &restoredMeta); err != nil {
+		t.Fatal(err)
+	}
+	v, build := fm.Restore()
+	if err := json.Unmarshal(blob, v); err != nil {
+		t.Fatal(err)
+	}
+	f := build(&restoredMeta, v).(*Fetcher)
+	f.Setup(testController(fm))
+	return f
+}
+
+func TestResolveFile(t *testing.T) {
+	for _, noMLST := range []bool{false, true} {
+		t.Run(fmt.Sprintf("noMLST=%v", noMLST), func(t *testing.T) {
+			srv := StartFTPServer(t, ServerOptions{NoMLST: noMLST})
+			data := RandomBytes(100*1024, 1)
+			srv.WriteFile(t, "pub/file name.bin", data)
+
+			f := buildFetcher(testManager(srv))
+			resolveTask(t, f, ftpURL(srv, "ftp", "", "pub/file%20name.bin"), nil)
+			res := f.Meta().Res
+			if res.Name != "" {
+				t.Fatalf("a file must not be a folder resource, got name %q", res.Name)
+			}
+			if len(res.Files) != 1 {
+				t.Fatalf("got %d files, want 1", len(res.Files))
+			}
+			file := res.Files[0]
+			if file.Name != "file name.bin" || file.Path != "" || file.Size != int64(len(data)) {
+				t.Fatalf("got file %+v, want name %q, empty path, size %d", file, "file name.bin", len(data))
+			}
+			if res.Size != int64(len(data)) {
+				t.Fatalf("resource size %d, want %d", res.Size, len(data))
+			}
+			if file.Ctime == nil || time.Since(*file.Ctime) > time.Hour {
+				t.Fatalf("modification time %v is missing or wrong", file.Ctime)
+			}
+		})
+	}
+}
+
+func writeTree(t *testing.T, srv *FTPServer) map[string]string {
+	t.Helper()
+	return map[string]string{
+		"a.txt":            srv.WriteFile(t, "pub/tree/a.txt", []byte("hello")),
+		"sub/b.bin":        srv.WriteFile(t, "pub/tree/sub/b.bin", RandomBytes(3*mib+17, 2)),
+		"sub/deeper/c.dat": srv.WriteFile(t, "pub/tree/sub/deeper/c.dat", RandomBytes(2000, 3)),
+		"sub/empty.txt":    srv.WriteFile(t, "pub/tree/sub/empty.txt", nil),
+	}
+}
+
+func TestResolveDir(t *testing.T) {
+	for _, noMLST := range []bool{false, true} {
+		for _, p := range []string{"pub/tree", "pub/tree/"} {
+			t.Run(fmt.Sprintf("noMLST=%v/%s", noMLST, p), func(t *testing.T) {
+				srv := StartFTPServer(t, ServerOptions{NoMLST: noMLST})
+				writeTree(t, srv)
+				if err := os.MkdirAll(filepath.Join(srv.Root, "pub/tree/void"), 0o755); err != nil {
+					t.Fatal(err)
+				}
+
+				f := buildFetcher(testManager(srv))
+				resolveTask(t, f, ftpURL(srv, "ftp", "", p), nil)
+				res := f.Meta().Res
+				if res.Name != "tree" {
+					t.Fatalf("folder name %q, want tree", res.Name)
+				}
+				var got []string
+				for _, file := range res.Files {
+					got = append(got, fmt.Sprintf("%s|%s|%d", file.Path, file.Name, file.Size))
+				}
+				want := []string{
+					"|a.txt|5",
+					"sub|b.bin|3145745",
+					"sub|empty.txt|0",
+					"sub/deeper|c.dat|2000",
+				}
+				if !slices.Equal(got, want) {
+					t.Fatalf("files\n got %q\nwant %q", got, want)
+				}
+				if res.Size != 5+3145745+2000 {
+					t.Fatalf("resource size %d", res.Size)
+				}
+			})
+		}
+	}
+}
+
+func TestResolveDirLimits(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	srv.WriteFile(t, "deep/1/2/3/4/5/6/7/8/f.txt", []byte("ok"))
+	srv.WriteFile(t, "deep9/1/2/3/4/5/6/7/8/9/f.txt", []byte("too deep"))
+	for i := 0; i < 4; i++ {
+		srv.WriteFile(t, fmt.Sprintf("many/f%d", i), []byte("x"))
+	}
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "deep"), nil)
+	if got := f.Meta().Res.Files[0].Path; got != "1/2/3/4/5/6/7/8" {
+		t.Fatalf("depth 8 path %q", got)
+	}
+
+	f = buildFetcher(testManager(srv))
+	err := resolveOpts(f, &base.Request{URL: ftpURL(srv, "ftp", "", "deep9")}, &base.Options{Path: t.TempDir()})
+	if err == nil || !strings.Contains(err.Error(), "8 levels") {
+		t.Fatalf("a tree deeper than 8 levels must fail and name the limit, got %v", err)
+	}
+
+	saved := maxWalkFiles
+	maxWalkFiles = 3
+	defer func() { maxWalkFiles = saved }()
+	f = buildFetcher(testManager(srv))
+	err = resolveOpts(f, &base.Request{URL: ftpURL(srv, "ftp", "", "many")}, &base.Options{Path: t.TempDir()})
+	if err == nil || !strings.Contains(err.Error(), "3 files") {
+		t.Fatalf("a tree over the file cap must fail and name the limit, got %v", err)
+	}
+}
+
+func TestDownloadPlain(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	data := RandomBytes(3*mib+12345, 4)
+	want := srv.WriteFile(t, "pub/plain.bin", data)
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "pub/plain.bin"), &pftp.OptsExtra{Connections: 4})
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+	if got := f.Progress().TotalDownloaded(); got != int64(len(data)) {
+		t.Fatalf("progress %d, want %d", got, len(data))
+	}
+	stats := ftpStats(t, f)
+	if len(stats.Connections) == 0 || len(stats.Connections) > 4 {
+		t.Fatalf("got %d connections in stats", len(stats.Connections))
+	}
+	var sum int64
+	for _, c := range stats.Connections {
+		sum += c.Downloaded
+		if !c.Completed || c.Failed {
+			t.Fatalf("connection stats %+v after success", c)
+		}
+	}
+	if sum != int64(len(data)) {
+		t.Fatalf("connections downloaded %d bytes, want %d", sum, len(data))
+	}
+}
+
+func TestDownloadDir(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	want := writeTree(t, srv)
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "pub/tree"), &pftp.OptsExtra{Connections: 2})
+	startAndWait(t, f)
+	root := f.Meta().FolderPath()
+	if root != filepath.Join(f.Meta().Opts.Path, "tree") {
+		t.Fatalf("folder path %q", root)
+	}
+	for rel, sum := range want {
+		checkFile(t, filepath.Join(root, filepath.FromSlash(rel)), sum)
+	}
+}
+
+func testDownloadTLS(t *testing.T, mode string, schemes map[string]string) {
+	srv := StartFTPServer(t, ServerOptions{TLS: mode})
+	data := RandomBytes(2*mib+999, 5)
+	want := srv.WriteFile(t, "secure.bin", data)
+	for scheme, reqTLS := range schemes {
+		t.Run(scheme+"+"+reqTLS, func(t *testing.T) {
+			f := buildFetcher(testManager(srv))
+			req := &base.Request{URL: ftpURL(srv, scheme, "", "secure.bin"), Extra: &pftp.ReqExtra{TLS: reqTLS}}
+			resolveRequest(t, f, req, &pftp.OptsExtra{Connections: 2})
+			startAndWait(t, f)
+			checkFile(t, f.Meta().SingleFilepath(), want)
+		})
+	}
+}
+
+func TestDownloadExplicitTLS(t *testing.T) {
+	testDownloadTLS(t, pftp.TLSExplicit, map[string]string{
+		"ftpes": "",
+		"ftp":   pftp.TLSExplicit,
+	})
+}
+
+func TestDownloadImplicitTLS(t *testing.T) {
+	testDownloadTLS(t, pftp.TLSImplicit, map[string]string{
+		"ftps": "",
+		"ftp":  pftp.TLSImplicit,
+	})
+}
+
+// The TLS mode of a plain ftp:// link lives on the request, so a task that is
+// saved and restored from JSON still logs in over TLS.
+func TestRestoredRequestKeepsTLSMode(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{TLS: pftp.TLSExplicit})
+	want := srv.WriteFile(t, "keep.bin", RandomBytes(2*mib+5, 12))
+	fm := testManager(srv)
+	f := buildFetcher(fm)
+	req := &base.Request{URL: ftpURL(srv, "ftp", "", "keep.bin"), Extra: &pftp.ReqExtra{TLS: pftp.TLSExplicit}}
+	resolveRequest(t, f, req, &pftp.OptsExtra{Connections: 2})
+
+	restored := restoreFetcher(t, fm, f.Meta(), storeData(t, fm, f))
+	if _, ok := restored.Meta().Req.Extra.(*pftp.ReqExtra); !ok {
+		t.Fatalf("restored request extra is %T, want *ftp.ReqExtra", restored.Meta().Req.Extra)
+	}
+	// Explicit mode refuses plain logins, so the download only finishes over TLS.
+	startAndWait(t, restored)
+	checkFile(t, restored.Meta().SingleFilepath(), want)
+}
+
+func TestBadCertRejectedByDefault(t *testing.T) {
+	for mode, scheme := range map[string]string{pftp.TLSExplicit: "ftpes", pftp.TLSImplicit: "ftps"} {
+		t.Run(mode, func(t *testing.T) {
+			srv := StartFTPServer(t, ServerOptions{TLS: mode})
+			want := srv.WriteFile(t, "f.bin", RandomBytes(4096, 6))
+			rawURL := ftpURL(srv, scheme, "", "f.bin")
+
+			// No injected roots: the self-signed certificate is unknown.
+			f := buildFetcher(testManager(nil))
+			err := resolveOpts(f, &base.Request{URL: rawURL}, &base.Options{Path: t.TempDir()})
+			var verifyErr *tls.CertificateVerificationError
+			if !errors.As(err, &verifyErr) {
+				t.Fatalf("want a certificate verification error, got %v", err)
+			}
+
+			// The request's existing skipVerifyCert switch accepts it.
+			f = buildFetcher(testManager(nil))
+			if err := resolveOpts(f, &base.Request{URL: rawURL, SkipVerifyCert: true}, &base.Options{Path: t.TempDir()}); err != nil {
+				t.Fatalf("skipVerifyCert resolve: %v", err)
+			}
+			startAndWait(t, f)
+			checkFile(t, f.Meta().SingleFilepath(), want)
+		})
+	}
+}
+
+func TestSegmentsUseRest(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	srv.ReadDelay.Store(int64(time.Millisecond))
+	size := 8 * mib
+	want := srv.WriteFile(t, "big.bin", RandomBytes(size, 7))
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "big.bin"), &pftp.OptsExtra{Connections: 4})
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+
+	rests := srv.RestOffsets()
+	for _, off := range []int64{2 * mib, 4 * mib, 6 * mib} {
+		if !slices.Contains(rests, off) {
+			t.Fatalf("REST offsets %v miss the segment start %d", rests, off)
+		}
+	}
+	for _, off := range rests {
+		if off <= 0 || off >= int64(size) {
+			t.Fatalf("REST offset %d out of range", off)
+		}
+	}
+	if got := len(ftpStats(t, f).Connections); got != 4 {
+		t.Fatalf("stats report %d connections, want 4", got)
+	}
+}
+
+func TestLoginCapFallsBack(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{MaxLogins: 1})
+	want := srv.WriteFile(t, "capped.bin", RandomBytes(4*mib+5, 8))
+
+	fm := testManager(srv)
+	f := buildFetcher(fm)
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "capped.bin"), &pftp.OptsExtra{Connections: 4})
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+
+	if srv.Refused() == 0 {
+		t.Fatal("the server never refused a login, so the cap was not exercised")
+	}
+	if got := len(ftpStats(t, f).Connections); got != 1 {
+		t.Fatalf("stats report %d connections, want 1", got)
+	}
+	var saved fetcherData
+	if err := json.Unmarshal(storeData(t, fm, f), &saved); err != nil {
+		t.Fatal(err)
+	}
+	if saved.MaxConns != 1 {
+		t.Fatalf("saved login ceiling %d, want 1", saved.MaxConns)
+	}
+}
+
+func TestNoRestSequential(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{NoRest: true})
+	srv.ReadDelay.Store(int64(time.Millisecond))
+	want := srv.WriteFile(t, "norest.bin", RandomBytes(4*mib+3, 9))
+
+	fm := testManager(srv)
+	f := buildFetcher(fm)
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "norest.bin"), &pftp.OptsExtra{Connections: 4})
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+
+	if rests := srv.RestOffsets(); len(rests) != 0 {
+		t.Fatalf("the server cannot have seen a REST, got %v", rests)
+	}
+	var saved fetcherData
+	if err := json.Unmarshal(storeData(t, fm, f), &saved); err != nil {
+		t.Fatal(err)
+	}
+	if !saved.NoRest {
+		t.Fatal("the missing REST support was not recorded")
+	}
+}
+
+// TestResumeAfterKill stops the server's transfers at a fixed byte count,
+// waits until the client has written exactly those bytes, then pauses, saves,
+// restores and finishes. No timing decides where the pause lands.
+func TestResumeAfterKill(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	size := int64(4*mib + 777)
+	want := srv.WriteFile(t, "resume.bin", RandomBytes(int(size), 10))
+	stallAt := size / 2
+	srv.StallAfter(stallAt)
+
+	fm := testManager(srv)
+	f := buildFetcher(fm)
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "resume.bin"), &pftp.OptsExtra{Connections: 2})
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case <-srv.Stalled():
+	case <-time.After(30 * time.Second):
+		t.Fatal("the server never reached the stall point")
+	}
+	deadline := time.Now().Add(30 * time.Second)
+	for f.Progress().TotalDownloaded() != stallAt {
+		if time.Now().After(deadline) {
+			t.Fatalf("progress %d, want the %d bytes the server sent", f.Progress().TotalDownloaded(), stallAt)
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	if err := f.Pause(); err != nil {
+		t.Fatal(err)
+	}
+	srv.Release()
+	blob := storeData(t, fm, f)
+
+	var saved fetcherData
+	if err := json.Unmarshal(blob, &saved); err != nil {
+		t.Fatal(err)
+	}
+	var savedTotal int64
+	resumeAt := map[int64]bool{}
+	for _, seg := range saved.Segments {
+		savedTotal += seg.Downloaded
+		if seg.Begin+seg.Downloaded <= seg.End {
+			resumeAt[seg.Begin+seg.Downloaded] = true
+		}
+	}
+	if savedTotal != stallAt {
+		t.Fatalf("saved progress %d, want %d", savedTotal, stallAt)
+	}
+
+	before := len(srv.RetrOffsets())
+	restored := restoreFetcher(t, fm, f.Meta(), blob)
+	if got := restored.Progress().TotalDownloaded(); got != savedTotal {
+		t.Fatalf("restored progress %d, want %d", got, savedTotal)
+	}
+	startAndWait(t, restored)
+	checkFile(t, restored.Meta().SingleFilepath(), want)
+
+	resumed := srv.RetrOffsets()[before:]
+	if len(resumed) == 0 {
+		t.Fatal("no transfer after resume")
+	}
+	for _, off := range resumed {
+		if !resumeAt[off] {
+			t.Fatalf("resumed RETR at %d, want one of the saved offsets %v", off, resumeAt)
+		}
+	}
+}
+
+// TestLateRefusalAfterQueueDrained: worker B holds the second file's segment
+// while the server takes its time to refuse B's login. Worker A finishes the
+// first file meanwhile and finds the queue empty. B must not leave too, or
+// nobody fetches the second file.
+func TestLateRefusalAfterQueueDrained(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{MaxLogins: 1, RefuseDelay: 500 * time.Millisecond})
+	want := map[string]string{
+		"a.bin": srv.WriteFile(t, "dir/a.bin", RandomBytes(1000, 16)),
+		"b.bin": srv.WriteFile(t, "dir/b.bin", RandomBytes(1000, 17)),
+	}
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "dir"), &pftp.OptsExtra{Connections: 2})
+	startAndWait(t, f)
+	for name, sum := range want {
+		checkFile(t, filepath.Join(f.Meta().FolderPath(), name), sum)
+	}
+	if srv.Refused() == 0 {
+		t.Fatal("the server never refused a login, so the late refusal was not exercised")
+	}
+}
+
+// TestLoginCapLoweredMidway: both workers have logged in when the server's
+// cap drops to one, as when another client takes a slot. The refused worker
+// leaves, the ceiling drops to one, and the task finishes.
+func TestLoginCapLoweredMidway(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	srv.ReadDelay.Store(int64(time.Millisecond))
+	want := map[string]string{}
+	for i := 0; i < 8; i++ {
+		name := fmt.Sprintf("f%d.bin", i)
+		want[name] = srv.WriteFile(t, "dir/"+name, RandomBytes(512<<10, byte(30+i)))
+	}
+
+	fm := testManager(srv)
+	f := buildFetcher(fm)
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "dir"), &pftp.OptsExtra{Connections: 2})
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	deadline := time.Now().Add(30 * time.Second)
+	for len(ftpStats(t, f).Connections) < 2 || f.Progress().TotalDownloaded() < 512<<10 {
+		if time.Now().After(deadline) {
+			t.Fatal("the two workers never got going")
+		}
+		time.Sleep(2 * time.Millisecond)
+	}
+	srv.SetMaxLogins(1)
+	if err := waitFetcher(t, f); err != nil {
+		t.Fatalf("download: %v", err)
+	}
+	for name, sum := range want {
+		checkFile(t, filepath.Join(f.Meta().FolderPath(), name), sum)
+	}
+	if srv.Refused() == 0 {
+		t.Fatal("the server never refused a login, so the lowered cap was not exercised")
+	}
+	for _, c := range ftpStats(t, f).Connections {
+		if c.Failed {
+			t.Fatalf("a refused worker failed: %+v", c)
+		}
+	}
+	var saved fetcherData
+	if err := json.Unmarshal(storeData(t, fm, f), &saved); err != nil {
+		t.Fatal(err)
+	}
+	if saved.MaxConns != 1 {
+		t.Fatalf("saved login ceiling %d, want 1", saved.MaxConns)
+	}
+}
+
+// TestDataConnectionsResumeOwnSession runs four FTPS workers against a server
+// that, like ProFTPD, accepts a data connection only when it resumes the TLS
+// session of its own control connection.
+func TestDataConnectionsResumeOwnSession(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{TLS: pftp.TLSImplicit, RequireSessionReuse: true})
+	srv.ReadDelay.Store(int64(200 * time.Microsecond))
+	want := srv.WriteFile(t, "reuse.bin", RandomBytes(8*mib, 18))
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftps", "", "reuse.bin"), &pftp.OptsExtra{Connections: 4})
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+	ok, bad := srv.SessionReuse()
+	if ok < 4 || bad != 0 {
+		t.Fatalf("data connections: %d resumed their own session, %d did not", ok, bad)
+	}
+	for _, c := range ftpStats(t, f).Connections {
+		if c.RetryTimes != 0 {
+			t.Fatalf("a worker needed retries: %+v", c)
+		}
+	}
+}
+
+func TestRetryAfterDroppedConnection(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	want := srv.WriteFile(t, "drop.bin", RandomBytes(3*mib, 11))
+	srv.DropAfter.Store(mib + 100)
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "drop.bin"), &pftp.OptsExtra{Connections: 1})
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+
+	offsets := srv.RetrOffsets()
+	if len(offsets) != 2 || offsets[0] != 0 || offsets[1] <= 0 || offsets[1] > mib+100 {
+		t.Fatalf("RETR offsets %v, want a restart at the dropped offset", offsets)
+	}
+	if got := ftpStats(t, f).Connections[0].RetryTimes; got != 1 {
+		t.Fatalf("retry count %d, want 1", got)
+	}
+}
+
+func TestPercentEncodedPassword(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{User: "u", Pass: "p@ss"})
+	want := srv.WriteFile(t, "secret.bin", RandomBytes(5000, 12))
+
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "u:p%40ss", "secret.bin"), nil)
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+
+	f = buildFetcher(testManager(srv))
+	err := resolveOpts(f, &base.Request{URL: ftpURL(srv, "ftp", "u:wrong", "secret.bin")}, &base.Options{Path: t.TempDir()})
+	if err == nil || !strings.Contains(err.Error(), "530") {
+		t.Fatalf("a wrong password must fail with 530, got %v", err)
+	}
+}
+
+func TestOldSaveFormatResumes(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	data := RandomBytes(2*mib+1, 13)
+	want := srv.WriteFile(t, "old.bin", data)
+
+	fm := testManager(srv)
+	f := buildFetcher(fm)
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "old.bin"), &pftp.OptsExtra{Connections: 1})
+
+	// A save blob that has only the segment fields every version writes.
+	const done = 700000
+	blob := []byte(fmt.Sprintf(`{"Segments":[{"Begin":0,"End":%d,"Downloaded":%d}]}`, len(data)-1, done))
+	name := f.Meta().SingleFilepath()
+	if err := os.WriteFile(name, append(data[:done:done], make([]byte, len(data)-done)...), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	restored := restoreFetcher(t, fm, f.Meta(), blob)
+	if got := restored.Progress().TotalDownloaded(); got != done {
+		t.Fatalf("restored progress %d, want %d", got, done)
+	}
+	startAndWait(t, restored)
+	checkFile(t, name, want)
+	if got := srv.RetrOffsets(); !slices.Equal(got, []int64{done}) {
+		t.Fatalf("RETR offsets %v, want [%d]", got, done)
+	}
+}
+
+func TestDownloadThroughSOCKS5(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{TLS: pftp.TLSExplicit})
+	want := srv.WriteFile(t, "proxied.bin", RandomBytes(2*mib+1, 14))
+
+	var dials atomic.Int32
+	proxySrv, err := socks5.New(&socks5.Config{
+		Dial: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			dials.Add(1)
+			var d net.Dialer
+			return d.DialContext(ctx, network, addr)
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	go proxySrv.Serve(ln)
+
+	f := buildFetcher(testManager(srv))
+	req := &base.Request{
+		URL: ftpURL(srv, "ftpes", "", "proxied.bin"),
+		Proxy: &base.RequestProxy{
+			Mode:   base.RequestProxyModeCustom,
+			Scheme: "socks5",
+			Host:   ln.Addr().String(),
+		},
+	}
+	if err := resolveOpts(f, req, &base.Options{Path: t.TempDir(), Extra: &pftp.OptsExtra{Connections: 2}}); err != nil {
+		t.Fatal(err)
+	}
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+	// Resolve's control and listing, then per worker one control and one
+	// data connection at least: every one of them went through the proxy.
+	if got := dials.Load(); got < 4 {
+		t.Fatalf("the proxy saw %d connections, want every control and data connection", got)
+	}
+}
+
+func TestHTTPProxyFallsBackToDirect(t *testing.T) {
+	srv := StartFTPServer(t, ServerOptions{})
+	want := srv.WriteFile(t, "direct.bin", RandomBytes(100000, 15))
+
+	var logs bytes.Buffer
+	logger := zerolog.New(&logs)
+	fm := testManager(srv)
+	f := fm.Build().(*Fetcher)
+	ctl := testController(fm)
+	ctl.Logger = &logger
+	f.Setup(ctl)
+	req := &base.Request{
+		URL: ftpURL(srv, "ftp", "", "direct.bin"),
+		Proxy: &base.RequestProxy{
+			Mode:   base.RequestProxyModeCustom,
+			Scheme: "http",
+			Host:   "127.0.0.1:1",
+			Usr:    "proxyuser",
+			Pwd:    "proxysecret",
+		},
+	}
+	if err := resolveOpts(f, req, &base.Options{Path: t.TempDir(), Extra: &pftp.OptsExtra{Connections: 2}}); err != nil {
+		t.Fatal(err)
+	}
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+
+	out := logs.String()
+	if n := strings.Count(out, "HTTP proxy"); n != 1 {
+		t.Fatalf("want exactly one HTTP proxy warning, got %d in %q", n, out)
+	}
+	if strings.Contains(out, "proxysecret") {
+		t.Fatalf("the proxy password leaked into the log: %q", out)
+	}
+}
+
+func TestTorrentNameIsFile(t *testing.T) {
+	fm := testManager(nil)
+	for _, u := range []string{"ftp://h/x.torrent", "ftps://h/x.torrent", "ftpes://h/x.torrent", "FTP://h/v.m3u8"} {
+		matched := false
+		for _, filter := range fm.Filters() {
+			if filter.Match(u) {
+				matched = true
+			}
+		}
+		if !matched {
+			t.Fatalf("%s is not matched by the FTP filters", u)
+		}
+	}
+	if fm.Name() != "ftp" {
+		t.Fatalf("manager name %q", fm.Name())
+	}
+
+	srv := StartFTPServer(t, ServerOptions{})
+	want := srv.WriteFile(t, "x.torrent", []byte("d8:announce0:e"))
+	f := buildFetcher(testManager(srv))
+	resolveTask(t, f, ftpURL(srv, "ftp", "", "x.torrent"), nil)
+	res := f.Meta().Res
+	if res.Name != "" || len(res.Files) != 1 || res.Files[0].Name != "x.torrent" {
+		t.Fatalf("x.torrent must resolve to one FTP file, got name %q and %d files", res.Name, len(res.Files))
+	}
+	startAndWait(t, f)
+	checkFile(t, f.Meta().SingleFilepath(), want)
+}
+
+func TestParseNameHidesCredentials(t *testing.T) {
+	fm := testManager(nil)
+	for u, want := range map[string]string{
+		"ftp://u:p%[email protected]/pub/a.iso": "a.iso",
+		"ftp://u:p%[email protected]/":          "example.com",
+		"ftps://u:p%[email protected]":          "example.com",
+		"ftp://u:p%[email protected]/pub/dir/":  "dir",
+	} {
+		if got := fm.ParseName(u); got != want {
+			t.Fatalf("ParseName(%q) = %q, want %q", u, got, want)
+		}
+	}
+}
+
+func TestUnsafeEntryNames(t *testing.T) {
+	for name, ok := range map[string]bool{
+		"a.txt": true, "..a": true, "a b": true,
+		"": false, ".": false, "..": false, "a/b": false, `a\b`: false, "../x": false, "x\x00y": false,
+	} {
+		if got := safeEntryName(name); got != ok {
+			t.Fatalf("safeEntryName(%q) = %v, want %v", name, got, ok)
+		}
+	}
+}

internal/protocol/ftp/testserver_test.go

@@ -0,0 +1,587 @@
+package ftp
+
+import (
+	"bufio"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/hex"
+	"errors"
+	"io"
+	"math/big"
+	"net"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	ftpserver "github.com/fclairamb/ftpserverlib"
+	"github.com/spf13/afero"
+
+	pftp "github.com/GopeedLab/gopeed/pkg/protocol/ftp"
+)
+
+// ServerOptions are the knobs of the in-process FTP test server.
+type ServerOptions struct {
+	// TLS is pftp.TLSNone (or empty), pftp.TLSExplicit or pftp.TLSImplicit.
+	// Explicit mode refuses plain logins, so a passing test proves TLS was used.
+	TLS string
+	// MaxLogins caps concurrent control connections. Beyond it the server
+	// greets with "421 Too many connections" and hangs up. Zero means no cap.
+	MaxLogins int
+	// NoRest answers "502" to REST. It filters the plain control stream, so it
+	// works with TLSNone and TLSImplicit only.
+	NoRest bool
+	// NoMLST disables MLST and MLSD, so clients fall back to SIZE and LIST.
+	NoMLST bool
+	// User and Pass are the only accepted credentials. An empty User accepts
+	// any login, anonymous included.
+	User string
+	Pass string
+	// RefuseDelay holds every 421 refusal back this long, like a server
+	// that answers slowly when it is full.
+	RefuseDelay time.Duration
+	// RequireSessionReuse makes every data connection resume the TLS
+	// session of the control connection that opened it, as ProFTPD's
+	// mod_tls does by default. A data connection that does not is refused.
+	// It needs TLSImplicit, where this test's wrapper sees the plain
+	// control stream and so learns which passive port belongs to whom.
+	RequireSessionReuse bool
+}
+
+// FTPServer is an ftpserverlib server over a temp directory.
+type FTPServer struct {
+	Addr string // host:port
+	Root string // directory served as "/"
+	// CA trusts the server's self-signed certificate.
+	CA *x509.CertPool
+
+	opts    ServerOptions
+	tlsConf *tls.Config
+	server  *ftpserver.FtpServer
+
+	// ReadDelay is slept before every read of a transferred file, in
+	// nanoseconds, to slow downloads down. Tests may change it at any time.
+	ReadDelay atomic.Int64
+
+	// DropAfter, when positive, makes the next transfer fail once after it
+	// has sent that many bytes, as if the data connection were killed.
+	DropAfter atomic.Int64
+
+	mu      sync.Mutex
+	active  int
+	retrs   []int64 // offset of every RETR, 0 when no REST came first
+	refused int
+	logins  int
+
+	// Passive port to the control connection that announced it, and the
+	// outcome of every data connection's session check.
+	pasvOwner map[int]string
+	reuseOK   int
+	reuseBad  int
+
+	// Stall state, see StallAfter. stallMu is held across file reads.
+	stallMu     sync.Mutex
+	stallAt     int64
+	sent        int64
+	stallCh     chan struct{}
+	stalled     chan struct{}
+	stalledOnce *sync.Once
+}
+
+// StartFTPServer starts a server and stops it when the test ends.
+func StartFTPServer(t *testing.T, opts ServerOptions) *FTPServer {
+	t.Helper()
+	s := &FTPServer{Root: t.TempDir(), opts: opts}
+	s.tlsConf, s.CA = selfSignedTLS(t)
+
+	base, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var ln net.Listener = base
+	if opts.RequireSessionReuse {
+		if opts.TLS != pftp.TLSImplicit {
+			t.Fatal("RequireSessionReuse needs TLSImplicit")
+		}
+		s.requireSessionReuse(t, base.Addr().(*net.TCPAddr).Port)
+	}
+	if opts.TLS == pftp.TLSImplicit {
+		ln = tls.NewListener(ln, s.tlsConf)
+	}
+	ln = &limitListener{Listener: ln, srv: s}
+
+	s.Addr = base.Addr().String()
+	s.server = ftpserver.NewFtpServer(&mainDriver{srv: s, listener: ln})
+	if err := s.server.Listen(); err != nil {
+		t.Fatal(err)
+	}
+	go s.server.Serve()
+	t.Cleanup(func() { _ = s.server.Stop() })
+	return s
+}
+
+// WriteFile creates a file under the served root and returns its SHA-256.
+func (s *FTPServer) WriteFile(t *testing.T, rel string, data []byte) string {
+	t.Helper()
+	name := filepath.Join(s.Root, filepath.FromSlash(rel))
+	if err := os.MkdirAll(filepath.Dir(name), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(name, data, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	return SHA256Hex(data)
+}
+
+// RetrOffsets returns the start offset of every RETR the server received.
+func (s *FTPServer) RetrOffsets() []int64 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return append([]int64(nil), s.retrs...)
+}
+
+// RestOffsets returns the non-zero RETR offsets, which only a REST sets.
+func (s *FTPServer) RestOffsets() []int64 {
+	var out []int64
+	for _, off := range s.RetrOffsets() {
+		if off != 0 {
+			out = append(out, off)
+		}
+	}
+	return out
+}
+
+// Refused returns how many connections were turned away with 421.
+func (s *FTPServer) Refused() int {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.refused
+}
+
+// Logins returns the number of successful logins.
+func (s *FTPServer) Logins() int {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.logins
+}
+
+// SetMaxLogins changes the login cap while the server runs, as when other
+// clients take slots.
+func (s *FTPServer) SetMaxLogins(n int) {
+	s.mu.Lock()
+	s.opts.MaxLogins = n
+	s.mu.Unlock()
+}
+
+// SessionReuse returns how many data connections resumed their own control
+// connection's TLS session, and how many did not.
+func (s *FTPServer) SessionReuse() (ok, bad int) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.reuseOK, s.reuseBad
+}
+
+// StallAfter makes every transfer stop sending once the server has sent n
+// bytes in total, until Release. Stalled is closed when that happens.
+func (s *FTPServer) StallAfter(n int64) {
+	s.stallMu.Lock()
+	defer s.stallMu.Unlock()
+	s.stallAt, s.sent = n, 0
+	s.stallCh = make(chan struct{})
+	s.stalled = make(chan struct{})
+	s.stalledOnce = &sync.Once{}
+}
+
+// Stalled is closed once a transfer has stopped at the StallAfter limit.
+func (s *FTPServer) Stalled() <-chan struct{} {
+	s.stallMu.Lock()
+	defer s.stallMu.Unlock()
+	return s.stalled
+}
+
+// Sent returns the bytes sent since StallAfter.
+func (s *FTPServer) Sent() int64 {
+	s.stallMu.Lock()
+	defer s.stallMu.Unlock()
+	return s.sent
+}
+
+// Release ends the stall. The stalled transfers fail.
+func (s *FTPServer) Release() {
+	s.stallMu.Lock()
+	defer s.stallMu.Unlock()
+	if s.stallAt > 0 {
+		s.stallAt = 0
+		close(s.stallCh)
+	}
+}
+
+var errStalled = errors.New("test server released a stalled transfer")
+
+// stall limits a read to the StallAfter budget, and blocks once the budget
+// is spent.
+func (s *FTPServer) stall(read func([]byte) (int, error), p []byte) (int, error) {
+	s.stallMu.Lock()
+	if s.stallAt <= 0 {
+		s.stallMu.Unlock()
+		return read(p)
+	}
+	allowed := s.stallAt - s.sent
+	if allowed <= 0 {
+		ch := s.stallCh
+		s.stalledOnce.Do(func() { close(s.stalled) })
+		s.stallMu.Unlock()
+		<-ch
+		return 0, errStalled
+	}
+	if int64(len(p)) > allowed {
+		p = p[:allowed]
+	}
+	n, err := read(p)
+	s.sent += int64(n)
+	s.stallMu.Unlock()
+	return n, err
+}
+
+var pasvReply = regexp.MustCompile(`^(?:229 [^(]*\(\|\|\|(\d+)\|\)|227 [^(]*\(\d+,\d+,\d+,\d+,(\d+),(\d+)\))`)
+
+// notePassive records the passive port a control connection announced.
+func (s *FTPServer) notePassive(owner string, reply []byte) {
+	m := pasvReply.FindSubmatch(reply)
+	if m == nil {
+		return
+	}
+	var port int
+	if len(m[1]) > 0 {
+		port, _ = strconv.Atoi(string(m[1]))
+	} else {
+		hi, _ := strconv.Atoi(string(m[2]))
+		lo, _ := strconv.Atoi(string(m[3]))
+		port = hi<<8 | lo
+	}
+	s.mu.Lock()
+	s.pasvOwner[port] = owner
+	s.mu.Unlock()
+}
+
+// requireSessionReuse stamps each control connection's session tickets with
+// its address, and checks that each data connection resumed a ticket of the
+// control connection that announced its passive port.
+func (s *FTPServer) requireSessionReuse(t *testing.T, controlPort int) {
+	base := s.tlsConf
+	var key [32]byte
+	if _, err := rand.Read(key[:]); err != nil {
+		t.Fatal(err)
+	}
+	base.SetSessionTicketKeys([][32]byte{key})
+	s.pasvOwner = map[int]string{}
+	stamp := func(owner string) func(tls.ConnectionState, *tls.SessionState) ([]byte, error) {
+		return func(cs tls.ConnectionState, ss *tls.SessionState) ([]byte, error) {
+			ss.Extra = [][]byte{[]byte(owner)}
+			return base.EncryptTicket(cs, ss)
+		}
+	}
+	base.GetConfigForClient = func(hello *tls.ClientHelloInfo) (*tls.Config, error) {
+		cfg := base.Clone()
+		cfg.GetConfigForClient = nil
+		local, _ := hello.Conn.LocalAddr().(*net.TCPAddr)
+		if local == nil || local.Port == controlPort {
+			cfg.WrapSession = stamp(hello.Conn.RemoteAddr().String())
+			return cfg, nil
+		}
+		s.mu.Lock()
+		owner := s.pasvOwner[local.Port]
+		s.mu.Unlock()
+		var resumedFrom string
+		cfg.UnwrapSession = func(identity []byte, cs tls.ConnectionState) (*tls.SessionState, error) {
+			ss, err := base.DecryptTicket(identity, cs)
+			if err != nil || ss == nil {
+				return nil, nil
+			}
+			if len(ss.Extra) > 0 {
+				resumedFrom = string(ss.Extra[0])
+			}
+			return ss, nil
+		}
+		cfg.WrapSession = stamp(owner)
+		cfg.VerifyConnection = func(cs tls.ConnectionState) error {
+			ok := owner != "" && cs.DidResume && resumedFrom == owner
+			s.mu.Lock()
+			if ok {
+				s.reuseOK++
+			} else {
+				s.reuseBad++
+			}
+			s.mu.Unlock()
+			if !ok {
+				return errors.New("data connection did not resume its control connection's TLS session")
+			}
+			return nil
+		}
+		return cfg, nil
+	}
+}
+
+func (s *FTPServer) acquire() bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.opts.MaxLogins > 0 && s.active >= s.opts.MaxLogins {
+		s.refused++
+		return false
+	}
+	s.active++
+	return true
+}
+
+func (s *FTPServer) release() {
+	s.mu.Lock()
+	s.active--
+	s.mu.Unlock()
+}
+
+// limitListener counts control connections and refuses those beyond
+// MaxLogins with a 421 greeting, like vsftpd's max_clients and max_per_ip.
+type limitListener struct {
+	net.Listener
+	srv *FTPServer
+}
+
+func (l *limitListener) Accept() (net.Conn, error) {
+	for {
+		c, err := l.Listener.Accept()
+		if err != nil {
+			return nil, err
+		}
+		if !l.srv.acquire() {
+			go func() {
+				time.Sleep(l.srv.opts.RefuseDelay)
+				_ = c.SetDeadline(time.Now().Add(5 * time.Second))
+				_, _ = io.WriteString(c, "421 Too many connections\r\n")
+				_ = c.Close()
+			}()
+			continue
+		}
+		cc := &countedConn{Conn: c, release: l.srv.release}
+		if l.srv.opts.RequireSessionReuse {
+			owner := c.RemoteAddr().String()
+			cc.sniff = func(b []byte) { l.srv.notePassive(owner, b) }
+		}
+		var conn net.Conn = cc
+		if l.srv.opts.NoRest {
+			conn = &noRestConn{countedConn: conn.(*countedConn), in: bufio.NewReader(c)}
+		}
+		return conn, nil
+	}
+}
+
+type countedConn struct {
+	net.Conn
+	once    sync.Once
+	release func()
+	sniff   func([]byte) // sees every reply the server writes
+}
+
+func (c *countedConn) Write(b []byte) (int, error) {
+	if c.sniff != nil {
+		c.sniff(b)
+	}
+	return c.Conn.Write(b)
+}
+
+func (c *countedConn) Close() error {
+	c.once.Do(c.release)
+	return c.Conn.Close()
+}
+
+// noRestConn answers REST itself with 502 and hides it from the server.
+type noRestConn struct {
+	*countedConn
+	in      *bufio.Reader
+	pending []byte
+}
+
+func (c *noRestConn) Read(p []byte) (int, error) {
+	for len(c.pending) == 0 {
+		line, err := c.in.ReadBytes('\n')
+		if len(line) > 0 {
+			if strings.HasPrefix(strings.ToUpper(string(line)), "REST ") {
+				if _, werr := io.WriteString(c.Conn, "502 REST not implemented\r\n"); werr != nil {
+					return 0, werr
+				}
+			} else {
+				c.pending = line
+			}
+		}
+		if err != nil {
+			if len(c.pending) > 0 {
+				break
+			}
+			return 0, err
+		}
+	}
+	n := copy(p, c.pending)
+	c.pending = c.pending[n:]
+	return n, nil
+}
+
+type mainDriver struct {
+	srv      *FTPServer
+	listener net.Listener
+}
+
+func (d *mainDriver) GetSettings() (*ftpserver.Settings, error) {
+	settings := &ftpserver.Settings{
+		Listener:    d.listener,
+		DisableMLSD: d.srv.opts.NoMLST,
+		DisableMLST: d.srv.opts.NoMLST,
+	}
+	switch d.srv.opts.TLS {
+	case pftp.TLSExplicit:
+		settings.TLSRequired = ftpserver.MandatoryEncryption
+	case pftp.TLSImplicit:
+		settings.TLSRequired = ftpserver.ImplicitEncryption
+	}
+	return settings, nil
+}
+
+func (d *mainDriver) ClientConnected(ftpserver.ClientContext) (string, error) {
+	return "gopeed test server", nil
+}
+
+func (d *mainDriver) ClientDisconnected(ftpserver.ClientContext) {}
+
+func (d *mainDriver) AuthUser(_ ftpserver.ClientContext, user, pass string) (ftpserver.ClientDriver, error) {
+	if d.srv.opts.User != "" && (user != d.srv.opts.User || pass != d.srv.opts.Pass) {
+		return nil, errors.New("bad credentials")
+	}
+	d.srv.mu.Lock()
+	d.srv.logins++
+	d.srv.mu.Unlock()
+	return &clientDriver{Fs: afero.NewBasePathFs(afero.NewOsFs(), d.srv.Root), srv: d.srv}, nil
+}
+
+func (d *mainDriver) GetTLSConfig() (*tls.Config, error) {
+	return d.srv.tlsConf, nil
+}
+
+type clientDriver struct {
+	afero.Fs
+	srv *FTPServer
+}
+
+// GetHandle sees the REST offset of every transfer. The server seeks the
+// returned file to that offset itself.
+func (d *clientDriver) GetHandle(name string, flags int, offset int64) (ftpserver.FileTransfer, error) {
+	f, err := d.Fs.OpenFile(name, flags, 0o644)
+	if err != nil {
+		return nil, err
+	}
+	if flags == os.O_RDONLY {
+		d.srv.mu.Lock()
+		d.srv.retrs = append(d.srv.retrs, offset)
+		d.srv.mu.Unlock()
+	}
+	return &slowFile{File: f, srv: d.srv, dropAfter: d.srv.DropAfter.Swap(0)}, nil
+}
+
+var errDropped = errors.New("test server dropped the transfer")
+
+type slowFile struct {
+	afero.File
+	srv       *FTPServer
+	sent      int64
+	dropAfter int64
+}
+
+func (f *slowFile) Read(p []byte) (int, error) {
+	if delay := time.Duration(f.srv.ReadDelay.Load()); delay > 0 {
+		time.Sleep(delay)
+		if len(p) > 16<<10 {
+			p = p[:16<<10]
+		}
+	}
+	if f.dropAfter > 0 {
+		if f.sent >= f.dropAfter {
+			return 0, errDropped
+		}
+		if rest := f.dropAfter - f.sent; int64(len(p)) > rest {
+			p = p[:rest]
+		}
+	}
+	n, err := f.srv.stall(f.File.Read, p)
+	f.sent += int64(n)
+	return n, err
+}
+
+// selfSignedTLS returns a server config with a fresh certificate for
+// 127.0.0.1 and localhost, and a pool that trusts it.
+func selfSignedTLS(t *testing.T) (*tls.Config, *x509.CertPool) {
+	t.Helper()
+	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tmpl := &x509.Certificate{
+		SerialNumber:          big.NewInt(time.Now().UnixNano()),
+		Subject:               pkix.Name{CommonName: "gopeed ftp test"},
+		NotBefore:             time.Now().Add(-time.Hour),
+		NotAfter:              time.Now().Add(time.Hour),
+		IPAddresses:           []net.IP{net.ParseIP("127.0.0.1")},
+		DNSNames:              []string{"localhost"},
+		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		IsCA:                  true,
+		BasicConstraintsValid: true,
+	}
+	der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &key.PublicKey, key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cert, err := x509.ParseCertificate(der)
+	if err != nil {
+		t.Fatal(err)
+	}
+	pool := x509.NewCertPool()
+	pool.AddCert(cert)
+	return &tls.Config{
+		Certificates: []tls.Certificate{{Certificate: [][]byte{der}, PrivateKey: key, Leaf: cert}},
+		MinVersion:   tls.VersionTLS12,
+	}, pool
+}
+
+func SHA256Hex(data []byte) string {
+	sum := sha256.Sum256(data)
+	return hex.EncodeToString(sum[:])
+}
+
+func FileSHA256(t *testing.T, name string) string {
+	t.Helper()
+	data, err := os.ReadFile(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return SHA256Hex(data)
+}
+
+// RandomBytes returns n reproducible pseudo-random bytes.
+func RandomBytes(n int, seed byte) []byte {
+	out := make([]byte, n)
+	x := uint32(seed) + 1
+	for i := range out {
+		x ^= x << 13
+		x ^= x >> 17
+		x ^= x << 5
+		out[i] = byte(x)
+	}
+	return out
+}

internal/protocol/ftp/walk.go

@@ -0,0 +1,187 @@
+package ftp
+
+import (
+	"cmp"
+	"fmt"
+	"path"
+	"slices"
+	"strings"
+	"time"
+
+	"github.com/jlaffaye/ftp"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+// Limits of a directory download. A tree past either one is refused with an
+// error that names the limit; it is never cut short.
+const maxWalkDepth = 8
+
+// maxWalkFiles is a variable so tests can lower it.
+var maxWalkFiles = 10000
+
+// resolveTarget describes the URL's path: one file, or a directory walked
+// into a multi-file resource whose paths are relative to it.
+func (f *Fetcher) resolveTarget(s *session, t *target) (*base.Resource, error) {
+	isDir, size, mtime, err := f.stat(s, t.path)
+	if err != nil {
+		return nil, err
+	}
+	if !isDir {
+		return &base.Resource{
+			Size:  size,
+			Range: true,
+			Files: []*base.FileInfo{{
+				Name:  path.Base(t.path),
+				Size:  size,
+				Ctime: mtime,
+			}},
+		}, nil
+	}
+
+	files, err := f.walk(s, t.path)
+	if err != nil {
+		return nil, err
+	}
+	name := path.Base(strings.TrimSuffix(t.path, "/"))
+	if name == "" || name == "." || name == "/" {
+		name = t.host
+	}
+	res := &base.Resource{Name: name, Range: true, Files: files}
+	res.CalcSize(nil)
+	return res, nil
+}
+
+// stat tells a file from a directory. MLST answers both at once. Without
+// it, SIZE answers for a file, and a directory is one we can change into.
+func (f *Fetcher) stat(s *session, p string) (isDir bool, size int64, mtime *time.Time, err error) {
+	if p == "" || strings.HasSuffix(p, "/") {
+		return true, 0, nil, nil
+	}
+	s.deadline()
+	if entry, mlstErr := s.GetEntry(p); mlstErr == nil {
+		switch entry.Type {
+		case ftp.EntryTypeFolder:
+			return true, 0, nil, nil
+		case ftp.EntryTypeFile:
+			if !entry.Time.IsZero() {
+				t := entry.Time
+				mtime = &t
+			}
+			return false, int64(entry.Size), mtime, nil
+		}
+		// A link: SIZE below follows it on the server.
+	}
+	// MLST is missing or refused the path: the older commands decide. A
+	// broken connection fails them too, with its own error.
+
+	s.deadline()
+	size, sizeErr := s.FileSize(p)
+	if sizeErr == nil {
+		if s.IsGetTimeSupported() {
+			s.deadline()
+			if t, err := s.GetTime(p); err == nil {
+				mtime = &t
+			}
+		}
+		return false, size, mtime, nil
+	}
+	if replyCode(sizeErr) == 0 {
+		return false, 0, nil, sizeErr
+	}
+
+	// SIZE failed: a directory, or a missing path.
+	s.deadline()
+	cwd, err := s.CurrentDir()
+	if err != nil {
+		return false, 0, nil, err
+	}
+	s.deadline()
+	if err := s.ChangeDir(p); err != nil {
+		return false, 0, nil, sizeErr
+	}
+	s.deadline()
+	if err := s.ChangeDir(cwd); err != nil {
+		return false, 0, nil, err
+	}
+	return true, 0, nil, nil
+}
+
+// safeEntryName reports whether a name from a listing can become a local
+// path element. A hostile server could otherwise list "../x" and write
+// outside the task directory.
+func safeEntryName(name string) bool {
+	if name == "" || name == "." || name == ".." {
+		return false
+	}
+	return !strings.ContainsAny(name, "/\\\x00")
+}
+
+// walk lists a directory tree, at most maxWalkDepth levels below root and
+// maxWalkFiles files. Files come back sorted by path, then name.
+func (f *Fetcher) walk(s *session, root string) ([]*base.FileInfo, error) {
+	type dir struct {
+		remote string // path on the server
+		rel    string // path below root, "" for root itself
+		depth  int
+	}
+	var files []*base.FileInfo
+	stack := []dir{{remote: strings.TrimSuffix(root, "/"), rel: "", depth: 0}}
+	for len(stack) > 0 {
+		d := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+
+		s.deadline()
+		entries, err := s.List(d.remote)
+		if err != nil {
+			return nil, err
+		}
+		for _, e := range entries {
+			if e.Name == "." || e.Name == ".." {
+				continue
+			}
+			if !safeEntryName(e.Name) {
+				f.warn("ftp: skipping a listed name that is not a safe file name: %q", e.Name)
+				continue
+			}
+			remote := path.Join(d.remote, e.Name)
+			rel := path.Join(d.rel, e.Name)
+			if d.remote == "" {
+				remote = e.Name
+			}
+			entryType, size := e.Type, int64(e.Size)
+			if entryType == ftp.EntryTypeLink {
+				// A link to a file has a size; a link to a directory is
+				// not followed, so a loop cannot make the walk endless.
+				s.deadline()
+				linkSize, err := s.FileSize(remote)
+				if err != nil {
+					f.warn("ftp: skipping link %q: %v", rel, err)
+					continue
+				}
+				entryType, size = ftp.EntryTypeFile, linkSize
+			}
+			switch entryType {
+			case ftp.EntryTypeFolder:
+				if d.depth+1 > maxWalkDepth {
+					return nil, fmt.Errorf("ftp: the folder is deeper than %d levels, the limit for a folder download", maxWalkDepth)
+				}
+				stack = append(stack, dir{remote: remote, rel: rel, depth: d.depth + 1})
+			case ftp.EntryTypeFile:
+				if len(files) >= maxWalkFiles {
+					return nil, fmt.Errorf("ftp: the folder has more than %d files, the limit for a folder download", maxWalkFiles)
+				}
+				fi := &base.FileInfo{Name: e.Name, Path: d.rel, Size: size}
+				if !e.Time.IsZero() {
+					t := e.Time
+					fi.Ctime = &t
+				}
+				files = append(files, fi)
+			}
+		}
+	}
+	slices.SortFunc(files, func(a, b *base.FileInfo) int {
+		return cmp.Or(strings.Compare(a.Path, b.Path), strings.Compare(a.Name, b.Name))
+	})
+	return files, nil
+}

internal/protocol/hls/fetcher.go

@@ -172,11 +172,11 @@ func (f *Fetcher) Meta() *fetcher.FetcherMeta {
 	return f.meta
 }
 
-func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) (err error) {
+func (f *Fetcher) Resolve(req *base.Request) (err error) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	f.meta.Req = req
-	f.meta.Opts = opts
+
 	f.extra = &ReqExtra{}
 	if err = base.ParseReqExtra[ReqExtra](req); err != nil {
 		return
@@ -194,10 +194,6 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) (err error) {
 	}
 	state.StagingID = randomStagingID()
 	f.state = state
-	// Pin the staging folder now so the very first persisted state already
-	// carries it: a crash right after create still resumes into the same
-	// folder.
-	f.resolveStagingDirLocked()
 	size := planTotalSize(state.Segments)
 	f.meta.Res = &base.Resource{
 		Range: false,

internal/protocol/hls/fetcher_test.go

@@ -80,7 +80,8 @@ func mustResolve(t *testing.T, f *Fetcher, playlistURL, referer string) {
 	if referer != "" {
 		req.Extra = &ReqExtra{Header: map[string]string{"Referer": referer}}
 	}
-	if err := f.Resolve(req, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(req); err != nil {
 		t.Fatalf("resolve: %v", err)
 	}
 }
@@ -207,7 +208,8 @@ func TestFetcherE2E_RefererEnforced(t *testing.T) {
 	// Without Referer the resolve itself must fail (403 on the playlist).
 	blocked := newTestFetcher(t, testConfig())
 	req := &base.Request{URL: server.URL + "/video.m3u8"}
-	if err := blocked.Resolve(req, &base.Options{Path: t.TempDir()}); err == nil {
+	blocked.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := blocked.Resolve(req); err == nil {
 		t.Fatal("resolve without Referer should fail")
 	}
 
@@ -217,7 +219,8 @@ func TestFetcherE2E_RefererEnforced(t *testing.T) {
 		URL:   server.URL + "/video.m3u8",
 		Extra: &ReqExtra{Header: map[string]string{"Referer": page}},
 	}
-	if err := allowed.Resolve(allowedReq, &base.Options{Path: t.TempDir()}); err != nil {
+	allowed.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := allowed.Resolve(allowedReq); err != nil {
 		t.Fatal(err)
 	}
 	mustRun(t, allowed)
@@ -560,7 +563,8 @@ func TestFetcherE2E_StoreRestoreAuthenticated(t *testing.T) {
 		URL:   server.URL + "/video.m3u8",
 		Extra: &ReqExtra{Header: map[string]string{"Referer": page}},
 	}
-	if err := f.Resolve(req, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(req); err != nil {
 		t.Fatal(err)
 	}
 	if err := f.Start(); err != nil {
@@ -630,7 +634,8 @@ func TestFetcherE2E_PatchPartialUpdate(t *testing.T) {
 		Extra: &ReqExtra{Header: map[string]string{"Referer": page}},
 	}
 	opts := &base.Options{Path: t.TempDir()}
-	if err := f.Resolve(req, opts); err != nil {
+	f.Meta().Opts = opts
+	if err := f.Resolve(req); err != nil {
 		t.Fatal(err)
 	}
 
@@ -713,7 +718,8 @@ func TestFetcherE2E_PatchWhileRunningRejected(t *testing.T) {
 	defer server.Close()
 
 	f := newTestFetcher(t, testConfig())
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	if err := f.Start(); err != nil {
@@ -767,7 +773,8 @@ func TestFetcherE2E_RetryAfterFailure(t *testing.T) {
 	cfg.MaxRetries = 0 // fail the run on the first bad segment
 	cfg.PrefetchContentLength = false
 	f := newTestFetcher(t, cfg)
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	if err := f.Start(); err != nil {
@@ -828,7 +835,8 @@ func TestFetcherE2E_StateMissingSelfHeal(t *testing.T) {
 	defer server.Close()
 
 	f := newTestFetcher(t, testConfig())
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	// Simulate the crash window where the engine persisted the task with its

internal/protocol/hls/media_validate_test.go

@@ -189,7 +189,8 @@ func TestHLSRealMedia_TS(t *testing.T) {
 	defer server.Close()
 
 	f := newTestFetcher(t, testConfig())
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	if err := f.Start(); err != nil {
@@ -225,7 +226,8 @@ func TestHLSRealMedia_FMP4(t *testing.T) {
 	defer server.Close()
 
 	f := newTestFetcher(t, testConfig())
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	if err := f.Start(); err != nil {
@@ -274,7 +276,8 @@ func TestHLSRealMedia_AES128(t *testing.T) {
 	defer server.Close()
 
 	f := newTestFetcher(t, testConfig())
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	if f.meta.Res.Size != 0 {

internal/protocol/hls/staging_test.go

@@ -50,15 +50,20 @@ func TestFetcherE2E_SameURLTwoTasks(t *testing.T) {
 	// user duplicating a task. The engine would rename the second output
 	// (AutoRename); mirror that here.
 	f1 := newTestFetcher(t, cfg)
-	if err := f1.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: dir}); err != nil {
+	f1.Meta().Opts = &base.Options{Path: dir}
+	if err := f1.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	f2 := newTestFetcher(t, cfg)
-	if err := f2.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: dir, Name: "video-2.ts"}); err != nil {
+	f2.Meta().Opts = &base.Options{Path: dir, Name: "video-2.ts"}
+	if err := f2.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
-	if f1.state.StagingDir == "" || f1.state.StagingDir == f2.state.StagingDir {
-		t.Fatalf("staging dirs must be distinct per task: %q vs %q", f1.state.StagingDir, f2.state.StagingDir)
+	if f1.state.StagingID == "" || f1.state.StagingID == f2.state.StagingID {
+		t.Fatal("staging identities must be distinct per task")
+	}
+	if f1.state.StagingDir != "" || f2.state.StagingDir != "" {
+		t.Fatal("Resolve pinned an output directory")
 	}
 
 	// Start task 1, let it stage some segments, then pause it.
@@ -135,7 +140,8 @@ func TestFetcherE2E_ForeignJournalDiscarded(t *testing.T) {
 	cfg := testConfig()
 	cfg.PrefetchContentLength = false
 	f := newTestFetcher(t, cfg)
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	// Plant a journal that does not belong to this plan (wrong fingerprint).
@@ -176,7 +182,8 @@ func TestFetcherE2E_MergeFailurePreservesStaging(t *testing.T) {
 	defer server.Close()
 
 	f := newTestFetcher(t, testConfig())
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	run := &hlsRun{
@@ -250,7 +257,8 @@ func TestFetcherE2E_ReMergeOverExistingOutput(t *testing.T) {
 	defer server.Close()
 
 	f := newTestFetcher(t, testConfig())
-	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}, &base.Options{Path: t.TempDir()}); err != nil {
+	f.Meta().Opts = &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/video.m3u8"}); err != nil {
 		t.Fatal(err)
 	}
 	tempDir := f.resolveStagingDirLocked()

internal/protocol/http/fetcher.go

@@ -2,8 +2,13 @@ package http
 
 import (
 	"context"
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"encoding/hex"
 	"errors"
 	"fmt"
+	"hash"
 	"io"
 	"net/http"
 	"net/url"
@@ -34,6 +39,11 @@ const (
 	stealMinChunkSize     = 512 * 1024 // Min steal size: 512KB (avoid tiny chunks)
 )
 
+// connReadBufferSize is the read buffer each connection allocates once and
+// reuses for its lifetime. 64 KiB keeps per-read overhead low on fast links;
+// at 256 connections it is 16 MiB per task.
+const connReadBufferSize = 64 * 1024
+
 var (
 	errRangeRequestIgnored  = errors.New("server ignored HTTP range request")
 	errInvalidRangeResponse = errors.New("invalid HTTP range response")
@@ -280,6 +290,12 @@ type Fetcher struct {
 	primaryReadyOnce sync.Once
 	primaryReadyCh   chan struct{}
 
+	// checksumFailed marks that the last completed download failed
+	// checksum verification, so the next retry must force a full
+	// re-download instead of skipping connections that already
+	// reported Completed.
+	checksumFailed atomic.Bool
+
 	// Start pending mechanism
 	startPending   atomic.Bool
 	resolvedCh     chan struct{} // Signal when resolve completes
@@ -287,8 +303,9 @@ type Fetcher struct {
 	resolveDataPos atomic.Int64 // How many bytes downloaded during resolve
 
 	// Resolve response - kept open for one-time URLs
-	resolveResp     *http.Response
-	resolveRespLock sync.Mutex
+	resolveResp       *http.Response
+	resolveRespCancel context.CancelFunc // Cancels the Resolve request
+	resolveRespLock   sync.Mutex
 
 	// Async prefetch during resolve phase
 	prefetchFile     *os.File      // Temporary file for prefetch data
@@ -300,13 +317,17 @@ type Fetcher struct {
 	resolveFallback  atomic.Bool   // Resolve prefetch is still available until the first Range request takes over
 
 	// Target file
-	file                  *os.File
-	fileMu                sync.Mutex
-	redirectURL           string
-	redirectLock          sync.Mutex
-	ifRange               string
-	rangeReprobeEligible  bool
-	rangeValidatorPinned  bool
+	file                 *os.File
+	fileMu               sync.Mutex
+	redirectURL          string
+	redirectLock         sync.Mutex
+	ifRange              string
+	rangeReprobeEligible bool
+	rangeValidatorPinned bool
+	// sizeKnown distinguishes a display estimate from an HTTP-confirmed length,
+	// including zero. Nil preserves the interpretation of legacy snapshots.
+	sizeKnown *bool
+	// An interrupted chunked sequential response must restart from byte zero.
 	sequentialSizeUnknown bool
 
 	// Lifecycle control
@@ -353,6 +374,40 @@ func (f *Fetcher) setState(s fetcherState) {
 	f.state.Store(int32(s))
 }
 
+// Size state is read under connMu or before download workers are started.
+func (f *Fetcher) hasKnownSize() bool {
+	if f.sizeKnown != nil {
+		return *f.sizeKnown
+	}
+	return f.meta != nil && f.meta.Res != nil && f.meta.Res.Size > 0 && !f.sequentialSizeUnknown
+}
+
+func (f *Fetcher) knownSize() int64 {
+	if f.hasKnownSize() {
+		return f.meta.Res.Size
+	}
+	return 0
+}
+
+func (f *Fetcher) sizeHint() int64 {
+	if f.meta.Opts != nil && f.meta.Opts.Size > 0 {
+		return f.meta.Opts.Size
+	}
+	return 0
+}
+
+// setResourceSizeLocked publishes the value and its authority in one snapshot.
+func (f *Fetcher) setResourceSizeLocked(size int64, known bool) {
+	if !known {
+		size = f.sizeHint()
+	}
+	f.sizeKnown = &known
+	f.meta.Res.Size = size
+	if len(f.meta.Res.Files) > 0 && f.meta.Res.Files[0] != nil {
+		f.meta.Res.Files[0].Size = size
+	}
+}
+
 // updateMaxConnTime updates maxConnTime if the new duration is larger
 func (f *Fetcher) updateMaxConnTime(d time.Duration) {
 	newVal := int64(d)
@@ -361,26 +416,21 @@ func (f *Fetcher) updateMaxConnTime(d time.Duration) {
 	}
 }
 
-func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
+func (f *Fetcher) Resolve(req *base.Request) error {
 	if err := base.ParseReqExtra[fhttp.ReqExtra](req); err != nil {
 		return err
 	}
 	f.meta.Req = req
-	f.meta.Opts = opts
-	if f.meta.Opts == nil {
-		f.meta.Opts = &base.Options{}
-	}
-
-	if err := f.initOptions(); err != nil {
-		return err
-	}
 
 	f.setState(stateResolving)
 
 	// Build HTTP request WITHOUT Range header (normal request)
 	// This allows the response to be reused for downloading (important for one-time URLs)
-	httpReq, err := f.buildRequest(context.TODO(), req)
+	// The body outlives Resolve, so the read timeout gets its own cancel func.
+	reqCtx, reqCancel := context.WithCancel(context.Background())
+	httpReq, err := f.buildRequest(reqCtx, req)
 	if err != nil {
+		reqCancel()
 		f.setState(stateError)
 		return err
 	}
@@ -392,6 +442,7 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 	connStartTime := time.Now()
 	resp, err := client.Do(httpReq)
 	if err != nil {
+		reqCancel()
 		f.setState(stateError)
 		return err
 	}
@@ -406,6 +457,7 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 
 	if resp.StatusCode != base.HttpCodeOK && resp.StatusCode != base.HttpCodePartialContent {
 		resp.Body.Close()
+		reqCancel()
 		f.setState(stateError)
 		return NewRequestError(resp.StatusCode)
 	}
@@ -417,13 +469,35 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 		res.Range = true
 	}
 
-	// Get content length from Content-Length header
-	contentLength := resp.Header.Get(base.HttpHeaderContentLength)
-	if contentLength != "" {
-		parse, err := strconv.ParseInt(contentLength, 10, 64)
-		if err == nil {
-			res.Size = parse
+	// A partial response describes one segment, not the whole resource.
+	reuseResolveBody := true
+	if resp.StatusCode == base.HttpCodePartialContent {
+		start, _, total, err := parseRangeResponse(resp)
+		if err != nil {
+			resp.Body.Close()
+			reqCancel()
+			f.setState(stateError)
+			return err
 		}
+		res.Size = total
+		res.Range = true
+		// Prefetch is a contiguous prefix copied at offset zero. A segment
+		// starting elsewhere must be fetched again through the Range path.
+		reuseResolveBody = start == 0
+	} else {
+		contentLength := resp.Header.Get(base.HttpHeaderContentLength)
+		if contentLength != "" {
+			if size, err := strconv.ParseInt(contentLength, 10, 64); err == nil {
+				res.Size = size
+			}
+		}
+	}
+	// A hint is only a display value, even when the origin advertises Range.
+	known := resp.StatusCode == base.HttpCodePartialContent || resp.ContentLength >= 0
+	f.sizeKnown = &known
+	f.sequentialSizeUnknown = !res.Range && !known
+	if !known {
+		res.Size = f.sizeHint()
 	}
 
 	// Parse last modified time
@@ -467,7 +541,14 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 	// IMPORTANT: Keep the response body open for downloading in Start phase
 	// This is crucial for one-time URLs that can only be accessed once
 	f.resolveRespLock.Lock()
-	f.resolveResp = resp
+	if reuseResolveBody {
+		f.resolveResp = resp
+		f.resolveRespCancel = reqCancel
+	} else {
+		resp.Body.Close()
+		reqCancel()
+		f.prefetchDone.Store(true)
+	}
 	f.resolveRespLock.Unlock()
 
 	f.setState(stateResolved)
@@ -479,7 +560,7 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 
 	// Start async prefetch in background (only for range-supported resources)
 	// For non-range resources, the response will be used directly in Start
-	if res.Range {
+	if res.Range && reuseResolveBody {
 		f.prefetchStopCh = make(chan struct{})
 		f.resolveFallback.Store(true)
 		go f.asyncPrefetch()
@@ -502,7 +583,7 @@ func (f *Fetcher) asyncPrefetch() {
 
 	// Get the resolve response
 	f.resolveRespLock.Lock()
-	resp := f.resolveResp
+	resp, cancel := f.resolveResp, f.resolveRespCancel
 	f.resolveRespLock.Unlock()
 
 	if resp == nil {
@@ -513,10 +594,7 @@ func (f *Fetcher) asyncPrefetch() {
 		// Close the response even if temporary-file setup fails or shutdown
 		// rejects a late prefetch. Otherwise the server can remain blocked writing.
 		f.resolveRespLock.Lock()
-		if f.resolveResp != nil {
-			f.resolveResp.Body.Close()
-			f.resolveResp = nil
-		}
+		f.closeResolveRespLocked()
 		f.resolveRespLock.Unlock()
 	}()
 
@@ -546,7 +624,7 @@ func (f *Fetcher) asyncPrefetch() {
 	f.prefetchFilePath = tmpFile.Name()
 
 	buf := make([]byte, 32*1024) // 32KB buffer
-	reader := f.responseReader(resp)
+	reader := f.responseReader(resp, cancel)
 
 	for {
 		select {
@@ -590,7 +668,7 @@ func (f *Fetcher) stopPrefetchAndCopyData() int64 {
 	}
 
 	// Wait for prefetch to finish (with timeout)
-	for i := 0; i < 1000 && !f.prefetchDone.Load(); i++ {
+	for i := 0; f.prefetchStopCh != nil && i < 1000 && !f.prefetchDone.Load(); i++ {
 		time.Sleep(10 * time.Millisecond)
 	}
 
@@ -645,8 +723,27 @@ func (f *Fetcher) cleanupPrefetchFile() {
 	f.resolveFallback.Store(false)
 }
 
+// prepareFullRedownload resets all fetcher connection and prefetch state
+// after a checksum mismatch so the subsequent Start takes the fresh-start path.
+func (f *Fetcher) prepareFullRedownload() {
+	f.connMu.Lock()
+	if f.meta.Res.Range {
+		f.connections = nil
+		f.resolveConn = nil
+		f.rangeReprobeEligible = false
+		f.rangeValidatorPinned = false
+	}
+	f.connMu.Unlock()
+
+	f.cleanupPrefetchFile()
+	f.resolveDataPos.Store(0)
+}
+
 // Options may be replaced between Resolve and Start when creating a resolved task.
 func (f *Fetcher) initOptions() error {
+	if f.meta.Opts == nil {
+		f.meta.Opts = &base.Options{}
+	}
 	opts := f.meta.Opts
 	// Parse options
 	if err := base.ParseOptExtra[fhttp.OptsExtra](opts); err != nil {
@@ -662,6 +759,9 @@ func (f *Fetcher) initOptions() error {
 			extra.Connections = 1
 		}
 	}
+	if err := extra.Checksum.Validate(); err != nil {
+		return err
+	}
 
 	return nil
 }
@@ -716,11 +816,26 @@ func (f *Fetcher) doStart() error {
 
 	// If retrying after error, reset connection states for retry
 	if state == stateError {
+		fullRedownload := f.checksumFailed.Swap(false)
+		if fullRedownload {
+			// Checksum mismatch: the file content itself is wrong even
+			// though every connection reported Completed. Truncate the
+			// corrupt file so stale bytes cannot linger if the retry is
+			// interrupted before every connection re-writes its chunk.
+			if err := os.Truncate(f.meta.SingleFilepath(), 0); err != nil && !os.IsNotExist(err) {
+				return fmt.Errorf("failed to reset file after checksum mismatch: %w", err)
+			}
+			f.prepareFullRedownload()
+		}
 		f.connMu.Lock()
 		for _, conn := range f.connections {
-			// Reset connections that can be retried
-			if !conn.Completed && conn.State != connCompleted {
-				if !f.hasSequentialPrefixLocked(conn) {
+			// On a normal error, only reset connections that didn't
+			// finish. On a checksum mismatch, reset EVERY connection —
+			// "Completed" only means the download loop finished, not
+			// that the bytes were verified correct.
+			shouldReset := fullRedownload || (!conn.Completed && conn.State != connCompleted)
+			if shouldReset {
+				if fullRedownload || !f.hasSequentialPrefixLocked(conn) {
 					f.resetConnectionForRestart(conn)
 				}
 				conn.State = connNotStarted
@@ -739,7 +854,7 @@ func (f *Fetcher) doStart() error {
 	_, err = os.Stat(name)
 	if err != nil {
 		if os.IsNotExist(err) {
-			file, err = f.ctl.Touch(name, f.meta.Res.Size)
+			file, err = f.ctl.Touch(name, f.knownSize())
 		} else {
 			return err
 		}
@@ -757,7 +872,7 @@ func (f *Fetcher) doStart() error {
 	// For non-range resources, the response will be used directly
 	var prefetchedBytes int64
 	if f.meta.Res.Range {
-		resolveComplete := f.meta.Res.Size > 0 && f.prefetchDone.Load() && f.prefetchErr == nil && f.prefetchSize.Load() >= f.meta.Res.Size
+		resolveComplete := f.knownSize() > 0 && f.prefetchDone.Load() && f.prefetchErr == nil && f.prefetchSize.Load() >= f.knownSize()
 		if f.resolveFallback.Load() && !resolveComplete {
 			// Keep Resolve downloading until the first Range response has been
 			// validated. The Range request starts at a stable snapshot; a valid
@@ -772,10 +887,7 @@ func (f *Fetcher) doStart() error {
 		if !f.resolveFallback.Load() {
 			// Also close resolve response if still open.
 			f.resolveRespLock.Lock()
-			if f.resolveResp != nil {
-				f.resolveResp.Body.Close()
-				f.resolveResp = nil
-			}
+			f.closeResolveRespLocked()
 			f.resolveRespLock.Unlock()
 		}
 	}
@@ -929,7 +1041,7 @@ func (f *Fetcher) expandConnections() {
 		return
 	}
 
-	totalSize := f.meta.Res.Size
+	totalSize := f.knownSize()
 
 	f.connMu.Lock()
 
@@ -951,8 +1063,14 @@ func (f *Fetcher) expandConnections() {
 			}
 			f.fileMu.Unlock()
 
-			f.setState(stateDone)
-			f.doneCh <- nil
+			var err error
+			if chkErr := f.verifyChecksum(); chkErr != nil {
+				err = chkErr
+				f.setState(stateError)
+			} else {
+				f.setState(stateDone)
+			}
+			f.doneCh <- err
 			return
 		}
 
@@ -1071,7 +1189,7 @@ func (f *Fetcher) runConnection(conn *connection) {
 
 	// Use fast-fail client for quick retry during download phase
 	client := f.buildFastFailClient()
-	buf := make([]byte, 8192)
+	buf := make([]byte, connReadBufferSize)
 
 	retries := 0
 	f.connMu.Lock()
@@ -1214,7 +1332,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 	rangeMode := f.meta.Res.Range
 	ifRange := ""
 	if resumeProbe {
-		end := f.meta.Res.Size - 1
+		end := f.knownSize() - 1
 		rangeEnd = &end
 		ifRange = f.ifRange
 	} else if rangeMode && (f.rangeValidatorPinned || f.resolveFallback.Load()) {
@@ -1222,7 +1340,11 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 	}
 	f.connMu.Unlock()
 
-	httpReq, err := f.buildRequest(conn.ctx, f.meta.Req)
+	// The read timeout cancels this request through its own context.
+	reqCtx, reqCancel := context.WithCancel(conn.ctx)
+	defer reqCancel()
+
+	httpReq, err := f.buildRequest(reqCtx, f.meta.Req)
 	if err != nil {
 		return err
 	}
@@ -1250,7 +1372,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 		// Check if this might be a redirect URL expiration error
 		// If so, try falling back to the original URL
 		if f.hasRedirectURL() && isRedirectExpiredError(originalErr) {
-			fallbackResp, fallbackErr := f.tryFallbackToOriginalURL(conn.ctx, client, rangeStart, rangeEnd, rangeRequested, ifRange)
+			fallbackResp, fallbackErr := f.tryFallbackToOriginalURL(reqCtx, client, rangeStart, rangeEnd, rangeRequested, ifRange)
 			if fallbackErr == nil && fallbackResp != nil {
 				// Fallback succeeded, use this response instead
 				resp = fallbackResp
@@ -1294,7 +1416,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 	}
 	if rangeRequested && resp.StatusCode == base.HttpCodePartialContent {
 		var responseTotal int64
-		expectedResponseLength, responseTotal, err = validateRangeResponse(resp, rangeStart, rangeEnd, f.meta.Res.Size)
+		expectedResponseLength, responseTotal, err = validateRangeResponse(resp, rangeStart, rangeEnd, f.knownSize())
 		if err != nil {
 			resp.Body.Close()
 			return err
@@ -1319,7 +1441,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 			f.rangeValidatorPinned = true
 			f.sequentialSizeUnknown = false
 			conn.Chunk.Begin = 0
-			conn.Chunk.setEnd(f.meta.Res.Size - 1)
+			conn.Chunk.setEnd(f.knownSize() - 1)
 			f.connMu.Unlock()
 		}
 	}
@@ -1344,7 +1466,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 				resp.Body.Close()
 				return err
 			}
-		} else if f.meta.Res.Size > 0 {
+		} else if f.hasKnownSize() && f.meta.Res.Size > 0 {
 			expectedResponseLength = f.meta.Res.Size
 			if resp.ContentLength >= 0 && resp.ContentLength != expectedResponseLength {
 				resp.Body.Close()
@@ -1371,7 +1493,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 		f.slowStart.onConnectSuccess()
 	}
 
-	reader := f.responseReader(resp)
+	reader := f.responseReader(resp, reqCancel)
 	var responseBytesRead int64
 	for {
 		if conn.ctx.Err() != nil {
@@ -1480,7 +1602,7 @@ func (f *Fetcher) commitResolveTakeover(conn *connection, requestedStart int64)
 	}
 
 	prefetched := f.stopPrefetchAndCopyData()
-	if prefetched < requestedStart || prefetched > f.meta.Res.Size {
+	if prefetched < requestedStart || prefetched > f.knownSize() {
 		return 0, fmt.Errorf("resolve prefetch advanced to invalid offset %d for range start %d", prefetched, requestedStart)
 	}
 	f.resolveDataPos.Store(prefetched)
@@ -1511,7 +1633,7 @@ func (f *Fetcher) completeFromResolveFallback(conn *connection) bool {
 		}
 		time.Sleep(10 * time.Millisecond)
 	}
-	knownSize := f.meta.Res.Size > 0
+	knownSize := f.hasKnownSize()
 	if f.prefetchErr != nil || (knownSize && f.prefetchSize.Load() != f.meta.Res.Size) {
 		f.cleanupPrefetchFile()
 		return false
@@ -1525,10 +1647,7 @@ func (f *Fetcher) completeFromResolveFallback(conn *connection) bool {
 
 	f.connMu.Lock()
 	if !knownSize {
-		f.meta.Res.Size = prefetched
-		if len(f.meta.Res.Files) > 0 && f.meta.Res.Files[0] != nil {
-			f.meta.Res.Files[0].Size = prefetched
-		}
+		f.setResourceSizeLocked(prefetched, true)
 	}
 	f.meta.Res.Range = false
 	f.rangeReprobeEligible = false
@@ -1544,27 +1663,41 @@ func (f *Fetcher) completeFromResolveFallback(conn *connection) bool {
 	return true
 }
 
-func validateRangeResponse(resp *http.Response, requestedStart int64, requestedEnd *int64, totalSize int64) (int64, int64, error) {
+// parseRangeResponse validates a single byte range with a known complete length.
+// Unknown totals are rejected: a segment length cannot stand in for resource size.
+func parseRangeResponse(resp *http.Response) (int64, int64, int64, error) {
 	contentRange := resp.Header.Get(base.HttpHeaderContentRange)
 	fields := strings.Fields(contentRange)
 	if len(fields) != 2 || !strings.EqualFold(fields[0], base.HttpHeaderBytes) {
-		return 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
+		return 0, 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
 	}
 
 	rangeAndTotal := strings.Split(fields[1], "/")
 	if len(rangeAndTotal) != 2 {
-		return 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
+		return 0, 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
 	}
 	bounds := strings.Split(rangeAndTotal[0], "-")
 	if len(bounds) != 2 {
-		return 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
+		return 0, 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
 	}
 
 	start, startErr := strconv.ParseInt(bounds[0], 10, 64)
 	end, endErr := strconv.ParseInt(bounds[1], 10, 64)
 	total, totalErr := strconv.ParseInt(rangeAndTotal[1], 10, 64)
 	if startErr != nil || endErr != nil || totalErr != nil || start < 0 || end < start || total <= end {
-		return 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
+		return 0, 0, 0, fmt.Errorf("%w: malformed Content-Range %q", errInvalidRangeResponse, contentRange)
+	}
+	expectedLength := end - start + 1
+	if resp.ContentLength >= 0 && resp.ContentLength != expectedLength {
+		return 0, 0, 0, fmt.Errorf("%w: Content-Length %d does not match range length %d", errInvalidRangeResponse, resp.ContentLength, expectedLength)
+	}
+	return start, end, total, nil
+}
+
+func validateRangeResponse(resp *http.Response, requestedStart int64, requestedEnd *int64, totalSize int64) (int64, int64, error) {
+	start, end, total, err := parseRangeResponse(resp)
+	if err != nil {
+		return 0, 0, err
 	}
 	if start != requestedStart || (requestedEnd != nil && end != *requestedEnd) || (requestedEnd == nil && end != total-1) {
 		return 0, 0, fmt.Errorf("%w: Content-Range %d-%d does not match requested range", errInvalidRangeResponse, start, end)
@@ -1573,11 +1706,7 @@ func validateRangeResponse(resp *http.Response, requestedStart int64, requestedE
 		return 0, 0, fmt.Errorf("%w: Content-Range total %d does not match resource size %d", errInvalidRangeResponse, total, totalSize)
 	}
 
-	expectedLength := end - start + 1
-	if resp.ContentLength >= 0 && resp.ContentLength != expectedLength {
-		return 0, 0, fmt.Errorf("%w: Content-Length %d does not match range length %d", errInvalidRangeResponse, resp.ContentLength, expectedLength)
-	}
-	return expectedLength, total, nil
+	return end - start + 1, total, nil
 }
 
 func (f *Fetcher) resolveOpenEndedRange(conn *connection, totalSize int64) error {
@@ -1600,10 +1729,7 @@ func (f *Fetcher) resolveOpenEndedRange(conn *connection, totalSize int64) error
 		f.connMu.Unlock()
 		return err
 	}
-	f.meta.Res.Size = totalSize
-	if len(f.meta.Res.Files) > 0 && f.meta.Res.Files[0] != nil {
-		f.meta.Res.Files[0].Size = totalSize
-	}
+	f.setResourceSizeLocked(totalSize, true)
 	conn.Chunk.setEnd(totalSize - 1)
 	f.connMu.Unlock()
 	return nil
@@ -1675,10 +1801,7 @@ func (f *Fetcher) resizeSequentialResource(size int64) error {
 		return err
 	}
 
-	f.meta.Res.Size = size
-	if len(f.meta.Res.Files) > 0 {
-		f.meta.Res.Files[0].Size = size
-	}
+	f.setResourceSizeLocked(size, true)
 	f.sequentialSizeUnknown = false
 	f.connMu.Unlock()
 	return nil
@@ -1703,10 +1826,7 @@ func (f *Fetcher) beginUnknownSizeSequentialResource() error {
 		return err
 	}
 
-	f.meta.Res.Size = 0
-	if len(f.meta.Res.Files) > 0 {
-		f.meta.Res.Files[0].Size = 0
-	}
+	f.setResourceSizeLocked(0, false)
 	f.sequentialSizeUnknown = true
 	f.ifRange = ""
 	f.rangeValidatorPinned = false
@@ -1723,12 +1843,12 @@ func (f *Fetcher) runConnectionWithResolveResp(conn *connection) {
 	conn.State = connConnecting
 	f.connMu.Unlock()
 
-	buf := make([]byte, 8192)
+	buf := make([]byte, connReadBufferSize)
 
 	// Get the resolve response
 	f.resolveRespLock.Lock()
-	resp := f.resolveResp
-	f.resolveResp = nil // Take ownership
+	resp, cancel := f.resolveResp, f.resolveRespCancel
+	f.resolveResp, f.resolveRespCancel = nil, nil // Take ownership
 	f.resolveRespLock.Unlock()
 
 	if resp == nil {
@@ -1737,6 +1857,9 @@ func (f *Fetcher) runConnectionWithResolveResp(conn *connection) {
 		return
 	}
 
+	if cancel != nil {
+		defer cancel()
+	}
 	defer resp.Body.Close()
 
 	f.connMu.Lock()
@@ -1753,7 +1876,7 @@ func (f *Fetcher) runConnectionWithResolveResp(conn *connection) {
 	}
 
 	// Download data from resolve response
-	reader := f.responseReader(resp)
+	reader := f.responseReader(resp, cancel)
 	for {
 		if conn.ctx.Err() != nil {
 			return
@@ -1790,11 +1913,9 @@ func (f *Fetcher) runConnectionWithResolveResp(conn *connection) {
 		if err != nil {
 			if err == io.EOF {
 				f.connMu.Lock()
-				if f.meta.Res.Size == 0 {
-					f.meta.Res.Size = conn.Downloaded
-					if len(f.meta.Res.Files) > 0 && f.meta.Res.Files[0] != nil {
-						f.meta.Res.Files[0].Size = conn.Downloaded
-					}
+				if !f.hasKnownSize() {
+					f.setResourceSizeLocked(conn.Downloaded, true)
+					f.sequentialSizeUnknown = false
 				}
 				conn.Completed = true
 				conn.State = connCompleted
@@ -1817,7 +1938,7 @@ func (f *Fetcher) runConnectionWithResolveResp(conn *connection) {
 func (f *Fetcher) runConnectionFallback(conn *connection) {
 	// Use fast-fail client for quick retry during download phase
 	client := f.buildFastFailClient()
-	buf := make([]byte, 8192)
+	buf := make([]byte, connReadBufferSize)
 
 	retries := 0
 	countedRetries := 0
@@ -1833,78 +1954,15 @@ func (f *Fetcher) runConnectionFallback(conn *connection) {
 		}
 
 		f.connMu.Lock()
+		if retries > 0 {
+			f.resetConnectionForRestart(conn)
+		}
 		conn.State = connConnecting
 		f.connMu.Unlock()
 
-		err := func() error {
-			httpReq, err := f.buildRequest(conn.ctx, f.meta.Req)
-			if err != nil {
-				return err
-			}
-
-			// Record connection start time for adaptive timeout tracking
-			connStartTime := time.Now()
-
-			resp, err := client.Do(httpReq)
-			if err != nil {
-				return err
-			}
-			defer resp.Body.Close()
-
-			if resp.StatusCode != base.HttpCodeOK && resp.StatusCode != base.HttpCodePartialContent {
-				return NewRequestError(resp.StatusCode)
-			}
-
-			// Record successful connection time for adaptive timeout
-			f.updateMaxConnTime(time.Since(connStartTime))
-
-			f.connMu.Lock()
-			conn.State = connDownloading
-			conn.failed = false
-			f.connMu.Unlock()
-
-			f.primaryReadyOnce.Do(func() {
-				close(f.primaryReadyCh)
-			})
-			if f.slowStart != nil {
-				f.slowStart.onConnectSuccess()
-			}
-
-			reader := f.responseReader(resp)
-			for {
-				if conn.ctx.Err() != nil {
-					return conn.ctx.Err()
-				}
-
-				n, err := reader.Read(buf)
-				if n > 0 {
-					f.connMu.Lock()
-					writeOffset := conn.Chunk.Downloaded
-					f.connMu.Unlock()
-
-					f.fileMu.Lock()
-					if f.file != nil {
-						_, writeErr := f.file.WriteAt(buf[:n], writeOffset)
-						if writeErr != nil {
-							f.fileMu.Unlock()
-							return writeErr
-						}
-					}
-					f.fileMu.Unlock()
-
-					f.connMu.Lock()
-					conn.Chunk.Downloaded += int64(n)
-					conn.Downloaded += int64(n)
-					f.connMu.Unlock()
-				}
-				if err != nil {
-					if err == io.EOF {
-						return nil
-					}
-					return err
-				}
-			}
-		}()
+		// Restored tasks without a reusable Resolve response need the same
+		// length handling and restart semantics as other sequential requests.
+		err := f.downloadChunkOnce(conn, client, buf)
 
 		if err == nil {
 			f.connMu.Lock()
@@ -2038,7 +2096,7 @@ func (f *Fetcher) resetConnectionForRestart(conn *connection) {
 	// so pause/retry must restart instead of continuing from the old offset.
 	if conn.Chunk == nil {
 		conn.Chunk = newChunk(0, 0)
-	} else {
+	} else if !f.meta.Res.Range {
 		conn.Chunk.Begin = 0
 		conn.Chunk.setEnd(0)
 		conn.Chunk.Downloaded = 0
@@ -2053,14 +2111,14 @@ func (f *Fetcher) resetConnectionForRestart(conn *connection) {
 // hasSequentialPrefixLocked reports whether a single sequential connection has
 // a useful contiguous prefix. The caller must hold connMu.
 func (f *Fetcher) hasSequentialPrefixLocked(conn *connection) bool {
-	if f.meta == nil || f.meta.Res == nil || f.meta.Res.Range || !f.rangeReprobeEligible || f.meta.Res.Size <= 0 {
+	if f.meta == nil || f.meta.Res == nil || f.meta.Res.Range || !f.rangeReprobeEligible || f.knownSize() <= 0 {
 		return false
 	}
 	if conn == nil || conn.ID != 0 || len(f.connections) != 1 || conn.Chunk == nil {
 		return false
 	}
 	downloaded := conn.Chunk.Downloaded
-	return downloaded > 0 && downloaded < f.meta.Res.Size
+	return downloaded > 0 && downloaded < f.knownSize()
 }
 
 // canProbeSequentialResumeLocked reports whether the prefix can be resumed
@@ -2146,7 +2204,7 @@ func (f *Fetcher) onDownloadComplete() {
 		needsMoreData := false
 		if f.meta.Res.Range {
 			needsMoreData = conn.Chunk != nil && (conn.Chunk.openEnded() || conn.Chunk.remain() > 0)
-		} else if f.meta.Res.Size > 0 {
+		} else if f.hasKnownSize() && f.meta.Res.Size > 0 {
 			needsMoreData = conn.Downloaded < f.meta.Res.Size
 		} else {
 			needsMoreData = !conn.Completed && conn.State != connCompleted
@@ -2156,7 +2214,7 @@ func (f *Fetcher) onDownloadComplete() {
 			// This connection has remaining work and isn't done
 			// Check if it failed with 403 (server limit) - these can be ignored if other connections completed the work
 			if conn.State == connFailed && conn.failed {
-				if re := extractRequestError(conn.lastErr); re != nil && re.Code == 403 {
+				if re := extractRequestError(conn.lastErr); re != nil && re.Code == 403 && f.hasKnownSize() {
 					// 403 is server connection limit, check if other connections will complete this chunk
 					continue
 				}
@@ -2167,7 +2225,7 @@ func (f *Fetcher) onDownloadComplete() {
 	}
 
 	// If total downloaded matches file size, consider it a success regardless of connection failures
-	downloadComplete := f.meta.Res.Size > 0 && totalDownloaded >= f.meta.Res.Size
+	downloadComplete := f.hasKnownSize() && f.meta.Res.Size > 0 && totalDownloaded >= f.meta.Res.Size
 
 	// Integrity errors must win over byte-count completion. A malformed response
 	// may be detected only after the expected bytes have already been written.
@@ -2184,7 +2242,7 @@ func (f *Fetcher) onDownloadComplete() {
 		for _, conn := range f.connections {
 			if conn.State == connFailed && conn.failed {
 				// Skip 403 errors (server connection limit) - these are expected when exceeding server's limit
-				if re := extractRequestError(conn.lastErr); re != nil && re.Code == 403 {
+				if re := extractRequestError(conn.lastErr); re != nil && re.Code == 403 && f.hasKnownSize() {
 					continue
 				}
 				if re := extractRequestError(conn.lastErr); re != nil {
@@ -2209,10 +2267,15 @@ func (f *Fetcher) onDownloadComplete() {
 	}
 	f.fileMu.Unlock()
 
-	if finalErr != nil {
-		f.setState(stateError)
+	if finalErr == nil {
+		if chkErr := f.verifyChecksum(); chkErr != nil {
+			finalErr = chkErr
+			f.setState(stateError)
+		} else {
+			f.setState(stateDone)
+		}
 	} else {
-		f.setState(stateDone)
+		f.setState(stateError)
 	}
 
 	select {
@@ -2221,6 +2284,51 @@ func (f *Fetcher) onDownloadComplete() {
 	}
 }
 
+func (f *Fetcher) verifyChecksum() error {
+	if f.meta == nil || f.meta.Opts == nil || f.meta.Opts.Extra == nil {
+		return nil
+	}
+	extra, ok := f.meta.Opts.Extra.(*fhttp.OptsExtra)
+	if !ok || extra.Checksum == nil {
+		return nil
+	}
+	chk := extra.Checksum
+	if chk.Algorithm == "" && chk.Expected == "" {
+		return nil
+	}
+	var h hash.Hash
+	switch strings.ToLower(strings.TrimSpace(chk.Algorithm)) {
+	case "md5":
+		h = md5.New()
+	case "sha1", "sha-1":
+		h = sha1.New()
+	case "sha256", "sha-256":
+		h = sha256.New()
+	default:
+		return fmt.Errorf("unsupported checksum algorithm: %s", chk.Algorithm)
+	}
+
+	filePath := f.meta.SingleFilepath()
+	file, err := os.Open(filePath)
+	if err != nil {
+		return fmt.Errorf("open file for checksum verification failed: %w", err)
+	}
+	defer file.Close()
+
+	buf := make([]byte, 64*1024)
+	if _, err := io.CopyBuffer(h, file, buf); err != nil {
+		return fmt.Errorf("calculate checksum failed: %w", err)
+	}
+
+	actual := hex.EncodeToString(h.Sum(nil))
+	expected := strings.ToLower(strings.TrimSpace(chk.Expected))
+	if !strings.EqualFold(actual, expected) {
+		f.checksumFailed.Store(true)
+		return fmt.Errorf("checksum mismatch: expected %s, got %s", expected, actual)
+	}
+	return nil
+}
+
 func (f *Fetcher) checkCompletion() bool {
 	// Check if all data has been downloaded
 	f.connMu.Lock()
@@ -2234,7 +2342,7 @@ func (f *Fetcher) checkCompletion() bool {
 		totalDownloaded += conn.Downloaded
 	}
 
-	if f.meta.Res.Size > 0 && totalDownloaded >= f.meta.Res.Size {
+	if f.hasKnownSize() && f.meta.Res.Size > 0 && totalDownloaded >= f.meta.Res.Size {
 		// Don't start a new goroutine - let the caller handle completion
 		return true
 	}
@@ -2261,6 +2369,14 @@ func (f *Fetcher) checkCompletion() bool {
 
 // Patch modifies the HTTP request information.
 func (f *Fetcher) Patch(req *base.Request, opts *base.Options) error {
+	if opts != nil && opts.Size > 0 {
+		f.connMu.Lock()
+		f.meta.Opts.Size = opts.Size
+		if f.meta.Res != nil && !f.hasKnownSize() {
+			f.setResourceSizeLocked(0, false)
+		}
+		f.connMu.Unlock()
+	}
 	// Patch request info
 	if req != nil {
 		if req.URL != "" {
@@ -2358,8 +2474,8 @@ func (f *Fetcher) Pause() error {
 				conn := f.connections[0]
 				if conn != nil && conn.ID == 0 && conn.Chunk != nil && !conn.Completed {
 					conn.Chunk.Begin = prefetched
-					if f.meta.Res.Size > 0 {
-						conn.Chunk.setEnd(f.meta.Res.Size - 1)
+					if f.knownSize() > 0 {
+						conn.Chunk.setEnd(f.knownSize() - 1)
 					} else {
 						conn.Chunk.End = nil
 					}
@@ -2375,10 +2491,7 @@ func (f *Fetcher) Pause() error {
 
 	// Clean up resolve response if still held
 	f.resolveRespLock.Lock()
-	if f.resolveResp != nil {
-		f.resolveResp.Body.Close()
-		f.resolveResp = nil
-	}
+	f.closeResolveRespLocked()
 	f.resolveRespLock.Unlock()
 
 	f.fileMu.Lock()
@@ -2496,9 +2609,25 @@ func (f *Fetcher) Wait() error {
 
 // Generated output can pause while its producer waits for processing capacity.
 // Its producer owns upstream deadlines; cancellation still closes the response.
-func (f *Fetcher) responseReader(resp *http.Response) io.Reader {
+// Otherwise a stalled read cancels the request via cancel, which must belong
+// to the request that produced resp.
+func (f *Fetcher) responseReader(resp *http.Response, cancel context.CancelFunc) io.Reader {
 	if f.ctl != nil && f.ctl.ManagedProduction != nil && resp.Request != nil && f.ctl.ManagedProduction(resp.Request.URL.String()) {
 		return resp.Body
 	}
-	return NewTimeoutReader(resp.Body, readTimeout)
+	return NewTimeoutReader(resp.Body, readTimeout, cancel)
+}
+
+// closeResolveRespLocked closes the kept Resolve response, if any, and
+// releases its request context. The caller must hold resolveRespLock.
+func (f *Fetcher) closeResolveRespLocked() {
+	if f.resolveResp == nil {
+		return
+	}
+	f.resolveResp.Body.Close()
+	f.resolveResp = nil
+	if f.resolveRespCancel != nil {
+		f.resolveRespCancel()
+		f.resolveRespCancel = nil
+	}
 }

internal/protocol/http/fetcher_checksum_retry_test.go

@@ -0,0 +1,391 @@
+package http
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	gohttp "net/http"
+	"net/http/httptest"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/protocol/http"
+)
+
+// serveRangeContent serves byte range requests or full responses from data.
+func serveRangeContent(w gohttp.ResponseWriter, r *gohttp.Request, data []byte) {
+	w.Header().Set(base.HttpHeaderAcceptRanges, base.HttpHeaderBytes)
+	rangeHdr := r.Header.Get(base.HttpHeaderRange)
+	total := int64(len(data))
+	if rangeHdr == "" {
+		w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", total))
+		w.WriteHeader(gohttp.StatusOK)
+		_, _ = w.Write(data)
+		return
+	}
+
+	// Parse bytes=start-end or bytes=start-
+	if !strings.HasPrefix(rangeHdr, "bytes=") {
+		w.WriteHeader(gohttp.StatusBadRequest)
+		return
+	}
+	spec := strings.TrimPrefix(rangeHdr, "bytes=")
+	parts := strings.Split(spec, "-")
+	start, err := strconv.ParseInt(parts[0], 10, 64)
+	if err != nil || start < 0 || start >= total {
+		w.WriteHeader(gohttp.StatusRequestedRangeNotSatisfiable)
+		return
+	}
+	end := total - 1
+	if len(parts) > 1 && parts[1] != "" {
+		if parsedEnd, err := strconv.ParseInt(parts[1], 10, 64); err == nil && parsedEnd >= start && parsedEnd < total {
+			end = parsedEnd
+		}
+	}
+
+	contentLength := end - start + 1
+	w.Header().Set(base.HttpHeaderContentRange, fmt.Sprintf("bytes %d-%d/%d", start, end, total))
+	w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", contentLength))
+	w.WriteHeader(gohttp.StatusPartialContent)
+	_, _ = w.Write(data[start : end+1])
+}
+
+func TestFetcher_ChecksumMismatch_Retry(t *testing.T) {
+	corruptContent := []byte("Corrupt Initial Download Data 33B")
+	correctContent := []byte("Correct Retried Download Data 33B")
+
+	correctSha256Hasher := sha256.New()
+	correctSha256Hasher.Write(correctContent)
+	correctSha256 := hex.EncodeToString(correctSha256Hasher.Sum(nil))
+
+	var phase atomic.Int32 // 0: serve corruptContent, 1: serve correctContent
+	server := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+		var served []byte
+		if phase.Load() == 0 {
+			served = corruptContent
+		} else {
+			served = correctContent
+		}
+		serveRangeContent(w, r, served)
+	}))
+	defer server.Close()
+
+	downloadDir := t.TempDir()
+	fileName := "test_checksum_retry.txt"
+
+	f := buildFetcher()
+	defer f.Close()
+
+	opts := &base.Options{
+		Path: downloadDir,
+		Name: fileName,
+		Extra: &http.OptsExtra{
+			Connections: 1,
+			Checksum: &http.ChecksumOption{
+				Algorithm: "sha256",
+				Expected:  correctSha256,
+			},
+		},
+	}
+
+	// 1. Initial attempt -> will download corruptContent, failing checksum verification
+	if err := f.Resolve(&base.Request{URL: server.URL + "/retry_test.txt"}); err != nil {
+		t.Fatalf("Resolve error: %v", err)
+	}
+	f.Meta().Opts = opts
+	if err := f.Start(); err != nil {
+		t.Fatalf("Start error: %v", err)
+	}
+	err := f.Wait()
+	if err == nil {
+		t.Fatal("expected checksum mismatch error on initial attempt, got nil")
+	}
+	if !strings.Contains(err.Error(), "checksum mismatch") {
+		t.Fatalf("expected 'checksum mismatch' in error, got %v", err)
+	}
+	if f.getState() != stateError {
+		t.Fatalf("expected stateError after checksum mismatch, got %v", f.getState())
+	}
+
+	// Flip phase to 1 after observing checksum mismatch
+	phase.Store(1)
+
+	// 2. Retry download -> should trigger forced full reset, truncate file, and re-download correctContent
+	if err := f.Start(); err != nil {
+		t.Fatalf("Start error on retry: %v", err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("Wait error on retry (expected success): %v", err)
+	}
+	if f.getState() != stateDone {
+		t.Fatalf("expected stateDone after successful retry, got %v", f.getState())
+	}
+
+	// 3. Verify on-disk file content matches the re-downloaded bytes
+	filePath := f.meta.SingleFilepath()
+	fileBytes, err := os.ReadFile(filePath)
+	if err != nil {
+		t.Fatalf("failed to read completed file: %v", err)
+	}
+	if string(fileBytes) != string(correctContent) {
+		t.Fatalf("on-disk file content mismatch:\ngot:  %q\nwant: %q", string(fileBytes), string(correctContent))
+	}
+
+	// 4. Compute hash independently and verify
+	actualHasher := sha256.New()
+	actualHasher.Write(fileBytes)
+	actualHash := hex.EncodeToString(actualHasher.Sum(nil))
+	if actualHash != correctSha256 {
+		t.Fatalf("re-computed on-disk hash mismatch: got %s, want %s", actualHash, correctSha256)
+	}
+}
+
+func TestFetcher_ChecksumMismatch_Retry_PartialPrefetch(t *testing.T) {
+	corruptContent := []byte("Corrupt Initial Download Data 33B")
+	correctContent := []byte("Correct Retried Download Data 33B")
+
+	correctSha256Hasher := sha256.New()
+	correctSha256Hasher.Write(correctContent)
+	correctSha256 := hex.EncodeToString(correctSha256Hasher.Sum(nil))
+
+	var phase atomic.Int32 // 0: corrupt, 1: correct
+	var isFirstRequest atomic.Bool
+	isFirstRequest.Store(true)
+
+	releasePrefetch := make(chan struct{})
+	var closeReleaseOnce sync.Once
+
+	var mu sync.Mutex
+	var phase1Ranges []string
+
+	server := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+		curPhase := phase.Load()
+		if curPhase == 1 {
+			mu.Lock()
+			phase1Ranges = append(phase1Ranges, r.Header.Get(base.HttpHeaderRange))
+			mu.Unlock()
+			serveRangeContent(w, r, correctContent)
+			return
+		}
+
+		// Phase 0: First request is Resolve GET without Range header.
+		// Write exactly 7 bytes and flush, then block until release channel closes or context is done.
+		if isFirstRequest.CompareAndSwap(true, false) {
+			w.Header().Set(base.HttpHeaderAcceptRanges, base.HttpHeaderBytes)
+			w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", len(corruptContent)))
+			w.WriteHeader(gohttp.StatusOK)
+			_, _ = w.Write(corruptContent[:7])
+			if flusher, ok := w.(gohttp.Flusher); ok {
+				flusher.Flush()
+			}
+			select {
+			case <-releasePrefetch:
+			case <-r.Context().Done():
+			}
+			return
+		}
+
+		// Subsequent requests in Phase 0 (such as Range request from Start)
+		serveRangeContent(w, r, corruptContent)
+	}))
+	defer server.Close()
+	defer closeReleaseOnce.Do(func() { close(releasePrefetch) })
+
+	downloadDir := t.TempDir()
+	fileName := "test_checksum_prefetch_retry.txt"
+
+	f := buildFetcher()
+	defer f.Close()
+
+	opts := &base.Options{
+		Path: downloadDir,
+		Name: fileName,
+		Extra: &http.OptsExtra{
+			Connections: 1,
+			Checksum: &http.ChecksumOption{
+				Algorithm: "sha256",
+				Expected:  correctSha256,
+			},
+		},
+	}
+
+	// 1. Resolve phase
+	if err := f.Resolve(&base.Request{URL: server.URL + "/prefetch_retry.txt"}); err != nil {
+		t.Fatalf("Resolve error: %v", err)
+	}
+	f.Meta().Opts = opts
+
+	// Wait until prefetch has received exactly 7 bytes
+	for i := 0; i < 200; i++ {
+		if f.prefetchSize.Load() >= 7 {
+			break
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	if f.prefetchSize.Load() < 7 {
+		t.Fatalf("expected at least 7 prefetched bytes, got %d", f.prefetchSize.Load())
+	}
+
+	// Release prefetch handler right before Start
+	closeReleaseOnce.Do(func() { close(releasePrefetch) })
+
+	// 2. Start initial download attempt (will complete with corruptContent and fail checksum)
+	if err := f.Start(); err != nil {
+		t.Fatalf("Start error: %v", err)
+	}
+	err := f.Wait()
+	if err == nil {
+		t.Fatal("expected checksum mismatch error on initial attempt, got nil")
+	}
+	if !strings.Contains(err.Error(), "checksum mismatch") {
+		t.Fatalf("expected 'checksum mismatch' in error, got %v", err)
+	}
+	if f.getState() != stateError {
+		t.Fatalf("expected stateError after checksum mismatch, got %v", f.getState())
+	}
+
+	// 3. Flip to phase 1 (correctContent) and retry
+	phase.Store(1)
+
+	if err := f.Start(); err != nil {
+		t.Fatalf("Start error on retry: %v", err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("Wait error on retry (expected success): %v", err)
+	}
+	if f.getState() != stateDone {
+		t.Fatalf("expected stateDone after successful retry, got %v", f.getState())
+	}
+
+	// Verify that in Phase 1 at least one Range request started at byte 0
+	mu.Lock()
+	rangesSeen := append([]string(nil), phase1Ranges...)
+	mu.Unlock()
+
+	hasByteZero := false
+	for _, r := range rangesSeen {
+		if strings.HasPrefix(r, "bytes=0-") {
+			hasByteZero = true
+			break
+		}
+	}
+	if !hasByteZero {
+		t.Fatalf("expected at least one Phase 1 Range request starting at byte 0, saw: %v", rangesSeen)
+	}
+
+	// Verify on-disk content matches correctContent exactly
+	filePath := f.meta.SingleFilepath()
+	fileBytes, err := os.ReadFile(filePath)
+	if err != nil {
+		t.Fatalf("failed to read completed file: %v", err)
+	}
+	if string(fileBytes) != string(correctContent) {
+		t.Fatalf("on-disk file content mismatch:\ngot:  %q\nwant: %q", string(fileBytes), string(correctContent))
+	}
+
+	// Compute hash independently and verify
+	actualHasher := sha256.New()
+	actualHasher.Write(fileBytes)
+	actualHash := hex.EncodeToString(actualHasher.Sum(nil))
+	if actualHash != correctSha256 {
+		t.Fatalf("re-computed on-disk hash mismatch: got %s, want %s", actualHash, correctSha256)
+	}
+}
+
+func TestFetcher_ChecksumMismatch_Retry_NonRange(t *testing.T) {
+	corruptContent := []byte("Corrupt Non-Range Initial Data 33B")
+	correctContent := []byte("Correct Non-Range Retried Data 33B")
+
+	correctSha256Hasher := sha256.New()
+	correctSha256Hasher.Write(correctContent)
+	correctSha256 := hex.EncodeToString(correctSha256Hasher.Sum(nil))
+
+	var phase atomic.Int32 // 0: corrupt, 1: correct
+	server := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+		// Server does not support Range (always returns full content 200 OK)
+		var served []byte
+		if phase.Load() == 0 {
+			served = corruptContent
+		} else {
+			served = correctContent
+		}
+		w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", len(served)))
+		w.WriteHeader(gohttp.StatusOK)
+		_, _ = w.Write(served)
+	}))
+	defer server.Close()
+
+	downloadDir := t.TempDir()
+	fileName := "test_checksum_nonrange_retry.txt"
+
+	f := buildFetcher()
+	defer f.Close()
+
+	opts := &base.Options{
+		Path: downloadDir,
+		Name: fileName,
+		Extra: &http.OptsExtra{
+			Connections: 1,
+			Checksum: &http.ChecksumOption{
+				Algorithm: "sha256",
+				Expected:  correctSha256,
+			},
+		},
+	}
+
+	// 1. Resolve and start initial attempt
+	if err := f.Resolve(&base.Request{URL: server.URL + "/nonrange_retry.txt"}); err != nil {
+		t.Fatalf("Resolve error: %v", err)
+	}
+	f.Meta().Opts = opts
+	if err := f.Start(); err != nil {
+		t.Fatalf("Start error: %v", err)
+	}
+	err := f.Wait()
+	if err == nil {
+		t.Fatal("expected checksum mismatch error on initial non-range attempt, got nil")
+	}
+	if !strings.Contains(err.Error(), "checksum mismatch") {
+		t.Fatalf("expected 'checksum mismatch' in error, got %v", err)
+	}
+	if f.getState() != stateError {
+		t.Fatalf("expected stateError after checksum mismatch, got %v", f.getState())
+	}
+
+	// 2. Switch phase and retry
+	phase.Store(1)
+
+	if err := f.Start(); err != nil {
+		t.Fatalf("Start error on non-range retry: %v", err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("Wait error on non-range retry (expected success): %v", err)
+	}
+	if f.getState() != stateDone {
+		t.Fatalf("expected stateDone after successful non-range retry, got %v", f.getState())
+	}
+
+	// 3. Verify on-disk file content
+	filePath := f.meta.SingleFilepath()
+	fileBytes, err := os.ReadFile(filePath)
+	if err != nil {
+		t.Fatalf("failed to read completed file: %v", err)
+	}
+	if string(fileBytes) != string(correctContent) {
+		t.Fatalf("on-disk file content mismatch:\ngot:  %q\nwant: %q", string(fileBytes), string(correctContent))
+	}
+
+	// 4. Compute hash independently and verify
+	actualHasher := sha256.New()
+	actualHasher.Write(fileBytes)
+	actualHash := hex.EncodeToString(actualHasher.Sum(nil))
+	if actualHash != correctSha256 {
+		t.Fatalf("re-computed on-disk hash mismatch: got %s, want %s", actualHash, correctSha256)
+	}
+}

internal/protocol/http/fetcher_checksum_test.go

@@ -0,0 +1,327 @@
+package http
+
+import (
+	"crypto/md5"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	gohttp "net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/internal/test"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/protocol/http"
+)
+
+func TestFetcher_ChecksumVerification(t *testing.T) {
+	content := []byte("Hello, Gopeed Checksum Verification Test Data!")
+	md5Hasher := md5.New()
+	md5Hasher.Write(content)
+	correctMd5 := hex.EncodeToString(md5Hasher.Sum(nil))
+
+	sha256Hasher := sha256.New()
+	sha256Hasher.Write(content)
+	correctSha256 := hex.EncodeToString(sha256Hasher.Sum(nil))
+
+	wrongHash := "0123456789abcdef0123456789abcdef"
+
+	server := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+		w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", len(content)))
+		w.Header().Set(base.HttpHeaderAcceptRanges, base.HttpHeaderBytes)
+		w.WriteHeader(gohttp.StatusOK)
+		_, _ = w.Write(content)
+	}))
+	defer server.Close()
+
+	t.Run("Valid MD5", func(t *testing.T) {
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_valid_md5.txt",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "md5",
+					Expected:  correctMd5,
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: server.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+
+		f.Meta().Opts = opts
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		if err := f.Wait(); err != nil {
+			t.Fatalf("Wait error (expected success): %v", err)
+		}
+	})
+
+	t.Run("Valid SHA256", func(t *testing.T) {
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_valid_sha256.txt",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "sha256",
+					Expected:  correctSha256,
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: server.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+
+		f.Meta().Opts = opts
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		if err := f.Wait(); err != nil {
+			t.Fatalf("Wait error (expected success): %v", err)
+		}
+	})
+
+	t.Run("Wrong MD5 mismatch", func(t *testing.T) {
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_wrong_md5.txt",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "md5",
+					Expected:  wrongHash,
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: server.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+
+		f.Meta().Opts = opts
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		err := f.Wait()
+		if err == nil {
+			t.Fatal("Wait expected checksum mismatch error, got nil")
+		}
+		if !strings.Contains(err.Error(), "checksum mismatch") {
+			t.Fatalf("expected 'checksum mismatch' in error, got %v", err)
+		}
+	})
+
+	t.Run("Unsupported Algorithm", func(t *testing.T) {
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_unsupported.txt",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "invalid-algo",
+					Expected:  wrongHash,
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: server.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		f.Meta().Opts = opts
+		err := f.Start()
+		if err == nil {
+			t.Fatal("Start expected error for unsupported algorithm, got nil")
+		}
+		if !strings.Contains(err.Error(), "unsupported checksum algorithm") {
+			t.Fatalf("expected 'unsupported checksum algorithm' in error, got %v", err)
+		}
+		if f.checksumFailed.Load() {
+			t.Fatal("checksumFailed flag should NOT be set on unsupported algorithm error")
+		}
+	})
+
+	t.Run("Case-Insensitive Hash Comparison", func(t *testing.T) {
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_case_insensitive.txt",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "sha256",
+					Expected:  strings.ToUpper(correctSha256),
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: server.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+
+		f.Meta().Opts = opts
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		if err := f.Wait(); err != nil {
+			t.Fatalf("Wait error (expected success with upper case hash): %v", err)
+		}
+	})
+
+	t.Run("Empty Expected Checksum (Skipped)", func(t *testing.T) {
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_empty_expected.txt",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "",
+					Expected:  "",
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: server.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+
+		f.Meta().Opts = opts
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		if err := f.Wait(); err != nil {
+			t.Fatalf("Wait error (expected skip and success): %v", err)
+		}
+	})
+
+	t.Run("Large File Multi-Chunk Streaming (>64KB)", func(t *testing.T) {
+		largeData := make([]byte, 128*1024)
+		for i := range largeData {
+			largeData[i] = byte(i % 256)
+		}
+		largeSha256Hasher := sha256.New()
+		largeSha256Hasher.Write(largeData)
+		largeSha256 := hex.EncodeToString(largeSha256Hasher.Sum(nil))
+
+		largeServer := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+			w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", len(largeData)))
+			w.Header().Set(base.HttpHeaderAcceptRanges, base.HttpHeaderBytes)
+			w.WriteHeader(gohttp.StatusOK)
+			_, _ = w.Write(largeData)
+		}))
+		defer largeServer.Close()
+
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_large_file.bin",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "sha256",
+					Expected:  largeSha256,
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: largeServer.URL + "/large.bin"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+
+		f.Meta().Opts = opts
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		if err := f.Wait(); err != nil {
+			t.Fatalf("Wait error (expected large file checksum success): %v", err)
+		}
+	})
+
+	t.Run("No Checksum (Opt-in backward compatibility)", func(t *testing.T) {
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: test.DownloadName,
+			Extra: &http.OptsExtra{
+				Connections: 1,
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: server.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+
+		f.Meta().Opts = opts
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		if err := f.Wait(); err != nil {
+			t.Fatalf("Wait error: %v", err)
+		}
+	})
+
+	t.Run("Invalid Checksum In Start Makes No Additional Requests", func(t *testing.T) {
+		var reqReceived atomic.Int32
+		customServer := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+			reqReceived.Add(1)
+			w.WriteHeader(gohttp.StatusOK)
+			_, _ = w.Write([]byte("some data"))
+		}))
+		defer customServer.Close()
+
+		f := buildFetcher()
+		defer f.Close()
+
+		opts := &base.Options{
+			Path: t.TempDir(),
+			Name: "test_invalid_checksum.txt",
+			Extra: &http.OptsExtra{
+				Connections: 1,
+				Checksum: &http.ChecksumOption{
+					Algorithm: "sha256",
+					Expected:  "invalid-hex-chars-not-valid-hex-00000000000000000000000000000000",
+				},
+			},
+		}
+
+		if err := f.Resolve(&base.Request{URL: customServer.URL + "/test.txt"}); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		requestsAfterResolve := reqReceived.Load()
+		f.Meta().Opts = opts
+		err := f.Start()
+		if err == nil {
+			t.Fatal("Start expected error for invalid checksum hash, got nil")
+		}
+		if got := reqReceived.Load(); got != requestsAfterResolve {
+			t.Fatalf("invalid checksum in Start issued additional requests: got %d, had %d after Resolve", got, requestsAfterResolve)
+		}
+	})
+}

internal/protocol/http/fetcher_manager.go

@@ -19,10 +19,11 @@ type fetcherData struct {
 	IfRange               string // Strong ETag or Last-Modified validator for safe resume
 	RangeReprobeEligible  bool   // Origin advertised Range before falling back to sequential mode
 	RangeValidatorPinned  bool   // Recovered Range mode must keep the same If-Range validator
-	SequentialSizeUnknown bool   // Interrupted chunked restart must retry from byte zero
+	SequentialSizeUnknown bool   // Interrupted chunked sequential streams restart from byte zero
+	SizeKnown             *bool  // Nil for legacy snapshots; false means Size is only a display estimate
 	Range                 *bool  // Authoritative Range mode; nil for records saved by older versions
-	ResourceSize          *int64 // Authoritative resource size from the same snapshot as Connections
-	FileSize              *int64 // Authoritative single-file size; nil for older records
+	ResourceSize          *int64 // Display size from the same snapshot; authority is recorded by SizeKnown
+	FileSize              *int64 // Single-file size from the same snapshot; nil for older records
 }
 
 // ============================================================================
@@ -93,6 +94,7 @@ func (fm *FetcherManager) Store(f fetcher.Fetcher) (data any, err error) {
 	rangeReprobeEligible := _f.rangeReprobeEligible
 	rangeValidatorPinned := _f.rangeValidatorPinned
 	sequentialSizeUnknown := _f.sequentialSizeUnknown
+	sizeKnown := _f.hasKnownSize()
 	var rangeMode *bool
 	var resourceSize *int64
 	var fileSize *int64
@@ -115,6 +117,7 @@ func (fm *FetcherManager) Store(f fetcher.Fetcher) (data any, err error) {
 		RangeReprobeEligible:  rangeReprobeEligible,
 		RangeValidatorPinned:  rangeValidatorPinned,
 		SequentialSizeUnknown: sequentialSizeUnknown,
+		SizeKnown:             &sizeKnown,
 		Range:                 rangeMode,
 		ResourceSize:          resourceSize,
 		FileSize:              fileSize,
@@ -168,6 +171,10 @@ func (fm *FetcherManager) Restore() (v any, f func(meta *fetcher.FetcherMeta, v
 		fetcher.rangeReprobeEligible = fd.RangeReprobeEligible
 		fetcher.rangeValidatorPinned = fd.RangeValidatorPinned
 		fetcher.sequentialSizeUnknown = fd.SequentialSizeUnknown
+		if fd.SizeKnown != nil {
+			known := *fd.SizeKnown
+			fetcher.sizeKnown = &known
+		}
 		if fd.Range != nil && fetcher.meta.Res != nil {
 			// Recovery-critical resource fields live in the same persisted snapshot
 			// as Connections, making them authoritative over task metadata that may

internal/protocol/http/fetcher_test.go

@@ -13,6 +13,7 @@ import (
 	"net/url"
 	"os"
 	"strings"
+	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -232,10 +233,11 @@ func TestFetcher_ResolveFilenameFromContentType(t *testing.T) {
 	defer fetcher.Pause()
 
 	const opaqueName = "OIP-C.u5nEXTXND3PJF0gNTgw5YgHaFP"
-	err := fetcher.Resolve(&base.Request{URL: server.URL + "/" + opaqueName}, &base.Options{
+	fetcher.Meta().Opts = &base.Options{
 		Name: test.DownloadName,
 		Path: test.Dir,
-	})
+	}
+	err := fetcher.Resolve(&base.Request{URL: server.URL + "/" + opaqueName})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -250,6 +252,10 @@ func TestFetcher_ResolveWithHostHeader(t *testing.T) {
 	defer listener.Close()
 
 	fetcher := buildFetcher()
+	fetcher.Meta().Opts = &base.Options{
+		Name: test.DownloadName,
+		Path: test.Dir,
+	}
 	err := fetcher.Resolve(&base.Request{
 		URL: "http://" + listener.Addr().String() + "/",
 		Extra: &http.ReqExtra{
@@ -257,9 +263,6 @@ func TestFetcher_ResolveWithHostHeader(t *testing.T) {
 				"Host": "test",
 			},
 		},
-	}, &base.Options{
-		Name: test.DownloadName,
-		Path: test.Dir,
 	})
 	// The server should return 400 for invalid Host header
 	if err == nil || !strings.Contains(err.Error(), "400") {
@@ -273,6 +276,10 @@ func TestFetcher_ResolveWithInvalidHeader(t *testing.T) {
 
 	fetcher := buildFetcher()
 	defer fetcher.Pause() // Close the resolve response to allow server shutdown
+	fetcher.Meta().Opts = &base.Options{
+		Name: test.DownloadName,
+		Path: test.Dir,
+	}
 	err := fetcher.Resolve(&base.Request{
 		URL: "http://" + listener.Addr().String() + "/",
 		Extra: &http.ReqExtra{
@@ -280,9 +287,6 @@ func TestFetcher_ResolveWithInvalidHeader(t *testing.T) {
 				"Referer": "\rtest",
 			},
 		},
-	}, &base.Options{
-		Name: test.DownloadName,
-		Path: test.Dir,
 	})
 	// Invalid header with \r should be sanitized by Go's http client, allowing the request to succeed
 	if err != nil {
@@ -302,12 +306,13 @@ func TestFetcher_ResolveAutomaticallyFallsBackToBrowserFingerprint(t *testing.T)
 
 	fetcher := buildFetcher()
 	defer fetcher.Pause()
+	fetcher.Meta().Opts = &base.Options{
+		Name: test.DownloadName,
+		Path: test.Dir,
+	}
 	err := fetcher.Resolve(&base.Request{
 		URL:            server.URL + "/file.bin",
 		SkipVerifyCert: true,
-	}, &base.Options{
-		Name: test.DownloadName,
-		Path: test.Dir,
 	})
 	if err != nil {
 		t.Fatalf("Resolve() error = %v", err)
@@ -368,11 +373,12 @@ func testResolve(startTestServer func() net.Listener, path string, t *testing.T,
 	defer listener.Close()
 	fetcher := buildFetcher()
 	defer fetcher.Pause() // Close the resolve response to allow server shutdown
-	err := fetcher.Resolve(&base.Request{
-		URL: "http://" + listener.Addr().String() + "/" + path,
-	}, &base.Options{
+	fetcher.Meta().Opts = &base.Options{
 		Name: test.DownloadName,
 		Path: test.Dir,
+	}
+	err := fetcher.Resolve(&base.Request{
+		URL: "http://" + listener.Addr().String() + "/" + path,
 	})
 	want, err := wantFn(err)
 	if err != nil {
@@ -424,13 +430,14 @@ func TestFetcher_PauseBeforeStartDiscardsPrefetchProgress(t *testing.T) {
 	defer server.Close()
 
 	fetcher := buildFetcher()
-	if err := fetcher.Resolve(&base.Request{URL: server.URL + "/" + test.BuildName}, &base.Options{
+	fetcher.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: test.DownloadName,
 		Extra: &http.OptsExtra{
 			Connections: 2,
 		},
-	}); err != nil {
+	}
+	if err := fetcher.Resolve(&base.Request{URL: server.URL + "/" + test.BuildName}); err != nil {
 		t.Fatal(err)
 	}
 	select {
@@ -771,13 +778,14 @@ func TestFetcher_SequentialRetryReprobesRange(t *testing.T) {
 			defer server.Close()
 
 			f := buildFetcher()
-			if err := f.Resolve(&base.Request{URL: server.URL + "/dynamic-range.data"}, &base.Options{
+			f.Meta().Opts = &base.Options{
 				Path: t.TempDir(),
 				Name: "dynamic-range.data",
 				Extra: &http.OptsExtra{
 					Connections: 4,
 				},
-			}); err != nil {
+			}
+			if err := f.Resolve(&base.Request{URL: server.URL + "/dynamic-range.data"}); err != nil {
 				t.Fatal(err)
 			}
 			if err := f.Start(); err != nil {
@@ -853,31 +861,44 @@ func TestFetcher_InitialIgnoredRangeUsesResponseSize(t *testing.T) {
 	resolvePayload := bytes.Repeat([]byte("resolve"), 64*1024)
 	replacement := bytes.Repeat([]byte("replacement"), 24*1024)
 	var rangeRequests atomic.Int32
+	rangeStarted := make(chan struct{})
+	releaseResolve := sync.OnceFunc(func() { close(rangeStarted) })
 
 	server := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
 		w.Header().Set(base.HttpHeaderAcceptRanges, base.HttpHeaderBytes)
 		if r.Header.Get(base.HttpHeaderRange) == "" {
 			w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", len(resolvePayload)))
 			w.WriteHeader(gohttp.StatusOK)
+			w.(gohttp.Flusher).Flush()
+			// Keep Resolve prefetch incomplete until the Range request starts.
+			// Otherwise Start may reuse the completed body and skip this scenario.
+			select {
+			case <-rangeStarted:
+			case <-r.Context().Done():
+				return
+			}
 			_, _ = w.Write(resolvePayload)
 			return
 		}
 
 		rangeRequests.Add(1)
+		releaseResolve()
 		w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", len(replacement)))
 		w.WriteHeader(gohttp.StatusOK)
 		_, _ = w.Write(replacement)
 	}))
 	defer server.Close()
+	defer releaseResolve()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/ignored-range.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: "ignored-range.data",
 		Extra: &http.OptsExtra{
 			Connections: 4,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/ignored-range.data"}); err != nil {
 		t.Fatal(err)
 	}
 	if err := f.Start(); err != nil {
@@ -968,13 +989,14 @@ func TestFetcher_InterruptedChunkedReplacementRestartsFromZero(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/chunked-replacement.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: "chunked-replacement.data",
 		Extra: &http.OptsExtra{
 			Connections: 4,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/chunked-replacement.data"}); err != nil {
 		t.Fatal(err)
 	}
 	if err := f.Start(); err != nil {
@@ -1154,13 +1176,14 @@ func TestFetcher_UsesResolveResponseWhenRangeTakeoverFails(t *testing.T) {
 			defer server.Close()
 
 			f := buildFetcher()
-			if err := f.Resolve(&base.Request{URL: server.URL + "/resolve-fallback.data"}, &base.Options{
+			f.Meta().Opts = &base.Options{
 				Path: t.TempDir(),
 				Name: "resolve-fallback.data",
 				Extra: &http.OptsExtra{
 					Connections: 1,
 				},
-			}); err != nil {
+			}
+			if err := f.Resolve(&base.Request{URL: server.URL + "/resolve-fallback.data"}); err != nil {
 				t.Fatal(err)
 			}
 			defer f.Close()
@@ -1233,13 +1256,14 @@ func TestFetcher_ValidRangeTakesOverResolveResponse(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/resolve-takeover.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: "resolve-takeover.data",
 		Extra: &http.OptsExtra{
 			Connections: 4,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/resolve-takeover.data"}); err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
@@ -1263,6 +1287,12 @@ func TestFetcher_ValidRangeTakesOverResolveResponse(t *testing.T) {
 }
 
 func TestFetcher_UnknownSizeRangeUsesOpenEndedWorker(t *testing.T) {
+	for _, hint := range []int64{0, 3, 8 * 1024 * 1024} {
+		t.Run(fmt.Sprint(hint), func(t *testing.T) { testFetcherUnknownSizeRange(t, hint) })
+	}
+}
+
+func testFetcherUnknownSizeRange(t *testing.T, hint int64) {
 	const resolveETag = `"unknown-size-v1"`
 	payload := make([]byte, 4*1024*1024)
 	for i := range payload {
@@ -1327,18 +1357,20 @@ func TestFetcher_UnknownSizeRangeUsesOpenEndedWorker(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/unknown-size-range.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
+		Size: hint,
 		Path: t.TempDir(),
 		Name: "unknown-size-range.data",
 		Extra: &http.OptsExtra{
 			Connections: 4,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/unknown-size-range.data"}); err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
 
-	if f.meta.Res.Size != 0 || !f.meta.Res.Range {
+	if f.meta.Res.Size != hint || f.hasKnownSize() || !f.meta.Res.Range {
 		t.Fatalf("resolved resource = %+v, want unknown size with Range support", f.meta.Res)
 	}
 	if err := f.Start(); err != nil {
@@ -1421,13 +1453,14 @@ func TestFetcher_UnknownSizeRangeRetriesShortPartialBody(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/short-range.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: "short-range.data",
 		Extra: &http.OptsExtra{
 			Connections: 1,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/short-range.data"}); err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
@@ -1480,13 +1513,14 @@ func TestFetcher_UnknownSizeRangeFallsBackToResolve(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/unknown-size-fallback.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: "unknown-size-fallback.data",
 		Extra: &http.OptsExtra{
 			Connections: 1,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/unknown-size-fallback.data"}); err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
@@ -1567,13 +1601,15 @@ func TestFetcher_UnknownSizeRangeRemainsOpenEndedAfterPause(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/pause-open-range.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
+		Size: 3,
 		Path: t.TempDir(),
 		Name: "pause-open-range.data",
 		Extra: &http.OptsExtra{
 			Connections: 1,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/pause-open-range.data"}); err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
@@ -1622,13 +1658,14 @@ func TestFetcher_UnknownSizeResolveReadErrorFailsTask(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/broken-chunked.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: "broken-chunked.data",
 		Extra: &http.OptsExtra{
 			Connections: 1,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/broken-chunked.data"}); err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
@@ -1654,13 +1691,14 @@ func TestFetcher_UnknownSizeResolveCleanEOFUpdatesSize(t *testing.T) {
 	defer server.Close()
 
 	f := buildFetcher()
-	if err := f.Resolve(&base.Request{URL: server.URL + "/unknown-size.data"}, &base.Options{
+	f.Meta().Opts = &base.Options{
 		Path: t.TempDir(),
 		Name: "unknown-size.data",
 		Extra: &http.OptsExtra{
 			Connections: 1,
 		},
-	}); err != nil {
+	}
+	if err := f.Resolve(&base.Request{URL: server.URL + "/unknown-size.data"}); err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
@@ -2256,14 +2294,15 @@ func TestFetcher_DownloadOneTimeURL(t *testing.T) {
 	defer listener.Close()
 
 	fetcher := buildFetcher()
-	err := fetcher.Resolve(&base.Request{
-		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-	}, &base.Options{
+	fetcher.Meta().Opts = &base.Options{
 		Name: test.DownloadName,
 		Path: test.Dir,
 		Extra: &http.OptsExtra{
 			Connections: 4, // Try to use multiple connections, but only first should work
 		},
+	}
+	err := fetcher.Resolve(&base.Request{
+		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -2322,14 +2361,15 @@ func TestFetcher_SlowStartExpansion(t *testing.T) {
 				Connections: tc.maxConns,
 			})
 
-			err := fetcher.Resolve(&base.Request{
-				URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-			}, &base.Options{
+			fetcher.Meta().Opts = &base.Options{
 				Name: test.DownloadName,
 				Path: test.Dir,
 				Extra: &http.OptsExtra{
 					Connections: tc.maxConns,
 				},
+			}
+			err := fetcher.Resolve(&base.Request{
+				URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 			})
 			if err != nil {
 				cleanup()
@@ -2385,14 +2425,15 @@ func TestFetcher_AsyncPrefetch(t *testing.T) {
 		defer listener.Close()
 
 		fetcher := buildFetcher()
-		err := fetcher.Resolve(&base.Request{
-			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-		}, &base.Options{
+		fetcher.Meta().Opts = &base.Options{
 			Name: test.DownloadName,
 			Path: test.Dir,
 			Extra: &http.OptsExtra{
 				Connections: 4,
 			},
+		}
+		err := fetcher.Resolve(&base.Request{
+			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 		})
 		if err != nil {
 			t.Fatal(err)
@@ -2456,14 +2497,15 @@ func TestFetcher_AsyncPrefetch(t *testing.T) {
 		defer listener.Close()
 
 		fetcher := buildFetcher()
-		err := fetcher.Resolve(&base.Request{
-			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-		}, &base.Options{
+		fetcher.Meta().Opts = &base.Options{
 			Name: test.DownloadName,
 			Path: test.Dir,
 			Extra: &http.OptsExtra{
 				Connections: 4,
 			},
+		}
+		err := fetcher.Resolve(&base.Request{
+			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 		})
 		if err != nil {
 			t.Fatal(err)
@@ -2538,14 +2580,15 @@ func TestFetcher_DownloadExpiringRedirectURL(t *testing.T) {
 		defer listener.Close()
 
 		fetcher := buildFetcher()
-		err := fetcher.Resolve(&base.Request{
-			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-		}, &base.Options{
+		fetcher.Meta().Opts = &base.Options{
 			Name: test.DownloadName,
 			Path: test.Dir,
 			Extra: &http.OptsExtra{
 				Connections: 4, // Use multiple connections to trigger redirect expiration
 			},
+		}
+		err := fetcher.Resolve(&base.Request{
+			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 		})
 		if err != nil {
 			t.Fatal(err)
@@ -2579,14 +2622,15 @@ func TestFetcher_DownloadExpiringRedirectURL(t *testing.T) {
 		defer listener.Close()
 
 		fetcher := buildFetcher()
-		err := fetcher.Resolve(&base.Request{
-			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-		}, &base.Options{
+		fetcher.Meta().Opts = &base.Options{
 			Name: test.DownloadName,
 			Path: test.Dir,
 			Extra: &http.OptsExtra{
 				Connections: 8,
 			},
+		}
+		err := fetcher.Resolve(&base.Request{
+			URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 		})
 		if err != nil {
 			t.Fatal(err)
@@ -2626,14 +2670,15 @@ func TestFetcher_RetryAfterError(t *testing.T) {
 	defer listener.Close()
 
 	fetcher := buildFetcher()
-	err := fetcher.Resolve(&base.Request{
-		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-	}, &base.Options{
+	fetcher.Meta().Opts = &base.Options{
 		Name: test.DownloadName,
 		Path: test.Dir,
 		Extra: &http.OptsExtra{
 			Connections: 1, // Use single connection to simplify test
 		},
+	}
+	err := fetcher.Resolve(&base.Request{
+		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -3054,9 +3099,10 @@ func doDownloadReady(f fetcher.Fetcher, listener net.Listener, connections int,
 		Path:  test.Dir,
 		Extra: extra,
 	}
+	f.Meta().Opts = opts
 	err := f.Resolve(&base.Request{
 		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-	}, opts)
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3105,7 +3151,8 @@ func downloadPost(listener net.Listener, connections int, t *testing.T) {
 			Body: fmt.Sprintf(`{"name":"%s"}`, test.BuildName),
 		},
 	}
-	err := f.Resolve(req, opts)
+	f.Meta().Opts = opts
+	err := f.Resolve(req)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3151,11 +3198,12 @@ func downloadContinue(listener net.Listener, connections int, t *testing.T) {
 
 func downloadError(listener net.Listener, connections int, t *testing.T) {
 	fetcher := buildFetcher()
-	err := fetcher.Resolve(&base.Request{
-		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-	}, &base.Options{
+	fetcher.Meta().Opts = &base.Options{
 		Name: test.DownloadName,
 		Path: test.Dir,
+	}
+	err := fetcher.Resolve(&base.Request{
+		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 	})
 	// With the new async design, Resolve may succeed (HTTP response received)
 	// but errors occur during async download or Start/Wait
@@ -3279,7 +3327,8 @@ func TestFetcher_Patch_URLChange(t *testing.T) {
 	}
 
 	// Step 1: Try to resolve with bad URL - should fail with error
-	err := f.Resolve(&base.Request{URL: badURL}, opts)
+	f.Meta().Opts = opts
+	err := f.Resolve(&base.Request{URL: badURL})
 	if err == nil {
 		t.Fatal("Expected error for bad URL, got nil")
 	}
@@ -3289,7 +3338,8 @@ func TestFetcher_Patch_URLChange(t *testing.T) {
 	f2 := buildFetcher()
 
 	// First resolve with good URL to create a valid fetcher state
-	err = f2.Resolve(&base.Request{URL: goodURL}, opts)
+	f2.Meta().Opts = opts
+	err = f2.Resolve(&base.Request{URL: goodURL})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3341,13 +3391,14 @@ func TestFetcher_Patch_Labels(t *testing.T) {
 		Extra: &http.OptsExtra{Connections: 1},
 	}
 
+	f.Meta().Opts = opts
 	err := f.Resolve(&base.Request{
 		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 		Labels: map[string]string{
 			"key1": "value1",
 			"key3": "value3",
 		},
-	}, opts)
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3398,6 +3449,7 @@ func TestFetcher_Patch_Extra(t *testing.T) {
 	}
 
 	// Resolve with initial Extra
+	f.Meta().Opts = opts
 	err := f.Resolve(&base.Request{
 		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
 		Extra: &http.ReqExtra{
@@ -3408,7 +3460,7 @@ func TestFetcher_Patch_Extra(t *testing.T) {
 				"X-Custom":      "original",
 			},
 		},
-	}, opts)
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3486,9 +3538,10 @@ func TestFetcher_Patch_NilData(t *testing.T) {
 		Extra: &http.OptsExtra{Connections: 1},
 	}
 
+	f.Meta().Opts = opts
 	err := f.Resolve(&base.Request{
 		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
-	}, opts)
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3538,6 +3591,7 @@ func TestFetcher_Patch_CookieExpired(t *testing.T) {
 
 	// Step 1: Resolve with old_token - should succeed (first request accepts old_token)
 	f := buildFetcher()
+	f.Meta().Opts = opts
 	err := f.Resolve(&base.Request{
 		URL: downloadURL,
 		Extra: &http.ReqExtra{
@@ -3545,7 +3599,7 @@ func TestFetcher_Patch_CookieExpired(t *testing.T) {
 				"Cookie": "session=old_token",
 			},
 		},
-	}, opts)
+	})
 	if err != nil {
 		t.Fatalf("Resolve should succeed with old_token: %v", err)
 	}

internal/protocol/http/resolve_range_test.go

@@ -0,0 +1,121 @@
+package http
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+	fhttp "github.com/GopeedLab/gopeed/pkg/protocol/http"
+)
+
+func TestResolveResponseSize(t *testing.T) {
+	for _, tc := range []struct {
+		name                 string
+		status               int
+		length, contentRange string
+		size                 int64
+		invalid              bool
+	}{
+		{"full", 200, "801571015", "", 801571015, false},
+		{"partial_prefix", 206, "472321339", "bytes 0-472321338/801571015", 801571015, false},
+		{"partial_nonzero", 206, "100000", "bytes 100000-199999/801571015", 801571015, false},
+		{"second_report", 206, "335134409", "bytes 0-335134408/552140234", 552140234, false},
+		{"length_mismatch", 206, "10", "bytes 0-19/100", 0, true},
+		{"unknown_total", 206, "472321339", "bytes 0-472321338/*", 0, true},
+		{"missing_range", 206, "10", "", 0, true},
+		{"malformed_range", 206, "10", "bytes invalid", 0, true},
+		{"invalid_bounds", 206, "10", "bytes 20-10/100", 0, true},
+		{"invalid_total", 206, "10", "bytes 0-9/9", 0, true},
+		{"overflow", 206, "10", "bytes 0-9/9223372036854775808", 0, true},
+		{"chunked_partial", 206, "", "bytes 0-9/100", 100, false},
+		{"unknown_full", 200, "", "", 0, false},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if tc.length != "" {
+					w.Header().Set("Content-Length", tc.length)
+				}
+				if tc.contentRange != "" {
+					w.Header().Set("Content-Range", tc.contentRange)
+				}
+				w.WriteHeader(tc.status)
+				w.(http.Flusher).Flush()
+			}))
+			defer server.Close()
+			f := buildFetcher()
+			defer f.Close()
+			f.Meta().Opts = &base.Options{Path: t.TempDir()}
+			err := f.Resolve(&base.Request{URL: server.URL + "/file"})
+			if tc.invalid {
+				if !errors.Is(err, errInvalidRangeResponse) {
+					t.Fatalf("Resolve error = %v, want invalid range", err)
+				}
+				if f.meta.Res != nil || f.resolveResp != nil || f.getState() != stateError {
+					t.Fatal("invalid response was retained or published")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			if f.meta.Res.Size != tc.size || f.meta.Res.Files[0].Size != tc.size {
+				t.Fatalf("resource/file size = %d/%d, want %d", f.meta.Res.Size, f.meta.Res.Files[0].Size, tc.size)
+			}
+			if tc.status == 206 && !f.meta.Res.Range {
+				t.Fatal("partial response must enable Range downloads")
+			}
+		})
+	}
+}
+
+func TestDownloadPartialResolve(t *testing.T) {
+	payload := make([]byte, 256*1024)
+	for i := range payload {
+		payload[i] = byte(i*31 + i/251)
+	}
+	for _, start := range []int{0, 100000} {
+		for _, connections := range []int{1, 4} {
+			t.Run(fmt.Sprintf("start_%d_connections_%d", start, connections), func(t *testing.T) {
+				server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					begin, end := start, start+9999
+					if h := r.Header.Get("Range"); h != "" {
+						if _, err := fmt.Sscanf(h, "bytes=%d-%d", &begin, &end); err != nil {
+							t.Errorf("invalid request range %q: %v", h, err)
+							w.WriteHeader(400)
+							return
+						}
+					}
+					w.Header().Set("Content-Length", fmt.Sprint(end-begin+1))
+					w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", begin, end, len(payload)))
+					w.WriteHeader(206)
+					w.Write(payload[begin : end+1])
+				}))
+				defer server.Close()
+				f := buildFetcher()
+				defer f.Close()
+				f.Meta().Opts = &base.Options{Path: t.TempDir(), Name: "file", Extra: &fhttp.OptsExtra{Connections: connections}}
+				if err := f.Resolve(&base.Request{URL: server.URL + "/file"}); err != nil {
+					t.Fatal(err)
+				}
+				if err := f.Start(); err != nil {
+					t.Fatal(err)
+				}
+				if err := f.Wait(); err != nil {
+					t.Fatal(err)
+				}
+				got, err := os.ReadFile(f.meta.SingleFilepath())
+				if err != nil {
+					t.Fatal(err)
+				}
+				if !bytes.Equal(got, payload) {
+					t.Fatalf("download content mismatch: got %d bytes, want %d", len(got), len(payload))
+				}
+			})
+		}
+	}
+}

internal/protocol/http/restore_prefetch_test.go

@@ -0,0 +1,79 @@
+package http
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/controller"
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/internal/test"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	fhttp "github.com/GopeedLab/gopeed/pkg/protocol/http"
+)
+
+func TestFetcher_RestoredStartSkipsAbsentPrefetch(t *testing.T) {
+	data := bytes.Repeat([]byte("0123456789abcdef"), 64*1024)
+	var firstRequest atomic.Int64
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		firstRequest.CompareAndSwap(0, time.Now().UnixNano())
+		http.ServeContent(w, r, "restored.bin", time.Time{}, bytes.NewReader(data))
+	}))
+	defer server.Close()
+
+	dir := t.TempDir()
+	size := int64(len(data))
+	half := size / 2
+	file := filepath.Join(dir, "restored.bin")
+	if err := os.WriteFile(file, data[:half], 0600); err != nil {
+		t.Fatal(err)
+	}
+	conn := &connection{ID: 0, Role: rolePrimary, State: connNotStarted, Chunk: newChunk(0, size-1), Downloaded: half}
+	conn.Chunk.Downloaded = half
+	rangeMode := true
+	saved := &fetcherData{Connections: []*connection{conn}, Range: &rangeMode, ResourceSize: &size, FileSize: &size}
+	meta := &fetcher.FetcherMeta{
+		Req:  &base.Request{URL: server.URL + "/restored.bin"},
+		Res:  &base.Resource{Size: size, Range: true, Files: []*base.FileInfo{{Name: "restored.bin", Size: size}}},
+		Opts: &base.Options{Path: dir, Name: "restored.bin", Extra: &fhttp.OptsExtra{Connections: 1}},
+	}
+	fm := new(FetcherManager)
+	_, restore := fm.Restore()
+	f := restore(meta, saved).(*Fetcher)
+	ctl := controller.NewController()
+	ctl.GetConfig = func(v any) {
+		if err := json.Unmarshal([]byte(test.ToJson(fm.DefaultConfig())), v); err != nil {
+			t.Error(err)
+		}
+	}
+	f.Setup(ctl)
+	defer f.Close()
+	started := time.Now()
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	actual, err := os.ReadFile(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(actual, data) {
+		t.Fatal("restored download differs from the complete server content")
+	}
+	if firstRequest.Load() == 0 {
+		t.Fatal("restored download did not request the remaining content")
+	}
+	delay := time.Duration(firstRequest.Load() - started.UnixNano())
+	t.Logf("first restored request after %s", delay)
+	if delay > 2*time.Second {
+		t.Errorf("restored download waited %s before its first request", delay)
+	}
+}

internal/protocol/http/size_hint_test.go

@@ -0,0 +1,245 @@
+package http
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+func TestFetcher_OptionsSizeHintAndPatch(t *testing.T) {
+	for _, known := range []bool{false, true} {
+		for _, payload := range []string{"", "0123456789"} {
+			t.Run(fmt.Sprintf("known=%v/bytes=%d", known, len(payload)), func(t *testing.T) {
+				server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+					if known {
+						w.Header().Set("Content-Length", fmt.Sprint(len(payload)))
+					}
+					w.(http.Flusher).Flush()
+					fmt.Fprint(w, payload)
+				}))
+				defer server.Close()
+				f := buildFetcher()
+				defer f.Close()
+				f.Meta().Opts = &base.Options{Size: 7, Path: t.TempDir(), Name: "output.bin"}
+				if err := f.Resolve(&base.Request{URL: server.URL}); err != nil {
+					t.Fatal(err)
+				}
+				want := int64(7)
+				if known {
+					want = int64(len(payload))
+				}
+				if f.meta.Res.Size != want || f.hasKnownSize() != known {
+					t.Fatalf("resolved size=%d known=%v", f.meta.Res.Size, f.hasKnownSize())
+				}
+				if err := f.Patch(nil, &base.Options{Size: 9}); err != nil {
+					t.Fatal(err)
+				}
+				if !known {
+					want = 9
+				}
+				if f.meta.Res.Size != want {
+					t.Fatal("hint update overrode a real size or failed to update an estimate")
+				}
+				if err := f.Start(); err != nil {
+					t.Fatal(err)
+				}
+				if err := f.Wait(); err != nil {
+					t.Fatal(err)
+				}
+				if f.meta.Res.Size != int64(len(payload)) || !f.hasKnownSize() {
+					t.Fatalf("final size=%d known=%v", f.meta.Res.Size, f.hasKnownSize())
+				}
+				snapshot, err := new(FetcherManager).Store(f)
+				if err != nil {
+					t.Fatal(err)
+				}
+				fd := snapshot.(*fetcherData)
+				if fd.SizeKnown == nil || !*fd.SizeKnown {
+					t.Fatal("snapshot lost confirmed size authority")
+				}
+				_, restore := new(FetcherManager).Restore()
+				restored := restore(f.meta, fd).(*Fetcher)
+				if !restored.hasKnownSize() || restored.knownSize() != int64(len(payload)) {
+					t.Fatal("restored size lost authority, including known zero")
+				}
+			})
+		}
+	}
+}
+
+func TestFetcher_SizeHintCannotCompleteForbiddenUnknownRange(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Range") != "" {
+			w.WriteHeader(http.StatusForbidden)
+			return
+		}
+		w.Header().Set("Accept-Ranges", "bytes")
+		w.(http.Flusher).Flush()
+		fmt.Fprint(w, "0123456789")
+		w.(http.Flusher).Flush()
+		<-r.Context().Done()
+	}))
+	defer server.Close()
+	f := buildFetcher()
+	defer f.Close()
+	f.Meta().Opts = &base.Options{Size: 3, Path: t.TempDir(), Name: "output.bin"}
+	if err := f.Resolve(&base.Request{URL: server.URL}); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err == nil {
+		t.Fatal("a failed unknown-length Range request was completed from an estimate")
+	}
+}
+
+func TestFetcher_SizeHintPreservesHTTPIntegrity(t *testing.T) {
+	for _, chunked := range []bool{false, true} {
+		for _, broken := range []bool{false, true} {
+			t.Run(fmt.Sprintf("chunked=%v/broken=%v", chunked, broken), func(t *testing.T) {
+				payload := []byte("0123456789")
+				server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+					if chunked && broken {
+						conn, rw, err := w.(http.Hijacker).Hijack()
+						if err != nil {
+							t.Error(err)
+							return
+						}
+						defer conn.Close()
+						fmt.Fprint(rw, "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\nConnection: close\r\n\r\na\r\n0123456789\r\n")
+						rw.Flush() // Omit the final chunk to simulate a connection interruption.
+						return
+					}
+					if !chunked {
+						length := len(payload)
+						if broken {
+							length++
+						}
+						w.Header().Set("Content-Length", fmt.Sprint(length))
+					}
+					w.(http.Flusher).Flush()
+					w.Write(payload)
+				}))
+				defer server.Close()
+				f := buildFetcher()
+				defer f.Close()
+				f.Meta().Opts = &base.Options{Size: 3, Path: t.TempDir(), Name: "output.bin"}
+				if err := f.Resolve(&base.Request{URL: server.URL}); err != nil {
+					t.Fatal(err)
+				}
+				if !chunked {
+					length := int64(len(payload))
+					if broken {
+						length++
+					}
+					if f.meta.Res.Size != length || f.sequentialSizeUnknown {
+						t.Fatal("HTTP length did not override size hint")
+					}
+				} else if f.meta.Res.Size != 3 || !f.sequentialSizeUnknown {
+					t.Fatal("unknown HTTP length did not retain the display hint")
+				}
+				if err := f.Start(); err != nil {
+					t.Fatal(err)
+				}
+				err := f.Wait()
+				if broken {
+					if err == nil {
+						t.Fatal("truncated HTTP response succeeded after exceeding the size hint")
+					}
+					return
+				}
+				if err != nil {
+					t.Fatal(err)
+				}
+				if f.meta.Res.Size != int64(len(payload)) || f.sequentialSizeUnknown {
+					t.Fatalf("completed size=%d unknown=%v", f.meta.Res.Size, f.sequentialSizeUnknown)
+				}
+			})
+		}
+	}
+}
+
+func TestFetcher_SizeHintSurvivesRestore(t *testing.T) {
+	for _, partial := range []bool{false, true} {
+		for _, fixedLength := range []bool{false, true} {
+			t.Run(fmt.Sprintf("partial=%v/fixedLength=%v", partial, fixedLength), func(t *testing.T) {
+				payload := []byte("0123456789")
+				var requests atomic.Int64
+				server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					request := requests.Add(1)
+					if got := r.Header.Get("Range"); got != "" {
+						t.Errorf("estimated sizes must not be used for resume ranges: %s", got)
+					}
+					if fixedLength && request > 1 {
+						w.Header().Set("Content-Length", fmt.Sprint(len(payload)))
+					}
+					w.(http.Flusher).Flush()
+					if fixedLength && request == 2 {
+						w.Write(payload[:4]) // Retry must discard this interrupted attempt.
+						return
+					}
+					w.Write(payload)
+				}))
+				defer server.Close()
+				f := buildFetcher()
+				opts := &base.Options{Size: 3, Path: t.TempDir(), Name: "output.bin"}
+				f.Meta().Opts = opts
+				if err := f.Resolve(&base.Request{URL: server.URL}); err != nil {
+					t.Fatal(err)
+				}
+				fm := new(FetcherManager)
+				snapshot, err := fm.Store(f)
+				if err != nil {
+					t.Fatal(err)
+				}
+				data, err := json.Marshal(snapshot)
+				if err != nil {
+					t.Fatal(err)
+				}
+				var saved fetcherData
+				if err := json.Unmarshal(data, &saved); err != nil {
+					t.Fatal(err)
+				}
+				if !saved.SequentialSizeUnknown || saved.SizeKnown == nil || *saved.SizeKnown || *saved.ResourceSize != 3 {
+					t.Fatal("snapshot lost the size hint or its advisory state")
+				}
+				f.Close()
+				// An interrupted earlier attempt left a tail longer than the new output.
+				if err := os.WriteFile(filepath.Join(opts.Path, opts.Name), bytes.Repeat([]byte("old"), 100), 0600); err != nil {
+					t.Fatal(err)
+				}
+				if partial {
+					chunk := newChunk(0, 0)
+					chunk.Downloaded = 7 // Already exceeds the display estimate.
+					saved.Connections = []*connection{{ID: 0, Role: rolePrimary, State: connNotStarted, Chunk: chunk, Downloaded: 7}}
+				}
+				_, restore := fm.Restore()
+				restored := restore(f.meta, &saved).(*Fetcher)
+				restored.Setup(f.ctl)
+				defer restored.Close()
+				if err := restored.Start(); err != nil {
+					t.Fatal(err)
+				}
+				if err := restored.Wait(); err != nil {
+					t.Fatal(err)
+				}
+				body, err := os.ReadFile(restored.meta.SingleFilepath())
+				if err != nil {
+					t.Fatal(err)
+				}
+				if !bytes.Equal(body, payload) || restored.meta.Res.Size != int64(len(payload)) || restored.Progress().TotalDownloaded() != int64(len(payload)) {
+					t.Fatalf("restored stream retained an estimate or stale bytes: body=%q size=%d progress=%d", body, restored.meta.Res.Size, restored.Progress().TotalDownloaded())
+				}
+			})
+		}
+	}
+}

internal/protocol/http/timeout_reader.go

@@ -6,35 +6,56 @@ import (
 	"time"
 )
 
+// TimeoutReader fails a Read that makes no progress within timeout.
+//
+// One timer per reader is armed when Read starts and stopped before it
+// returns, so time the caller spends between reads is not counted. If the
+// timer fires, it calls cancel, which should cancel the HTTP request the
+// reader belongs to so the transport unblocks the pending Read. Read still
+// waits for the underlying Read to return; that Read and every later one
+// return context.DeadlineExceeded. Errors from any other cancellation are
+// returned unchanged, and closing the response body is left to the caller.
+//
+// With a nil cancel the pending Read cannot be interrupted; it still reports
+// context.DeadlineExceeded, but only once it returns.
+//
+// TimeoutReader is not safe for concurrent use.
 type TimeoutReader struct {
-	reader  io.Reader
-	timeout time.Duration
+	reader   io.Reader
+	timeout  time.Duration
+	cancel   context.CancelFunc
+	timer    *time.Timer
+	timedOut bool
 }
 
-func NewTimeoutReader(r io.Reader, timeout time.Duration) *TimeoutReader {
+func NewTimeoutReader(r io.Reader, timeout time.Duration, cancel context.CancelFunc) *TimeoutReader {
+	if cancel == nil {
+		cancel = func() {}
+	}
 	return &TimeoutReader{
 		reader:  r,
 		timeout: timeout,
+		cancel:  cancel,
 	}
 }
 
 func (tr *TimeoutReader) Read(p []byte) (n int, err error) {
-	ctx, cancel := context.WithTimeout(context.Background(), tr.timeout)
-	defer cancel()
-
-	done := make(chan struct{})
-	var readErr error
-	var bytesRead int
-
-	go func() {
-		bytesRead, readErr = tr.reader.Read(p)
-		close(done)
-	}()
-
-	select {
-	case <-done:
-		return bytesRead, readErr
-	case <-ctx.Done():
-		return 0, ctx.Err()
+	if tr.timedOut {
+		return 0, context.DeadlineExceeded
 	}
+	if tr.timer == nil {
+		tr.timer = time.AfterFunc(tr.timeout, tr.cancel)
+	} else {
+		tr.timer.Reset(tr.timeout)
+	}
+
+	n, err = tr.reader.Read(p)
+
+	if !tr.timer.Stop() {
+		// The timer fired during this Read and cancelled the request, so err is
+		// whatever the interrupted read produced. Report the timeout instead.
+		tr.timedOut = true
+		return n, context.DeadlineExceeded
+	}
+	return n, err
 }

internal/protocol/http/timeout_reader_test.go

@@ -2,17 +2,26 @@ package http
 
 import (
 	"bytes"
+	"compress/gzip"
 	"context"
+	"crypto/tls"
+	"crypto/x509"
 	"errors"
 	"io"
+	gohttp "net/http"
+	"net/http/httptest"
+	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
+
+	"github.com/GopeedLab/gopeed/internal/httpclient"
 )
 
 func TestTimeoutReader_Read(t *testing.T) {
 	data := []byte("Hello, World!")
 	reader := bytes.NewReader(data)
-	timeoutReader := NewTimeoutReader(reader, 1*time.Second)
+	timeoutReader := NewTimeoutReader(reader, 1*time.Second, nil)
 
 	buf := make([]byte, len(data))
 	n, err := timeoutReader.Read(buf)
@@ -29,7 +38,7 @@ func TestTimeoutReader_Read(t *testing.T) {
 
 func TestTimeoutReader_ReadTimeout(t *testing.T) {
 	reader := &slowReader{delay: 2 * time.Second}
-	timeoutReader := NewTimeoutReader(reader, 1*time.Second)
+	timeoutReader := NewTimeoutReader(reader, 1*time.Second, nil)
 
 	buf := make([]byte, 8192)
 	_, err := timeoutReader.Read(buf)
@@ -49,3 +58,340 @@ func (sr *slowReader) Read(p []byte) (n int, err error) {
 	time.Sleep(sr.delay)
 	return 0, io.EOF
 }
+
+// The timer must only cover time spent inside Read, not caller work between reads.
+func TestTimeoutReader_IdleBetweenReads(t *testing.T) {
+	var cancelled atomic.Bool
+	timeoutReader := NewTimeoutReader(bytes.NewReader([]byte("abcdef")), 50*time.Millisecond, func() {
+		cancelled.Store(true)
+	})
+
+	buf := make([]byte, 3)
+	if _, err := timeoutReader.Read(buf); err != nil {
+		t.Fatalf("first read: %v", err)
+	}
+	time.Sleep(200 * time.Millisecond)
+	if _, err := timeoutReader.Read(buf); err != nil {
+		t.Fatalf("second read after idle: %v", err)
+	}
+	if cancelled.Load() {
+		t.Fatal("request was cancelled while idle between reads")
+	}
+}
+
+// A timed-out Read must not return while the underlying Read can still write
+// into the caller's buffer, and must leave closing the reader to the caller.
+func TestTimeoutReader_TimedOutReadDoesNotOutliveCaller(t *testing.T) {
+	reader := &lateWriteReader{cancelled: make(chan struct{})}
+	timeoutReader := NewTimeoutReader(reader, 50*time.Millisecond, reader.cancel)
+
+	buf := make([]byte, 8)
+	_, err := timeoutReader.Read(buf)
+	if !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatalf("expected %v, got %v", context.DeadlineExceeded, err)
+	}
+	if !reader.returned.Load() {
+		t.Fatal("Read returned before the underlying Read finished")
+	}
+	if _, err := timeoutReader.Read(buf); !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatalf("read after timeout: expected %v, got %v", context.DeadlineExceeded, err)
+	}
+	if reader.closed.Load() {
+		t.Fatal("reader was closed by the timeout")
+	}
+}
+
+// lateWriteReader blocks until cancelled, then writes into p before returning.
+type lateWriteReader struct {
+	cancelOnce sync.Once
+	cancelled  chan struct{}
+	returned   atomic.Bool
+	closed     atomic.Bool
+}
+
+func (r *lateWriteReader) Read(p []byte) (int, error) {
+	<-r.cancelled
+	time.Sleep(20 * time.Millisecond)
+	p[0] = 'x'
+	r.returned.Store(true)
+	return 0, context.Canceled
+}
+
+func (r *lateWriteReader) cancel() {
+	r.cancelOnce.Do(func() { close(r.cancelled) })
+}
+
+func (r *lateWriteReader) Close() error {
+	r.closed.Store(true)
+	return nil
+}
+
+type timeoutReaderClientCase struct {
+	name   string
+	http2  bool
+	client func(t *testing.T, server *httptest.Server) *gohttp.Client
+}
+
+func timeoutReaderClientCases() []timeoutReaderClientCase {
+	newClient := func(mode httpclient.ImpersonationMode) func(t *testing.T, server *httptest.Server) *gohttp.Client {
+		return func(t *testing.T, server *httptest.Server) *gohttp.Client {
+			var tlsConfig *tls.Config
+			if server.TLS != nil {
+				roots := x509.NewCertPool()
+				roots.AddCert(server.Certificate())
+				tlsConfig = &tls.Config{RootCAs: roots}
+			}
+			client, err := httpclient.NewClient(httpclient.Options{
+				Transport: httpclient.TransportOptions{
+					TLSClientConfig: tlsConfig,
+				},
+				Impersonation: httpclient.ImpersonationOptions{
+					Mode:    mode,
+					Browser: httpclient.BrowserChrome,
+				},
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+			return client
+		}
+	}
+	var cases []timeoutReaderClientCase
+	for _, mode := range []httpclient.ImpersonationMode{httpclient.ImpersonationNative, httpclient.ImpersonationFixed} {
+		cases = append(cases,
+			timeoutReaderClientCase{name: string(mode) + "/http1", client: newClient(mode)},
+			timeoutReaderClientCase{name: string(mode) + "/http2", http2: true, client: newClient(mode)},
+		)
+	}
+	return cases
+}
+
+func startTimeoutReaderServer(t *testing.T, useHTTP2 bool, handler gohttp.HandlerFunc) *httptest.Server {
+	server := httptest.NewUnstartedServer(handler)
+	if useHTTP2 {
+		server.EnableHTTP2 = true
+		server.StartTLS()
+	} else {
+		server.Start()
+	}
+	t.Cleanup(server.Close)
+	return server
+}
+
+// readBodyWithTimeout sends the request under its own context derived from
+// ctx, as the fetcher does, and reads the body through a TimeoutReader.
+func readBodyWithTimeout(t *testing.T, ctx context.Context, client *gohttp.Client, url string, timeout time.Duration, wantProto int) ([]byte, error) {
+	t.Helper()
+	reqCtx, cancel := context.WithCancel(ctx)
+	defer cancel()
+	req, err := gohttp.NewRequestWithContext(reqCtx, gohttp.MethodGet, url, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.ProtoMajor != wantProto {
+		t.Fatalf("expected HTTP/%d, got %s", wantProto, resp.Proto)
+	}
+
+	type result struct {
+		data []byte
+		err  error
+	}
+	done := make(chan result, 1)
+	go func() {
+		data, err := io.ReadAll(NewTimeoutReader(resp.Body, timeout, cancel))
+		done <- result{data, err}
+	}()
+	select {
+	case r := <-done:
+		return r.data, r.err
+	case <-time.After(timeout + 10*time.Second):
+		t.Fatal("Read did not return after the read timeout")
+		return nil, nil
+	}
+}
+
+func TestTimeoutReader_StalledHTTPBodyTimesOut(t *testing.T) {
+	for _, tc := range timeoutReaderClientCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			server := startTimeoutReaderServer(t, tc.http2, func(w gohttp.ResponseWriter, r *gohttp.Request) {
+				w.Header().Set("Content-Length", "1048576")
+				w.Write(bytes.Repeat([]byte("a"), 1024))
+				w.(gohttp.Flusher).Flush()
+				<-r.Context().Done()
+			})
+
+			wantProto := 1
+			if tc.http2 {
+				wantProto = 2
+			}
+			const timeout = 200 * time.Millisecond
+			start := time.Now()
+			data, err := readBodyWithTimeout(t, context.Background(), tc.client(t, server), server.URL, timeout, wantProto)
+			if !errors.Is(err, context.DeadlineExceeded) {
+				t.Fatalf("expected %v, got %v", context.DeadlineExceeded, err)
+			}
+			if len(data) != 1024 {
+				t.Fatalf("expected the 1024 bytes sent before the stall, got %d", len(data))
+			}
+			if elapsed := time.Since(start); elapsed < timeout {
+				t.Fatalf("timed out after %v, before the %v read timeout", elapsed, timeout)
+			}
+		})
+	}
+}
+
+func TestTimeoutReader_SlowSteadyHTTPBodyDoesNotTimeOut(t *testing.T) {
+	const (
+		timeout  = 300 * time.Millisecond
+		interval = 30 * time.Millisecond
+		chunks   = 40 // 1.2s in total, four times the read timeout
+	)
+	for _, tc := range timeoutReaderClientCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			server := startTimeoutReaderServer(t, tc.http2, func(w gohttp.ResponseWriter, r *gohttp.Request) {
+				for i := 0; i < chunks; i++ {
+					w.Write([]byte("0123456789"))
+					w.(gohttp.Flusher).Flush()
+					time.Sleep(interval)
+				}
+			})
+
+			wantProto := 1
+			if tc.http2 {
+				wantProto = 2
+			}
+			data, err := readBodyWithTimeout(t, context.Background(), tc.client(t, server), server.URL, timeout, wantProto)
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+			if len(data) != chunks*10 {
+				t.Fatalf("expected %d bytes, got %d", chunks*10, len(data))
+			}
+		})
+	}
+}
+
+// A gzip-encoded body that stalls must time out without racing the caller's
+// Body.Close against the decompressing reader.
+func TestTimeoutReader_StalledGzipHTTPBodyTimesOut(t *testing.T) {
+	payload := bytes.Repeat([]byte("gopeed"), 1024)
+	stages := []struct {
+		name  string
+		write func(w io.Writer)
+		want  int
+	}{
+		{
+			// The first bytes of a gzip header, so the client blocks inside
+			// gzip.NewReader.
+			name:  "incomplete-header",
+			write: func(w io.Writer) { w.Write([]byte{0x1f, 0x8b, 0x08, 0x00}) },
+			want:  0,
+		},
+		{
+			// A complete header and some compressed data, flushed without
+			// finishing the gzip stream.
+			name: "stalled-body",
+			write: func(w io.Writer) {
+				gz := gzip.NewWriter(w)
+				gz.Write(payload)
+				gz.Flush()
+			},
+			want: len(payload),
+		},
+	}
+	for _, stage := range stages {
+		for _, tc := range timeoutReaderClientCases() {
+			t.Run(stage.name+"/"+tc.name, func(t *testing.T) {
+				server := startTimeoutReaderServer(t, tc.http2, func(w gohttp.ResponseWriter, r *gohttp.Request) {
+					w.Header().Set("Content-Encoding", "gzip")
+					stage.write(w)
+					w.(gohttp.Flusher).Flush()
+					<-r.Context().Done()
+				})
+
+				wantProto := 1
+				if tc.http2 {
+					wantProto = 2
+				}
+				data, err := readBodyWithTimeout(t, context.Background(), tc.client(t, server), server.URL, 200*time.Millisecond, wantProto)
+				if !errors.Is(err, context.DeadlineExceeded) {
+					t.Fatalf("expected %v, got %v", context.DeadlineExceeded, err)
+				}
+				if len(data) != stage.want {
+					t.Fatalf("expected the %d bytes sent before the stall, got %d", stage.want, len(data))
+				}
+			})
+		}
+	}
+}
+
+// Cancelling the caller's context must not be reported as a read timeout.
+func TestTimeoutReader_CallerCancellationIsNotTimeout(t *testing.T) {
+	for _, tc := range timeoutReaderClientCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			server := startTimeoutReaderServer(t, tc.http2, func(w gohttp.ResponseWriter, r *gohttp.Request) {
+				w.Header().Set("Content-Length", "1048576")
+				w.Write(bytes.Repeat([]byte("a"), 1024))
+				w.(gohttp.Flusher).Flush()
+				<-r.Context().Done()
+			})
+
+			wantProto := 1
+			if tc.http2 {
+				wantProto = 2
+			}
+			// Cancel once the client has read the first bytes, so the next
+			// Read is the one blocked when the caller cancels.
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+			client := tc.client(t, server)
+			next := client.Transport
+			client.Transport = roundTripFunc(func(r *gohttp.Request) (*gohttp.Response, error) {
+				resp, err := next.RoundTrip(r)
+				if err == nil {
+					resp.Body = &cancelAfterFirstRead{ReadCloser: resp.Body, cancel: cancel}
+				}
+				return resp, err
+			})
+
+			const timeout = 5 * time.Second
+			start := time.Now()
+			data, err := readBodyWithTimeout(t, ctx, client, server.URL, timeout, wantProto)
+			if !errors.Is(err, context.Canceled) {
+				t.Fatalf("expected %v, got %v", context.Canceled, err)
+			}
+			if len(data) == 0 {
+				t.Fatal("cancelled before any data was read")
+			}
+			if elapsed := time.Since(start); elapsed >= timeout {
+				t.Fatalf("read returned after %v, not on cancellation", elapsed)
+			}
+		})
+	}
+}
+
+type roundTripFunc func(*gohttp.Request) (*gohttp.Response, error)
+
+func (f roundTripFunc) RoundTrip(r *gohttp.Request) (*gohttp.Response, error) {
+	return f(r)
+}
+
+// cancelAfterFirstRead calls cancel once a Read has returned data.
+type cancelAfterFirstRead struct {
+	io.ReadCloser
+	once   sync.Once
+	cancel context.CancelFunc
+}
+
+func (b *cancelAfterFirstRead) Read(p []byte) (int, error) {
+	n, err := b.ReadCloser.Read(p)
+	if n > 0 {
+		b.once.Do(b.cancel)
+	}
+	return n, err
+}

pkg/api/routes.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"fmt"
+	"net/url"
 	pathpkg "path"
 	"strings"
 )
@@ -75,7 +76,11 @@ func (r RouteSpec) Match(rawPath string) (map[string]string, bool) {
 	params := make(map[string]string)
 	for index, part := range r.parts {
 		if part.param != "" {
-			params[part.param] = segments[index]
+			value, err := url.PathUnescape(segments[index])
+			if err != nil {
+				return nil, false
+			}
+			params[part.param] = value
 			continue
 		}
 		if part.literal != segments[index] {

pkg/api/service.go

@@ -2,7 +2,9 @@ package api
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -62,6 +64,8 @@ func NewService(downloader *download.Downloader) (*Service, error) {
 		newRoute(http.MethodGet, "/api/v1/tasks/{id}/status", service.getTaskStatus),
 		newRoute(http.MethodGet, "/api/v1/tasks", service.getTasks),
 		newRoute(http.MethodGet, "/api/v1/tasks/{id}/stats", service.getStats),
+		newRoute(http.MethodPost, "/api/v1/protocols/{protocol}/jobs/{name}/trigger", service.triggerProtocolJob),
+		newRoute(http.MethodPost, "/api/v1/mirrors/{provider}/candidates", service.mirrorCandidates),
 		newRoute(http.MethodGet, "/api/v1/config", service.getConfig),
 		newRoute(http.MethodPut, "/api/v1/config", service.putConfig),
 		newRoute(http.MethodPost, "/api/v1/extensions", service.installExtension),
@@ -139,7 +143,7 @@ func (s *Service) resolve(ctx *Context) *Response {
 	if response := decodeRequest(ctx.Body, &request); response != nil {
 		return response
 	}
-	result, err := s.Downloader.Resolve(request.Req, request.Opts)
+	result, err := s.Downloader.Resolve(request.Req)
 	if err != nil {
 		return newErrorResponse(err.Error())
 	}
@@ -176,11 +180,11 @@ func (s *Service) createTaskBatch(ctx *Context) *Response {
 	if len(request.Reqs) == 0 {
 		return newErrorResponse("param invalid: reqs", restmodel.CodeInvalidParam)
 	}
-	taskIDs, err := s.Downloader.CreateDirectBatch(&request)
+	result, err := s.Downloader.CreateDirectBatchWithResult(&request)
 	if err != nil {
 		return newErrorResponse(err.Error())
 	}
-	return newOKResponse(taskIDs)
+	return newOKResponse(result)
 }
 
 func (s *Service) patchTask(ctx *Context) *Response {
@@ -188,7 +192,7 @@ func (s *Service) patchTask(ctx *Context) *Response {
 	if taskID == "" {
 		return invalidIDResponse()
 	}
-	var request restmodel.ResolveTask
+	var request restmodel.PatchTask
 	if response := decodeRequest(ctx.Body, &request); response != nil {
 		return response
 	}
@@ -294,6 +298,36 @@ func (s *Service) getStats(ctx *Context) *Response {
 	return newOKResponse(stats)
 }
 
+func (s *Service) triggerProtocolJob(ctx *Context) *Response {
+	if err := s.Downloader.TriggerProtocolJob(context.Background(), ctx.PathParam("protocol"), ctx.PathParam("name")); err != nil {
+		status := http.StatusBadRequest
+		if errors.Is(err, download.ErrUnSupportedProtocol) || errors.Is(err, download.ErrProtocolJobNotFound) {
+			status = http.StatusNotFound
+		}
+		return newStatusResponse(status, restmodel.NewErrorResult(err.Error()))
+	}
+	return newNilResponse()
+}
+
+func (s *Service) mirrorCandidates(ctx *Context) *Response {
+	var request restmodel.MirrorCandidatesReq
+	if response := decodeRequest(ctx.Body, &request); response != nil {
+		return response
+	}
+	urls, err := s.Downloader.GetMirrorCandidates(ctx.PathParam("provider"), request.URL)
+	if err != nil {
+		status := http.StatusInternalServerError
+		switch {
+		case errors.Is(err, download.ErrMirrorProviderNotFound):
+			status = http.StatusNotFound
+		case errors.Is(err, download.ErrInvalidMirrorURL):
+			status = http.StatusBadRequest
+		}
+		return newStatusResponse(status, restmodel.NewErrorResult(err.Error()))
+	}
+	return newOKResponse(&restmodel.MirrorCandidatesResp{URLs: urls})
+}
+
 func (s *Service) getConfig(_ *Context) *Response {
 	config, err := s.Downloader.GetConfig()
 	if err != nil {

pkg/api/service_test.go

@@ -0,0 +1,331 @@
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	httpProtocol "github.com/GopeedLab/gopeed/internal/protocol/http"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/download"
+	restmodel "github.com/GopeedLab/gopeed/pkg/rest/model"
+)
+
+func TestResolveThenCreateWithDownloadOptions(t *testing.T) {
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Disposition", `attachment; filename="payload.txt"`)
+		w.Header().Set("Content-Length", "4")
+		_, _ = w.Write([]byte("test"))
+	}))
+	t.Cleanup(upstream.Close)
+	d := download.NewDownloader(&download.DownloaderConfig{StorageDir: t.TempDir()})
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if err := d.Close(); err != nil {
+			t.Error(err)
+		}
+	})
+	// Resolving must work even when the default download directory is unusable.
+	blocked := filepath.Join(t.TempDir(), "not-a-directory")
+	if err := os.WriteFile(blocked, nil, 0600); err != nil {
+		t.Fatal(err)
+	}
+	current, err := d.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	config := *current
+	config.DownloadDir = blocked
+	config.MaxRunning = 0 // Inspect the created task before it starts downloading.
+	if err := d.PutConfig(&config); err != nil {
+		t.Fatal(err)
+	}
+	service, err := NewService(d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resolved := serviceTestRequest[*download.ResolveResult](t, service, http.MethodPost, "/api/v1/resolve", &restmodel.ResolveTask{
+		Req: &base.Request{URL: upstream.URL},
+	})
+	if resolved.ID == "" || resolved.Res.Size != 4 || resolved.Res.Files[0].Name != "payload.txt" {
+		t.Fatalf("unexpected resolved resource: %+v", resolved)
+	}
+	dir := filepath.Join(t.TempDir(), "chosen-after-resolve")
+	opts := &base.Options{Path: dir, Name: "renamed.txt", SelectFiles: []int{0}}
+	id := serviceTestRequest[string](t, service, http.MethodPost, "/api/v1/tasks", &restmodel.CreateTask{Rid: resolved.ID, Opts: opts})
+	task := serviceTestRequest[*download.Task](t, service, http.MethodGet, "/api/v1/tasks/"+id, nil)
+	if task.Meta.Opts.Path != dir || task.Meta.Opts.Name != opts.Name || !reflect.DeepEqual(task.Meta.Opts.SelectFiles, opts.SelectFiles) {
+		t.Fatalf("creation lost submitted download options: %+v", task.Meta.Opts)
+	}
+}
+
+func serviceTestRequest[T any](t *testing.T, service *Service, method, path string, body any) T {
+	t.Helper()
+	encoded, err := json.Marshal(body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	status, response := service.JSON(method, path, nil, encoded, nil)
+	var result restmodel.Result[T]
+	if err := json.Unmarshal(response, &result); err != nil {
+		t.Fatal(err)
+	}
+	if status != http.StatusOK || result.Code != restmodel.CodeOk {
+		t.Fatalf("%s %s failed: status=%d response=%s", method, path, status, response)
+	}
+	return result.Data
+}
+
+func TestFullConfigDispatch(t *testing.T) {
+	d := download.NewDownloader(&download.DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir(), FetchManagers: []fetcher.FetcherManager{&httpProtocol.FetcherManager{}}})
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	defer d.Close()
+	service, err := NewService(d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	response := service.Dispatch(http.MethodPut, "/api/v1/config", nil, []byte(`{"protocolConfig":{"http":{"connections":3,"useServerCtime":false}}}`), nil)
+	if response.StatusCode != http.StatusOK {
+		t.Fatalf("%+v", response)
+	}
+	status, body := service.JSON(http.MethodGet, "/api/v1/config", nil, nil, nil)
+	var result struct {
+		Data struct {
+			ProtocolConfig map[string]struct {
+				Connections int `json:"connections"`
+			} `json:"protocolConfig"`
+		} `json:"data"`
+	}
+	if err := json.Unmarshal(body, &result); err != nil {
+		t.Fatal(err)
+	}
+	if status != http.StatusOK || result.Data.ProtocolConfig["http"].Connections != 3 {
+		t.Fatalf("%d %s", status, body)
+	}
+	if response := service.Dispatch(http.MethodPost, "/api/v1/protocols/http/jobs/missing/trigger", nil, nil, nil); response.StatusCode != http.StatusNotFound {
+		t.Fatalf("%+v", response)
+	}
+}
+
+func TestNativePathParametersAreDecodedOnce(t *testing.T) {
+	route := newRoute(http.MethodGet, "/api/v1/tasks/{id}/status", func(c *Context) *Response { return newOKResponse(c.PathParam("id")) })
+	for _, test := range []struct{ path, want string }{
+		{"/api/v1/tasks/%E5%BC%80%E5%8F%91%E8%80%85%40name/status", "开发者@name"},
+		{"/api/v1/tasks/literal%252Fname/status", "literal%2Fname"},
+	} {
+		response := (&Service{routes: []RouteSpec{route}}).Dispatch(http.MethodGet, test.path, nil, nil, nil)
+		raw, _ := json.Marshal(response.Body)
+		var body struct {
+			Data string `json:"data"`
+		}
+		_ = json.Unmarshal(raw, &body)
+		if body.Data != test.want {
+			t.Fatalf("%s => %q", test.path, body.Data)
+		}
+	}
+}
+
+func TestMirrorCandidates(t *testing.T) {
+	d := download.NewDownloader(&download.DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir(), FetchManagers: []fetcher.FetcherManager{&httpProtocol.FetcherManager{}}})
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	defer d.Close()
+	cfg, _ := d.GetConfig()
+	cfg.GithubMirror = &base.GithubMirrorConfig{Enabled: true, Mirrors: []base.GithubMirror{
+		{Type: "jsdelivr", URL: "https://cdn.example/gh"},
+		{Type: "ghProxy", URL: "https://proxy.example"},
+		{Type: "ghProxy", URL: "https://proxy.example"},
+	}}
+	if err := d.PutConfig(cfg); err != nil {
+		t.Fatal(err)
+	}
+	service, err := NewService(d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, official := range []string{
+		"https://github.com/GopeedLab/gopeed/releases/download/v2.0.0/package.zip",
+		"https://raw.githubusercontent.com/owner/repo/main/trackers.txt",
+	} {
+		request, _ := json.Marshal(map[string]string{"url": official})
+		status, raw := service.JSON(http.MethodPost, "/api/v1/mirrors/github/candidates", nil, request, nil)
+		var body struct {
+			Data struct {
+				URLs []string `json:"urls"`
+			} `json:"data"`
+		}
+		if err := json.Unmarshal(raw, &body); err != nil {
+			t.Fatal(err)
+		}
+		want := 2
+		if official == "https://raw.githubusercontent.com/owner/repo/main/trackers.txt" {
+			want = 3
+		}
+		urls := body.Data.URLs
+		if status != http.StatusOK || len(urls) != want || urls[0] != official || urls[len(urls)-1] != "https://proxy.example/"+official {
+			t.Fatalf("%d %s", status, raw)
+		}
+	}
+	for _, invalid := range []string{"https://api.github.com/repos/GopeedLab/gopeed/releases?per_page=10", "", "https://example.com/x", "http://github.com/x", "https://github.com.evil.test/x", "https://[email protected]/x", "https://github.com:443/x", "https://github.com:/x", "https://github.com/x#fragment", "https://github.com/x#", "/relative", "https://github.com%2fevil.test/x"} {
+		request, _ := json.Marshal(map[string]string{"url": invalid})
+		if response := service.Dispatch(http.MethodPost, "/api/v1/mirrors/github/candidates", nil, request, nil); response.StatusCode != http.StatusBadRequest {
+			t.Fatalf("accepted %s: %+v", invalid, response)
+		}
+	}
+	cfg.GithubMirror.Enabled = false
+	if err := d.PutConfig(cfg); err != nil {
+		t.Fatal(err)
+	}
+	status, raw := service.JSON(http.MethodPost, "/api/v1/mirrors/github/candidates", nil, []byte(`{"url":"https://github.com/owner/repo"}`), nil)
+	var body struct {
+		Data struct {
+			URLs []string `json:"urls"`
+		} `json:"data"`
+	}
+	if err := json.Unmarshal(raw, &body); err != nil || status != http.StatusOK || len(body.Data.URLs) != 1 || body.Data.URLs[0] != "https://github.com/owner/repo" {
+		t.Fatalf("%d %s", status, raw)
+	}
+
+	for _, provider := range []string{"unknown", "GitHub"} {
+		if response := service.Dispatch(http.MethodPost, "/api/v1/mirrors/"+provider+"/candidates", nil, []byte(`{"url":"https://github.com/owner/repo"}`), nil); response.StatusCode != http.StatusNotFound {
+			t.Fatalf("unknown provider accepted: %+v", response)
+		}
+	}
+}
+
+type apiJobState struct {
+	Runs int `json:"runs"`
+}
+type apiJobConfig struct {
+	fetcher.ConfigState[apiJobState]
+	Writable int `json:"writable"`
+}
+type apiStateJobManager struct{ httpProtocol.FetcherManager }
+
+func (*apiStateJobManager) Name() string       { return "state-api" }
+func (*apiStateJobManager) DefaultConfig() any { return &apiJobConfig{Writable: 7} }
+func (*apiStateJobManager) CronJobs(host fetcher.ProtocolHost) []fetcher.CronJob {
+	return []fetcher.CronJob{{Name: "refresh", Every: time.Hour, Timeout: time.Second, Run: func(_ context.Context, source fetcher.TriggerSource) error {
+		if source == fetcher.TriggerScheduled {
+			return fetcher.ErrJobSkipped
+		}
+		return fetcher.UpdateState[apiJobConfig, apiJobState](host, func(cfg *apiJobConfig, state *apiJobState) error { cfg.Writable = 999; state.Runs++; return nil })
+	}}}
+}
+
+func TestFullConfigAndJobTriggerShareProtectedProtocolState(t *testing.T) {
+	d := download.NewDownloader(&download.DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir(), FetchManagers: []fetcher.FetcherManager{&apiStateJobManager{}}})
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	defer d.Close()
+	service, err := NewService(d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	put := []byte(`{"protocolConfig":{"state-api":{"writable":9,"state":"ignore forged state"}}}`)
+	if response := service.Dispatch(http.MethodPut, "/api/v1/config", nil, put, nil); response.StatusCode != http.StatusOK {
+		t.Fatalf("%+v", response)
+	}
+	if response := service.Dispatch(http.MethodPost, "/api/v1/protocols/state-api/jobs/refresh/trigger", nil, nil, nil); response.StatusCode != http.StatusOK {
+		t.Fatalf("%+v", response)
+	}
+	status, raw := service.JSON(http.MethodGet, "/api/v1/config", nil, nil, nil)
+	var response struct {
+		Data struct {
+			ProtocolConfig map[string]apiJobConfig `json:"protocolConfig"`
+		} `json:"data"`
+	}
+	if err := json.Unmarshal(raw, &response); err != nil {
+		t.Fatal(err)
+	}
+	cfg := response.Data.ProtocolConfig["state-api"]
+	if status != http.StatusOK || cfg.Writable != 9 || cfg.State.Runs != 1 {
+		t.Fatalf("%d %s", status, raw)
+	}
+	// Replaying an old full PUT must not undo the manual job's state change.
+	if response := service.Dispatch(http.MethodPut, "/api/v1/config", nil, put, nil); response.StatusCode != http.StatusOK {
+		t.Fatalf("%+v", response)
+	}
+	_, raw = service.JSON(http.MethodGet, "/api/v1/config", nil, nil, nil)
+	if err := json.Unmarshal(raw, &response); err != nil {
+		t.Fatal(err)
+	}
+	if response.Data.ProtocolConfig["state-api"].State.Runs != 1 {
+		t.Fatalf("job state overwritten: %s", raw)
+	}
+}
+
+func TestBatchResolvedAndDirectCreation(t *testing.T) {
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Length", "4")
+		_, _ = w.Write([]byte("test"))
+	}))
+	t.Cleanup(upstream.Close)
+	d := download.NewDownloader(&download.DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir(), FetchManagers: []fetcher.FetcherManager{&httpProtocol.FetcherManager{}}})
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { d.Close() })
+	cfg, err := d.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	cfg.MaxRunning = 0
+	if err := d.PutConfig(cfg); err != nil {
+		t.Fatal(err)
+	}
+	service, err := NewService(d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, grouped := range []bool{false, true} {
+		resolved := serviceTestRequest[*download.ResolveResult](t, service, http.MethodPost, "/api/v1/resolve", &restmodel.ResolveTask{Req: &base.Request{URL: upstream.URL + "/resolved"}})
+		result := serviceTestRequest[map[string]json.RawMessage](t, service, http.MethodPost, "/api/v1/tasks/batch", &base.CreateTaskBatch{
+			Group: grouped, GroupName: "folder", Opts: &base.Options{Path: t.TempDir()},
+			Reqs: []*base.CreateTaskBatchItem{
+				{Rid: "invalid"},
+				{Rid: resolved.ID, Req: &base.Request{URL: "unsupported://ignored"}, Opts: &base.Options{SelectFiles: []int{0}}},
+				{Req: &base.Request{URL: upstream.URL + "/direct"}},
+			},
+		})
+		var ids []string
+		if err := json.Unmarshal(result["taskIds"], &ids); err != nil || len(ids) != 2 {
+			t.Fatalf("unexpected task IDs: %+v, %v", result, err)
+		}
+		wantFields := 1
+		if grouped {
+			wantFields = 2
+		}
+		if len(result) != wantFields {
+			t.Fatalf("unexpected response fields: %+v", result)
+		}
+		var parentID string
+		if grouped {
+			if err := json.Unmarshal(result["parentId"], &parentID); err != nil || parentID == "" {
+				t.Fatalf("missing parent ID: %+v", result)
+			}
+		}
+		task := serviceTestRequest[*download.Task](t, service, http.MethodGet, "/api/v1/tasks/"+ids[0], nil)
+		if task.ParentID != parentID || !reflect.DeepEqual(task.Meta.Opts.SelectFiles, []int{0}) {
+			t.Fatalf("resolved task lost membership or selection: %+v", task)
+		}
+		status, response := service.JSON(http.MethodPost, "/api/v1/tasks/batch", nil, []byte(`{"reqs":[{"rid":"missing"},{"req":{"url":"unsupported://bad"}}]}`), nil)
+		var failed restmodel.Result[any]
+		if err := json.Unmarshal(response, &failed); err != nil || status != http.StatusOK || failed.Code == restmodel.CodeOk {
+			t.Fatalf("all-failed batch succeeded: %d %s", status, response)
+		}
+	}
+}

pkg/base/github_mirror.go

@@ -0,0 +1,11 @@
+package base
+
+import "github.com/GopeedLab/gopeed/internal/githubmirror"
+
+// Preserve downloader configuration type names and the existing JSON schema.
+type GithubMirror = githubmirror.Mirror
+type GithubMirrorConfig = githubmirror.Config
+
+func DefaultGithubMirrorConfig() *GithubMirrorConfig {
+	return githubmirror.DefaultConfig()
+}

pkg/base/model.go

@@ -1,9 +1,11 @@
 package base
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"net/url"
+	"path/filepath"
 	"sync"
 	"time"
 
@@ -26,11 +28,17 @@ type Request struct {
 }
 
 // SetLabels replaces all labels on the request.
+//
+// Deprecated: In onResolve and onDone, assign request labels directly.
+// In onStart and onError, use task.meta.req.setLabels instead.
 func (r *Request) SetLabels(labels map[string]string) {
 	r.Labels = labels
 }
 
 // PutLabel sets a label on the request.
+//
+// Deprecated: In onResolve and onDone, assign request labels directly.
+// In onStart and onError, use task.meta.req.putLabel instead.
 func (r *Request) PutLabel(key, value string) {
 	if r.Labels == nil {
 		r.Labels = make(map[string]string)
@@ -39,6 +47,9 @@ func (r *Request) PutLabel(key, value string) {
 }
 
 // DelLabel deletes a label from the request.
+//
+// Deprecated: In onResolve and onDone, delete request labels directly.
+// In onStart and onError, use task.meta.req.delLabel instead.
 func (r *Request) DelLabel(key string) {
 	delete(r.Labels, key)
 }
@@ -126,12 +137,18 @@ type FileInfo struct {
 
 // Options for download
 type Options struct {
+	// Size is an optional HTTP download size estimate. HTTP metadata and clean EOF take precedence.
+	// Other protocols ignore it.
+	Size int64 `json:"size,omitempty"`
 	// Download file name
 	Name string `json:"name"`
 	// Download file path
 	Path string `json:"path"`
 	// Use this path as the default download directory after creation succeeds
 	AsDefaultPath bool `json:"asDefaultPath,omitempty"`
+	// SkipAutoCategorize keeps the base download directory of this task instead
+	// of routing it to the category directory of its resolved file
+	SkipAutoCategorize bool `json:"skipAutoCategorize,omitempty"`
 	// Select file indexes to download
 	SelectFiles []int `json:"selectFiles"`
 	// Extra info for specific fetcher
@@ -183,11 +200,14 @@ func ParseOptExtra[E any](opts *Options) error {
 }
 
 type CreateTaskBatch struct {
-	Reqs []*CreateTaskBatchItem `json:"reqs"`
-	Opts *Options               `json:"opts"`
+	Reqs      []*CreateTaskBatchItem `json:"reqs"`
+	Opts      *Options               `json:"opts"`
+	Group     bool                   `json:"group"`
+	GroupName string                 `json:"groupName"`
 }
 
 type CreateTaskBatchItem struct {
+	Rid  string   `json:"rid,omitempty"`
 	Req  *Request `json:"req"`
 	Opts *Options `json:"opts"`
 }
@@ -199,12 +219,15 @@ type DownloaderStoreConfig struct {
 	DownloadDir                string                 `json:"downloadDir"`    // DownloadDir is the default directory to save the downloaded files
 	MaxRunning                 int                    `json:"maxRunning"`     // MaxRunning is the max running download count
 	ProtocolConfig             map[string]any         `json:"protocolConfig"` // ProtocolConfig is special config for each protocol
+	GithubMirror               *GithubMirrorConfig    `json:"githubMirror"`
 	Extra                      map[string]any         `json:"extra"`
 	Proxy                      *DownloaderProxyConfig `json:"proxy"`
 	Webhook                    *WebhookConfig         `json:"webhook"`                    // Webhook is the webhook configuration
 	Script                     *ScriptConfig          `json:"script"`                     // Script is the script execution configuration
 	AutoTorrent                *AutoTorrentConfig     `json:"autoTorrent"`                // AutoTorrent is the auto torrent task creation configuration
 	Archive                    *ArchiveConfig         `json:"archive"`                    // Archive is the archive extraction configuration
+	Categories                 []*DownloadCategory    `json:"categories"`                 // Categories is the download directory category configuration
+	AutoCategorize             *bool                  `json:"autoCategorize,omitempty"`   // AutoCategorize routes downloads to category directories by file extension; unset defaults to disabled
 	API                        *APIServerConfig       `json:"api"`                        // API is the optional REST server configuration
 	AutoStartTasks             bool                   `json:"autoStartTasks"`             // AutoStartTasks continues all unfinished tasks when the backend starts
 	AutoDeleteMissingFileTasks bool                   `json:"autoDeleteMissingFileTasks"` // AutoDeleteMissingFileTasks enables automatic deletion of tasks with missing files
@@ -217,6 +240,9 @@ func (cfg *DownloaderStoreConfig) Init() *DownloaderStoreConfig {
 	if cfg.ProtocolConfig == nil {
 		cfg.ProtocolConfig = make(map[string]any)
 	}
+	if cfg.GithubMirror == nil {
+		cfg.GithubMirror = DefaultGithubMirrorConfig()
+	}
 	if cfg.Proxy == nil {
 		cfg.Proxy = &DownloaderProxyConfig{}
 	}
@@ -238,9 +264,85 @@ func (cfg *DownloaderStoreConfig) Init() *DownloaderStoreConfig {
 			DeleteAfterExtract: false,
 		}
 	}
+	// Seed the built-in categories for deployments that never run the flutter
+	// startup flow, e.g. headless api servers.
+	if len(cfg.Categories) == 0 && cfg.DownloadDir != "" {
+		cfg.Categories = []*DownloadCategory{
+			builtinSeedCategory("categoryMusic", "Music", cfg.DownloadDir),
+			builtinSeedCategory("categoryVideo", "Video", cfg.DownloadDir),
+			builtinSeedCategory("categoryDocument", "Document", cfg.DownloadDir),
+			builtinSeedCategory("categoryProgram", "Program", cfg.DownloadDir),
+		}
+	}
 	return cfg
 }
 
+// builtinCategoryExtensions mirrors the flutter side
+// kDefaultCategoryExtensions, keep both maps in sync.
+var builtinCategoryExtensions = map[string][]string{
+	"categoryProgram":  {"exe", "msi", "msix", "apk", "dmg", "deb", "rpm", "pkg", "appimage"},
+	"categoryVideo":    {"mp4", "mkv", "avi", "mov", "wmv", "flv", "webm", "m4v", "mpg", "mpeg", "3gp"},
+	"categoryMusic":    {"mp3", "flac", "wav", "aac", "ogg", "m4a", "wma", "ape"},
+	"categoryDocument": {"pdf", "doc", "docx", "xls", "xlsx", "ppt", "pptx", "txt", "md", "csv", "epub", "rtf"},
+}
+
+func builtinSeedCategory(nameKey, name, downloadDir string) *DownloadCategory {
+	return &DownloadCategory{
+		Name:       "",
+		Path:       filepath.Join(downloadDir, name),
+		NameKey:    nameKey,
+		IsBuiltIn:  true,
+		Extensions: append([]string(nil), builtinCategoryExtensions[nameKey]...),
+	}
+}
+
+// MigrateLegacyExtraCategories moves the extra.downloadCategories list written
+// by v2.0.0-beta builds into the top level categories field and clears the
+// legacy key. The legacy list predates extension based routing, so built-in
+// entries regain their default extension lists from their name key, while user
+// created folders keep their empty list until edited in settings. It reports
+// whether the config changed so the caller can persist the cleared key.
+func (cfg *DownloaderStoreConfig) MigrateLegacyExtraCategories() bool {
+	if len(cfg.Categories) > 0 || cfg.Extra == nil {
+		return false
+	}
+	raw, ok := cfg.Extra["downloadCategories"]
+	if !ok {
+		return false
+	}
+	data, err := json.Marshal(raw)
+	if err != nil {
+		return false
+	}
+	var legacy []*DownloadCategory
+	if err := json.Unmarshal(data, &legacy); err != nil {
+		return false
+	}
+	categories := make([]*DownloadCategory, 0, len(legacy))
+	for _, category := range legacy {
+		if category == nil {
+			continue
+		}
+		if extensions, exist := builtinCategoryExtensions[category.NameKey]; exist && len(category.Extensions) == 0 {
+			category.Extensions = append([]string(nil), extensions...)
+		}
+		categories = append(categories, category)
+	}
+	if len(categories) == 0 {
+		return false
+	}
+	cfg.Categories = categories
+	delete(cfg.Extra, "downloadCategories")
+	return true
+}
+
+// AutoCategorizeEnabled reports whether downloads are routed to category
+// directories by file extension. The switch is optional: an unset value keeps
+// the feature off, so an older config that never saved the field stays off.
+func (cfg *DownloaderStoreConfig) AutoCategorizeEnabled() bool {
+	return cfg.AutoCategorize != nil && *cfg.AutoCategorize
+}
+
 func (cfg *DownloaderStoreConfig) Merge(beforeCfg *DownloaderStoreConfig) *DownloaderStoreConfig {
 	if beforeCfg == nil {
 		return cfg
@@ -257,6 +359,9 @@ func (cfg *DownloaderStoreConfig) Merge(beforeCfg *DownloaderStoreConfig) *Downl
 	if cfg.Extra == nil {
 		cfg.Extra = beforeCfg.Extra
 	}
+	if cfg.GithubMirror == nil {
+		cfg.GithubMirror = beforeCfg.GithubMirror
+	}
 	if cfg.Proxy == nil {
 		cfg.Proxy = beforeCfg.Proxy
 	}
@@ -272,6 +377,12 @@ func (cfg *DownloaderStoreConfig) Merge(beforeCfg *DownloaderStoreConfig) *Downl
 	if cfg.Archive == nil {
 		cfg.Archive = beforeCfg.Archive
 	}
+	if cfg.Categories == nil {
+		cfg.Categories = beforeCfg.Categories
+	}
+	if cfg.AutoCategorize == nil {
+		cfg.AutoCategorize = beforeCfg.AutoCategorize
+	}
 	if cfg.API == nil {
 		cfg.API = beforeCfg.API
 	}
@@ -320,6 +431,16 @@ type ArchiveConfig struct {
 	DeleteAfterExtract bool `json:"deleteAfterExtract"` // DeleteAfterExtract deletes the archive after successful extraction
 }
 
+// DownloadCategory is a download directory category that files can be routed to by extension
+type DownloadCategory struct {
+	Name       string   `json:"name"`                 // Name is the category display name, empty for built-in categories that use NameKey
+	Path       string   `json:"path"`                 // Path is the download directory of the category
+	NameKey    string   `json:"nameKey,omitempty"`    // NameKey is the i18n key of the built-in category name
+	IsBuiltIn  bool     `json:"isBuiltIn,omitempty"`  // IsBuiltIn marks the category as built-in
+	IsDeleted  bool     `json:"isDeleted,omitempty"`  // IsDeleted marks the built-in category as deleted
+	Extensions []string `json:"extensions,omitempty"` // Extensions is the file extension list routed to the category, without leading dots
+}
+
 type DownloaderProxyConfig struct {
 	Enable bool `json:"enable"`
 	// System is the flag that use system proxy

pkg/base/model_test.go

@@ -1,8 +1,13 @@
 package base
 
 import (
+	"encoding/json"
+	"path/filepath"
 	"reflect"
+	"strings"
 	"testing"
+
+	"github.com/GopeedLab/gopeed/pkg/util"
 )
 
 func TestDownloaderStoreConfig_Init(t *testing.T) {
@@ -15,6 +20,7 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 			"Init",
 			&DownloaderStoreConfig{},
 			&DownloaderStoreConfig{
+				GithubMirror:   DefaultGithubMirrorConfig(),
 				MaxRunning:     5,
 				ProtocolConfig: map[string]any{},
 				Proxy:          &DownloaderProxyConfig{},
@@ -36,6 +42,7 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 				MaxRunning: 10,
 			},
 			&DownloaderStoreConfig{
+				GithubMirror:   DefaultGithubMirrorConfig(),
 				MaxRunning:     10,
 				ProtocolConfig: map[string]any{},
 				Proxy:          &DownloaderProxyConfig{},
@@ -59,7 +66,8 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 				},
 			},
 			&DownloaderStoreConfig{
-				MaxRunning: 5,
+				GithubMirror: DefaultGithubMirrorConfig(),
+				MaxRunning:   5,
 				ProtocolConfig: map[string]any{
 					"key": "value",
 				},
@@ -84,6 +92,7 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 				},
 			},
 			&DownloaderStoreConfig{
+				GithubMirror:   DefaultGithubMirrorConfig(),
 				MaxRunning:     5,
 				ProtocolConfig: map[string]any{},
 				Proxy: &DownloaderProxyConfig{
@@ -110,6 +119,7 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 				},
 			},
 			&DownloaderStoreConfig{
+				GithubMirror:   DefaultGithubMirrorConfig(),
 				MaxRunning:     5,
 				ProtocolConfig: map[string]any{},
 				Proxy:          &DownloaderProxyConfig{},
@@ -134,6 +144,7 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 				},
 			},
 			&DownloaderStoreConfig{
+				GithubMirror:   DefaultGithubMirrorConfig(),
 				MaxRunning:     5,
 				ProtocolConfig: map[string]any{},
 				Proxy:          &DownloaderProxyConfig{},
@@ -149,6 +160,20 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:   "Init explicitly disabled mirrors with empty list",
+			fields: &DownloaderStoreConfig{GithubMirror: &GithubMirrorConfig{Enabled: false, Mirrors: []GithubMirror{}}},
+			want: &DownloaderStoreConfig{
+				MaxRunning:     5,
+				ProtocolConfig: map[string]any{},
+				GithubMirror:   &GithubMirrorConfig{Enabled: false, Mirrors: []GithubMirror{}},
+				Proxy:          &DownloaderProxyConfig{},
+				Webhook:        &WebhookConfig{},
+				Script:         &ScriptConfig{},
+				AutoTorrent:    &AutoTorrentConfig{},
+				Archive:        &ArchiveConfig{},
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -157,6 +182,7 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 				DownloadDir:    tt.fields.DownloadDir,
 				MaxRunning:     tt.fields.MaxRunning,
 				ProtocolConfig: tt.fields.ProtocolConfig,
+				GithubMirror:   tt.fields.GithubMirror,
 				Extra:          tt.fields.Extra,
 				Proxy:          tt.fields.Proxy,
 				Webhook:        tt.fields.Webhook,
@@ -171,6 +197,202 @@ func TestDownloaderStoreConfig_Init(t *testing.T) {
 	}
 }
 
+func TestDownloaderStoreConfig_InitSeedsBuiltInCategories(t *testing.T) {
+	t.Run("fresh config with a download dir gets the built-in categories", func(t *testing.T) {
+		dir := t.TempDir()
+		cfg := &DownloaderStoreConfig{DownloadDir: dir}
+		cfg.Init()
+
+		wantKeys := []string{"categoryMusic", "categoryVideo", "categoryDocument", "categoryProgram"}
+		wantNames := []string{"Music", "Video", "Document", "Program"}
+		if len(cfg.Categories) != len(wantKeys) {
+			t.Fatalf("categories = %d, want %d", len(cfg.Categories), len(wantKeys))
+		}
+		for i, category := range cfg.Categories {
+			if category.NameKey != wantKeys[i] {
+				t.Errorf("category[%d].NameKey = %q, want %q", i, category.NameKey, wantKeys[i])
+			}
+			if !category.IsBuiltIn {
+				t.Errorf("category[%d] %q is not built-in", i, category.NameKey)
+			}
+			if category.Path != filepath.Join(dir, wantNames[i]) {
+				t.Errorf("category[%d].Path = %q, want %q", i, category.Path, filepath.Join(dir, wantNames[i]))
+			}
+			if len(category.Extensions) == 0 {
+				t.Errorf("category[%d] %q has no default extensions", i, category.NameKey)
+			}
+		}
+	})
+
+	// Init itself never reads the legacy key: Setup calls
+	// MigrateLegacyExtraCategories first, and only a config that skipped the
+	// migration ends up with the built-in seed.
+	t.Run("legacy extra downloadCategories is not read by Init alone", func(t *testing.T) {
+		cfg := &DownloaderStoreConfig{
+			DownloadDir: t.TempDir(),
+			Extra: map[string]any{
+				"downloadCategories": []any{map[string]any{"name": "Music", "path": "/old/Music"}},
+			},
+		}
+		cfg.Init()
+		if len(cfg.Categories) != 4 {
+			t.Fatalf("categories = %d, want the 4 built-ins seeded anyway", len(cfg.Categories))
+		}
+	})
+
+	t.Run("existing categories and missing download dirs are untouched", func(t *testing.T) {
+		existing := []*DownloadCategory{{Name: "Mine", Path: "/downloads/Mine"}}
+		cfg := &DownloaderStoreConfig{DownloadDir: t.TempDir(), Categories: existing}
+		cfg.Init()
+		if len(cfg.Categories) != 1 || cfg.Categories[0].Name != "Mine" {
+			t.Fatalf("categories = %v, want the existing one", cfg.Categories)
+		}
+
+		empty := &DownloaderStoreConfig{}
+		empty.Init()
+		if len(empty.Categories) != 0 {
+			t.Fatalf("categories = %d, want 0 without a download dir", len(empty.Categories))
+		}
+	})
+}
+
+func TestDownloaderStoreConfig_AutoCategorizeEnabled(t *testing.T) {
+	// A config written before the switch existed has no value, and stays off.
+	if (&DownloaderStoreConfig{}).AutoCategorizeEnabled() {
+		t.Fatal("unset auto categorize = enabled, want disabled by default")
+	}
+	if !(&DownloaderStoreConfig{AutoCategorize: util.BoolPtr(true)}).AutoCategorizeEnabled() {
+		t.Fatal("explicit on = disabled, want the opt-in preserved")
+	}
+	if (&DownloaderStoreConfig{AutoCategorize: util.BoolPtr(false)}).AutoCategorizeEnabled() {
+		t.Fatal("explicit off = enabled, want the opt-out preserved")
+	}
+}
+
+func TestDownloaderStoreConfig_MigrateLegacyExtraCategories(t *testing.T) {
+	t.Run("legacy built-ins move to the top level with their default extensions", func(t *testing.T) {
+		cfg := &DownloaderStoreConfig{
+			DownloadDir: "/downloads",
+			Extra: map[string]any{
+				"downloadCategories": []any{
+					map[string]any{"name": "", "path": "/old/Music", "isBuiltIn": true, "nameKey": "categoryMusic"},
+					map[string]any{"name": "Games", "path": "/old/Games"},
+				},
+				"themeMode": "dark",
+			},
+		}
+		if !cfg.MigrateLegacyExtraCategories() {
+			t.Fatal("migration reported no change")
+		}
+		if len(cfg.Categories) != 2 {
+			t.Fatalf("categories = %d, want the 2 legacy entries", len(cfg.Categories))
+		}
+		builtIn := cfg.Categories[0]
+		if builtIn.NameKey != "categoryMusic" || !builtIn.IsBuiltIn || builtIn.Path != "/old/Music" {
+			t.Fatalf("built-in category = %+v, want the legacy entry", builtIn)
+		}
+		if len(builtIn.Extensions) == 0 {
+			t.Fatal("migrated built-in must regain its default extensions")
+		}
+		custom := cfg.Categories[1]
+		if custom.Name != "Games" || custom.Path != "/old/Games" || len(custom.Extensions) != 0 {
+			t.Fatalf("custom category = %+v, want the legacy folder untouched", custom)
+		}
+		if _, ok := cfg.Extra["downloadCategories"]; ok {
+			t.Fatal("legacy key must be cleared")
+		}
+		if cfg.Extra["themeMode"] != "dark" {
+			t.Fatalf("unrelated extra entries must survive, got %v", cfg.Extra)
+		}
+
+		// Setup runs Init after the migration, which must not seed over it.
+		cfg.Init()
+		if len(cfg.Categories) != 2 {
+			t.Fatalf("categories after Init = %d, want the migrated list kept", len(cfg.Categories))
+		}
+	})
+
+	t.Run("existing top level categories are left alone", func(t *testing.T) {
+		cfg := &DownloaderStoreConfig{
+			Extra: map[string]any{
+				"downloadCategories": []any{map[string]any{"name": "Old", "path": "/old/Default"}},
+			},
+			Categories: []*DownloadCategory{{Name: "Mine", Path: "/downloads/Mine"}},
+		}
+		if cfg.MigrateLegacyExtraCategories() {
+			t.Fatal("migration must not overwrite existing categories")
+		}
+		if len(cfg.Categories) != 1 || cfg.Categories[0].Name != "Mine" {
+			t.Fatalf("categories = %v, want the existing one", cfg.Categories)
+		}
+		if _, ok := cfg.Extra["downloadCategories"]; !ok {
+			t.Fatal("legacy key must stay for a manual move")
+		}
+	})
+
+	t.Run("missing, empty and malformed legacy lists are a no-op", func(t *testing.T) {
+		if (&DownloaderStoreConfig{}).MigrateLegacyExtraCategories() {
+			t.Fatal("empty config reported a change")
+		}
+		unrelated := &DownloaderStoreConfig{
+			Extra: map[string]any{"themeMode": "dark"},
+		}
+		if unrelated.MigrateLegacyExtraCategories() {
+			t.Fatal("config without the legacy key reported a change")
+		}
+		empty := &DownloaderStoreConfig{
+			Extra: map[string]any{"downloadCategories": []any{}},
+		}
+		if empty.MigrateLegacyExtraCategories() {
+			t.Fatal("empty legacy list reported a change")
+		}
+		malformed := &DownloaderStoreConfig{
+			Extra: map[string]any{"downloadCategories": "not-a-list"},
+		}
+		if malformed.MigrateLegacyExtraCategories() {
+			t.Fatal("malformed legacy list reported a change")
+		}
+		if _, ok := malformed.Extra["downloadCategories"]; !ok {
+			t.Fatal("malformed legacy key must stay untouched")
+		}
+	})
+
+	t.Run("a nil entry in the legacy list is skipped", func(t *testing.T) {
+		cfg := &DownloaderStoreConfig{
+			DownloadDir: "/downloads",
+			Extra: map[string]any{
+				"downloadCategories": []any{
+					nil,
+					map[string]any{"name": "Games", "path": "/old/Games"},
+				},
+			},
+		}
+		if !cfg.MigrateLegacyExtraCategories() {
+			t.Fatal("migration reported no change")
+		}
+		if len(cfg.Categories) != 1 || cfg.Categories[0].Name != "Games" {
+			t.Fatalf("categories = %+v, want the single valid legacy entry", cfg.Categories)
+		}
+	})
+}
+
+func TestDownloaderStoreConfig_AutoCategorizeJSON(t *testing.T) {
+	unset, err := json.Marshal(&DownloaderStoreConfig{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(string(unset), `"autoCategorize"`) {
+		t.Fatalf("unset autoCategorize must be omitted from the api json, got %s", unset)
+	}
+	off, err := json.Marshal(&DownloaderStoreConfig{AutoCategorize: util.BoolPtr(false)})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(off), `"autoCategorize":false`) {
+		t.Fatalf("explicit autoCategorize=false must be emitted, got %s", off)
+	}
+}
+
 func TestDownloaderStoreConfig_Merge(t *testing.T) {
 	type args struct {
 		beforeCfg *DownloaderStoreConfig
@@ -215,6 +437,24 @@ func TestDownloaderStoreConfig_Merge(t *testing.T) {
 				DownloadDir: "after",
 			},
 		},
+		{
+			"Merge Categories and AutoCategorize Override",
+			&DownloaderStoreConfig{},
+			args{
+				beforeCfg: &DownloaderStoreConfig{
+					Categories: []*DownloadCategory{
+						{Name: "Music", Path: "/downloads/Music"},
+					},
+					AutoCategorize: util.BoolPtr(true),
+				},
+			},
+			&DownloaderStoreConfig{
+				Categories: []*DownloadCategory{
+					{Name: "Music", Path: "/downloads/Music"},
+				},
+				AutoCategorize: util.BoolPtr(true),
+			},
+		},
 		{
 			"Merge MaxRunning No Override",
 			&DownloaderStoreConfig{
@@ -428,6 +668,8 @@ func TestDownloaderStoreConfig_Merge(t *testing.T) {
 				Webhook:        tt.fields.Webhook,
 				AutoTorrent:    tt.fields.AutoTorrent,
 				Archive:        tt.fields.Archive,
+				Categories:     tt.fields.Categories,
+				AutoCategorize: tt.fields.AutoCategorize,
 			}
 			if got := cfg.Merge(tt.args.beforeCfg); !reflect.DeepEqual(got, tt.want) {
 				t.Errorf("Merge() = %v, want %v", got, tt.want)

pkg/download/backend_services_test.go

@@ -0,0 +1,245 @@
+package download
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	btProtocol "github.com/GopeedLab/gopeed/internal/protocol/bt"
+	httpProtocol "github.com/GopeedLab/gopeed/internal/protocol/http"
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+type testJobManager struct {
+	httpProtocol.FetcherManager
+	job fetcher.CronJob
+}
+
+func (m *testJobManager) Name() string { return "test" }
+func (m *testJobManager) CronJobs(fetcher.ProtocolHost) []fetcher.CronJob {
+	return []fetcher.CronJob{m.job}
+}
+func testBackendDownloader(t *testing.T, managers ...fetcher.FetcherManager) *Downloader {
+	t.Helper()
+	d := NewDownloader(&DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir(), FetchManagers: managers})
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if err := d.Close(); err != nil {
+			t.Error(err)
+		}
+	})
+	return d
+}
+func TestProtocolJobCoalescesAndCancelsOnClose(t *testing.T) {
+	entered := make(chan struct{})
+	var calls atomic.Int32
+	manager := &testJobManager{job: fetcher.CronJob{Name: "refresh", Every: time.Hour, Timeout: time.Minute, Run: func(ctx context.Context, _ fetcher.TriggerSource) error {
+		if calls.Add(1) == 1 {
+			close(entered)
+		}
+		<-ctx.Done()
+		return ctx.Err()
+	}}}
+	d := testBackendDownloader(t, manager)
+	result := make(chan error, 2)
+	go func() { result <- d.TriggerProtocolJob(context.Background(), "test", "refresh") }()
+	<-entered
+	waiterCtx, cancel := context.WithCancel(context.Background())
+	// A canceled waiter joins the existing work without canceling it.
+	cancel()
+	if err := d.TriggerProtocolJob(waiterCtx, "test", "refresh"); !errors.Is(err, context.Canceled) {
+		t.Fatal(err)
+	}
+	if calls.Load() != 1 {
+		t.Fatalf("executed %d times", calls.Load())
+	}
+	if err := d.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := <-result; !errors.Is(err, context.Canceled) {
+		t.Fatal(err)
+	}
+	if err := d.TriggerProtocolJob(context.Background(), "test", "missing"); !errors.Is(err, ErrProtocolJobNotFound) {
+		t.Fatal(err)
+	}
+}
+func TestProtocolJobPersistsSuccess(t *testing.T) {
+	manager := &testJobManager{job: fetcher.CronJob{Name: "refresh", Every: time.Hour, Timeout: time.Minute, Run: func(context.Context, fetcher.TriggerSource) error { return nil }}}
+	d := testBackendDownloader(t, manager)
+	if err := d.TriggerProtocolJob(context.Background(), "test", "refresh"); err != nil {
+		t.Fatal(err)
+	}
+	var state protocolJobState
+	exists, err := d.storage.Get(bucketProtocolJobs, "test/refresh", &state)
+	if err != nil || !exists || state.LastSuccess.IsZero() {
+		t.Fatalf("state %+v: %v", state, err)
+	}
+}
+func TestRaceResourceValidatesResponsesAndCancelsLosers(t *testing.T) {
+	loserCanceled := make(chan struct{})
+	loserStarted := make(chan struct{})
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.Method == http.MethodConnect:
+			http.Error(w, "official unavailable", http.StatusBadGateway)
+		case strings.HasPrefix(r.URL.Path, "/bad/"):
+			io.WriteString(w, "<html>proxy landing page</html>")
+		case strings.HasPrefix(r.URL.Path, "/good/"):
+			<-loserStarted
+			io.WriteString(w, `{"ok":true}`)
+		case strings.HasPrefix(r.URL.Path, "/slow/"):
+			close(loserStarted)
+			<-r.Context().Done()
+			close(loserCanceled)
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer server.Close()
+	d := testBackendDownloader(t, &httpProtocol.FetcherManager{})
+	cfg, _ := d.GetConfig()
+	cfg.Proxy = &base.DownloaderProxyConfig{Enable: true, Scheme: "http", Host: strings.TrimPrefix(server.URL, "http://")}
+	cfg.GithubMirror = &base.GithubMirrorConfig{Enabled: true, Mirrors: []base.GithubMirror{
+		{Type: "ghProxy", URL: server.URL + "/bad"},
+		{Type: "ghProxy", URL: server.URL + "/slow"},
+		{Type: "ghProxy", URL: server.URL + "/good"},
+	}}
+	if err := d.PutConfig(cfg); err != nil {
+		t.Fatal(err)
+	}
+	body, err := d.fetchResource(context.Background(), "https://raw.githubusercontent.com/owner/repo/main/test.json", 1024, false, func(body []byte) error {
+		if !json.Valid(body) {
+			return errors.New("invalid JSON")
+		}
+		return nil
+	})
+	if err != nil || string(body) != `{"ok":true}` {
+		t.Fatalf("%s %v", body, err)
+	}
+	select {
+	case <-loserCanceled:
+	case <-time.After(time.Second):
+		t.Fatal("losing request was not canceled")
+	}
+}
+
+func TestProtocolConfigInitializesCurrentSchema(t *testing.T) {
+	d := NewDownloader(&DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir(), FetchManagers: []fetcher.FetcherManager{&httpProtocol.FetcherManager{}}})
+	d.cfg.DownloaderStoreConfig = &base.DownloaderStoreConfig{
+		GithubMirror:   &base.GithubMirrorConfig{Enabled: false, Mirrors: []base.GithubMirror{}},
+		ProtocolConfig: map[string]any{"http": map[string]any{"connections": 3}},
+	}
+	if err := d.storage.Setup([]string{bucketConfig}); err != nil {
+		t.Fatal(err)
+	}
+	defer d.storage.Close()
+	if err := d.initProtocolConfigs(); err != nil {
+		t.Fatal(err)
+	}
+	if d.cfg.GithubMirror.Enabled || len(d.cfg.GithubMirror.Mirrors) != 0 {
+		t.Fatal("explicit disabled/empty mirrors lost")
+	}
+	value, err := d.readProtocolConfig("http")
+	if err != nil {
+		t.Fatal(err)
+	}
+	raw, _ := json.Marshal(value)
+	var cfg struct {
+		Connections int `json:"connections"`
+	}
+	if err := json.Unmarshal(raw, &cfg); err != nil || cfg.Connections != 3 {
+		t.Fatalf("current protocol config: %s %v", raw, err)
+	}
+	if err := d.initProtocolConfigs(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestProtocolConfigDoesNotImportOldExtraSettings(t *testing.T) {
+	d := NewDownloader(&DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir(), FetchManagers: []fetcher.FetcherManager{&btProtocol.FetcherManager{}}})
+	d.cfg.DownloaderStoreConfig = &base.DownloaderStoreConfig{
+		Extra: map[string]any{
+			"githubMirror": "obsolete invalid value",
+			"bt":           map[string]any{"customTrackers": []string{"udp://old.example:80/announce"}, "autoUpdateTrackers": true},
+		},
+		ProtocolConfig: map[string]any{"bt": map[string]any{"autoUpdateTrackers": false, "listenPort": 6881}},
+	}
+	if err := d.storage.Setup([]string{bucketConfig}); err != nil {
+		t.Fatal(err)
+	}
+	defer d.storage.Close()
+	if err := d.initProtocolConfigs(); err != nil {
+		t.Fatal(err)
+	}
+	if !d.cfg.GithubMirror.Enabled || len(d.cfg.GithubMirror.Mirrors) != 4 {
+		t.Fatal("missing root mirror config must use new defaults")
+	}
+	value, err := d.readProtocolConfig("bt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	raw, _ := json.Marshal(value)
+	var cfg struct {
+		ListenPort         int      `json:"listenPort"`
+		AutoUpdateTrackers bool     `json:"autoUpdateTrackers"`
+		CustomTrackers     []string `json:"customTrackers"`
+	}
+	if err := json.Unmarshal(raw, &cfg); err != nil || cfg.ListenPort != 6881 || cfg.AutoUpdateTrackers || len(cfg.CustomTrackers) != 0 {
+		t.Fatalf("old extra settings affected protocol config: %s %v", raw, err)
+	}
+}
+
+func TestProtocolJobsRunAutomaticallyAndRestoreSuccess(t *testing.T) {
+	dir := t.TempDir()
+	executed := make(chan fetcher.TriggerSource, 4)
+	manager := func() *testJobManager {
+		return &testJobManager{job: fetcher.CronJob{Name: "refresh", Every: time.Hour, Timeout: time.Second, Run: func(_ context.Context, source fetcher.TriggerSource) error { executed <- source; return nil }}}
+	}
+	makeDownloader := func() *Downloader {
+		d := NewDownloader(&DownloaderConfig{Storage: NewBoltStorage(dir), StorageDir: dir, TempDir: t.TempDir(), FetchManagers: []fetcher.FetcherManager{manager()}})
+		if err := d.Setup(); err != nil {
+			t.Fatal(err)
+		}
+		return d
+	}
+	d := makeDownloader()
+	select {
+	case source := <-executed:
+		if source != fetcher.TriggerScheduled {
+			t.Fatal(source)
+		}
+	case <-time.After(3 * time.Second):
+		t.Fatal("overdue job was not run")
+	}
+	entry := d.protocolJobs.jobs["test/refresh"]
+	entry.mu.Lock()
+	run := entry.active
+	entry.mu.Unlock()
+	if run != nil {
+		<-run.done
+	}
+	if err := d.Close(); err != nil {
+		t.Fatal(err)
+	}
+	d = makeDownloader()
+	defer d.Close()
+	state := d.protocolJobs.jobs["test/refresh"].state
+	if state.LastSuccess.IsZero() {
+		t.Fatal("successful execution not restored")
+	}
+	select {
+	case <-executed:
+		t.Fatal("recently successful job ran again on restart")
+	case <-time.After(30 * time.Millisecond):
+	}
+}

pkg/download/category.go

@@ -0,0 +1,193 @@
+package download
+
+import (
+	"errors"
+	"path"
+	"strings"
+	"unicode"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+// categoryForResource returns the category that receives the resolved
+// resource, or nil when auto categorize does not apply. Only a single file
+// resource is routed: a folder or a multi file resource keeps its directory
+// layout, so its files are never matched one by one, not even when only a
+// single one of them is selected.
+func categoryForResource(cfg *base.DownloaderStoreConfig, res *base.Resource) *base.DownloadCategory {
+	if !cfg.AutoCategorizeEnabled() || len(cfg.Categories) == 0 {
+		return nil
+	}
+	if res == nil || res.Name != "" || len(res.Files) != 1 {
+		return nil
+	}
+	return matchDownloadCategory(cfg, res.Files[0].Name)
+}
+
+// decideDownloadDir returns the download directory of a task. The base
+// directory is the one the task asked for, or the configured download
+// directory when the task left it empty. A task that did not skip auto
+// categorize is routed to the category directory of its resolved resource
+// when one matches. Path placeholders are expanded and the white list check
+// runs on the result, so a category directory the white list rejects falls
+// back to the base directory of this task instead of failing it.
+func (d *Downloader) decideDownloadDir(opts *base.Options, res *base.Resource) (string, error) {
+	return d.decideDownloadDirForTask(opts, res, nil)
+}
+
+func (d *Downloader) decideDownloadDirForTask(opts *base.Options, res *base.Resource, group *TaskGroup) (string, error) {
+	if opts == nil {
+		opts = &base.Options{}
+	}
+	cfg, err := d.GetConfig()
+	if err != nil {
+		return "", err
+	}
+	base := dartTrimSpace(opts.Path)
+	if base == "" {
+		base = cfg.DownloadDir
+	}
+	// Refuse to fall through to the process working directory when neither the
+	// task nor the config names a directory.
+	if base == "" {
+		return "", errors.New("download directory is empty")
+	}
+	if group != nil && opts.SkipAutoCategorize {
+		return d.initDownloadPathForTask(base, group)
+	}
+	target := base
+	if !opts.SkipAutoCategorize {
+		if category := categoryForResource(cfg, res); category != nil {
+			target = dartTrimSpace(category.Path)
+		}
+	}
+	dir, err := d.initDownloadPath(target)
+	if err != nil && target != base {
+		d.Logger.Warn().Err(err).Msgf("category directory %q rejected by white list, falling back to %q", target, base)
+		dir, err = d.initDownloadPath(base)
+	}
+	if err != nil {
+		return "", err
+	}
+	return dir, nil
+}
+
+// suggestedDownloadDir returns the category directory a task would be routed
+// to, or an empty string when auto categorize does not apply. It only reports
+// the decision of decideDownloadDir, it expands no directory and writes
+// nothing.
+func (d *Downloader) suggestedDownloadDir(res *base.Resource) string {
+	cfg, err := d.GetConfig()
+	if err != nil {
+		return ""
+	}
+	category := categoryForResource(cfg, res)
+	if category == nil {
+		return ""
+	}
+	dir, err := d.initDownloadPath(dartTrimSpace(category.Path))
+	if err != nil {
+		return ""
+	}
+	return dir
+}
+
+// asciiLower lowercases the ascii letters of s and leaves the rest alone. The
+// ui lowercases the same way, because the unicode case tables of the two
+// languages disagree for some code points and would let the two sides pick a
+// different category for the same file.
+func asciiLower(s string) string {
+	hasUpper := false
+	for i := 0; i < len(s); i++ {
+		if c := s[i]; c >= 'A' && c <= 'Z' {
+			hasUpper = true
+			break
+		}
+	}
+	if !hasUpper {
+		return s
+	}
+	b := []byte(s)
+	for i, c := range b {
+		if c >= 'A' && c <= 'Z' {
+			b[i] = c + ('a' - 'A')
+		}
+	}
+	return string(b)
+}
+
+// matchDownloadCategory returns the first category whose extension list
+// contains the extension of the given file name, or nil when nothing matches.
+// An empty extension list never matches.
+func matchDownloadCategory(cfg *base.DownloaderStoreConfig, name string) *base.DownloadCategory {
+	ext := fileExtension(name)
+	if ext == "" {
+		return nil
+	}
+	for _, category := range cfg.Categories {
+		if category == nil || category.IsDeleted || dartTrimSpace(category.Path) == "" {
+			continue
+		}
+		for _, e := range normalizeCategoryExtensions(category.Extensions) {
+			if e == ext {
+				return category
+			}
+		}
+	}
+	return nil
+}
+
+// normalizeCategoryExtensions mirrors the dart side: entries are split on
+// commas and whitespace, trimmed, lowercased, stripped of leading dots and
+// deduplicated while keeping the input order, so a stored value like
+// "exe, msi" behaves the same in the backend as it does in the ui.
+func normalizeCategoryExtensions(raw []string) []string {
+	var result []string
+	seen := make(map[string]struct{}, len(raw))
+	for _, item := range raw {
+		for _, part := range strings.FieldsFunc(item, func(r rune) bool {
+			return r == ',' || isECMAScriptSpace(r)
+		}) {
+			ext := asciiLower(strings.TrimLeft(dartTrimSpace(part), "."))
+			if ext == "" {
+				continue
+			}
+			if _, ok := seen[ext]; ok {
+				continue
+			}
+			seen[ext] = struct{}{}
+			result = append(result, ext)
+		}
+	}
+	return result
+}
+
+// fileExtension returns the lower case extension of a file name without the
+// leading dot, e.g. "setup.exe" -> "exe". Windows style separators are
+// treated like the ui does, so a dot inside a directory segment never counts
+// as an extension.
+func fileExtension(name string) string {
+	name = strings.ReplaceAll(name, `\`, "/")
+	return strings.TrimPrefix(asciiLower(path.Ext(name)), ".")
+}
+
+// dartTrimSpace trims the whitespace the dart String.trim() removes, which is
+// the unicode white space set plus the byte order mark. The ui trims the
+// category paths and the extension lists with it, so the backend uses the same
+// set instead of the narrower unicode.IsSpace.
+func dartTrimSpace(s string) string {
+	return strings.TrimFunc(s, func(r rune) bool {
+		return unicode.IsSpace(r) || r == 0xFEFF
+	})
+}
+
+// isECMAScriptSpace reports whether r belongs to the whitespace class of the
+// ECMAScript regular expressions. The ui splits its extension lists with that
+// class, so the backend uses the same one instead of the wider unicode.IsSpace.
+func isECMAScriptSpace(r rune) bool {
+	switch r {
+	case '\t', '\n', '\v', '\f', '\r', ' ', 0x00A0, 0x1680, 0x2028, 0x2029, 0x202F, 0x205F, 0x3000, 0xFEFF:
+		return true
+	}
+	return r >= 0x2000 && r <= 0x200A
+}

pkg/download/category_preparation_test.go

@@ -0,0 +1,566 @@
+package download
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"reflect"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/util"
+)
+
+type failNextTaskPutStorage struct {
+	Storage
+	fail          atomic.Bool
+	failBucket    string
+	beforeTaskPut func(*Task)
+}
+
+func (s *failNextTaskPutStorage) Put(bucket string, key string, value any) error {
+	if bucket == bucketTask && s.beforeTaskPut != nil {
+		s.beforeTaskPut(value.(*Task))
+	}
+	failBucket := s.failBucket
+	if failBucket == "" {
+		failBucket = bucketTask
+	}
+	if bucket == failBucket && (bucket != bucketTask || !value.(*Task).NeedsPreparation) && s.fail.CompareAndSwap(true, false) {
+		return errors.New("task snapshot write failed")
+	}
+	return s.Storage.Put(bucket, key, value)
+}
+
+func TestDownloader_PreparationSaveFailureCanRetry(t *testing.T) {
+	for _, failBucket := range []string{bucketSave, bucketTask} {
+		for _, restart := range []bool{false, true} {
+			t.Run(fmt.Sprintf("%s/restart=%t", failBucket, restart), func(t *testing.T) {
+				url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+				downloadDir := t.TempDir()
+				storageDir := t.TempDir()
+				storage := &failNextTaskPutStorage{Storage: NewBoltStorage(storageDir), failBucket: failBucket}
+				downloader := NewDownloader(&DownloaderConfig{Storage: storage, StorageDir: storageDir})
+				if err := downloader.Setup(); err != nil {
+					t.Fatal(err)
+				}
+				t.Cleanup(func() { downloader.Close() })
+				categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+				if err := os.MkdirAll(categoryDir, 0755); err != nil {
+					t.Fatal(err)
+				}
+				if err := os.WriteFile(filepath.Join(categoryDir, "setup.data"), []byte("existing"), 0644); err != nil {
+					t.Fatal(err)
+				}
+				failed := watchTaskError(t, downloader)
+				storage.fail.Store(true)
+				id, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{Path: downloadDir})
+				if err != nil {
+					t.Fatal(err)
+				}
+				waitTaskError(t, failed)
+				task := downloader.GetTask(id)
+				if !task.NeedsPreparation || task.Meta.Opts.Path != downloadDir || task.Meta.Opts.Name != "" {
+					t.Fatal("failed preparation changed the original directory, name or flag")
+				}
+				if restart {
+					if err := downloader.Close(); err != nil {
+						t.Fatal(err)
+					}
+					downloader = NewDownloader(&DownloaderConfig{Storage: NewBoltStorage(storageDir), StorageDir: storageDir})
+					if err := downloader.Setup(); err != nil {
+						t.Fatal(err)
+					}
+				}
+				done := watchTaskDone(t, downloader)
+				if err := downloader.Continue(&TaskFilter{IDs: []string{id}}); err != nil {
+					t.Fatal(err)
+				}
+				waitTaskDone(t, done)
+				task = downloader.GetTask(id)
+				if task.NeedsPreparation || task.Meta.Opts.Path != categoryDir || task.Meta.Opts.Name != "setup (1).data" {
+					t.Fatalf("retry did not prepare the final directory and duplicate name: %+v", task.Meta.Opts)
+				}
+				data, err := os.ReadFile(filepath.Join(categoryDir, "setup (1).data"))
+				if err != nil || string(data) != "0123456789" {
+					t.Fatalf("downloaded content = %q, %v", data, err)
+				}
+			})
+		}
+	}
+}
+
+// watchTaskError subscribes to the error event, so a failing task can be
+// awaited instead of polled.
+func watchTaskError(t *testing.T, d *Downloader) <-chan struct{} {
+	t.Helper()
+	failed := make(chan struct{}, 1)
+	d.Listener(func(event *Event) {
+		if event.Key == EventKeyError {
+			select {
+			case failed <- struct{}{}:
+			default:
+			}
+		}
+	})
+	return failed
+}
+
+func waitTaskError(t *testing.T, failed <-chan struct{}) {
+	t.Helper()
+	select {
+	case <-failed:
+	case <-time.After(30 * time.Second):
+		t.Fatal("task did not fail")
+	}
+}
+
+// waitTaskStatus waits until the task reaches one of the given statuses.
+func waitTaskStatus(t *testing.T, d *Downloader, task *Task, statuses ...base.Status) base.Status {
+	t.Helper()
+	deadline := time.Now().Add(30 * time.Second)
+	for time.Now().Before(deadline) {
+		status := d.taskStatus(task)
+		for _, want := range statuses {
+			if status == want {
+				return status
+			}
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	t.Fatalf("task status = %q, want one of %v", d.taskStatus(task), statuses)
+	return ""
+}
+
+// setMaxRunning limits the number of tasks that run at the same time.
+func setMaxRunning(t *testing.T, d *Downloader, max int) {
+	t.Helper()
+	cfg, err := d.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	cfg.MaxRunning = max
+	if err := d.PutConfig(cfg); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// A task that waits in the queue is prepared when it starts, the first
+// preparation must not be skipped by the wait status.
+func TestDownloader_QueuedTaskIsPreparedWhenItStarts(t *testing.T) {
+	release := make(chan struct{})
+	slow := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		<-release
+		w.Header().Set("Content-Disposition", `attachment; filename="slow.bin"`)
+		w.Write([]byte("slow"))
+	}))
+	defer slow.Close()
+	fast := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	setMaxRunning(t, downloader, 1)
+
+	// The blocker takes the only running slot.
+	blockerID, err := downloader.CreateDirect(&base.Request{URL: slow.URL}, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	blocker := downloader.GetTask(blockerID)
+	if blocker == nil {
+		t.Fatal("blocker task not found")
+	}
+	waitTaskStatus(t, downloader, blocker, base.DownloadStatusRunning)
+
+	queuedID, err := downloader.CreateDirect(&base.Request{URL: fast}, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	queued := downloader.GetTask(queuedID)
+	if queued == nil {
+		t.Fatal("task not found")
+	}
+	if queued.Status != base.DownloadStatusWait {
+		t.Fatalf("queued task status = %q, want wait", queued.Status)
+	}
+
+	close(release)
+	waitTaskStatus(t, downloader, queued, base.DownloadStatusDone, base.DownloadStatusError)
+
+	if queued.Meta.Opts.Path != categoryDir {
+		t.Fatalf("queued task path = %q, want the category dir %q", queued.Meta.Opts.Path, categoryDir)
+	}
+	if _, err := os.Stat(filepath.Join(categoryDir, "setup.data")); err != nil {
+		t.Fatalf("categorized file missing: %v", err)
+	}
+}
+
+// A task that failed before it was prepared is prepared when it continues.
+func TestDownloader_FailedTaskIsPreparedWhenItContinues(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	allowedDir := t.TempDir()
+
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	// The white list rejects the base directory, so the first start fails.
+	downloader.cfg.WhiteDownloadDirs = []string{allowedDir}
+
+	failed := watchTaskError(t, downloader)
+	taskID, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskError(t, failed)
+	waitTaskStatus(t, downloader, task, base.DownloadStatusError)
+	if !task.NeedsPreparation {
+		t.Fatal("a failed preparation must keep the needs preparation flag")
+	}
+
+	// The white list accepts the base directory now, the retry prepares the
+	// task again.
+	downloader.cfg.WhiteDownloadDirs = []string{allowedDir, downloadDir, categoryDir}
+	done := watchTaskDone(t, downloader)
+	if err := downloader.Continue(&TaskFilter{IDs: []string{taskID}}); err != nil {
+		t.Fatal(err)
+	}
+	waitTaskDone(t, done)
+
+	if task.Meta.Opts.Path != categoryDir {
+		t.Fatalf("retried task path = %q, want the category dir %q", task.Meta.Opts.Path, categoryDir)
+	}
+	if task.NeedsPreparation {
+		t.Fatal("a prepared task must clear the needs preparation flag")
+	}
+}
+
+// A failed preparation save leaves the live task untouched, so the next
+// attempt starts from the original base directory and name.
+func TestDownloader_PreparationSaveFailureKeepsOriginalData(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	storage := &failNextTaskPutStorage{Storage: NewMemStorage()}
+	downloader := NewDownloader(&DownloaderConfig{Storage: storage})
+	if err := downloader.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		downloader.Delete(nil, true)
+		downloader.Clear()
+	})
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	setMaxRunning(t, downloader, 0)
+
+	result, err := downloader.Resolve(&base.Request{URL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+	taskID, err := downloader.CreateWithOptions(result.ID, &base.Options{
+		Path: downloadDir,
+		Name: "renamed?.data",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	originalMeta := util.DeepClone(task.Meta)
+	originalRequest := task.Meta.Req
+	storage.beforeTaskPut = func(snapshot *Task) {
+		if !task.NeedsPreparation || !reflect.DeepEqual(task.Meta, originalMeta) {
+			t.Error("preparation was published before the snapshot was saved")
+		}
+		if snapshot.NeedsPreparation || snapshot.Meta.Opts.Path != categoryDir {
+			t.Error("the snapshot must contain the prepared directory and cleared flag")
+		}
+	}
+
+	storage.fail.Store(true)
+	if err := downloader.prepareTask(task); err == nil {
+		t.Fatal("prepareTask() succeeded, want a storage error")
+	}
+	if !task.NeedsPreparation {
+		t.Fatal("a failed save must keep the needs preparation flag")
+	}
+	if !reflect.DeepEqual(task.Meta, originalMeta) {
+		t.Fatalf("task metadata changed after a failed save:\n got: %#v\nwant: %#v", task.Meta, originalMeta)
+	}
+	if !reflect.DeepEqual(task.fetcher.Meta(), originalMeta) {
+		t.Fatalf("fetcher metadata changed after a failed save:\n got: %#v\nwant: %#v", task.fetcher.Meta(), originalMeta)
+	}
+
+	if err := downloader.prepareTask(task); err != nil {
+		t.Fatal(err)
+	}
+	if task.NeedsPreparation {
+		t.Fatal("a successful retry must clear the needs preparation flag")
+	}
+	if task.Meta.Opts.Path != categoryDir {
+		t.Fatalf("retried task path = %q, want %q", task.Meta.Opts.Path, categoryDir)
+	}
+	if task.Meta != task.fetcher.Meta() || task.Meta.Req != originalRequest {
+		t.Fatal("preparation must preserve the shared metadata and resolved request")
+	}
+	storage.beforeTaskPut = nil
+	task.Meta.Res.Size++
+	var saved Task
+	if _, err := storage.Get(bucketTask, taskID, &saved); err != nil {
+		t.Fatal(err)
+	}
+	if saved.Meta.Res.Size != originalMeta.Res.Size {
+		t.Fatal("live metadata changes must not alter the saved task snapshot")
+	}
+}
+
+// The white list is checked on every start, a task that was rejected once
+// keeps failing instead of writing into the rejected directory.
+func TestDownloader_WhiteListIsCheckedOnEveryStart(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	allowedDir := t.TempDir()
+
+	downloader := newSetupCategoryDownloader(t)
+	putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	downloader.cfg.WhiteDownloadDirs = []string{allowedDir}
+
+	failed := watchTaskError(t, downloader)
+	taskID, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskError(t, failed)
+	waitTaskStatus(t, downloader, task, base.DownloadStatusError)
+
+	// The task is continued, the white list still rejects the directory.
+	failed = watchTaskError(t, downloader)
+	if err := downloader.Continue(&TaskFilter{IDs: []string{taskID}}); err != nil {
+		t.Fatal(err)
+	}
+	waitTaskError(t, failed)
+	waitTaskStatus(t, downloader, task, base.DownloadStatusError)
+
+	if _, err := os.Stat(filepath.Join(downloadDir, "setup.data")); err == nil {
+		t.Fatalf("the file was written into the rejected dir %q", downloadDir)
+	}
+}
+
+// The white list is checked on every start, even for a task that was prepared
+// before the white list changed.
+func TestDownloader_WhiteListIsCheckedForAPreparedTask(t *testing.T) {
+	// The first request is truncated, so the download fails after the task was
+	// prepared and the retry can show that the directory is checked again.
+	var requests int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Disposition", `attachment; filename="setup.data"`)
+		w.Header().Set("Content-Length", "8")
+		w.WriteHeader(http.StatusOK)
+		if atomic.AddInt32(&requests, 1) == 1 {
+			w.Write([]byte("0123"))
+			return
+		}
+		w.Write([]byte("01234567"))
+	}))
+	defer server.Close()
+
+	downloadDir := t.TempDir()
+	allowedDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	downloader.cfg.WhiteDownloadDirs = []string{allowedDir, downloadDir, categoryDir}
+
+	failed := watchTaskError(t, downloader)
+	taskID, err := downloader.CreateDirect(&base.Request{URL: server.URL}, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskError(t, failed)
+	waitTaskStatus(t, downloader, task, base.DownloadStatusError)
+	if task.Meta.Opts.Path != categoryDir {
+		t.Fatalf("task path = %q, want the category dir %q", task.Meta.Opts.Path, categoryDir)
+	}
+
+	// The white list no longer accepts the prepared directory, the task must
+	// not download into it.
+	downloader.cfg.WhiteDownloadDirs = []string{allowedDir}
+	requestsBeforeRetry := atomic.LoadInt32(&requests)
+	failed = watchTaskError(t, downloader)
+	if err := downloader.Continue(&TaskFilter{IDs: []string{taskID}}); err != nil {
+		t.Fatal(err)
+	}
+	waitTaskError(t, failed)
+	waitTaskStatus(t, downloader, task, base.DownloadStatusError)
+
+	if atomic.LoadInt32(&requests) != requestsBeforeRetry {
+		t.Fatalf("the task downloaded into the rejected dir %q", categoryDir)
+	}
+}
+
+// A prepared task keeps its directory, a later start never classifies it
+// again.
+func TestDownloader_PreparedTaskKeepsItsDirectory(t *testing.T) {
+	// The first request is truncated, so the download fails after the task was
+	// prepared and the retry can show that the directory is kept.
+	var requests int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Disposition", `attachment; filename="setup.data"`)
+		w.Header().Set("Content-Length", "8")
+		w.WriteHeader(http.StatusOK)
+		if atomic.AddInt32(&requests, 1) == 1 {
+			w.Write([]byte("0123"))
+			return
+		}
+		w.Write([]byte("01234567"))
+	}))
+	defer server.Close()
+
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+
+	failed := watchTaskError(t, downloader)
+	taskID, err := downloader.CreateDirect(&base.Request{URL: server.URL}, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskError(t, failed)
+	waitTaskStatus(t, downloader, task, base.DownloadStatusError)
+	if task.Meta.Opts.Path != categoryDir {
+		t.Fatalf("task path = %q, want the category dir %q", task.Meta.Opts.Path, categoryDir)
+	}
+	if task.NeedsPreparation {
+		t.Fatal("a prepared task must clear the needs preparation flag")
+	}
+
+	// The category no longer matches the file, the prepared task keeps the
+	// directory it was prepared with.
+	putCategoryConfig(t, downloader, downloadDir, true, []string{"iso"})
+	done := watchTaskDone(t, downloader)
+	if err := downloader.Continue(&TaskFilter{IDs: []string{taskID}}); err != nil {
+		t.Fatal(err)
+	}
+	waitTaskDone(t, done)
+
+	if task.Meta.Opts.Path != categoryDir {
+		t.Fatalf("task path = %q, want the prepared dir %q", task.Meta.Opts.Path, categoryDir)
+	}
+	if _, err := os.Stat(filepath.Join(categoryDir, "setup.data")); err != nil {
+		t.Fatalf("the file was not written into the prepared dir: %v", err)
+	}
+}
+
+// The global default download directory is only saved when the user named the
+// directory explicitly, an auto categorized task never becomes the default.
+func TestDownloader_DefaultPathNeedsTheSkipFlag(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	chosenDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	done := watchTaskDone(t, downloader)
+
+	// The skip flag is missing, the task keeps the auto categorize decision
+	// and the global default stays untouched.
+	if _, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{
+		Path:          chosenDir,
+		AsDefaultPath: true,
+	}); err != nil {
+		t.Fatal(err)
+	}
+	waitTaskDone(t, done)
+	cfg, err := downloader.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.DownloadDir == chosenDir {
+		t.Fatalf("default download dir = %q, want it unchanged", cfg.DownloadDir)
+	}
+
+	// The user named the directory, so it becomes the global default.
+	if _, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{
+		Path:               chosenDir,
+		AsDefaultPath:      true,
+		SkipAutoCategorize: true,
+	}); err != nil {
+		t.Fatal(err)
+	}
+	waitTaskDone(t, done)
+	cfg, err = downloader.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.DownloadDir != chosenDir {
+		t.Fatalf("default download dir = %q, want %q", cfg.DownloadDir, chosenDir)
+	}
+}
+
+// Every task of a batch decides its own directory, the shared options of the
+// batch do not leak into the single tasks.
+func TestDownloader_BatchTasksDecideTheirOwnDirectory(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	chosenDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	done := watchTaskDone(t, downloader)
+
+	taskIDs, err := downloader.CreateDirectBatch(&base.CreateTaskBatch{
+		Reqs: []*base.CreateTaskBatchItem{
+			{
+				Req:  &base.Request{URL: url},
+				Opts: &base.Options{Path: chosenDir, SkipAutoCategorize: true},
+			},
+			{
+				Req:  &base.Request{URL: url},
+				Opts: &base.Options{Path: downloadDir},
+			},
+		},
+		Opts: &base.Options{Path: downloadDir},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(taskIDs) != 2 {
+		t.Fatalf("task count = %d, want 2", len(taskIDs))
+	}
+	waitTaskDone(t, done)
+	waitTaskDone(t, done)
+
+	skipped := downloader.GetTask(taskIDs[0])
+	if skipped == nil {
+		t.Fatal("task not found")
+	}
+	if skipped.Meta.Opts.Path != chosenDir {
+		t.Fatalf("skipped task path = %q, want %q", skipped.Meta.Opts.Path, chosenDir)
+	}
+	categorized := downloader.GetTask(taskIDs[1])
+	if categorized == nil {
+		t.Fatal("task not found")
+	}
+	if categorized.Meta.Opts.Path != categoryDir {
+		t.Fatalf("categorized task path = %q, want %q", categorized.Meta.Opts.Path, categoryDir)
+	}
+}

pkg/download/category_test.go

@@ -0,0 +1,727 @@
+package download
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"slices"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/util"
+)
+
+func newTestCategoryConfig() *base.DownloaderStoreConfig {
+	return &base.DownloaderStoreConfig{
+		DownloadDir:    "./downloads",
+		AutoCategorize: util.BoolPtr(true),
+		Categories: []*base.DownloadCategory{
+			{Name: "Music", Path: filepath.Join("./downloads", "Music"), Extensions: []string{"mp3", "flac"}},
+			{Name: "Video", Path: filepath.Join("./downloads", "Video"), Extensions: []string{"mp4", "mkv"}},
+			{Name: "Program", Path: filepath.Join("./downloads", "Program"), Extensions: []string{"exe", "msi"}},
+		},
+	}
+}
+
+// singleFileResource is the resource shape of a one file task: no folder name
+// and a single file entry.
+func singleFileResource(name string) *base.Resource {
+	return &base.Resource{Files: []*base.FileInfo{{Name: name, Size: 1}}}
+}
+
+// folderResource is the resource shape of a multi file task: a folder name and
+// one entry per file, even when only one of them is selected later.
+func folderResource(name string, files ...string) *base.Resource {
+	res := &base.Resource{Name: name}
+	for _, file := range files {
+		res.Files = append(res.Files, &base.FileInfo{Name: file, Size: 1})
+	}
+	return res
+}
+
+func newUnitCategoryDownloader(cfg *base.DownloaderStoreConfig) *Downloader {
+	d := NewDownloader(nil)
+	d.cfg.DownloaderStoreConfig = cfg
+	return d
+}
+
+func TestDecideDownloadDir(t *testing.T) {
+	programDir := filepath.Join("./downloads", "Program")
+
+	tests := []struct {
+		name string
+		cfg  func(cfg *base.DownloaderStoreConfig)
+		opts *base.Options
+		res  *base.Resource
+		want string
+	}{
+		{
+			name: "matching single file routes to the category",
+			opts: &base.Options{},
+			res:  singleFileResource("setup.exe"),
+			want: programDir,
+		},
+		{
+			name: "an explicit base directory is routed too",
+			opts: &base.Options{Path: "./elsewhere"},
+			res:  singleFileResource("setup.exe"),
+			want: programDir,
+		},
+		{
+			name: "skip flag keeps the configured download directory",
+			opts: &base.Options{Path: "./downloads", SkipAutoCategorize: true},
+			res:  singleFileResource("setup.exe"),
+			want: "./downloads",
+		},
+		{
+			name: "skip flag keeps an explicit directory",
+			opts: &base.Options{Path: "./elsewhere", SkipAutoCategorize: true},
+			res:  singleFileResource("setup.exe"),
+			want: "./elsewhere",
+		},
+		{
+			name: "switch off keeps the base directory",
+			cfg:  func(cfg *base.DownloaderStoreConfig) { cfg.AutoCategorize = util.BoolPtr(false) },
+			opts: &base.Options{},
+			res:  singleFileResource("setup.exe"),
+			want: "./downloads",
+		},
+		{
+			name: "no categories keeps the base directory",
+			cfg:  func(cfg *base.DownloaderStoreConfig) { cfg.Categories = nil },
+			opts: &base.Options{},
+			res:  singleFileResource("setup.exe"),
+			want: "./downloads",
+		},
+		{
+			name: "unknown extension keeps the base directory",
+			opts: &base.Options{},
+			res:  singleFileResource("archive.zip"),
+			want: "./downloads",
+		},
+		{
+			name: "a name without an extension keeps the base directory",
+			opts: &base.Options{},
+			res:  singleFileResource("README"),
+			want: "./downloads",
+		},
+		{
+			name: "a deleted category is skipped",
+			cfg: func(cfg *base.DownloaderStoreConfig) {
+				cfg.Categories = []*base.DownloadCategory{
+					{Name: "Program", Path: programDir, Extensions: []string{"exe"}, IsDeleted: true},
+				}
+			},
+			opts: &base.Options{},
+			res:  singleFileResource("setup.exe"),
+			want: "./downloads",
+		},
+		{
+			name: "a category without a path is skipped",
+			cfg: func(cfg *base.DownloaderStoreConfig) {
+				cfg.Categories = []*base.DownloadCategory{
+					{Name: "Program", Path: "  ", Extensions: []string{"exe"}},
+				}
+			},
+			opts: &base.Options{},
+			res:  singleFileResource("setup.exe"),
+			want: "./downloads",
+		},
+		{
+			name: "a multi file resource keeps its layout",
+			opts: &base.Options{},
+			res:  folderResource("bundle", "setup.exe", "readme.txt"),
+			want: "./downloads",
+		},
+		{
+			name: "a multi file resource with one match still keeps its layout",
+			opts: &base.Options{SelectFiles: []int{0}},
+			res:  folderResource("bundle", "setup.exe", "readme.txt"),
+			want: "./downloads",
+		},
+		{
+			name: "a single file inside a folder resource is not routed",
+			opts: &base.Options{},
+			res:  folderResource("bundle", "setup.exe"),
+			want: "./downloads",
+		},
+		{
+			name: "a missing resource keeps the base directory",
+			opts: &base.Options{},
+			res:  nil,
+			want: "./downloads",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := newTestCategoryConfig()
+			if tt.cfg != nil {
+				tt.cfg(cfg)
+			}
+			d := newUnitCategoryDownloader(cfg)
+			got, err := d.decideDownloadDir(tt.opts, tt.res)
+			if err != nil {
+				t.Fatalf("decideDownloadDir() error = %v", err)
+			}
+			if got != tt.want {
+				t.Fatalf("decideDownloadDir() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestDecideDownloadDirWhiteList(t *testing.T) {
+	defaultDir := filepath.ToSlash(t.TempDir())
+	categoryDir := defaultDir + "/Program"
+	newConfig := func() *base.DownloaderStoreConfig {
+		cfg := newTestCategoryConfig()
+		cfg.DownloadDir = defaultDir
+		cfg.Categories = []*base.DownloadCategory{
+			{Name: "Program", Path: categoryDir, Extensions: []string{"exe"}},
+		}
+		return cfg
+	}
+
+	t.Run("a rejected category directory falls back to the base directory", func(t *testing.T) {
+		d := newUnitCategoryDownloader(newConfig())
+		d.cfg.WhiteDownloadDirs = []string{defaultDir}
+
+		got, err := d.decideDownloadDir(&base.Options{Path: defaultDir}, singleFileResource("setup.exe"))
+		if err != nil {
+			t.Fatalf("expected white list fallback, got %v", err)
+		}
+		if got != defaultDir {
+			t.Fatalf("path = %q, want the base directory %q", got, defaultDir)
+		}
+	})
+
+	t.Run("a rejected base directory is an error", func(t *testing.T) {
+		d := newUnitCategoryDownloader(newConfig())
+		d.cfg.WhiteDownloadDirs = []string{defaultDir}
+
+		_, err := d.decideDownloadDir(&base.Options{Path: defaultDir + "/Other", SkipAutoCategorize: true}, singleFileResource("setup.exe"))
+		if err == nil {
+			t.Fatal("expected a white list error for an explicit directory")
+		}
+	})
+
+	t.Run("equivalent category paths still fall back to the allowed spelling", func(t *testing.T) {
+		cfg := newConfig()
+		cfg.Categories[0].Path = defaultDir + "/."
+		d := newUnitCategoryDownloader(cfg)
+		d.cfg.WhiteDownloadDirs = []string{defaultDir}
+		got, err := d.decideDownloadDir(&base.Options{Path: defaultDir}, singleFileResource("setup.exe"))
+		if err != nil || got != defaultDir {
+			t.Fatalf("decideDownloadDir() = %q, %v; want %q, nil", got, err, defaultDir)
+		}
+	})
+
+	t.Run("an empty base directory is an error", func(t *testing.T) {
+		cfg := newConfig()
+		cfg.DownloadDir = ""
+		d := newUnitCategoryDownloader(cfg)
+
+		_, err := d.decideDownloadDir(&base.Options{SkipAutoCategorize: true}, singleFileResource("setup.exe"))
+		if err == nil {
+			t.Fatal("expected an error for an empty download directory")
+		}
+	})
+}
+
+func TestDecideGroupDownloadDirWhiteList(t *testing.T) {
+	parent := t.TempDir()
+	root := filepath.Join(parent, "folder")
+	nested := filepath.Join(root, "nested")
+	for _, test := range []struct {
+		name    string
+		path    string
+		group   *TaskGroup
+		allowed string
+		wantErr bool
+	}{
+		{name: "group root", path: root, group: &TaskGroup{Path: root}, allowed: filepath.Join(parent, "*")},
+		{name: "nested member", path: nested, group: &TaskGroup{Path: root}, allowed: filepath.Join(parent, "*")},
+		{name: "ordinary nested task", path: nested, allowed: filepath.Join(parent, "*"), wantErr: true},
+		{name: "member outside group", path: filepath.Join(parent, "other"), group: &TaskGroup{Path: root}, allowed: filepath.Join(parent, "*"), wantErr: true},
+		{name: "group permission revoked", path: nested, group: &TaskGroup{Path: root}, allowed: nested, wantErr: true},
+		{name: "literal group name", path: filepath.Join(parent, "%year%", "nested"), group: &TaskGroup{Path: filepath.Join(parent, "%year%")}, allowed: filepath.Join(parent, "*")},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			d := newUnitCategoryDownloader(newTestCategoryConfig())
+			d.cfg.WhiteDownloadDirs = []string{test.allowed}
+			got, err := d.decideDownloadDirForTask(&base.Options{Path: test.path, SkipAutoCategorize: true}, singleFileResource("file.txt"), test.group)
+			if (err != nil) != test.wantErr {
+				t.Fatalf("decideDownloadDirForTask() = %q, %v; want error = %v", got, err, test.wantErr)
+			}
+			if err == nil && got != test.path {
+				t.Fatalf("path = %q, want %q", got, test.path)
+			}
+		})
+	}
+}
+
+func TestSuggestedDownloadDir(t *testing.T) {
+	programDir := filepath.Join("./downloads", "Program")
+
+	tests := []struct {
+		name string
+		cfg  func(cfg *base.DownloaderStoreConfig)
+		res  *base.Resource
+		want string
+	}{
+		{name: "a matching single file is suggested", res: singleFileResource("setup.exe"), want: programDir},
+		{
+			name: "a padded category path matches the creation decision",
+			cfg:  func(cfg *base.DownloaderStoreConfig) { cfg.Categories[2].Path = "  " + programDir + "  " },
+			res:  singleFileResource("setup.exe"),
+			want: programDir,
+		},
+		{
+			name: "the switch off suggests nothing",
+			cfg:  func(cfg *base.DownloaderStoreConfig) { cfg.AutoCategorize = util.BoolPtr(false) },
+			res:  singleFileResource("setup.exe"),
+			want: "",
+		},
+		{name: "a multi file resource suggests nothing", res: folderResource("bundle", "setup.exe"), want: ""},
+		{name: "a folder resource suggests nothing", res: folderResource("bundle", "setup.exe", "a.txt"), want: ""},
+		{name: "an unknown extension suggests nothing", res: singleFileResource("archive.zip"), want: ""},
+		{name: "a missing resource suggests nothing", res: nil, want: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := newTestCategoryConfig()
+			if tt.cfg != nil {
+				tt.cfg(cfg)
+			}
+			d := newUnitCategoryDownloader(cfg)
+			if got := d.suggestedDownloadDir(tt.res); got != tt.want {
+				t.Fatalf("suggestedDownloadDir() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+
+	t.Run("a rejected category directory suggests nothing", func(t *testing.T) {
+		dir := filepath.ToSlash(t.TempDir())
+		cfg := newTestCategoryConfig()
+		cfg.DownloadDir = dir
+		cfg.Categories = []*base.DownloadCategory{
+			{Name: "Program", Path: dir + "/Program", Extensions: []string{"exe"}},
+		}
+		d := newUnitCategoryDownloader(cfg)
+		d.cfg.WhiteDownloadDirs = []string{dir}
+
+		if got := d.suggestedDownloadDir(singleFileResource("setup.exe")); got != "" {
+			t.Fatalf("suggestedDownloadDir() = %q, want an empty suggestion", got)
+		}
+	})
+}
+
+func TestNormalizeCategoryExtensions(t *testing.T) {
+	tests := []struct {
+		raw  []string
+		want []string
+	}{
+		{[]string{"exe, msi"}, []string{"exe", "msi"}},
+		{[]string{" mp3 ", "..exe", "MUSIC"}, []string{"mp3", "exe", "music"}},
+		{[]string{"zip", "ZIP", "zip"}, []string{"zip"}},
+		{[]string{"  ", "..", ""}, nil},
+		{nil, nil},
+	}
+	for _, tt := range tests {
+		got := normalizeCategoryExtensions(tt.raw)
+		if len(got) != len(tt.want) {
+			t.Fatalf("normalizeCategoryExtensions(%q) = %q, want %q", tt.raw, got, tt.want)
+		}
+		for i := range got {
+			if got[i] != tt.want[i] {
+				t.Fatalf("normalizeCategoryExtensions(%q) = %q, want %q", tt.raw, got, tt.want)
+			}
+		}
+	}
+}
+
+// startCategoryFileServer serves a nameless url whose real file name only
+// shows up in the Content-Disposition header.
+func startCategoryFileServer(t *testing.T, fileName string, data []byte) string {
+	t.Helper()
+	mux := http.NewServeMux()
+	mux.HandleFunc("/download", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Disposition", `attachment; filename="`+fileName+`"`)
+		w.Header().Set("Content-Type", "application/octet-stream")
+		http.ServeContent(w, r, fileName, time.Time{}, bytes.NewReader(data))
+	})
+	server := httptest.NewServer(mux)
+	t.Cleanup(server.Close)
+	return server.URL + "/download"
+}
+
+func newSetupCategoryDownloader(t *testing.T) *Downloader {
+	t.Helper()
+	downloader := NewDownloader(nil)
+	if err := downloader.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		downloader.Delete(nil, true)
+		downloader.Clear()
+	})
+	return downloader
+}
+
+func putCategoryConfig(t *testing.T, d *Downloader, downloadDir string, autoCategorize bool, extensions []string) string {
+	t.Helper()
+	categoryDir := filepath.Join(downloadDir, "Program")
+	cfg, err := d.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	cfg.DownloadDir = downloadDir
+	cfg.AutoCategorize = util.BoolPtr(autoCategorize)
+	cfg.Categories = []*base.DownloadCategory{
+		{Name: "Program", Path: categoryDir, Extensions: extensions},
+	}
+	if err := d.PutConfig(cfg); err != nil {
+		t.Fatal(err)
+	}
+	return categoryDir
+}
+
+// watchTaskDone subscribes to the done event before the task is created, so a
+// fast task can not finish before the test starts listening.
+func watchTaskDone(t *testing.T, d *Downloader) <-chan struct{} {
+	t.Helper()
+	done := make(chan struct{}, 1)
+	d.Listener(func(event *Event) {
+		if event.Key == EventKeyDone {
+			select {
+			case done <- struct{}{}:
+			default:
+			}
+		}
+	})
+	return done
+}
+
+func waitTaskDone(t *testing.T, done <-chan struct{}) {
+	t.Helper()
+	select {
+	case <-done:
+	case <-time.After(30 * time.Second):
+		t.Fatal("task did not finish")
+	}
+}
+
+func TestDownloader_CreateDirectAutoCategorize(t *testing.T) {
+	// The url carries no extension, the category is matched on the file name
+	// of the resolved resource.
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	done := watchTaskDone(t, downloader)
+
+	taskID, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskDone(t, done)
+	if task.Meta.Opts.Path != categoryDir {
+		t.Fatalf("task path = %q, want the category dir %q", task.Meta.Opts.Path, categoryDir)
+	}
+	if _, err := os.Stat(filepath.Join(categoryDir, "setup.data")); err != nil {
+		t.Fatalf("categorized file missing: %v", err)
+	}
+}
+
+func TestDownloader_CreateDirectDoesNotMatchTheRename(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	putCategoryConfig(t, downloader, downloadDir, true, []string{"exe"})
+	done := watchTaskDone(t, downloader)
+
+	// opts.Name only renames the saved file, it never decides the category.
+	taskID, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{
+		Path: downloadDir,
+		Name: "renamed.exe",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskDone(t, done)
+	if task.Meta.Opts.Path != downloadDir {
+		t.Fatalf("task path = %q, want the base dir %q", task.Meta.Opts.Path, downloadDir)
+	}
+	if _, err := os.Stat(filepath.Join(downloadDir, "renamed.exe")); err != nil {
+		t.Fatalf("renamed file missing: %v", err)
+	}
+}
+
+func TestDownloader_CreateDirectSkipAutoCategorize(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	chosenDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	done := watchTaskDone(t, downloader)
+
+	taskID, err := downloader.CreateDirect(&base.Request{URL: url}, &base.Options{
+		Path:               chosenDir,
+		SkipAutoCategorize: true,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskDone(t, done)
+	if task.Meta.Opts.Path != chosenDir {
+		t.Fatalf("task path = %q, want the chosen dir %q", task.Meta.Opts.Path, chosenDir)
+	}
+	if _, err := os.Stat(filepath.Join(chosenDir, "setup.data")); err != nil {
+		t.Fatalf("file missing in the chosen dir: %v", err)
+	}
+}
+
+func TestDownloader_CreateWithOptionsAutoCategorize(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	done := watchTaskDone(t, downloader)
+
+	rr, err := downloader.Resolve(&base.Request{URL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if rr.SuggestedDownloadDir != categoryDir {
+		t.Fatalf("suggested dir = %q, want %q", rr.SuggestedDownloadDir, categoryDir)
+	}
+	taskID, err := downloader.CreateWithOptions(rr.ID, &base.Options{Path: downloadDir})
+	if err != nil {
+		t.Fatal(err)
+	}
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	waitTaskDone(t, done)
+	if task.Meta.Opts.Path != categoryDir {
+		t.Fatalf("task path = %q, want the category dir %q", task.Meta.Opts.Path, categoryDir)
+	}
+}
+
+func TestDownloader_CreateWithOptionsKeepsTheDefaultDirectory(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+	done := watchTaskDone(t, downloader)
+
+	rr, err := downloader.Resolve(&base.Request{URL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+	taskID, err := downloader.CreateWithOptions(rr.ID, &base.Options{
+		Path:          downloadDir,
+		AsDefaultPath: true,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	waitTaskDone(t, done)
+
+	// The task lands in the category directory, but that must not become the
+	// global default download directory.
+	task := downloader.GetTask(taskID)
+	if task == nil {
+		t.Fatal("task not found")
+	}
+	if task.Meta.Opts.Path == downloadDir {
+		t.Fatalf("task path = %q, want the category dir", task.Meta.Opts.Path)
+	}
+	cfg, err := downloader.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.DownloadDir != downloadDir {
+		t.Fatalf("default download dir = %q, want the base dir %q", cfg.DownloadDir, downloadDir)
+	}
+}
+
+func TestDownloader_ResolveSuggestsWithoutSideEffects(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	categoryDir := putCategoryConfig(t, downloader, downloadDir, true, []string{"data"})
+
+	rr, err := downloader.Resolve(&base.Request{URL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if rr.SuggestedDownloadDir != categoryDir {
+		t.Fatalf("suggested dir = %q, want %q", rr.SuggestedDownloadDir, categoryDir)
+	}
+	if _, err := os.Stat(categoryDir); !os.IsNotExist(err) {
+		t.Fatalf("resolve created the suggested directory: %v", err)
+	}
+	cfg, err := downloader.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.DownloadDir != downloadDir {
+		t.Fatalf("resolve changed the download dir to %q", cfg.DownloadDir)
+	}
+}
+
+func TestDownloader_ResolveSuggestsNothingWhenTheSwitchIsOff(t *testing.T) {
+	url := startCategoryFileServer(t, "setup.data", []byte("0123456789"))
+	downloadDir := t.TempDir()
+	downloader := newSetupCategoryDownloader(t)
+	putCategoryConfig(t, downloader, downloadDir, false, []string{"data"})
+
+	rr, err := downloader.Resolve(&base.Request{URL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if rr.SuggestedDownloadDir != "" {
+		t.Fatalf("suggested dir = %q, want an empty suggestion", rr.SuggestedDownloadDir)
+	}
+}
+
+func TestDownloader_SetupMigratesLegacyExtraCategories(t *testing.T) {
+	storage := NewMemStorage()
+	if err := storage.Setup([]string{bucketConfig}); err != nil {
+		t.Fatal(err)
+	}
+	legacy := &base.DownloaderStoreConfig{
+		DownloadDir: t.TempDir(),
+		Extra: map[string]any{
+			"downloadCategories": []any{
+				map[string]any{"name": "", "path": filepath.Join(t.TempDir(), "Music"), "isBuiltIn": true, "nameKey": "categoryMusic"},
+			},
+		},
+	}
+	if err := storage.Put(bucketConfig, "config", legacy); err != nil {
+		t.Fatal(err)
+	}
+
+	downloader := NewDownloader(&DownloaderConfig{Storage: storage, StorageDir: t.TempDir()})
+	if err := downloader.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		downloader.Delete(nil, true)
+		downloader.Clear()
+	}()
+
+	cfg, err := downloader.GetConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(cfg.Categories) != 1 || cfg.Categories[0].NameKey != "categoryMusic" || len(cfg.Categories[0].Extensions) == 0 {
+		t.Fatalf("categories = %+v, want the migrated built-in with its default extensions", cfg.Categories)
+	}
+	if _, ok := cfg.Extra["downloadCategories"]; ok {
+		t.Fatal("in memory config still carries the legacy key")
+	}
+
+	// The cleared key has to be persisted, not only held in memory.
+	var stored base.DownloaderStoreConfig
+	exist, err := storage.Get(bucketConfig, "config", &stored)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !exist {
+		t.Fatal("stored config missing")
+	}
+	if _, ok := stored.Extra["downloadCategories"]; ok {
+		t.Fatal("stored config still carries the legacy key")
+	}
+	if len(stored.Categories) != 1 || stored.Categories[0].NameKey != "categoryMusic" {
+		t.Fatalf("stored categories = %+v, want the migrated list", stored.Categories)
+	}
+}
+
+// readOnlyConfigStorage refuses every config write, so the setup can not
+// persist a migrated category list.
+type readOnlyConfigStorage struct {
+	Storage
+}
+
+func (s *readOnlyConfigStorage) Put(bucket string, key string, v any) error {
+	if bucket == bucketConfig {
+		return errors.New("config storage is read only")
+	}
+	return s.Storage.Put(bucket, key, v)
+}
+
+func TestDownloader_SetupFailsWhenTheMigrationCanNotBePersisted(t *testing.T) {
+	storage := NewMemStorage()
+	if err := storage.Setup([]string{bucketConfig}); err != nil {
+		t.Fatal(err)
+	}
+	legacy := &base.DownloaderStoreConfig{
+		DownloadDir: t.TempDir(),
+		Extra: map[string]any{
+			"downloadCategories": []any{
+				map[string]any{"name": "Music", "path": filepath.Join(t.TempDir(), "Music")},
+			},
+		},
+	}
+	if err := storage.Put(bucketConfig, "config", legacy); err != nil {
+		t.Fatal(err)
+	}
+
+	// The migrated list can not be persisted, so the setup reports the write
+	// error instead of continuing with a category list that is lost on restart.
+	downloader := NewDownloader(&DownloaderConfig{Storage: &readOnlyConfigStorage{Storage: storage}, StorageDir: t.TempDir()})
+	if err := downloader.Setup(); err == nil {
+		t.Fatal("setup reported no error, want the failed config write")
+	}
+}
+
+// categoryMatchingCases is the shared extension rule table of the backend and
+// the ui. The ui runs the same file, see
+// ui/flutter/test/api/downloader_config_test.dart, so a rule that only changes
+// on one side breaks the other side's test.
+type categoryMatchingCases struct {
+	NormalizeExtensions []struct {
+		Input    []string `json:"input"`
+		Expected []string `json:"expected"`
+	} `json:"normalizeExtensions"`
+}
+
+func TestSharedCategoryMatchingRules(t *testing.T) {
+	data, err := os.ReadFile(filepath.Join("testdata", "category_matching_cases.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var cases categoryMatchingCases
+	if err := json.Unmarshal(data, &cases); err != nil {
+		t.Fatal(err)
+	}
+	for _, c := range cases.NormalizeExtensions {
+		got := normalizeCategoryExtensions(c.Input)
+		if !slices.Equal(got, c.Expected) {
+			t.Errorf("normalizeCategoryExtensions(%q) = %q, want %q", c.Input, got, c.Expected)
+		}
+	}
+}

pkg/download/engine/extension_headers_test.go

@@ -0,0 +1,222 @@
+package engine_test
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/pkg/download/engine"
+)
+
+// Exercise server-side header permissions, including formerly forbidden names,
+// download authentication, metadata and non-safelisted no-cors values.
+var extensionRequestHeaders = [][2]string{
+	{"Accept-Charset", "utf-8"}, {"Accept-Encoding", "identity"},
+	{"Access-Control-Request-Headers", "authorization, x-download"},
+	{"Access-Control-Request-Method", "POST"}, {"Connection", "close"},
+	{"Connection", "keep-alive"},
+	{"Content-Length", "4"}, {"Cookie", "sid=manual"}, {"Cookie2", "legacy=1"},
+	{"Date", "Fri, 09 Oct 2026 00:00:00 GMT"}, {"DNT", "1"},
+	{"Host", "download.example:1234"}, {"Origin", "https://download.example"},
+	{"Permissions-Policy", "camera=()"}, {"Referer", "https://download.example/file"},
+	{"TE", "trailers"}, {"Trailer", "X-Checksum"}, {"Set-Cookie", "sid=request"},
+	{"Set-Cookie2", "legacy=request"}, {"Via", "1.1 proxy"},
+	{"Proxy-Authorization", "Basic dGVzdA=="}, {"Proxy-", "custom"},
+	{"Sec-Fetch-Site", "same-origin"}, {"Sec-Fetch-Mode", "custom"},
+	{"Sec-CH-UA", `"Download client"`}, {"Sec-", "custom"},
+	{"X-HTTP-Method", "TRACE"}, {"X-HTTP-Method-Override", "CONNECT"},
+	{"X-Method-Override", "TRACK"}, {"Authorization", "Bearer token"},
+	{"User-Agent", "Gopeed extension"}, {"Content-Type", "application/json"},
+	{"Range", "bytes=0-1,3-4"}, {"X-Download-Token", "custom"},
+	{"Accept-Language", strings.Repeat("x", 129)},
+}
+
+func TestExtensionRequestsSendNodeHeaders(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
+		body, err := io.ReadAll(request.Body)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		name := request.URL.Query().Get("header")
+		value := request.Header.Get(name)
+		if name == "Host" {
+			value = request.Host
+		}
+		_ = json.NewEncoder(w).Encode([]string{value, string(body)})
+	}))
+	t.Cleanup(server.Close)
+	clients := []struct{ name, script string }{
+		{"fetch record", `const response = await fetch(url, {method: "POST", body: "test", headers: {[name]: value}}); return (await response.text()).trim();`},
+		{"fetch no-cors Headers", `const response = await fetch(url, {method: "POST", body: "test", mode: "no-cors", headers: new Headers([[name.toLowerCase(), value]])}); return (await response.text()).trim();`},
+		{"fetch Request clone", `const request = new Request(url, {method: "POST", body: "test", mode: "same-origin", headers: [[name.toUpperCase(), value]]}); const response = await fetch(request.clone()); return (await response.text()).trim();`},
+	}
+	for _, credentials := range []bool{false, true} {
+		clients = append(clients, struct{ name, script string }{
+			fmt.Sprintf("XHR credentials=%t", credentials),
+			fmt.Sprintf(`return new Promise((resolve, reject) => {
+				const xhr = new XMLHttpRequest();
+				xhr.open("POST", url);
+				xhr.withCredentials = %t;
+				xhr.setRequestHeader(name.toLowerCase(), value);
+				xhr.onload = () => resolve(xhr.responseText.trim());
+				xhr.onerror = () => reject(new Error("XHR failed"));
+				xhr.send("test");
+			});`, credentials),
+		})
+	}
+	for _, header := range extensionRequestHeaders {
+		for _, client := range clients {
+			t.Run(header[0]+"/"+client.name, func(t *testing.T) {
+				runtime := engine.NewEngine(nil)
+				t.Cleanup(runtime.Close)
+				value, err := runtime.RunString(fmt.Sprintf(`(async () => {
+					const name = %q, value = %q;
+					const url = %q + "?header=" + encodeURIComponent(name);
+					%s
+				})()`, header[0], header[1], server.URL, client.script))
+				if err != nil {
+					t.Fatal(err)
+				}
+				want, _ := json.Marshal([]string{header[1], "test"})
+				if value != string(want) {
+					t.Fatalf("server received %#v, want %s", value, want)
+				}
+			})
+		}
+	}
+}
+
+func TestExtensionHeaderMutationsMatchNode(t *testing.T) {
+	headers := append([][2]string(nil), extensionRequestHeaders...)
+	// Node stores these in Headers/Request, but rejects them during fetch.
+	headers = append(headers, [2]string{"Expect", "100-continue"}, [2]string{"Keep-Alive", "timeout=5"}, [2]string{"Transfer-Encoding", "chunked"}, [2]string{"Upgrade", "websocket"})
+	data, _ := json.Marshal(headers)
+	runtime := engine.NewEngine(nil)
+	t.Cleanup(runtime.Close)
+	_, err := runtime.RunString(fmt.Sprintf(`(() => {
+		for (const mode of ["cors", "same-origin", "no-cors"]) {
+			for (const [name, value] of %s) {
+				const request = new Request("http://example.com", {mode, headers: {[name]: value}});
+				const headers = request.headers;
+				if (headers.get(name) !== value) throw new Error("Filtered init " + name + " in " + mode);
+				headers.delete(name.toUpperCase());
+				if (headers.has(name)) throw new Error("Cannot delete " + name);
+				headers.append(name, value);
+				if (headers.get(name) !== value) throw new Error("Cannot append " + name);
+				headers.set(name, value);
+				if (request.clone().headers.get(name) !== value) throw new Error("Cannot clone " + name);
+			}
+		}
+		return true;
+	})()`, data))
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestExtensionRequestsIgnoreUnsupportedTransportHeaders(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
+		body, err := io.ReadAll(request.Body)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		value := request.Header.Get(request.URL.Query().Get("header"))
+		_ = json.NewEncoder(w).Encode([]string{value, string(body)})
+	}))
+	t.Cleanup(server.Close)
+	for _, header := range [][2]string{
+		{"Expect", "100-continue"}, {"Keep-Alive", "timeout=5"},
+		{"Transfer-Encoding", "chunked"}, {"Upgrade", "websocket"},
+		{"Connection", "upgrade"}, {"Content-Length", "3"},
+		{"Content-Length", "5"}, {"Content-Length", "invalid"},
+		{"Content-Length", "-1"}, {"Content-Length", ""},
+	} {
+		for _, xhr := range []bool{false, true} {
+			t.Run(fmt.Sprintf("%s=%s/XHR=%t", header[0], header[1], xhr), func(t *testing.T) {
+				runtime := engine.NewEngine(nil)
+				t.Cleanup(runtime.Close)
+				value, err := runtime.RunString(fmt.Sprintf(`(async () => {
+					const name = %q, value = %q;
+					const url = %q + "?header=" + encodeURIComponent(name);
+					if (%t) return new Promise((resolve, reject) => {
+						const xhr = new XMLHttpRequest();
+						xhr.open("POST", url);
+						xhr.setRequestHeader(name, value);
+						xhr.onload = () => resolve(xhr.responseText.trim());
+						xhr.onerror = () => reject(new Error("XHR failed"));
+						xhr.send("test");
+					});
+					const response = await fetch(url, {method: "POST", body: "test", headers: {[name]: value}});
+					return (await response.text()).trim();
+				})()`, header[0], header[1], server.URL, xhr))
+				if err != nil {
+					t.Fatal(err)
+				}
+				wireValue := ""
+				if header[0] == "Content-Length" {
+					wireValue = "4"
+				}
+				want, _ := json.Marshal([]string{wireValue, "test"})
+				if value != string(want) {
+					t.Fatalf("server received %#v, want %s", value, want)
+				}
+			})
+		}
+	}
+}
+
+func TestExtensionResponseExposesSetCookie(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Add("Set-Cookie", "sid=one; HttpOnly")
+		w.Header().Add("Set-Cookie", "token=two")
+		w.Header().Set("Set-Cookie2", "legacy=three")
+		_, _ = w.Write([]byte("ok"))
+	}))
+	t.Cleanup(server.Close)
+	runtime := engine.NewEngine(nil)
+	t.Cleanup(runtime.Close)
+	value, err := runtime.RunString(fmt.Sprintf(`(async () => {
+		const response = await fetch(%q);
+		const clone = response.clone();
+		await response.text(); await clone.text();
+		let immutable = false;
+		try { response.headers.set("Set-Cookie", "changed=1"); } catch (error) { immutable = error instanceof TypeError; }
+		const synthetic = new Response(null, {headers: {"Set-Cookie": "initial=1"}});
+		synthetic.headers.append("Set-Cookie", "appended=2");
+		return JSON.stringify({cookies: clone.headers.getSetCookie(), legacy: response.headers.get("set-cookie2"), immutable, synthetic: synthetic.headers.getSetCookie()});
+	})()`, server.URL))
+	if err != nil {
+		t.Fatal(err)
+	}
+	const want = `{"cookies":["sid=one; HttpOnly","token=two"],"legacy":"legacy=three","immutable":true,"synthetic":["initial=1","appended=2"]}`
+	if value != want {
+		t.Fatalf("unexpected response headers: got %#v want %s", value, want)
+	}
+}
+
+func TestExtensionHeadersRejectInvalidSyntax(t *testing.T) {
+	runtime := engine.NewEngine(nil)
+	t.Cleanup(runtime.Close)
+	_, err := runtime.RunString(`(() => {
+		for (const [name, value] of [["Bad Header", "ok"], ["", "ok"], ["X:Header", "ok"],
+			["X-Test", "a\nb"], ["X-Test", "a\rb"], ["X-Test", "\0"], ["X-Test", "\u0100"]]) {
+			for (const create of [() => new Headers([[name, value]]),
+				() => new Request("http://example.com", {mode: "no-cors", headers: {[name]: value}}),
+				() => { const xhr = new XMLHttpRequest(); xhr.open("GET", "http://example.com"); xhr.setRequestHeader(name, value); }]) {
+				let rejected = false;
+				try { create(); } catch (error) { rejected = error instanceof TypeError; }
+				if (!rejected) throw new Error("Accepted invalid HTTP header syntax");
+			}
+		}
+		return true;
+	})()`)
+	if err != nil {
+		t.Fatal(err)
+	}
+}

pkg/download/engine/fetch_integration_test.go

@@ -105,6 +105,105 @@ func TestXMLHttpRequestUsesFetch(t *testing.T) {
 	}
 }
 
+func TestExtensionRequestsSendExplicitCookie(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
+		_, _ = w.Write([]byte(request.Header.Get("Cookie")))
+	}))
+	t.Cleanup(server.Close)
+
+	type requestTest struct {
+		name   string
+		script string
+	}
+	tests := []requestTest{
+		{"fetch record", `const response = await fetch(url, {headers: {Cookie: cookie}}); return response.text();`},
+		{"fetch Headers", `const response = await fetch(url, {headers: new Headers({cookie})}); return response.text();`},
+		{"fetch pairs", `const response = await fetch(url, {headers: [["cOoKiE", cookie]]}); return response.text();`},
+		{"fetch repeated Cookie", `const headers = new Headers([["Cookie", "sid=manual"], ["cookie", "token=provided"]]); if (headers.get("cookie") !== cookie) throw new Error("Incorrect Cookie separator"); const response = await fetch(url, {headers}); return response.text();`},
+		{"fetch Request clone", `const request = new Request(url, {headers: {Cookie: cookie}}); const response = await fetch(request.clone()); return response.text();`},
+		{"fetch Request set", `const request = new Request(url); request.headers.set("Cookie", cookie); const response = await fetch(request); return response.text();`},
+		{"fetch Request append", `const request = new Request(url); request.headers.append("Cookie", cookie); const response = await fetch(request); return response.text();`},
+		{"fetch no-cors mutations", `const request = new Request(url, {mode: "no-cors"}); request.headers.set("Cookie", "removed=1"); request.headers.delete("COOKIE"); if (request.headers.has("cookie")) throw new Error("Cookie was not deleted"); request.headers.append("Cookie", cookie); const response = await fetch(request.clone()); return response.text();`},
+	}
+	for _, mode := range []string{"cors", "same-origin", "no-cors"} {
+		for _, credentials := range []string{"omit", "same-origin", "include"} {
+			tests = append(tests, requestTest{
+				name:   "fetch " + mode + " " + credentials,
+				script: fmt.Sprintf(`const response = await fetch(url, {headers: {Cookie: cookie}, mode: %q, credentials: %q}); return response.text();`, mode, credentials),
+			})
+		}
+	}
+	for _, withCredentials := range []bool{false, true} {
+		tests = append(tests, requestTest{
+			name: fmt.Sprintf("XHR withCredentials=%t", withCredentials),
+			script: fmt.Sprintf(`return new Promise((resolve, reject) => {
+				const xhr = new XMLHttpRequest();
+				xhr.open("GET", url);
+				xhr.withCredentials = %t;
+				xhr.setRequestHeader("cOoKiE", cookie);
+				xhr.onload = () => resolve(xhr.responseText);
+				xhr.onerror = () => reject(new Error("XHR failed"));
+				xhr.send();
+			});`, withCredentials),
+		})
+	}
+	tests = append(tests, requestTest{"XHR repeated Cookie", `return new Promise((resolve, reject) => {
+		const xhr = new XMLHttpRequest();
+		xhr.open("GET", url);
+		xhr.setRequestHeader("Cookie", "sid=manual");
+		xhr.setRequestHeader("cookie", "token=provided");
+		xhr.onload = () => resolve(xhr.responseText);
+		xhr.onerror = () => reject(new Error("XHR failed"));
+		xhr.send();
+	});`})
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			runtime := engine.NewEngine(nil)
+			t.Cleanup(runtime.Close)
+			const cookie = "sid=manual; token=provided"
+			value, err := runtime.RunString(fmt.Sprintf(`(async () => {
+				const url = %q;
+				const cookie = %q;
+				%s
+			})()`, server.URL, cookie, test.script))
+			if err != nil {
+				t.Fatal(err)
+			}
+			if value != cookie {
+				t.Fatalf("server received Cookie %q, want %q", value, cookie)
+			}
+		})
+	}
+}
+
+func TestFetchExplicitCookieWithCookieJar(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
+		if request.URL.Path == "/seed" {
+			http.SetCookie(w, &http.Cookie{Name: "stored", Value: "jar", Path: "/"})
+		}
+		_, _ = w.Write([]byte(request.Header.Get("Cookie")))
+	}))
+	t.Cleanup(server.Close)
+	runtime := engine.NewEngine(nil)
+	t.Cleanup(runtime.Close)
+	value, err := runtime.RunString(fmt.Sprintf(`(async () => {
+		const url = %q;
+		await (await fetch(url + "/seed")).text();
+		const automatic = await (await fetch(url)).text();
+		const combined = await (await fetch(url, {headers: {Cookie: "manual=provided"}})).text();
+		const omitted = await (await fetch(url, {credentials: "omit", headers: {Cookie: "manual=provided"}})).text();
+		const empty = await (await fetch(url, {credentials: "omit"})).text();
+		return JSON.stringify({automatic, combined, omitted, empty});
+	})()`, server.URL))
+	if err != nil {
+		t.Fatal(err)
+	}
+	const want = `{"automatic":"stored=jar","combined":"manual=provided; stored=jar","omitted":"manual=provided","empty":""}`
+	if value != want {
+		t.Fatalf("unexpected CookieJar result: got %#v want %s", value, want)
+	}
+}
+
 func TestFetchResponseAndRequestCloneHaveIndependentBodies(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
 		if request.Method == http.MethodPost {

pkg/download/engine/ffmpeg/README.md

@@ -30,6 +30,21 @@ support must remain disabled. Do not declare the sum of the input sizes as the
 output size. The downloader reads the merged output as one file; FFmpeg errors
 propagate through the stream instead of completing a partial download.
 
+Extension resolve results can set `files[].size` to an estimated output size,
+for example the sum of the selected video and audio input lengths. Clients forward
+this value as the optional task creation `opts.size` for HTTP downloads only
+(including Blob URLs served over HTTP). Other protocols, including HLS, ignore
+this option. The estimate is persisted
+and displayed while queued and downloading. A valid HTTP total length (including
+zero) always overrides it; otherwise a clean EOF records the actual output length.
+Estimates never determine byte ranges, file allocation, integrity checks, or task
+completion. Size authority is persisted alongside HTTP connection state for
+pause/retry and process restart.
+
+Blob options are unchanged: `createObjectURL`'s `size` is an exact source length,
+not an estimate. Leave it unset for generated merge output and pass any estimate
+through the extension resolve file instead.
+
 ## JS inputs, including SABR
 
 Stream inputs **must** be created by an `inputs({ signal })` callback. It returns
@@ -130,7 +145,8 @@ associates its input progress with that Blob. No public progress callback or
 extra `createObjectURL` argument is required. Return the merge stream itself;
 wrapping it in another stream loses this association. Downloaded bytes count
 unique input offsets; speed counts received input bytes, including re-fetches.
-The task stays downloading with unknown total size while queued or merging;
+The task stays downloading while queued or merging, displaying the optional
+`files[].size` estimate (or an unknown total when omitted);
 once input traffic stops the displayed speed settles to zero. Completion uses
 the actual merged output size. Generated output waits are governed by producer
 cancellation/errors rather than the HTTP body idle timeout; HTTP media inputs

pkg/download/engine/inject/fetch/fetch.js

@@ -122,7 +122,7 @@
       if (name === "set-cookie") {
         for (const value of values) result.push([name, value]);
       } else {
-        result.push([name, values.join(", ")]);
+        result.push([name, values.join(name === "cookie" ? "; " : ", ")]);
       }
     }
     return result;
@@ -158,49 +158,10 @@
     return iterator;
   }
 
-  function forbiddenRequestHeader(name, value) {
-    if (name.startsWith("proxy-") || name.startsWith("sec-")) return true;
-    if ([
-      "accept-charset", "accept-encoding", "access-control-request-headers",
-      "access-control-request-method", "connection", "content-length", "cookie",
-      "cookie2", "date", "dnt", "expect", "host", "keep-alive", "origin",
-      "permissions-policy", "referer", "te", "trailer", "transfer-encoding",
-      "set-cookie", "upgrade", "via",
-    ].includes(name)) return true;
-    if (["x-http-method", "x-http-method-override", "x-method-override"].includes(name)) {
-      return String(value).split(",").some((method) => {
-        method = method.trim().toUpperCase();
-        return method === "CONNECT" || method === "TRACE" || method === "TRACK";
-      });
-    }
-    return false;
-  }
-
-  function noCORSSafelistedRequestHeader(name, value) {
-    if (value.length > 128) return false;
-    const hasUnsafeByte = /[\x00-\x08\x0A-\x1F\x7F"():<>?@\[\\\]{}]/.test(value);
-    if (name === "accept") return !hasUnsafeByte;
-    if (name === "accept-language" || name === "content-language") {
-      return /^[0-9A-Za-z *,\-.;=]*$/.test(value);
-    }
-    if (name === "content-type") {
-      if (hasUnsafeByte) return false;
-      const essence = value.split(";", 1)[0].trim().toLowerCase();
-      return essence === "application/x-www-form-urlencoded" ||
-        essence === "multipart/form-data" || essence === "text/plain";
-    }
-    if (name === "range") return /^bytes=[0-9]+-[0-9]*$/.test(value);
-    return false;
-  }
-
-  function blockedByGuard(headers, name, value) {
+  function assertMutableHeaders(headers) {
+    // Match Node/Undici: HTTP syntax and immutability still apply, but browser
+    // forbidden-header and no-cors safelist rules do not apply to extensions.
     if (headers._guard === "immutable") throw new TypeError("Headers are immutable");
-    if (headers._guard === "request") return forbiddenRequestHeader(name, value);
-    if (headers._guard === "request-no-cors") {
-      return forbiddenRequestHeader(name, value) || !noCORSSafelistedRequestHeader(name, value);
-    }
-    if (headers._guard === "response") return name === "set-cookie" || name === "set-cookie2";
-    return false;
   }
 
   class Headers {
@@ -235,27 +196,21 @@
       name = normalizeHeaderName(name);
       value = normalizeHeaderValue(value);
       const values = this._values.get(name);
-      const combinedValue = values && name !== "set-cookie" ? values.join(", ") + ", " + value : value;
-	  if (blockedByGuard(this, name, combinedValue)) return;
+      assertMutableHeaders(this);
       if (values) values.push(value);
       else this._values.set(name, [value]);
     }
 
     delete(name) {
-	  name = normalizeHeaderName(name);
-	  if (this._guard === "immutable") throw new TypeError("Headers are immutable");
-	  if (this._guard === "request-no-cors") {
-		if (forbiddenRequestHeader(name, "") || !["accept", "accept-language", "content-language", "content-type", "range"].includes(name)) return;
-		this._values.delete(name);
-		return;
-	  }
-	  if (blockedByGuard(this, name, "")) return;
+      name = normalizeHeaderName(name);
+      assertMutableHeaders(this);
       this._values.delete(name);
     }
 
     get(name) {
-      const values = this._values.get(normalizeHeaderName(name));
-      return values ? values.join(", ") : null;
+      name = normalizeHeaderName(name);
+      const values = this._values.get(name);
+      return values ? values.join(name === "cookie" ? "; " : ", ") : null;
     }
 
     getSetCookie() {
@@ -268,10 +223,10 @@
     }
 
     set(name, value) {
-	  name = normalizeHeaderName(name);
-	  value = normalizeHeaderValue(value);
-	  if (blockedByGuard(this, name, value)) return;
-	  this._values.set(name, [value]);
+      name = normalizeHeaderName(name);
+      value = normalizeHeaderValue(value);
+      assertMutableHeaders(this);
+      this._values.set(name, [value]);
     }
 
     keys() { return createHeadersIterator(this, "key"); }
@@ -484,7 +439,7 @@
       }
       this._duplex = "half";
       const headerInit = init.headers !== undefined ? init.headers : (source ? source.headers : undefined);
-      this._headers = new Headers(headerInit, this._mode === "no-cors" ? "request-no-cors" : "request");
+      this._headers = new Headers(headerInit, "request");
       let body = init.body !== undefined ? init.body : (source ? source._bodyInit : null);
       if (source && !bodyWasOverridden && source.body) body = transferReadableStream(source.body);
       const bodyIsStream = typeof ReadableStream !== "undefined" && body instanceof ReadableStream;

pkg/download/engine/inject/fetch/module.go

@@ -302,6 +302,23 @@ func (r *registry) Open(fingerprint string, proxyHandler func(*http.Request) (*u
 		return nil, err
 	}
 	for _, header := range metadata.Headers {
+		// Ignore transport controls unsupported by Node/Undici rather than
+		// applying a browser forbidden-header list or failing the whole request.
+		switch strings.ToLower(header[0]) {
+		case "expect", "keep-alive", "transfer-encoding", "upgrade", "content-length":
+			// Content-Length is generated from the buffered request body below.
+			continue
+		case "connection":
+			if value := strings.ToLower(header[1]); value != "close" && value != "keep-alive" {
+				continue
+			}
+		case "trailer":
+			// Fetch supplies a declaration, not a Go Request.Trailer payload.
+			// Keep its lower-case wire name so Go's writer does not omit it as
+			// the canonical Trailer field it normally generates itself.
+			httpRequest.Header["trailer"] = append(httpRequest.Header["trailer"], header[1])
+			continue
+		}
 		httpRequest.Header.Add(header[0], header[1])
 	}
 	if host := httpRequest.Header.Get("Host"); host != "" {

pkg/download/engine/testdata/wpt/UPSTREAM.md

@@ -9,7 +9,7 @@ The files under `fetch/` are copied from the official
 
 Gopeed executes applicable worker-style Fetch API tests at the extension
 JavaScript boundary. The checked-in runner currently executes unchanged WPT
-tests for Headers, no-CORS header guards, Request construction and body
+tests for Headers syntax and iteration, Request construction and body
 consumption, ReadableStream bodies, keepalive, Request errors, Response
 construction and body consumption, immutable network response headers, and
 the Response static constructors.
@@ -19,10 +19,34 @@ a claim that Gopeed is a browser. Browser-only suites that require a document,
 CORS origin enforcement or preflight, CSP, Mixed Content, Service Workers,
 browser HTTP cache, navigation, browser authentication UI, or WPT's
 multi-origin server infrastructure are intentionally excluded. Gopeed also
-keeps one extension-specific behavior: `redirect: "manual"` exposes the HTTP
+keeps extension-specific behavior: `redirect: "manual"` exposes the HTTP
 redirect response so download extensions can inspect `Location`, instead of
 returning a browser `opaqueredirect` response.
 
+Header permissions follow [Node/Undici's server-side Fetch API](https://github.com/nodejs/undici/blob/main/README.md#forbidden-and-safelisted-header-names). Gopeed does not
+apply browser forbidden request/response header lists or no-CORS safelists.
+Extensions may supply authentication, referrer, origin, host, proxy and fetch
+metadata headers, and read `Set-Cookie` response headers. Network response
+headers remain immutable; invalid header syntax still raises an error.
+Repeated `Cookie` values are combined with `; `, as in Node/Undici.
+
+The runner excludes the browser-only `headers-no-cors.any.js` and
+`headers-forbidden-override.any.js` suites, the filtering assertions within
+`request-headers.any.js`, and the forbidden-response-cookie assertion within
+`header-setcookie.any.js`. Gopeed's `extension_headers_test.go` replaces those
+restrictions with integration tests that check headers actually received by
+an HTTP server through fetch and XMLHttpRequest, plus header mutations,
+cloning and response cookies. The upstream test files remain unchanged.
+
+Gopeed deliberately ignores transport controls that Node/Undici rejects:
+`Expect`, `Keep-Alive`, `Transfer-Encoding`, `Upgrade`, and `Connection` values
+other than `close` or `keep-alive`. `Content-Length` is generated from the
+actual request body, ignoring a supplied length. Explicit `Host` and
+`Sec-Fetch-Mode` values are preserved rather than replaced by defaults.
+These transport behaviors are also covered by integration tests.
+`credentials: "omit"` disables automatic CookieJar cookies but preserves
+explicit headers; Gopeed retains its extension CookieJar support.
+
 `wpt_harness.js` is a small Goja adapter maintained by Gopeed; it is not copied
 from WPT. Test logic below `fetch/` is unchanged; the checked-in copy may only
 normalize a final newline.

pkg/download/engine/wpt_fetch_test.go

@@ -20,9 +20,6 @@ var wptFetchUtils string
 //go:embed testdata/wpt/fetch/api/request/request-error.js
 var wptRequestError string
 
-//go:embed testdata/wpt/fetch/api/cors/resources/not-cors-safelisted.json
-var wptNoCORSSafelistedHeaders []byte
-
 //go:embed testdata/wpt/fetch/api/headers/*.any.js
 var wptHeaders embed.FS
 
@@ -30,31 +27,19 @@ var wptHeaders embed.FS
 var wptRequestResponse embed.FS
 
 func TestWPTHeaders(t *testing.T) {
-	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, _ *http.Request) {
-		response.Header().Set("Content-Type", "application/json")
-		_, _ = response.Write(wptNoCORSSafelistedHeaders)
-	}))
-	t.Cleanup(server.Close)
-
 	tests := []string{
 		"header-setcookie.any.js",
 		"headers-basic.any.js",
 		"headers-casing.any.js",
 		"headers-combine.any.js",
 		"headers-errors.any.js",
-		"headers-forbidden-override.any.js",
 		"headers-normalize.any.js",
-		"headers-no-cors.any.js",
 		"headers-record.any.js",
 		"headers-structure.any.js",
 	}
 	for _, name := range tests {
 		t.Run(name, func(t *testing.T) {
-			setup := ""
-			if name == "headers-no-cors.any.js" {
-				setup = fmt.Sprintf("globalThis.location = new URL(%q);", server.URL+"/fetch/api/headers/test.any.js")
-			}
-			runWPTFile(t, wptHeaders, path.Join("testdata/wpt/fetch/api/headers", name), setup)
+			runWPTFile(t, wptHeaders, path.Join("testdata/wpt/fetch/api/headers", name), "")
 		})
 	}
 }
@@ -110,7 +95,30 @@ func runWPTFile(t *testing.T, files embed.FS, name, setup string) {
 	}
 	runtime := engine.NewEngine(nil)
 	t.Cleanup(runtime.Close)
-	value, err := runtime.RunString(setup + "\n" + wptHarness + "\n" + wptFetchUtils + "\n" + wptRequestError + "\n" + string(source) + "\n__wptFinish();")
+	adaptation := ""
+	if name == "testdata/wpt/fetch/api/request/request-headers.any.js" {
+		// Node-style header permissions are covered by extension integration tests.
+		// Keep upstream tests unchanged and exclude browser-only restrictions.
+		adaptation = `
+			const upstreamTest = globalThis.test;
+			globalThis.test = function (callback, name) {
+				if (name.startsWith('Adding invalid request header ') ||
+					name.startsWith('Adding invalid no-cors request header ') ||
+					name.startsWith('Check that request constructor is filtering headers ') ||
+					name.startsWith('Check that no-cors request constructor is filtering headers ')) return;
+				upstreamTest(callback, name);
+			};
+		`
+	} else if name == "testdata/wpt/fetch/api/headers/header-setcookie.any.js" {
+		adaptation = `
+			const upstreamTest = globalThis.test;
+			globalThis.test = function (callback, name) {
+				if (name === 'Set-Cookie is a forbidden response header') return;
+				upstreamTest(callback, name);
+			};
+		`
+	}
+	value, err := runtime.RunString(setup + "\n" + wptHarness + "\n" + wptFetchUtils + "\n" + wptRequestError + "\n" + adaptation + "\n" + string(source) + "\n__wptFinish();")
 	if err != nil {
 		t.Fatal(err)
 	}

pkg/download/extension.go

@@ -1,16 +1,19 @@
 package download
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"io"
+	"net/url"
 	"os"
-	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"time"
 
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/internal/githubmirror"
 	"github.com/GopeedLab/gopeed/internal/logger"
 	"github.com/GopeedLab/gopeed/pkg/base"
 	"github.com/GopeedLab/gopeed/pkg/download/engine"
@@ -195,50 +198,85 @@ func (d *Downloader) getExtension(identity string) *Extension {
 	return nil
 }
 
-func (d *Downloader) fetchExtensionByGit(url string, handler func(tempExtPath string, devMode bool) (*Extension, error)) (*Extension, error) {
-	if !strings.HasPrefix(url, "https://") && !strings.HasPrefix(url, "http://") {
-		url = "https://" + url
-	}
+// waitForExtensionGit waits for clones and their install/check handlers before
+// shutdown releases storage and temporary files. Close cancels backgroundCtx first.
+func (d *Downloader) waitForExtensionGit() {
+	d.extensionGitLock.Lock()
+	d.extensionGitLock.Unlock()
+	d.extensionGitWG.Wait()
+}
 
-	// resolve project path
-	parentPath, projectPath := path.Split(url)
-	// resolve project name and sub path
-	pathArr := strings.SplitN(projectPath, "#", 2)
-	projectPath = strings.TrimSuffix(pathArr[0], gitSuffix)
-	subPath := ""
-	if len(pathArr) > 1 {
-		subPath = pathArr[1]
+func (d *Downloader) fetchExtensionByGit(rawURL string, handler func(string, bool) (*Extension, error)) (*Extension, error) {
+	// Pair admission with shutdown so no operation is added after its wait starts.
+	d.extensionGitLock.Lock()
+	if d.closed.Load() {
+		d.extensionGitLock.Unlock()
+		return nil, fmt.Errorf("downloader is closed")
 	}
-
-	// Use unique suffix to avoid concurrent conflicts when multiple git operations
-	// target the same extension (e.g., install and update check happening simultaneously)
-	tempExtDir, err := os.MkdirTemp(d.cfg.TempDir, "gopeed-extension-")
+	d.extensionGitWG.Add(1)
+	d.extensionGitLock.Unlock()
+	defer d.extensionGitWG.Done()
+	ctx := d.backgroundCtx
+	if !strings.HasPrefix(rawURL, "https://") && !strings.HasPrefix(rawURL, "http://") {
+		rawURL = "https://" + rawURL
+	}
+	parsed, err := url.Parse(rawURL)
+	if err != nil || parsed.Host == "" {
+		return nil, fmt.Errorf("invalid extension repository URL")
+	}
+	subPath := filepath.FromSlash(parsed.Fragment)
+	if filepath.IsAbs(subPath) || subPath == ".." || strings.HasPrefix(filepath.Clean(subPath), ".."+string(filepath.Separator)) {
+		return nil, fmt.Errorf("invalid extension directory")
+	}
+	parsed.Fragment = ""
+	parsed.Path = strings.TrimSuffix(strings.TrimRight(parsed.Path, "/"), gitSuffix) + gitSuffix
+	officialURL := parsed.String()
+	cfg, err := d.GetConfig()
 	if err != nil {
 		return nil, err
 	}
-	if err := d.tempFiles.Track(tempExtDir); err != nil {
-		return nil, err
-	}
-	defer d.tempFiles.Remove(tempExtDir)
-
 	proxyOptions := transport.ProxyOptions{}
-	proxyUrl := d.cfg.DownloaderStoreConfig.Proxy.ToUrl()
-	if proxyUrl != nil {
-		proxyOptions.URL = proxyUrl.Scheme + "://" + proxyUrl.Host
-		proxyOptions.Username = proxyUrl.User.Username()
-		proxyOptions.Password, _ = proxyUrl.User.Password()
+	if proxyURL := cfg.Proxy.ToUrl(); proxyURL != nil {
+		proxyOptions.URL = proxyURL.Scheme + "://" + proxyURL.Host
+		if proxyURL.User != nil {
+			proxyOptions.Username = proxyURL.User.Username()
+			proxyOptions.Password, _ = proxyURL.User.Password()
+		}
 	}
-	// clone project to extension temp dir
-	gitUrl := parentPath + projectPath + gitSuffix
-	if _, err := git.PlainClone(tempExtDir, false, &git.CloneOptions{
-		URL:          gitUrl,
-		Depth:        1,
-		ProxyOptions: proxyOptions,
-	}); err != nil {
+	tempDir, err := os.MkdirTemp(d.cfg.TempDir, "gopeed-extension-")
+	if err != nil {
 		return nil, err
 	}
-
-	return handler(filepath.Join(tempExtDir, subPath), false)
+	if err = d.tempFiles.Track(tempDir); err != nil {
+		_ = os.RemoveAll(tempDir)
+		return nil, err
+	}
+	defer d.tempFiles.Remove(tempDir)
+	repoDir := filepath.Join(tempDir, "repo")
+	repo, err := githubmirror.Fallback(ctx, cfg.GithubMirror, officialURL,
+		githubmirror.Options[*git.Repository]{Kind: githubmirror.Repository},
+		func(ctx context.Context, candidate string) (*git.Repository, error) {
+			if err := os.RemoveAll(repoDir); err != nil {
+				return nil, err
+			}
+			return git.PlainCloneContext(ctx, repoDir, false, &git.CloneOptions{URL: candidate, Depth: 1, ProxyOptions: proxyOptions})
+		},
+	)
+	if err != nil {
+		return nil, err
+	}
+	// Preserve the canonical source instead of persisting a selected mirror.
+	repoConfig, err := repo.Config()
+	if err != nil {
+		return nil, err
+	}
+	if remote := repoConfig.Remotes["origin"]; remote != nil {
+		remote.URLs = []string{officialURL}
+	}
+	if err = repo.SetConfig(repoConfig); err != nil {
+		return nil, err
+	}
+	return handler(filepath.Join(repoDir, subPath), false)
 }
 
 func (d *Downloader) parseExtensionByPath(path string) (*Extension, error) {
@@ -733,6 +771,14 @@ type OnDoneContext struct {
 // only some fields can be modified, such as request info.
 type ExtensionTask struct {
 	*Task
+	Meta *ExtensionTaskMeta `json:"meta"`
+}
+
+// ExtensionTaskMeta preserves metadata fields while exposing request operations
+// at the existing meta.req path.
+type ExtensionTaskMeta struct {
+	*fetcher.FetcherMeta
+	Req *ExtensionTaskRequest `json:"req"`
 }
 
 // OnErrorExtensionTask adds error-recovery controls to ExtensionTask.
@@ -744,13 +790,24 @@ type OnErrorExtensionTask struct {
 }
 
 func cloneExtensionTask(task *Task) *Task {
+	if task.statusLock != nil {
+		task.statusLock.Lock()
+		defer task.statusLock.Unlock()
+	}
 	newTask := task.clone()
 	newTask.Meta.Req = task.Meta.Req
 	return newTask
 }
 
 func newExtensionTask(task *Task) *ExtensionTask {
-	return &ExtensionTask{Task: cloneExtensionTask(task)}
+	view := cloneExtensionTask(task)
+	return &ExtensionTask{
+		Task: view,
+		Meta: &ExtensionTaskMeta{
+			FetcherMeta: view.Meta,
+			Req:         &ExtensionTaskRequest{Request: view.Meta.Req, task: view},
+		},
+	}
 }
 
 func newOnStartExtensionTask(task *Task) *ExtensionTask {
@@ -769,8 +826,10 @@ func newOnDoneExtensionTask(task *Task) *Task {
 }
 
 // SetUrl replaces the task request URL.
+//
+// Deprecated: Use task.meta.req.setUrl instead.
 func (t *ExtensionTask) SetUrl(url string) {
-	t.Meta.Req.URL = url
+	t.Meta.Req.SetUrl(url)
 }
 
 func (t *OnErrorExtensionTask) Continue() error {

pkg/download/extension_compat_test.go

@@ -0,0 +1,89 @@
+package download
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+func TestExtensionDeprecatedRequestAPIs(t *testing.T) {
+	for _, event := range []ActivationEvent{EventOnResolve, EventOnStart, EventOnError, EventOnDone} {
+		for _, withLabels := range []bool{false, true} {
+			t.Run(fmt.Sprintf("%s/labels=%v", event, withLabels), func(t *testing.T) {
+				d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir()})
+				if err := d.Setup(); err != nil {
+					t.Fatal(err)
+				}
+				defer d.Clear()
+
+				extDir := t.TempDir()
+				manifest := fmt.Sprintf(`{"name":"legacy-request","title":"Legacy request APIs","version":"0.0.1","scripts":[{"event":%q,"match":{"urls":["*://example.com/*"]},"entry":"index.js"}]}`, event)
+				request := "ctx.task.meta.req"
+				urlMutation := ""
+				if event == EventOnResolve {
+					request = "ctx.req"
+				} else if event == EventOnStart || event == EventOnError {
+					urlMutation = `await ctx.task.setUrl('https://example.com/legacy');
+  if (req.url !== 'https://example.com/legacy') throw new Error('legacy URL did not write through');
+  await req.setUrl('https://example.com/new');
+  if (req.url !== 'https://example.com/new') throw new Error('new URL did not write through');
+  await ctx.task.setUrl('https://example.com/final');`
+				}
+				script := fmt.Sprintf(`gopeed.events.%s(async ctx => {
+  const req = %s;
+  await req.delLabel('missing');
+  await req.putLabel('initial', 'yes');
+  if (req.labels.initial !== 'yes') throw new Error('putLabel did not initialize labels');
+  await req.setLabels({keep: 'yes', remove: 'yes'});
+  if (req.labels.initial !== undefined || req.labels.old !== undefined) throw new Error('setLabels did not replace labels');
+  await req.putLabel('added', 'yes');
+  await req.delLabel('remove');
+  if (req.labels.keep !== 'yes' || req.labels.added !== 'yes' || req.labels.remove !== undefined) throw new Error('label mutation failed');
+  %s
+  await req.putLabel('completed', 'yes');
+});`, event, request, urlMutation)
+				for name, content := range map[string]string{"manifest.json": manifest, "index.js": script} {
+					if err := os.WriteFile(filepath.Join(extDir, name), []byte(content), 0600); err != nil {
+						t.Fatal(err)
+					}
+				}
+				if _, err := d.InstallExtensionByFolder(extDir, false); err != nil {
+					t.Fatal(err)
+				}
+				req := &base.Request{URL: "https://example.com/original"}
+				if withLabels {
+					req.Labels = map[string]string{"old": "yes"}
+				}
+				task := &Task{Protocol: "http", Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}}
+				switch event {
+				case EventOnResolve:
+					if _, err := d.triggerOnResolve(req); err != nil {
+						t.Fatal(err)
+					}
+				case EventOnStart:
+					d.triggerOnStart(task)
+				case EventOnError:
+					d.triggerOnError(task, errors.New("retry"))
+				case EventOnDone:
+					d.triggerOnDone(task)
+				}
+				if !reflect.DeepEqual(req.Labels, map[string]string{"keep": "yes", "added": "yes", "completed": "yes"}) {
+					t.Fatalf("legacy handler did not update the original request: %#v", req.Labels)
+				}
+				expectedURL := "https://example.com/original"
+				if urlMutation != "" {
+					expectedURL = "https://example.com/final"
+				}
+				if req.URL != expectedURL {
+					t.Fatalf("URL = %q, want %q", req.URL, expectedURL)
+				}
+			})
+		}
+	}
+}

pkg/download/extension_extra_mutation_test.go

@@ -0,0 +1,188 @@
+package download
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	btProtocol "github.com/GopeedLab/gopeed/pkg/protocol/bt"
+	httpProtocol "github.com/GopeedLab/gopeed/pkg/protocol/http"
+	"github.com/dop251/goja"
+)
+
+func TestExtensionProtocolMethods(t *testing.T) {
+	for _, extra := range []any{nil, map[string]any{"header": map[string]any{"Keep": "yes"}}, &httpProtocol.ReqExtra{Header: map[string]string{"Keep": "yes"}}} {
+		vm := goja.New()
+		vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
+		req := &base.Request{Extra: extra}
+		task := &Task{Protocol: "http", Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}}
+		if err := vm.Set("task", newOnStartExtensionTask(task)); err != nil {
+			t.Fatal(err)
+		}
+		_, err := vm.RunString(`task.meta.req.setMethod('POST'); task.meta.req.setBody('payload'); task.meta.req.putHeader('Authorization','Bearer token'); task.meta.req.putHeader('Remove','remove'); task.meta.req.delHeader('REMOVE');`)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := base.ParseReqExtra[httpProtocol.ReqExtra](req); err != nil {
+			t.Fatal(err)
+		}
+		got := req.Extra.(*httpProtocol.ReqExtra)
+		if got.Method != "POST" || got.Body != "payload" || got.Header["Authorization"] != "Bearer token" {
+			t.Fatalf("mutation not applied: %#v", got)
+		}
+		if _, ok := got.Header["Remove"]; ok {
+			t.Fatal("header deletion failed")
+		}
+		if extra != nil && got.Header["Keep"] != "yes" {
+			t.Fatal("existing header lost")
+		}
+	}
+	vm := goja.New()
+	vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
+	req := &base.Request{Extra: &btProtocol.ReqExtra{Trackers: []string{"old"}}}
+	task := &Task{Protocol: "bt", Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}}
+	if err := vm.Set("task", newOnStartExtensionTask(task)); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := vm.RunString(`task.meta.req.setTrackers(['new','another']);`); err != nil {
+		t.Fatal(err)
+	}
+	got := req.Extra.(*btProtocol.ReqExtra).Trackers
+	if len(got) != 2 || got[0] != "new" || got[1] != "another" {
+		t.Fatalf("trackers = %#v", got)
+	}
+}
+
+func TestExtensionProtocolMethodsRejectInvalidMutation(t *testing.T) {
+	vm := goja.New()
+	vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
+	original := &httpProtocol.ReqExtra{Method: "POST", Header: map[string]string{"authorization": "old", "Keep": "yes"}}
+	req := &base.Request{Extra: original}
+	task := newOnStartExtensionTask(&Task{Protocol: "http", Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}})
+	if err := vm.Set("task", task); err != nil {
+		t.Fatal(err)
+	}
+	for _, script := range []string{`task.meta.req.setHeaders({Keep:null})`, `task.meta.req.setHeaders({Keep:123})`, `task.meta.req.setHeaders({a:'1',A:'2'})`} {
+		if _, err := vm.RunString(script); err == nil {
+			t.Fatalf("accepted invalid mutation: %s", script)
+		}
+		if req.Extra != original || original.Header["Keep"] != "yes" {
+			t.Fatal("invalid operation changed original extra")
+		}
+	}
+	if _, err := vm.RunString(`task.meta.req.putHeader('Authorization','new');`); err != nil {
+		t.Fatal(err)
+	}
+	got := req.Extra.(*httpProtocol.ReqExtra)
+	if len(got.Header) != 2 || got.Header["Authorization"] != "new" || original.Header["authorization"] != "old" {
+		t.Fatalf("header update = %#v", got.Header)
+	}
+	if _, err := vm.RunString(`task.meta.req.setHeaders({Only:'one'});`); err != nil {
+		t.Fatal(err)
+	}
+	got = req.Extra.(*httpProtocol.ReqExtra)
+	if got.Method != "POST" || len(got.Header) != 1 {
+		t.Fatalf("setHeaders = %#v", got)
+	}
+	req.Extra = map[string]any{"header": 123}
+	if _, err := vm.RunString(`task.meta.req.setBody('new')`); err == nil {
+		t.Fatal("invalid protocol extra accepted")
+	}
+	if req.Extra.(map[string]any)["header"] != 123 {
+		t.Fatal("conversion failure mutated extra")
+	}
+}
+
+func TestExtensionProtocolMethodsOtherProtocolsAreNoOp(t *testing.T) {
+	for _, protocol := range []string{"http", "bt", "hls"} {
+		for _, onError := range []bool{false, true} {
+			t.Run(fmt.Sprintf("%s/onError=%v", protocol, onError), func(t *testing.T) {
+				vm := goja.New()
+				vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
+				// An invalid extra proves that unrelated methods skip conversion entirely.
+				original := map[string]any{"unchanged": true, "header": 123}
+				req := &base.Request{Extra: original}
+				task := &Task{Protocol: protocol, Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}}
+				var wrapper any = newOnStartExtensionTask(task)
+				if onError {
+					wrapper = newOnErrorExtensionTask(nil, task)
+				}
+				if err := vm.Set("task", wrapper); err != nil {
+					t.Fatal(err)
+				}
+				if protocol != "http" {
+					if _, err := vm.RunString(`task.meta.req.setMethod('POST');task.meta.req.setBody('body');task.meta.req.setHeaders({a:null});task.meta.req.putHeader('A','value');task.meta.req.delHeader('A');`); err != nil {
+						t.Fatal(err)
+					}
+				}
+				if protocol != "bt" {
+					if _, err := vm.RunString(`task.meta.req.setTrackers(['udp://example.com']);`); err != nil {
+						t.Fatal(err)
+					}
+				}
+				if !reflect.DeepEqual(req.Extra, original) {
+					t.Fatalf("extra changed: %#v", req.Extra)
+				}
+				original["same-object"] = true
+				if req.Extra.(map[string]any)["same-object"] != true {
+					t.Fatal("no-op replaced extra")
+				}
+			})
+		}
+	}
+}
+
+func TestExtensionOnErrorRequestWritesToOriginalTask(t *testing.T) {
+	vm := goja.New()
+	vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
+	req := &base.Request{URL: "https://example.com", Extra: &httpProtocol.ReqExtra{Header: map[string]string{"Keep": "yes"}}}
+	task := &Task{Protocol: "http", Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}}
+	if err := vm.Set("task", newOnErrorExtensionTask(nil, task)); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := vm.RunString(`
+   if (typeof task.continue !== 'function') throw new Error('missing continue');
+   if (typeof task.putHeader !== 'undefined') throw new Error('task still exposes protocol methods');
+   if (typeof task.req !== 'undefined') throw new Error('legacy task.req');
+   const request = task.meta.req;
+   if (request.url !== 'https://example.com' || request.extra.header.Keep !== 'yes') throw new Error('request data missing');
+   if (!task.meta.opts) throw new Error('metadata fields missing');
+   request.setHeaders({Keep:'new'});
+   request.putHeader('Authorization','Bearer new');
+   request.setMethod('POST');
+   if (typeof task.setUrl !== 'function' || typeof task.extra !== 'undefined') throw new Error('unexpected legacy task API');
+   request.setUrl('https://example.com/new');
+   request.setLabels({keep:'yes',remove:'yes'});
+   request.putLabel('new','value');
+   request.delLabel('remove');
+   if (request.url !== 'https://example.com/new' || request.labels.new !== 'value' || request.extra.method !== 'POST' || request.extra.header.Authorization !== 'Bearer new') throw new Error('request data did not refresh');
+ `); err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(req.Labels, map[string]string{"keep": "yes", "new": "value"}) {
+		t.Fatalf("labels = %#v", req.Labels)
+	}
+	got := req.Extra.(*httpProtocol.ReqExtra)
+	if got.Method != "POST" || got.Header["Keep"] != "new" || got.Header["Authorization"] != "Bearer new" || req.URL != "https://example.com/new" {
+		t.Fatalf("original request not updated: %#v, %#v", req, got)
+	}
+}
+
+func TestExtensionBTRequestInitializesNilExtra(t *testing.T) {
+	vm := goja.New()
+	vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
+	req := &base.Request{}
+	task := &Task{Protocol: "bt", Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}}
+	if err := vm.Set("task", newOnStartExtensionTask(task)); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := vm.RunString(`task.meta.req.setTrackers(['udp://example.com']);`); err != nil {
+		t.Fatal(err)
+	}
+	got, ok := req.Extra.(*btProtocol.ReqExtra)
+	if !ok || !reflect.DeepEqual(got.Trackers, []string{"udp://example.com"}) {
+		t.Fatalf("extra = %#v", req.Extra)
+	}
+}

pkg/download/extension_extra_test.go

@@ -0,0 +1,104 @@
+package download
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+	httpProtocol "github.com/GopeedLab/gopeed/pkg/protocol/http"
+)
+
+func TestExtensionExtraMutationHTTP(t *testing.T) {
+	for _, resolved := range []bool{false, true} {
+		for _, invalid := range []bool{false, true} {
+			t.Run(fmt.Sprintf("resolved=%v/invalid=%v", resolved, invalid), func(t *testing.T) {
+				var updatedRequests atomic.Int32
+				server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					if r.Header.Get("X-New") == "new" {
+						updatedRequests.Add(1)
+						if r.Header.Get("X-Old") != "" {
+							t.Error("extra mutation retained the old header")
+						}
+					}
+					http.ServeContent(w, r, "test.txt", time.Time{}, strings.NewReader("extra mutation payload"))
+				}))
+				defer server.Close()
+				d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir()})
+				if err := d.Setup(); err != nil {
+					t.Fatal(err)
+				}
+				defer d.Clear()
+				extDir := t.TempDir()
+				manifest := `{"name":"http-methods","title":"HTTP methods test","version":"0.0.1","scripts":[{"event":"onStart","match":{"labels":["test"]},"entry":"index.js"}]}`
+				mutation := `await ctx.task.meta.req.setMethod('GET');
+                  await ctx.task.meta.req.setBody('');
+                  await ctx.task.meta.req.delHeader('x-old');
+                  await ctx.task.meta.req.putHeader('X-New', 'new');`
+				if invalid {
+					mutation = `try { await ctx.task.meta.req.setHeaders({'X-New':123}); }
+                      catch (err) { await ctx.task.meta.req.putLabel('rejected','true'); } ` + mutation
+				}
+				script := `gopeed.events.onStart(async ctx => { ` + mutation + ` });`
+				for name, content := range map[string]string{"manifest.json": manifest, "index.js": script} {
+					if err := os.WriteFile(filepath.Join(extDir, name), []byte(content), 0600); err != nil {
+						t.Fatal(err)
+					}
+				}
+				if _, err := d.InstallExtensionByFolder(extDir, false); err != nil {
+					t.Fatal(err)
+				}
+				done := make(chan error, 1)
+				d.Listener(func(event *Event) {
+					if event.Key == EventKeyFinally {
+						done <- event.Err
+					}
+				})
+				req := &base.Request{URL: server.URL + "/test.txt", Labels: map[string]string{"test": "true"}, Extra: &httpProtocol.ReqExtra{Header: map[string]string{"X-Old": "old"}}}
+				opts := &base.Options{Path: t.TempDir()}
+				var id string
+				var err error
+				if resolved {
+					rr, resolveErr := d.Resolve(req)
+					if resolveErr != nil {
+						t.Fatal(resolveErr)
+					}
+					id, err = d.CreateWithOptions(rr.ID, opts)
+				} else {
+					id, err = d.CreateDirect(req, opts)
+				}
+				if err != nil {
+					t.Fatal(err)
+				}
+				select {
+				case err = <-done:
+				case <-time.After(10 * time.Second):
+					t.Fatal("download timed out")
+				}
+				if invalid && d.GetTask(id).Meta.Req.Labels["rejected"] != "true" {
+					t.Fatal("invalid header was not rejected")
+				}
+				if err != nil {
+					t.Fatal(err)
+				}
+				got, ok := d.GetTask(id).Meta.Req.Extra.(*httpProtocol.ReqExtra)
+				if !ok || got.Header["X-New"] != "new" || len(got.Header) != 1 {
+					t.Fatalf("unexpected protocol extra: %#v", d.GetTask(id).Meta.Req.Extra)
+				}
+				if !resolved && updatedRequests.Load() == 0 {
+					t.Fatal("download did not use the extension headers")
+				}
+				data, err := os.ReadFile(filepath.Join(opts.Path, "test.txt"))
+				if err != nil || string(data) != "extra mutation payload" {
+					t.Fatalf("download content = %q, error = %v", data, err)
+				}
+			})
+		}
+	}
+}

pkg/download/extension_git_mirror_test.go

@@ -0,0 +1,210 @@
+package download
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/cgi"
+	"net/http/httptest"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	httpProtocol "github.com/GopeedLab/gopeed/internal/protocol/http"
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+// Exercise real Git clone/install/check/update without depending on GitHub or
+// public mirror availability. The proxy deliberately rejects the official URL.
+// github.com/gopeed-test/repo is a placeholder: the successful mirror serves
+// the temporary local repository through git http-backend instead.
+func newExtensionGitFixture(t *testing.T) (*Downloader, func(string), *atomic.Int32, *atomic.Int32) {
+	t.Helper()
+	git, err := exec.LookPath("git")
+	if err != nil {
+		t.Skip("Git executable required for HTTP Git fixture")
+	}
+	root := t.TempDir()
+	bare := filepath.Join(root, "repo.git")
+	work := t.TempDir()
+	command := func(args ...string) {
+		t.Helper()
+		cmd := exec.Command(git, args...)
+		if output, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("git %v: %v: %s", args, err, output)
+		}
+	}
+	command("-c", "init.defaultBranch=main", "init", "--bare", bare)
+	command("clone", bare, work)
+	command("-C", work, "config", "user.name", "Gopeed Test")
+	command("-C", work, "config", "user.email", "[email protected]")
+	publish := func(version string) {
+		t.Helper()
+		directory := filepath.Join(work, "nested", "extension")
+		if err := os.MkdirAll(directory, 0700); err != nil {
+			t.Fatal(err)
+		}
+		manifest := map[string]any{"name": "mirror-test", "author": "test", "title": "Mirror test", "version": version, "repository": map[string]string{"url": "https://github.com/gopeed-test/repo", "directory": "nested/extension"}}
+		body, _ := json.Marshal(manifest)
+		if err := os.WriteFile(filepath.Join(directory, "manifest.json"), body, 0600); err != nil {
+			t.Fatal(err)
+		}
+		command("-C", work, "add", ".")
+		command("-C", work, "commit", "-m", version)
+		command("-C", work, "push", "origin", "HEAD:main")
+	}
+	publish("1.0.0")
+	var official, badMirror atomic.Int32
+	backend := &cgi.Handler{Path: git, Args: []string{"http-backend"}, Env: []string{"GIT_PROJECT_ROOT=" + root, "GIT_HTTP_EXPORT_ALL=1"}}
+	mirror := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		r.URL.Path = strings.TrimPrefix(r.URL.Path, "/https://github.com/gopeed-test")
+		r.RequestURI = r.URL.RequestURI()
+		backend.ServeHTTP(w, r)
+	}))
+	t.Cleanup(mirror.Close)
+	failed := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { badMirror.Add(1); http.Error(w, "mirror offline", 502) }))
+	t.Cleanup(failed.Close)
+	direct := &http.Transport{}
+	t.Cleanup(direct.CloseIdleConnections)
+	proxy := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == http.MethodConnect || r.URL.Hostname() == "github.com" {
+			official.Add(1)
+			http.Error(w, "official unavailable", 502)
+			return
+		}
+		request := r.Clone(r.Context())
+		request.RequestURI = ""
+		response, err := direct.RoundTrip(request)
+		if err != nil {
+			http.Error(w, err.Error(), 502)
+			return
+		}
+		defer response.Body.Close()
+		for key, values := range response.Header {
+			for _, value := range values {
+				w.Header().Add(key, value)
+			}
+		}
+		w.WriteHeader(response.StatusCode)
+		_, _ = io.Copy(w, response.Body)
+	}))
+	t.Cleanup(proxy.Close)
+	d := testBackendDownloader(t, &httpProtocol.FetcherManager{})
+	config, _ := d.GetConfig()
+	config.Proxy = &base.DownloaderProxyConfig{Enable: true, Scheme: "http", Host: strings.TrimPrefix(proxy.URL, "http://")}
+	config.GithubMirror = &base.GithubMirrorConfig{Enabled: true, Mirrors: []base.GithubMirror{{Type: "ghProxy", URL: failed.URL}, {Type: "ghProxy", URL: mirror.URL}}}
+	if err := d.PutConfig(config); err != nil {
+		t.Fatal(err)
+	}
+	return d, publish, &official, &badMirror
+}
+func testInstallExtensionGitURL(t *testing.T, raw string) {
+	d, _, official, badMirror := newExtensionGitFixture(t)
+	extension, err := d.InstallExtensionByGit(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if extension.Version != "1.0.0" || extension.Identity != "test@mirror-test" {
+		t.Fatalf("%+v", extension)
+	}
+	if official.Load() == 0 || badMirror.Load() == 0 {
+		t.Fatal("ordered fallback was not exercised")
+	}
+	if _, err := os.Stat(filepath.Join(d.ExtensionPath(extension), "manifest.json")); err != nil {
+		t.Fatal(err)
+	}
+}
+func TestExtensionGitMirrorInstallAndUpdate(t *testing.T) {
+	d, publish, official, badMirror := newExtensionGitFixture(t)
+	extension, err := d.InstallExtensionByGit("https://github.com/gopeed-test/repo#nested/extension")
+	if err != nil {
+		t.Fatal(err)
+	}
+	publish("1.1.0")
+	version, err := d.UpgradeCheckExtension(extension.Identity)
+	if err != nil || version != "1.1.0" {
+		t.Fatalf("%s %v", version, err)
+	}
+	if err = d.UpgradeExtension(extension.Identity); err != nil {
+		t.Fatal(err)
+	}
+	updated, err := d.GetExtension(extension.Identity)
+	if err != nil || updated.Version != "1.1.0" {
+		t.Fatalf("%+v %v", updated, err)
+	}
+	if updated.Repository.Url != "https://github.com/gopeed-test/repo" {
+		t.Fatal("mirror URL replaced canonical repository")
+	}
+	if official.Load() != 3 || badMirror.Load() != 3 {
+		t.Fatalf("attempts official=%d mirror=%d", official.Load(), badMirror.Load())
+	}
+}
+
+func TestExtensionGitShutdownWaitsForHandler(t *testing.T) {
+	d, _, _, _ := newExtensionGitFixture(t)
+	started := make(chan string, 1)
+	release := make(chan struct{})
+	t.Cleanup(func() {
+		select {
+		case <-release:
+		default:
+			close(release)
+		}
+	})
+	finished := make(chan error, 1)
+	go func() {
+		_, err := d.fetchExtensionByGit("https://github.com/gopeed-test/repo#nested/extension", func(path string, _ bool) (*Extension, error) {
+			started <- path
+			<-release
+			return d.parseExtensionByPath(path)
+		})
+		finished <- err
+	}()
+	var path string
+	select {
+	case path = <-started:
+	case err := <-finished:
+		t.Fatalf("Git operation finished before handler: %v", err)
+	case <-time.After(5 * time.Second):
+		t.Fatal("Git handler did not start")
+	}
+	closed := make(chan error, 1)
+	go func() { closed <- d.Close() }()
+	select {
+	case <-d.backgroundCtx.Done():
+	case <-time.After(5 * time.Second):
+		t.Fatal("shutdown did not cancel Git context")
+	}
+	select {
+	case err := <-closed:
+		t.Fatalf("shutdown returned before handler finished: %v", err)
+	case <-time.After(100 * time.Millisecond):
+	}
+	if _, err := os.Stat(filepath.Join(path, "manifest.json")); err != nil {
+		t.Fatalf("shutdown removed files still used by handler: %v", err)
+	}
+	if _, err := d.InstallExtensionByGit("https://github.com/gopeed-test/repo"); err == nil || !strings.Contains(err.Error(), "downloader is closed") {
+		t.Fatalf("expected new Git operations to be rejected during shutdown: %v", err)
+	}
+	close(release)
+	select {
+	case err := <-finished:
+		if err != nil {
+			t.Fatal(err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("Git handler did not finish")
+	}
+	select {
+	case err := <-closed:
+		if err != nil {
+			t.Fatal(err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("shutdown did not finish after Git handler")
+	}
+}

pkg/download/extension_git_transport.go

@@ -0,0 +1,62 @@
+package download
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"time"
+
+	gitclient "github.com/go-git/go-git/v5/plumbing/transport/client"
+	githttp "github.com/go-git/go-git/v5/plumbing/transport/http"
+)
+
+func init() {
+	// go-git exposes a process-wide protocol registry. Register once during
+	// initialization, rather than changing it during concurrent clones. Proxy
+	// settings still come from each clone's ProxyOptions.
+	transport := githttp.NewClient(newExtensionGitHTTPClient(10*time.Second, 60*time.Second))
+	gitclient.InstallProtocol("http", transport)
+	gitclient.InstallProtocol("https", transport)
+}
+
+func newExtensionGitHTTPClient(connectTimeout, idleTimeout time.Duration) *http.Client {
+	dialer := &net.Dialer{Timeout: connectTimeout, KeepAlive: 30 * time.Second}
+	// A socket read deadline must apply to one transfer, rather than a shared
+	// HTTP/2 connection carrying traffic from other requests.
+	protocols := new(http.Protocols)
+	protocols.SetHTTP1(true)
+	return &http.Client{Transport: &http.Transport{
+		Proxy: http.ProxyFromEnvironment,
+		DialContext: func(ctx context.Context, network, address string) (net.Conn, error) {
+			conn, err := dialer.DialContext(ctx, network, address)
+			if err != nil {
+				return nil, err
+			}
+			return &gitIdleConn{Conn: conn, timeout: idleTimeout}, nil
+		},
+		TLSHandshakeTimeout: connectTimeout,
+		IdleConnTimeout:     idleTimeout,
+		Protocols:           protocols,
+	}}
+}
+
+type gitIdleConn struct {
+	net.Conn
+	timeout time.Duration
+}
+
+func (c *gitIdleConn) Read(p []byte) (int, error) {
+	if err := c.Conn.SetReadDeadline(time.Now().Add(c.timeout)); err != nil {
+		return 0, err
+	}
+	return c.Conn.Read(p)
+}
+
+// Refresh an already-pending read when a pooled HTTP/1 connection starts the
+// next request; time spent idle in the pool must not consume its read allowance.
+func (c *gitIdleConn) Write(p []byte) (int, error) {
+	if err := c.Conn.SetReadDeadline(time.Now().Add(c.timeout)); err != nil {
+		return 0, err
+	}
+	return c.Conn.Write(p)
+}

pkg/download/extension_git_transport_test.go

@@ -0,0 +1,189 @@
+package download
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/http/httptrace"
+	"net/url"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/githubmirror"
+)
+
+func TestExtensionGitHTTPTransportAllowsSlowStreaming(t *testing.T) {
+	const chunks = 24
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		for range chunks {
+			if _, err := io.WriteString(w, "x"); err != nil {
+				return
+			}
+			w.(http.Flusher).Flush()
+			select {
+			case <-time.After(50 * time.Millisecond):
+			case <-r.Context().Done():
+				return
+			}
+		}
+	}))
+	defer server.Close()
+	client := newExtensionGitHTTPClient(time.Second, time.Second)
+	defer client.CloseIdleConnections()
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	request, _ := http.NewRequestWithContext(ctx, http.MethodGet, server.URL, nil)
+	response, err := client.Do(request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer response.Body.Close()
+	// A regularly streaming response lasts longer than the idle allowance.
+	body, err := io.ReadAll(response.Body)
+	if err != nil || len(body) != chunks {
+		t.Fatalf("received %d bytes, error=%v", len(body), err)
+	}
+}
+
+func TestExtensionGitHTTPTransportTimesOutStalledReads(t *testing.T) {
+	for _, bodyStarted := range []bool{false, true} {
+		name := "headers"
+		if bodyStarted {
+			name = "body"
+		}
+		t.Run(name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if bodyStarted {
+					_, _ = io.WriteString(w, "partial")
+					w.(http.Flusher).Flush()
+				}
+				<-r.Context().Done()
+			}))
+			defer server.Close()
+			client := newExtensionGitHTTPClient(time.Second, 100*time.Millisecond)
+			defer client.CloseIdleConnections()
+			ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+			defer cancel()
+			request, _ := http.NewRequestWithContext(ctx, http.MethodGet, server.URL, nil)
+			response, err := client.Do(request)
+			if err == nil {
+				defer response.Body.Close()
+				_, err = io.ReadAll(response.Body)
+			}
+			var timeout net.Error
+			if !errors.As(err, &timeout) || !timeout.Timeout() || ctx.Err() != nil {
+				t.Fatalf("expected idle timeout before parent deadline: error=%v context=%v", err, ctx.Err())
+			}
+		})
+	}
+}
+
+func TestExtensionGitIdleTimeoutFallsBackThroughProxy(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Hostname() == "github.com" {
+			_, _ = io.WriteString(w, "partial")
+			w.(http.Flusher).Flush()
+			<-r.Context().Done()
+			return
+		}
+		_, _ = io.WriteString(w, "complete")
+	}))
+	defer server.Close()
+	client := newExtensionGitHTTPClient(time.Second, 100*time.Millisecond)
+	defer client.CloseIdleConnections()
+	proxy, _ := url.Parse(server.URL)
+	client.Transport.(*http.Transport).Proxy = http.ProxyURL(proxy)
+	config := &githubmirror.Config{Enabled: true, Mirrors: []githubmirror.Mirror{{Type: "ghProxy", URL: server.URL}}}
+	source := "http://github.com/test/repo.git"
+	var tried []string
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	result, err := githubmirror.Fallback(ctx, config, source, githubmirror.Options[string]{Kind: githubmirror.Repository}, func(ctx context.Context, candidate string) (string, error) {
+		tried = append(tried, candidate)
+		request, _ := http.NewRequestWithContext(ctx, http.MethodGet, candidate, nil)
+		response, err := client.Do(request)
+		if err != nil {
+			return "", err
+		}
+		defer response.Body.Close()
+		body, err := io.ReadAll(response.Body)
+		return string(body), err
+	})
+	if err != nil || result != "complete" || !reflect.DeepEqual(tried, []string{source, server.URL + "/" + source}) {
+		t.Fatalf("result=%q tried=%v error=%v", result, tried, err)
+	}
+}
+
+func TestExtensionGitHTTPTransportCancelsStalledBody(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.(http.Flusher).Flush()
+		<-r.Context().Done()
+	}))
+	defer server.Close()
+	client := newExtensionGitHTTPClient(time.Second, time.Minute)
+	defer client.CloseIdleConnections()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	request, _ := http.NewRequestWithContext(ctx, http.MethodGet, server.URL, nil)
+	response, err := client.Do(request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer response.Body.Close()
+	cancel()
+	done := make(chan error, 1)
+	go func() { _, err := io.ReadAll(response.Body); done <- err }()
+	select {
+	case err := <-done:
+		if !errors.Is(err, context.Canceled) {
+			t.Fatalf("error=%v", err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("parent cancellation did not interrupt the body")
+	}
+}
+
+func TestExtensionGitHTTPTransportRefreshesReusedConnection(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/slow" {
+			select {
+			case <-time.After(500 * time.Millisecond):
+			case <-r.Context().Done():
+				return
+			}
+		}
+		_, _ = io.WriteString(w, "ok")
+	}))
+	defer server.Close()
+	client := newExtensionGitHTTPClient(time.Second, time.Second)
+	defer client.CloseIdleConnections()
+	response, err := client.Get(server.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = io.Copy(io.Discard, response.Body)
+	_ = response.Body.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(700 * time.Millisecond)
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	reused := false
+	ctx = httptrace.WithClientTrace(ctx, &httptrace.ClientTrace{GotConn: func(info httptrace.GotConnInfo) { reused = info.Reused }})
+	request, _ := http.NewRequestWithContext(ctx, http.MethodGet, server.URL+"/slow", nil)
+	response, err = client.Do(request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer response.Body.Close()
+	body, err := io.ReadAll(response.Body)
+	if err != nil || string(body) != "ok" || !reused {
+		t.Fatalf("reused=%v body=%q error=%v", reused, body, err)
+	}
+}

pkg/download/extension_match_test.go

@@ -0,0 +1,56 @@
+package download
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+func TestDownloader_Extension_MagnetMatch(t *testing.T) {
+	const magnetURL = "magnet:?xt=urn:btih:0123456789abcdef0123456789abcdef01234567"
+	for _, pattern := range []string{"magnet:*", "magnet:?*"} {
+		t.Run(pattern, func(t *testing.T) {
+			d := NewDownloader(&DownloaderConfig{
+				Storage:    NewMemStorage(),
+				StorageDir: t.TempDir(),
+				TempDir:    t.TempDir(),
+			})
+			if err := d.Setup(); err != nil {
+				t.Fatal(err)
+			}
+			defer d.Clear()
+
+			extDir := t.TempDir()
+			manifest := fmt.Sprintf(`{"name":"magnet-match","author":"test","title":"Magnet match","version":"1.0.0","scripts":[{"event":"onResolve","match":{"urls":[%q]},"entry":"index.js"}]}`, pattern)
+			script := `gopeed.events.onResolve(ctx => {
+  ctx.res = {files: [{name: "resolved.txt", size: 1, req: {url: "https://example.com/resolved.txt"}}]};
+});`
+			for name, content := range map[string]string{"manifest.json": manifest, "index.js": script} {
+				if err := os.WriteFile(filepath.Join(extDir, name), []byte(content), 0600); err != nil {
+					t.Fatal(err)
+				}
+			}
+			if _, err := d.InstallExtensionByFolder(extDir, true); err != nil {
+				t.Fatal(err)
+			}
+
+			for _, req := range []*base.Request{
+				{URL: magnetURL},
+				{URL: "https://example.com/rewritten", RawURL: magnetURL},
+			} {
+				// Exercise extension activation without falling back to a live
+				// BitTorrent metadata lookup when the pattern fails to match.
+				res, err := d.triggerOnResolve(req)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if res == nil || len(res.Files) != 1 || res.Files[0].Name != "resolved.txt" {
+					t.Fatalf("magnet extension did not resolve request %+v: %+v", req, res)
+				}
+			}
+		})
+	}
+}

pkg/download/extension_resolve_size_test.go

@@ -0,0 +1,159 @@
+package download
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+func TestExtensionResolveSizeThroughTaskCreation(t *testing.T) {
+	for _, mode := range []string{"http", "blob"} {
+		for _, known := range []bool{false, true} {
+			t.Run(fmt.Sprintf("%s/known=%v", mode, known), func(t *testing.T) {
+				payload := []byte("0123456789")
+				server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					body := payload
+					if r.URL.Path == "/empty" {
+						body = nil
+					}
+					if known {
+						w.Header().Set("Content-Length", fmt.Sprint(len(body)))
+					}
+					w.(http.Flusher).Flush()
+					w.Write(body)
+				}))
+				defer server.Close()
+				d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir(), TempDir: t.TempDir()})
+				if err := d.Setup(); err != nil {
+					t.Fatal(err)
+				}
+				defer d.Clear()
+				d.cfg.MaxRunning = 0 // Inspect persisted queued tasks before HTTP resolution.
+				extDir := t.TempDir()
+				manifest := `{"name":"size-hint","author":"test","title":"Size hint","version":"1.0.0","scripts":[{"event":"onResolve","match":{"urls":["https://example.com/size-hint"]},"entry":"index.js"}]}`
+				script := fmt.Sprintf(`gopeed.events.onResolve(async ctx=>{
+  const mode=%q, origin=%q;
+  const file=async(name,size,empty)=>({name,size,req:{url:mode==='http'?origin+(empty?'/empty':'/data'):
+    await gopeed.runtime.blob.createObjectURL(()=>new ReadableStream({start(c){if(!empty)c.enqueue(new Uint8Array([48,49,50,51,52,53,54,55,56,57]));c.close();}}))}});
+  ctx.res={files:[await file('under.bin',3,false),await file('over.bin',1048576,false),await file('empty.bin',99,true)]};
+});`, mode, server.URL)
+				for name, contents := range map[string]string{"manifest.json": manifest, "index.js": script} {
+					if err := os.WriteFile(filepath.Join(extDir, name), []byte(contents), 0600); err != nil {
+						t.Fatal(err)
+					}
+				}
+				if _, err := d.InstallExtensionByFolder(extDir, true); err != nil {
+					t.Fatal(err)
+				}
+				rr, err := d.Resolve(&base.Request{URL: "https://example.com/size-hint"})
+				if err != nil {
+					t.Fatal(err)
+				}
+				output := t.TempDir()
+				batch := &base.CreateTaskBatch{}
+				for _, file := range rr.Res.Files {
+					batch.Reqs = append(batch.Reqs, &base.CreateTaskBatchItem{Req: file.Req, Opts: &base.Options{Size: file.Size, Name: file.Name, Path: output}})
+				}
+				wire, err := json.Marshal(batch)
+				if err != nil {
+					t.Fatal(err)
+				}
+				var submitted base.CreateTaskBatch
+				if err := json.Unmarshal(wire, &submitted); err != nil {
+					t.Fatal(err)
+				}
+				batchResult, err := d.CreateDirectBatch(&submitted)
+				if err != nil {
+					t.Fatal(err)
+				}
+				ids := batchResult
+				for i, id := range ids {
+					task := d.GetTask(id)
+					if task.Meta.Res != nil {
+						t.Fatal("a size estimate must not mark the task resolved")
+					}
+					status, err := d.RuntimeStatus(id)
+					if err != nil || status.Total != rr.Res.Files[i].Size {
+						t.Fatalf("queued size lost: status=%+v err=%v", status, err)
+					}
+					var saved Task
+					if _, err := d.storage.Get(bucketTask, id, &saved); err != nil || saved.Meta.Opts.Size != status.Total {
+						t.Fatal("queued estimate was not persisted", err)
+					}
+					if err := d.doStart(task); err != nil {
+						t.Fatal(err)
+					}
+					waitForTaskTerminal(t, d, id, 5*time.Second)
+					body, err := os.ReadFile(filepath.Join(output, rr.Res.Files[i].Name))
+					if err != nil {
+						t.Fatal(err)
+					}
+					want := payload
+					if i == 2 {
+						want = nil
+					}
+					if !bytes.Equal(body, want) {
+						t.Fatalf("estimate changed output: %q", body)
+					}
+					status, err = d.RuntimeStatus(id)
+					if err != nil || status.Total != int64(len(want)) || status.Downloaded != int64(len(want)) || task.Meta.Res.Files[0].Size != int64(len(want)) {
+						t.Fatalf("final size not updated: %+v err=%v", status, err)
+					}
+				}
+			})
+		}
+	}
+}
+
+func TestResolvedHTTPSizeEstimateAtCreation(t *testing.T) {
+	for _, known := range []bool{false, true} {
+		t.Run(fmt.Sprintf("known=%v", known), func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+				if known {
+					w.Header().Set("Content-Length", "10")
+				}
+				w.(http.Flusher).Flush()
+				w.Write([]byte("0123456789"))
+			}))
+			defer server.Close()
+			d := NewDownloader(&DownloaderConfig{StorageDir: t.TempDir(), TempDir: t.TempDir()})
+			if err := d.Setup(); err != nil {
+				t.Fatal(err)
+			}
+			defer d.Clear()
+			d.cfg.MaxRunning = 0
+			rr, err := d.Resolve(&base.Request{URL: server.URL})
+			if err != nil {
+				t.Fatal(err)
+			}
+			id, err := d.CreateWithOptions(rr.ID, &base.Options{Size: 3, Path: t.TempDir(), Name: "output.bin"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			want := int64(3)
+			if known {
+				want = 10
+			}
+			status, err := d.RuntimeStatus(id)
+			if err != nil || status.Total != want || d.GetTask(id).Meta.Res.Files[0].Size != want {
+				t.Fatalf("resolve-before-create size=%+v want=%d err=%v", status, want, err)
+			}
+			if err := d.doStart(d.GetTask(id)); err != nil {
+				t.Fatal(err)
+			}
+			waitForTaskTerminal(t, d, id, 5*time.Second)
+			task := d.GetTask(id)
+			if task.Status != base.DownloadStatusDone || task.Meta.Res.Size != 10 {
+				t.Fatalf("estimate changed completion: status=%s size=%d", task.Status, task.Meta.Res.Size)
+			}
+		})
+	}
+}

pkg/download/extension_size_hint_test.go

@@ -0,0 +1,212 @@
+package download
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+func TestExtensionFileSizeIsAdvisory(t *testing.T) {
+	video, err := os.ReadFile("engine/testdata/ffmpeg/video.mp4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	audio, err := os.ReadFile("engine/testdata/ffmpeg/audio.mp4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, mode := range []string{"plain", "merge", "wrapped-merge"} {
+		var expected []byte
+		for _, size := range []int64{0, 3, 1 << 20} {
+			t.Run(fmt.Sprintf("%s/size=%d", mode, size), func(t *testing.T) {
+				d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir(), TempDir: t.TempDir(), RefreshInterval: 50})
+				if err := d.Setup(); err != nil {
+					t.Fatal(err)
+				}
+				defer d.Clear()
+				e, _ := d.newExtensionEngine()
+				defer e.Close()
+				e.Runtime.Set("videoBytes", e.Runtime.NewArrayBuffer(video))
+				e.Runtime.Set("audioBytes", e.Runtime.NewArrayBuffer(audio))
+				e.Runtime.Set("mode", mode)
+				result, err := e.RunString(`__gopeed_blob_create_object_url(()=>{
+  const source=b=>new ReadableStream({start(c){c.enqueue(new Uint8Array(b));c.close();}});
+  if (mode==='plain') return source([0,1,2,3,4,5,6,7,8,9]);
+  const output=__gopeed_ffmpeg.merge({inputs:()=>({video:source(videoBytes),audio:source(audioBytes)})});
+  if (mode==='merge') return output;
+  const reader=output.getReader();
+  return new ReadableStream({async pull(c){const {done,value}=await reader.read();if(done)c.close();else c.enqueue(value);},cancel(r){return reader.cancel(r);}});
+},{contentType:'video/mp4',range:false})`)
+				if err != nil {
+					t.Fatal(err)
+				}
+				output := t.TempDir()
+				id, err := d.CreateDirect(&base.Request{URL: fmt.Sprint(result)}, &base.Options{Size: size, Path: output, Name: "output.bin"})
+				if err != nil {
+					t.Fatal(err)
+				}
+				waitForTaskTerminal(t, d, id, 30*time.Second)
+				body, err := os.ReadFile(filepath.Join(output, "output.bin"))
+				if err != nil {
+					t.Fatal(err)
+				}
+				if size == 0 {
+					expected = body
+					if mode == "plain" && !bytes.Equal(body, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}) {
+						t.Fatalf("unexpected stream output: %v", body)
+					}
+					if mode != "plain" && !bytes.Contains(body, []byte("moof")) {
+						t.Fatal("invalid merged output")
+					}
+				} else if !bytes.Equal(body, expected) {
+					t.Fatalf("size hint changed output: got %d bytes, want %d", len(body), len(expected))
+				}
+				task := d.GetTask(id)
+				task.lock.Lock()
+				defer task.lock.Unlock()
+				if task.Meta.Res.Size != int64(len(body)) || task.Meta.Res.Files[0].Size != int64(len(body)) {
+					t.Fatalf("final metadata must use actual size: %#v", task.Meta.Res)
+				}
+			})
+		}
+	}
+}
+
+func TestExtensionFileSizeYieldsToBlobContentLength(t *testing.T) {
+	for _, materialized := range []bool{false, true} {
+		for _, size := range []int64{3, 1 << 20} {
+			t.Run(fmt.Sprintf("materialized=%v/estimate=%d", materialized, size), func(t *testing.T) {
+				d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir(), TempDir: t.TempDir()})
+				if err := d.Setup(); err != nil {
+					t.Fatal(err)
+				}
+				defer d.Clear()
+				e, _ := d.newExtensionEngine()
+				defer e.Close()
+				e.Runtime.Set("materialized", materialized)
+				result, err := e.RunString(`(()=>{
+  const payload=new Uint8Array([0,1,2,3,4,5,6,7,8,9]);
+  const source=materialized?new Blob([payload]):()=>new ReadableStream({start(c){c.enqueue(payload);c.close();}});
+  return __gopeed_blob_create_object_url(source,{size:10});
+})()`)
+				if err != nil {
+					t.Fatal(err)
+				}
+				output := t.TempDir()
+				id, err := d.CreateDirect(&base.Request{URL: fmt.Sprint(result)}, &base.Options{Size: size, Path: output, Name: "output.bin"})
+				if err != nil {
+					t.Fatal(err)
+				}
+				waitForTaskTerminal(t, d, id, 5*time.Second)
+				body, err := os.ReadFile(filepath.Join(output, "output.bin"))
+				if err != nil || !bytes.Equal(body, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}) {
+					t.Fatalf("unexpected body=%v err=%v", body, err)
+				}
+				task := d.GetTask(id)
+				if task.Meta.Res.Size != 10 || task.Meta.Res.Files[0].Size != 10 {
+					t.Fatalf("Blob Content-Length did not override estimate: %+v", task.Meta.Res)
+				}
+			})
+		}
+	}
+}
+
+func TestExtensionFileSizeHintWaitsForEOF(t *testing.T) {
+	for _, fail := range []bool{false, true} {
+		for _, size := range []int64{3, 1 << 20} {
+			t.Run(fmt.Sprintf("fail=%v/size=%d", fail, size), func(t *testing.T) {
+				d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir(), TempDir: t.TempDir(), RefreshInterval: 50})
+				if err := d.Setup(); err != nil {
+					t.Fatal(err)
+				}
+				defer d.Clear()
+				e, _ := d.newExtensionEngine()
+				defer e.Close()
+				e.Runtime.Set("fail", fail)
+				result, err := e.RunString(`__gopeed_blob_create_object_url(()=>new ReadableStream({
+  start(c){c.enqueue(new Uint8Array([0,1,2,3,4,5,6,7,8,9]));globalThis.finish=()=>{if(fail)c.error(new Error('upstream failed'));else c.close();};}
+}),{})`)
+				if err != nil {
+					t.Fatal(err)
+				}
+				output := t.TempDir()
+				id, err := d.CreateDirect(&base.Request{URL: fmt.Sprint(result)}, &base.Options{Size: size, Path: output, Name: "output.bin"})
+				if err != nil {
+					t.Fatal(err)
+				}
+				waitForTaskDownloadedBetween(t, d, id, 10, 10, 5*time.Second)
+				task := d.GetTask(id)
+				task.lock.Lock()
+				if task.Meta.Res.Size != size || d.taskStatus(task) != base.DownloadStatusRunning {
+					t.Errorf("hint must remain visible until EOF: size=%d status=%s", task.Meta.Res.Size, d.taskStatus(task))
+				}
+				task.lock.Unlock()
+				stat, err := os.Stat(filepath.Join(output, "output.bin"))
+				if err != nil || stat.Size() != 10 {
+					t.Fatalf("hint must not preallocate or truncate output: stat=%v err=%v", stat, err)
+				}
+				if _, err := e.RunString(`finish()`); err != nil {
+					t.Fatal(err)
+				}
+				if fail {
+					waitForTaskStatus(t, d, id, base.DownloadStatusError, 5*time.Second)
+				} else {
+					waitForTaskTerminal(t, d, id, 5*time.Second)
+				}
+			})
+		}
+	}
+}
+
+func TestExtensionFileSizeHintPauseContinue(t *testing.T) {
+	for _, size := range []int64{3, 1 << 20} {
+		t.Run(fmt.Sprint(size), func(t *testing.T) {
+			d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir(), TempDir: t.TempDir(), RefreshInterval: 50})
+			if err := d.Setup(); err != nil {
+				t.Fatal(err)
+			}
+			defer d.Clear()
+			e, _ := d.newExtensionEngine()
+			defer e.Close()
+			result, err := e.RunString(`(()=>{
+  let opens=0;
+  return __gopeed_blob_create_object_url(()=>new ReadableStream({start(c){
+    if (++opens===1) c.enqueue(new Uint8Array([0,1,2,3,4,5,6,7,8,9]));
+    else {c.enqueue(new Uint8Array([5,6]));c.close();}
+  }}),{});
+})()`)
+			if err != nil {
+				t.Fatal(err)
+			}
+			output := t.TempDir()
+			id, err := d.CreateDirect(&base.Request{URL: fmt.Sprint(result)}, &base.Options{Size: size, Path: output, Name: "output.bin"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			waitForTaskDownloadedBetween(t, d, id, 10, 10, 5*time.Second)
+			filter := &TaskFilter{IDs: []string{id}}
+			if err := d.Pause(filter); err != nil {
+				t.Fatal(err)
+			}
+			if err := d.Continue(filter); err != nil {
+				t.Fatal(err)
+			}
+			waitForTaskTerminal(t, d, id, 5*time.Second)
+			body, err := os.ReadFile(filepath.Join(output, "output.bin"))
+			if err != nil {
+				t.Fatal(err)
+			}
+			task := d.GetTask(id)
+			task.lock.Lock()
+			defer task.lock.Unlock()
+			if !bytes.Equal(body, []byte{5, 6}) || task.Meta.Res.Size != 2 {
+				t.Fatalf("resumed stream kept an estimate or stale bytes: body=%v size=%d", body, task.Meta.Res.Size)
+			}
+		})
+	}
+}

pkg/download/extension_task_request.go

@@ -0,0 +1,140 @@
+package download
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+	btProtocol "github.com/GopeedLab/gopeed/pkg/protocol/bt"
+	httpProtocol "github.com/GopeedLab/gopeed/pkg/protocol/http"
+	"github.com/GopeedLab/gopeed/pkg/util"
+	"github.com/dop251/goja"
+)
+
+// ExtensionTaskRequest exposes request operations without exposing the backing task.
+// It always reads the current request so a retained handle sees subsequent updates.
+type ExtensionTaskRequest struct {
+	*base.Request
+	task *Task
+}
+
+// SetUrl replaces the task request URL.
+func (r *ExtensionTaskRequest) SetUrl(url string) { r.task.Meta.Req.URL = url }
+
+// SetLabels replaces all labels on the request.
+func (r *ExtensionTaskRequest) SetLabels(labels map[string]string) {
+	r.Labels = labels
+}
+
+// PutLabel sets a label on the request.
+func (r *ExtensionTaskRequest) PutLabel(key, value string) {
+	if r.Labels == nil {
+		r.Labels = make(map[string]string)
+	}
+	r.Labels[key] = value
+}
+
+// DelLabel deletes a label from the request.
+func (r *ExtensionTaskRequest) DelLabel(key string) {
+	delete(r.Labels, key)
+}
+
+// mutateTaskExtra converts into an independent protocol value before mutation.
+// Other protocols are a no-op. Failed conversion or mutation must not change the live request.
+func mutateTaskExtra[E any](task *Task, protocol string, mutate func(*E) error) error {
+	if task.Protocol != protocol {
+		return nil
+	}
+	if task.Meta == nil || task.Meta.Req == nil {
+		return fmt.Errorf("task request is missing")
+	}
+	var extra E
+	if err := util.MapToStruct(task.Meta.Req.Extra, &extra); err != nil {
+		return err
+	}
+	if err := mutate(&extra); err != nil {
+		return err
+	}
+	task.Meta.Req.Extra = &extra
+	return nil
+}
+
+func (t *ExtensionTaskRequest) SetMethod(method string) error {
+	return mutateTaskExtra(t.task, "http", func(extra *httpProtocol.ReqExtra) error { extra.Method = method; return nil })
+}
+
+func (t *ExtensionTaskRequest) SetBody(body string) error {
+	return mutateTaskExtra(t.task, "http", func(extra *httpProtocol.ReqExtra) error { extra.Body = body; return nil })
+}
+
+// decodeHeaders omits undefined properties and rejects non-string values.
+func decodeHeaders(value *goja.Object) (map[string]string, error) {
+	if value == nil {
+		return nil, fmt.Errorf("headers must be an object")
+	}
+	data, err := value.MarshalJSON()
+	if err != nil {
+		return nil, err
+	}
+	var input map[string]*string
+	if err := json.Unmarshal(data, &input); err != nil {
+		return nil, err
+	}
+	if input == nil {
+		return nil, fmt.Errorf("headers must be an object")
+	}
+	headers := make(map[string]string, len(input))
+	seen := make(map[string]bool, len(input))
+	for name, value := range input {
+		if value == nil {
+			return nil, fmt.Errorf("header %q must be a string", name)
+		}
+		lower := strings.ToLower(name)
+		if seen[lower] {
+			return nil, fmt.Errorf("duplicate header name %q", name)
+		}
+		seen[lower] = true
+		headers[http.CanonicalHeaderKey(name)] = *value
+	}
+	return headers, nil
+}
+
+func (t *ExtensionTaskRequest) SetHeaders(headers *goja.Object) error {
+	return mutateTaskExtra(t.task, "http", func(extra *httpProtocol.ReqExtra) error {
+		values, err := decodeHeaders(headers)
+		if err != nil {
+			return err
+		}
+		extra.Header = values
+		return nil
+	})
+}
+
+func (t *ExtensionTaskRequest) PutHeader(name, value string) error {
+	return mutateTaskExtra(t.task, "http", func(extra *httpProtocol.ReqExtra) error {
+		if extra.Header == nil {
+			extra.Header = make(map[string]string)
+		}
+		deleteHeader(extra.Header, name)
+		extra.Header[http.CanonicalHeaderKey(name)] = value
+		return nil
+	})
+}
+
+func (t *ExtensionTaskRequest) DelHeader(name string) error {
+	return mutateTaskExtra(t.task, "http", func(extra *httpProtocol.ReqExtra) error { deleteHeader(extra.Header, name); return nil })
+}
+
+func deleteHeader(headers map[string]string, name string) {
+	for key := range headers {
+		if strings.EqualFold(key, name) {
+			delete(headers, key)
+		}
+	}
+}
+
+func (t *ExtensionTaskRequest) SetTrackers(trackers []string) error {
+	return mutateTaskExtra(t.task, "bt", func(extra *btProtocol.ReqExtra) error { extra.Trackers = append([]string{}, trackers...); return nil })
+}

pkg/download/extension_test.go

@@ -14,10 +14,12 @@ import (
 	"testing"
 	"time"
 
+	"github.com/GopeedLab/gopeed/internal/fetcher"
 	"github.com/GopeedLab/gopeed/internal/logger"
 	"github.com/GopeedLab/gopeed/pkg/base"
 	gojaerror "github.com/GopeedLab/gopeed/pkg/download/engine/inject/error"
 	enginewebview "github.com/GopeedLab/gopeed/pkg/download/engine/webview"
+	httpProtocol "github.com/GopeedLab/gopeed/pkg/protocol/http"
 	"github.com/dop251/goja"
 )
 
@@ -30,7 +32,7 @@ func TestDownloader_InstallExtensionByFolder(t *testing.T) {
 			URL:    "https://github.com/test",
 			Labels: map[string]string{"original": "true"},
 		}
-		rr, err := downloader.Resolve(req, nil)
+		rr, err := downloader.Resolve(req)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -38,13 +40,13 @@ func TestDownloader_InstallExtensionByFolder(t *testing.T) {
 			t.Fatal("resolve error")
 		}
 		if req.Labels["replaced"] != "true" || req.Labels["modified"] != "true" {
-			t.Fatalf("request label methods did not update labels: %#v", req.Labels)
+			t.Fatalf("declarative labels did not update: %#v", req.Labels)
 		}
 		if _, ok := req.Labels["original"]; ok {
-			t.Fatalf("setLabels did not replace existing labels: %#v", req.Labels)
+			t.Fatalf("label assignment did not replace existing labels: %#v", req.Labels)
 		}
 		if _, ok := req.Labels["removed"]; ok {
-			t.Fatalf("delLabel did not remove label: %#v", req.Labels)
+			t.Fatalf("declarative label deletion failed: %#v", req.Labels)
 		}
 	})
 }
@@ -56,7 +58,7 @@ func TestDownloader_InstallExtensionByFolderDevMode(t *testing.T) {
 		}
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://github.com/test",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -74,7 +76,7 @@ func TestDownloader_Extension_BlobBlob(t *testing.T) {
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://example.com/blob",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -128,7 +130,7 @@ func TestDownloader_Extension_BlobFunctionOpener(t *testing.T) {
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://example.com/opener",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -164,7 +166,7 @@ func TestDownloader_Extension_BlobFunctionOpenerUnknownSize(t *testing.T) {
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://example.com/opener-unknown",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -220,7 +222,7 @@ func TestDownloader_Extension_BlobSourceSizePropagatesToCreatedTask(t *testing.T
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://example.com/opener",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -301,7 +303,7 @@ func TestDownloader_Extension_BlobFetchDrainedStreamReportsEarlyProgress(t *test
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: fmt.Sprintf("%s/single-fetch-stream?size=%d", server.URL, len(payload)),
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -417,7 +419,7 @@ func TestDownloader_Extension_BlobRangeFetchDrainedStreamReportsEarlyProgress(t
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: fmt.Sprintf("%s/range-fetch-stream?size=%d", server.URL, len(payload)),
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -492,7 +494,7 @@ func TestDownloader_Extension_BlobMultiplexFetchStreamsReportEarlyProgress(t *te
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: server.URL + "/multiplex-fetch-stream",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -548,7 +550,7 @@ func TestDownloader_Extension_BlobFunctionOpenerRangeResume(t *testing.T) {
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://example.com/opener-range",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -681,7 +683,7 @@ func TestDownloader_Extension_BlobResumeAfterRestartViaOnError(t *testing.T) {
 
 	rr, err := downloader.Resolve(&base.Request{
 		URL: server.URL + "/restart-range",
-	}, nil)
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -853,7 +855,7 @@ func TestDownloader_Extension_BlobPauseContinueKeepsSource(t *testing.T) {
 
 			rr, err := downloader.Resolve(&base.Request{
 				URL: tc.url,
-			}, nil)
+			})
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -930,7 +932,7 @@ func TestDownloader_Extension_BlobUnknownSizePauseContinueKeepsSource(t *testing
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://example.com/opener-unknown",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1007,7 +1009,7 @@ func TestDownloader_Extension_BlobRecoverOnError(t *testing.T) {
 			path := path
 			t.Run(path, func(t *testing.T) {
 				rawURL := "https://example.com/" + path
-				rr, err := downloader.Resolve(&base.Request{URL: rawURL}, nil)
+				rr, err := downloader.Resolve(&base.Request{URL: rawURL})
 				if err != nil {
 					t.Fatal(err)
 				}
@@ -1068,54 +1070,15 @@ func TestDownloader_Extension_BlobRecoverOnError(t *testing.T) {
 }
 
 func TestDownloader_InstallExtensionByGit(t *testing.T) {
-	setupDownloader(func(downloader *Downloader) {
-		if _, err := downloader.InstallExtensionByGit("https://github.com/GopeedLab/gopeed-extension-samples#github-release-sample"); err != nil {
-			t.Fatal(err)
-		}
-		rr, err := downloader.Resolve(&base.Request{
-			URL: "https://github.com/GopeedLab/gopeed/releases",
-		}, nil)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if len(rr.Res.Files) == 1 {
-			t.Fatal("resolve error")
-		}
-	})
+	testInstallExtensionGitURL(t, "https://github.com/gopeed-test/repo#nested/extension")
 }
 
 func TestDownloader_InstallExtensionByGitSimple(t *testing.T) {
-	setupDownloader(func(downloader *Downloader) {
-		if _, err := downloader.InstallExtensionByGit("github.com/GopeedLab/gopeed-extension-samples#github-release-sample"); err != nil {
-			t.Fatal(err)
-		}
-		rr, err := downloader.Resolve(&base.Request{
-			URL: "https://github.com/GopeedLab/gopeed/releases",
-		}, nil)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if len(rr.Res.Files) == 1 {
-			t.Fatal("resolve error")
-		}
-	})
+	testInstallExtensionGitURL(t, "github.com/gopeed-test/repo#nested/extension")
 }
 
 func TestDownloader_InstallExtensionByGitFull(t *testing.T) {
-	setupDownloader(func(downloader *Downloader) {
-		if _, err := downloader.InstallExtensionByGit("https://github.com/GopeedLab/gopeed-extension-samples.git#github-release-sample"); err != nil {
-			t.Fatal(err)
-		}
-		rr, err := downloader.Resolve(&base.Request{
-			URL: "https://github.com/GopeedLab/gopeed/releases",
-		}, nil)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if len(rr.Res.Files) == 1 {
-			t.Fatal("resolve error")
-		}
-	})
+	testInstallExtensionGitURL(t, "https://github.com/gopeed-test/repo.git#nested/extension")
 }
 
 func TestDownloader_UpgradeExtension(t *testing.T) {
@@ -1178,7 +1141,7 @@ func TestDownloader_UpgradeExtension(t *testing.T) {
 
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://test.com",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1188,6 +1151,37 @@ func TestDownloader_UpgradeExtension(t *testing.T) {
 	})
 }
 
+func TestDownloader_Extension_OnStartExtraMutation(t *testing.T) {
+	d := NewDownloader(&DownloaderConfig{Storage: NewMemStorage(), StorageDir: t.TempDir()})
+	if err := d.Setup(); err != nil {
+		t.Fatal(err)
+	}
+	defer d.Clear()
+	if _, err := d.InstallExtensionByFolder("./testdata/extensions/on_start", false); err != nil {
+		t.Fatal(err)
+	}
+	for _, extra := range []any{nil, &httpProtocol.ReqExtra{
+		Method: "POST", Body: "old body", Header: map[string]string{"Old": "value"},
+	}} {
+		req := &base.Request{URL: "https://github.com/test", Extra: extra}
+		task := &Task{Protocol: "http", Meta: &fetcher.FetcherMeta{Req: req, Opts: &base.Options{}}}
+		d.triggerOnStart(task)
+		if err := base.ParseReqExtra[httpProtocol.ReqExtra](req); err != nil {
+			t.Fatal(err)
+		}
+		got, ok := req.Extra.(*httpProtocol.ReqExtra)
+		if !ok || got.Header["X-Gopeed-Test"] != "on-start" {
+			t.Fatalf("setHeaders did not update the original request: %#v", req.Extra)
+		}
+		if len(got.Header) != 1 {
+			t.Fatalf("headers not replaced: %#v", got)
+		}
+		if original, ok := extra.(*httpProtocol.ReqExtra); ok && (got.Method != original.Method || got.Body != original.Body) {
+			t.Fatalf("setHeaders changed unrelated fields: %#v", got)
+		}
+	}
+}
+
 func TestDownloader_Extension_OnStart(t *testing.T) {
 	downloadAndCheck := func(req *base.Request) {
 		setupDownloader(func(downloader *Downloader) {
@@ -1322,7 +1316,7 @@ func TestDownloader_Extension_Errors(t *testing.T) {
 		}
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://github.com/test",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1337,7 +1331,7 @@ func TestDownloader_Extension_Errors(t *testing.T) {
 		}
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://github.com/test",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1352,7 +1346,7 @@ func TestDownloader_Extension_Errors(t *testing.T) {
 		}
 		_, err := downloader.Resolve(&base.Request{
 			URL: "https://github.com/test",
-		}, nil)
+		})
 		if err == nil {
 			t.Fatalf("except error, but got nil")
 		}
@@ -1374,7 +1368,7 @@ func TestDownloader_Extension_Settings(t *testing.T) {
 		}
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://github.com/test",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1395,7 +1389,7 @@ func TestDownloader_Extension_Settings(t *testing.T) {
 		})
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://github.com/test",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1412,7 +1406,7 @@ func TestDownloader_ExtensionStorage(t *testing.T) {
 		}
 		rr, err := downloader.Resolve(&base.Request{
 			URL: "https://github.com/test",
-		}, nil)
+		})
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -2050,8 +2044,13 @@ func waitForTaskStatus(t *testing.T, downloader *Downloader, id string, status b
 	deadline := time.Now().Add(timeout)
 	for time.Now().Before(deadline) {
 		task := downloader.GetTask(id)
-		if task != nil && task.Status == status {
-			return
+		if task != nil && downloader.taskStatus(task) == status {
+			if status != base.DownloadStatusDone {
+				return
+			}
+			if _, watching := downloader.watchedTasks.Load(id); !watching {
+				return
+			}
 		}
 		time.Sleep(10 * time.Millisecond)
 	}
@@ -2059,9 +2058,6 @@ func waitForTaskStatus(t *testing.T, downloader *Downloader, id string, status b
 	if task == nil {
 		t.Fatalf("timeout waiting for task %s status %s: task not found", id, status)
 	}
-	total := int64(0)
-	if task.Meta != nil && task.Meta.Res != nil {
-		total = task.Meta.Res.Size
-	}
-	t.Fatalf("timeout waiting for task %s status %s: got %s downloaded=%d total=%d", id, status, task.Status, task.Progress.Downloaded, total)
+	snapshot, err := downloader.RuntimeStatus(id)
+	t.Fatalf("timeout waiting for task %s status %s: got %+v, error=%v", id, status, snapshot, err)
 }

pkg/download/extension_unnamed_resource_test.go

@@ -24,7 +24,7 @@ func TestExtensionUnnamedResource(t *testing.T) {
 	if _, err = d.InstallExtensionByFolder(dir, true); err != nil {
 		t.Fatal(err)
 	}
-	res, err := d.Resolve(&base.Request{URL: "https://example.com/unnamed"}, nil)
+	res, err := d.Resolve(&base.Request{URL: "https://example.com/unnamed"})
 	if err != nil {
 		t.Fatal(err)
 	}

pkg/download/ftp_test.go

@@ -0,0 +1,57 @@
+package download
+
+import (
+	"testing"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/protocol/ftp"
+	"github.com/GopeedLab/gopeed/pkg/protocol/http"
+)
+
+// TestTorrentNameIsFile checks the default manager order: an FTP URL whose
+// name looks like a torrent or a playlist is still an FTP download.
+func TestTorrentNameIsFile(t *testing.T) {
+	d := NewDownloader(nil)
+	for u, want := range map[string]string{
+		"ftp://h/x.torrent":    "ftp",
+		"ftp://h/v.m3u8":       "ftp",
+		"ftps://h/x.torrent":   "ftp",
+		"ftpes://h/a.bin":      "ftp",
+		"https://h/v.m3u8":     "hls",
+		"https://h/x.torrent":  "http",
+		"magnet:?xt=urn:btih:": "bt",
+	} {
+		fm, err := d.parseFm(u)
+		if err != nil {
+			t.Fatalf("%s: %v", u, err)
+		}
+		if fm.Name() != want {
+			t.Fatalf("%s goes to %q, want %q", u, fm.Name(), want)
+		}
+	}
+}
+
+func TestPostDownloadExtraAcceptsFTP(t *testing.T) {
+	yes := true
+	file := &base.Resource{Files: []*base.FileInfo{{Name: "a.zip"}}}
+	folder := &base.Resource{Name: "dir", Files: []*base.FileInfo{{Name: "a.zip"}}}
+
+	httpExtra := &http.OptsExtra{AutoExtract: &yes}
+	if got := postDownloadExtra(&fetcher.FetcherMeta{Res: file, Opts: &base.Options{Extra: httpExtra}}); got != httpExtra {
+		t.Fatalf("HTTP options must pass through unchanged, got %+v", got)
+	}
+
+	ftpExtra := &ftp.OptsExtra{Connections: 4, AutoTorrent: &yes, DeleteTorrentAfterDownload: &yes, AutoExtract: &yes, ArchivePassword: "pw", DeleteAfterExtract: true}
+	got := postDownloadExtra(&fetcher.FetcherMeta{Res: file, Opts: &base.Options{Extra: ftpExtra}})
+	if got == nil || got.AutoTorrent != &yes || got.DeleteTorrentAfterDownload != &yes || got.AutoExtract != &yes ||
+		got.ArchivePassword != "pw" || !got.DeleteAfterExtract {
+		t.Fatalf("FTP options were not carried over: %+v", got)
+	}
+	if got := postDownloadExtra(&fetcher.FetcherMeta{Res: folder, Opts: &base.Options{Extra: ftpExtra}}); got != nil {
+		t.Fatalf("an FTP folder has no single file to extract, got %+v", got)
+	}
+	if got := postDownloadExtra(&fetcher.FetcherMeta{Res: file, Opts: &base.Options{}}); got != nil {
+		t.Fatalf("no options, got %+v", got)
+	}
+}

pkg/download/github_mirror.go

@@ -0,0 +1,151 @@
+package download
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/githubmirror"
+	"github.com/GopeedLab/gopeed/internal/httpclient"
+)
+
+func (d *Downloader) resourceClient(publicOnly bool) (*http.Client, error) {
+	cfg, err := d.GetConfig()
+	if err != nil {
+		return nil, err
+	}
+	options := httpclient.Options{
+		Client:    httpclient.ClientOptions{Timeout: 30 * time.Second},
+		Transport: httpclient.TransportOptions{Proxy: cfg.Proxy.ToHandler(), TLSHandshakeTimeout: 10 * time.Second},
+	}
+	if publicOnly {
+		// A configured upstream proxy is trusted, but target URLs are still checked.
+		options.Client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
+			if len(via) >= 5 {
+				return errors.New("too many redirects")
+			}
+			return validatePublicURL(req.Context(), req.URL.String())
+		}
+		if cfg.Proxy == nil || !cfg.Proxy.Enable {
+			options.Transport.DialContext = func(ctx context.Context, network, address string) (net.Conn, error) {
+				host, port, err := net.SplitHostPort(address)
+				if err != nil {
+					return nil, err
+				}
+				ips, err := publicIPs(ctx, host)
+				if err != nil {
+					return nil, err
+				}
+				var last error
+				for _, ip := range ips {
+					conn, err := (&net.Dialer{Timeout: 10 * time.Second}).DialContext(ctx, network, net.JoinHostPort(ip.String(), port))
+					if err == nil {
+						return conn, nil
+					}
+					last = err
+				}
+				return nil, last
+			}
+		}
+	}
+	return httpclient.NewClient(options)
+}
+func publicIPs(ctx context.Context, host string) ([]net.IPAddr, error) {
+	ips, err := net.DefaultResolver.LookupIPAddr(ctx, host)
+	if err != nil {
+		return nil, err
+	}
+	if len(ips) == 0 {
+		return nil, errors.New("target has no addresses")
+	}
+	for _, ip := range ips {
+		if !ip.IP.IsGlobalUnicast() || ip.IP.IsPrivate() || ip.IP.IsLoopback() || ip.IP.IsLinkLocalUnicast() || ip.IP.IsUnspecified() {
+			return nil, errors.New("private or local resource target is not allowed")
+		}
+	}
+	return ips, nil
+}
+func validatePublicURL(ctx context.Context, raw string) error {
+	u, err := url.Parse(raw)
+	if err != nil || u == nil || (u.Scheme != "https" && u.Scheme != "http") || u.Host == "" || u.User != nil {
+		return errors.New("invalid resource URL")
+	}
+	_, err = publicIPs(ctx, u.Hostname())
+	return err
+}
+func (d *Downloader) fetchPublicResource(ctx context.Context, raw string, limit int64, validate func([]byte) error) ([]byte, error) {
+	return d.fetchResource(ctx, raw, limit, true, validate)
+}
+
+// fetchResource races complete, validated responses. A successful HEAD alone
+// cannot win, and failed candidates never discard a usable official response.
+func (d *Downloader) fetchResource(ctx context.Context, raw string, limit int64, publicOnly bool, validate func([]byte) error) ([]byte, error) {
+	cfg, err := d.GetConfig()
+	if err != nil {
+		return nil, err
+	}
+	client, err := d.resourceClient(publicOnly)
+	if err != nil {
+		return nil, err
+	}
+	defer client.CloseIdleConnections()
+	return githubmirror.Race(ctx, cfg.GithubMirror, raw,
+		githubmirror.Options[[]byte]{Kind: githubmirror.Resource, Timeout: 30 * time.Second},
+		func(ctx context.Context, candidate string) ([]byte, error) {
+			if publicOnly {
+				if err := validatePublicURL(ctx, candidate); err != nil {
+					return nil, err
+				}
+			}
+			request, err := http.NewRequestWithContext(ctx, http.MethodGet, candidate, nil)
+			if err != nil {
+				return nil, err
+			}
+			response, err := client.Do(request)
+			if err != nil {
+				return nil, err
+			}
+			defer response.Body.Close()
+			if response.StatusCode != http.StatusOK {
+				return nil, fmt.Errorf("resource returned HTTP %d", response.StatusCode)
+			}
+			body, err := io.ReadAll(io.LimitReader(response.Body, limit+1))
+			if err != nil {
+				return nil, err
+			}
+			if int64(len(body)) > limit {
+				return nil, errors.New("resource exceeds size limit")
+			}
+			if len(body) == 0 {
+				return nil, errors.New("empty resource")
+			}
+			if validate != nil {
+				if err := validate(body); err != nil {
+					return nil, err
+				}
+			}
+			return body, nil
+		},
+	)
+}
+
+// githubResourceCandidates accepts official GitHub HTTPS resource URLs only.
+func githubResourceCandidates(config *githubmirror.Config, raw string) ([]string, error) {
+	u, err := url.Parse(raw)
+	if err != nil || u == nil || u.Scheme != "https" || u.User != nil || u.Port() != "" || u.Fragment != "" || strings.Contains(raw, "#") {
+		return nil, ErrInvalidMirrorURL
+	}
+	u.Host = strings.ToLower(u.Host)
+	switch u.Host {
+	case "github.com", "raw.githubusercontent.com":
+	default:
+		return nil, ErrInvalidMirrorURL
+	}
+	return githubmirror.Candidates(config, u.String(), githubmirror.Resource), nil
+}

pkg/download/hls_live_test.go

@@ -40,7 +40,7 @@ func TestDownloader_HlsLiveSite(t *testing.T) {
 	if referer != "" {
 		req.Extra = map[string]any{"header": map[string]string{"Referer": referer}}
 	}
-	rr, err := downloader.Resolve(req, nil)
+	rr, err := downloader.Resolve(req)
 	if err != nil {
 		t.Fatalf("resolve: %v", err)
 	}

pkg/download/hls_protocol_test.go

@@ -89,7 +89,7 @@ func TestDownloader_HlsProtocolEndToEnd(t *testing.T) {
 
 	req := hlsResolveReferer()
 	req.URL = server.URL + "/master.m3u8"
-	rr, err := downloader.Resolve(req, nil)
+	rr, err := downloader.Resolve(req)
 	if err != nil {
 		t.Fatal(err)
 	}