Merge PR #1583: optimize extension API loading

# Conflicts:
#	ui/flutter/lib/features/extensions/presentation/widgets/extension_detail_view.dart

.gitattributes

@@ -0,0 +1,2 @@
+# Keep upstream plugin sources recognizable and collapsed in GitHub reviews.
+ui/flutter/third_party/** linguist-vendored whitespace=-blank-at-eol,-blank-at-eof

.github/workflows/test.yml

@@ -77,6 +77,8 @@ jobs:
         include:
           - name: Windows
             os: windows-latest
+          - name: Linux
+            os: ubuntu-latest
           - name: macOS
             os: macos-latest
     runs-on: ${{ matrix.os }}
@@ -89,9 +91,25 @@ jobs:
         if: runner.os == 'macOS'
         with:
           flutter-version: ${{ env.FLUTTER_VERSION }}
+      - name: Install Linux WebView dependencies
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update -y
+          sudo apt-get install -y libgtk-3-dev libwebkit2gtk-4.1-dev xvfb
+      - name: Test webview
+        if: runner.os == 'Linux'
+        # Match the full suite's coverage instrumentation and repeat on the same
+        # GTK event loop to catch queued callbacks after engine destruction.
+        run: |
+          PACKAGES=$(go list ./... | awk '!/\/bind\// && (!/\/cmd\// || /\/cmd\/web$/)')
+          go test -c -tags webview -coverpkg=$(echo "$PACKAGES" | paste -sd "," -) -covermode=count -o "$RUNNER_TEMP/goprovider.test" ./internal/webview/goprovider
+          xvfb-run -a "$RUNNER_TEMP/goprovider.test" -test.v -test.count=5 -test.timeout=300s -test.coverprofile="$RUNNER_TEMP/webview-coverage.out"
+        env:
+          CGO_ENABLED: 1
       - name: Test webview
         if: runner.os == 'Windows'
-        run: go test -tags webview -v -count=1 -timeout 300s ./internal/webview/goprovider/
+        # Repeat close/reopen coverage to catch browser shutdown races.
+        run: go test -tags webview -v -count=3 -timeout 300s ./internal/webview/goprovider/
         env:
           CGO_ENABLED: 1
       - name: Test webview

README.md

@@ -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 1](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.1)
+- [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

@@ -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 1 をダウンロード](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.1)
+- [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

@@ -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 1](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.1)
+- [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

@@ -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 1](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.1)
+- [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

@@ -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 1](https://github.com/GopeedLab/gopeed/releases/tag/v2.0.0-beta.1)
+- [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。
 

bind/mobile/main.go

@@ -7,6 +7,7 @@ import (
 
 	nativebridge "github.com/GopeedLab/gopeed/bind/native"
 	"github.com/GopeedLab/gopeed/internal/webview/rpcprovider"
+	goapi "github.com/GopeedLab/gopeed/pkg/api"
 	"github.com/GopeedLab/gopeed/pkg/rest"
 	"github.com/GopeedLab/gopeed/pkg/rest/model"
 )
@@ -90,3 +91,14 @@ func applyWebViewProvider(config *model.StartConfig) {
 	}
 	config.WebViewProvider = rpcprovider.New(*config.WebViewRPCConfig)
 }
+
+func LiveActivityTaskEventMask() int64 {
+	return int64(
+		goapi.TaskEventDone |
+			goapi.TaskEventError |
+			goapi.TaskEventStart |
+			goapi.TaskEventProgress |
+			goapi.TaskEventPause |
+			goapi.TaskEventDelete,
+	)
+}

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/updater/updater_windows.go

@@ -37,15 +37,17 @@ func installByInstaller(killSignalChan chan<- any, packagePath, destDir string)
 	}
 	defer reader.Close()
 
-	// Find the installer file
 	var installerPath string
 	for _, file := range reader.File {
+		cleanName := filepath.Clean(file.Name)
+		if strings.HasPrefix(cleanName, "..") || filepath.IsAbs(cleanName) {
+			continue
+		}
 		if file.FileInfo().IsDir() {
 			continue
 		}
 
-		// Extract file
-		path := filepath.Join(tempDir, file.Name)
+		path := filepath.Join(tempDir, cleanName)
 
 		if err := os.MkdirAll(filepath.Dir(path), os.ModePerm); err != nil {
 			return err
@@ -101,7 +103,11 @@ func installByPortable(killSignalChan chan<- any, packagePath, destDir string) e
 	defer reader.Close()
 
 	for _, file := range reader.File {
-		path := filepath.Join(destDir, file.Name)
+		cleanName := filepath.Clean(file.Name)
+		if strings.HasPrefix(cleanName, "..") || filepath.IsAbs(cleanName) {
+			continue
+		}
+		path := filepath.Join(destDir, cleanName)
 
 		if file.FileInfo().IsDir() {
 			os.MkdirAll(path, file.Mode())

cmd/web/flags.go

@@ -13,6 +13,7 @@ import (
 )
 
 type args struct {
+	TempDir           *string  `json:"tempDir"`
 	Address           *string  `json:"address"`
 	Port              *int     `json:"port"`
 	Username          *string  `json:"username"`
@@ -54,6 +55,7 @@ func loadCliArgs() *args {
 	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")
 	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")
 	flag.StringVar(cfg.StorageDir, "storage-dir", "", "Storage directory")
 	whiteDownloadDirs := flag.String("white-download-dirs", "", "White download directories, comma-separated")
@@ -89,6 +91,8 @@ func overrideWithCliArgs(cfg *args, cliConfig *args) {
 			cfg.ApiToken = cliConfig.ApiToken
 		case "mcp-enable":
 			cfg.MCPEnable = cliConfig.MCPEnable
+		case "temp-dir":
+			cfg.TempDir = cliConfig.TempDir
 		case "d", "storage-dir":
 			cfg.StorageDir = cliConfig.StorageDir
 		case "white-download-dirs":
@@ -101,6 +105,9 @@ func overrideWithCliArgs(cfg *args, cliConfig *args) {
 
 // setDefaults sets default values for any unset configuration fields
 func setDefaults(cfg *args, cliConfig *args) {
+	if cfg.TempDir == nil {
+		cfg.TempDir = cliConfig.TempDir
+	}
 	if cfg.Address == nil {
 		cfg.Address = cliConfig.Address
 	}

cmd/web/main.go

@@ -43,11 +43,16 @@ func main() {
 		storageDir = filepath.Join(filepath.Dir(exe), "storage")
 	}
 
+	tempDir := ""
+	if args.TempDir != nil {
+		tempDir = *args.TempDir
+	}
 	cfg := &model.StartConfig{
 		Network:           "tcp",
 		Address:           fmt.Sprintf("%s:%d", *args.Address, *args.Port),
 		Storage:           model.StorageBolt,
 		StorageDir:        storageDir,
+		TempDir:           tempDir,
 		WhiteDownloadDirs: args.WhiteDownloadDirs,
 		ApiToken:          *args.ApiToken,
 		MCPEnable:         args.MCPEnable,

go.mod

@@ -3,13 +3,15 @@ module github.com/GopeedLab/gopeed
 go 1.25.4
 
 require (
-	github.com/GopeedLab/webview_go v0.0.0-20260423085439-7a2f88b6e9b5
+	codeberg.org/gruf/go-ffmpreg v0.6.23-0.20260827095416-df1836cb5be0
+	github.com/GopeedLab/webview_go v0.0.0-20260918010912-0d4c27bb7914
 	github.com/anacrolix/torrent v1.60.1-0.20251217073903-486bcbe758e0
 	github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5
 	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/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
@@ -21,6 +23,7 @@ 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/tetratelabs/wazero v1.12.0
 	github.com/xiaoqidun/setft v0.0.0-20220310121541-be86327699ad
 	go.etcd.io/bbolt v1.4.3
 	golang.org/x/exp v0.0.0-20251219203646-944ab1f22d93
@@ -38,7 +41,6 @@ require (
 	github.com/felixge/fgprof v0.9.5 // indirect
 	github.com/go-task/slim-sprig/v3 v3.0.0 // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
-	github.com/google/jsonschema-go v0.4.3 // indirect
 	github.com/hashicorp/errwrap v1.1.0 // indirect
 	github.com/hashicorp/go-multierror v1.1.1 // indirect
 	github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
@@ -156,7 +158,7 @@ require (
 	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 v0.41.0 // indirect
+	golang.org/x/sys v0.44.0 // indirect
 	golang.org/x/text v0.34.0
 	golang.org/x/time v0.15.0 // indirect
 	golang.org/x/tools v0.42.0 // indirect

go.sum

@@ -14,6 +14,8 @@ cloud.google.com/go/pubsub v1.0.1/go.mod h1:R0Gpsv3s54REJCy4fxDixWD93lHJMoZTyQ2k
 cloud.google.com/go/pubsub v1.1.0/go.mod h1:EwwdRX2sKPjnvnqCa270oGRyludottCI76h+R3AArQw=
 cloud.google.com/go/storage v1.0.0/go.mod h1:IhtSnM/ZTZV8YYJWCY8RULGVqBDmpoyjwiyrjsg+URw=
 cloud.google.com/go/storage v1.5.0/go.mod h1:tpKbwo567HUNpVclU5sGELwQWBDZ8gh0ZeosJ0Rtdos=
+codeberg.org/gruf/go-ffmpreg v0.6.23-0.20260827095416-df1836cb5be0 h1:AqNFl60o4xhTTOxmzAvSf7pazXHKBGuV5ATw7sETIRA=
+codeberg.org/gruf/go-ffmpreg v0.6.23-0.20260827095416-df1836cb5be0/go.mod h1:XM6eW8CSgAuZRKRynm5nDiSNedm0rav30IychqygOHE=
 crawshaw.io/iox v0.0.0-20181124134642-c51c3df30797/go.mod h1:sXBiorCo8c46JlQV3oXPKINnZ8mcqnye1EkVkqsectk=
 crawshaw.io/sqlite v0.3.2/go.mod h1:igAO5JulrQ1DbdZdtVq48mnZUBAPOeFzer7VhDWNtW4=
 dario.cat/mergo v1.0.0 h1:AGCNq9Evsj31mOgNPcLyXc+4PNABt905YmuqPYYpBWk=
@@ -23,8 +25,20 @@ filippo.io/edwards25519 v1.0.0-rc.1 h1:m0VOOB23frXZvAOK44usCgLWvtsxIoMCTBGJZlpmG
 filippo.io/edwards25519 v1.0.0-rc.1/go.mod h1:N1IkdkCkiLB6tki+MYJoSx2JTY9NUlxZE7eHn5EwJns=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
-github.com/GopeedLab/webview_go v0.0.0-20260423085439-7a2f88b6e9b5 h1:86LVTaNDM/j/uTAD2HedkXNO9LIQlt642VAdbU/0D/M=
-github.com/GopeedLab/webview_go v0.0.0-20260423085439-7a2f88b6e9b5/go.mod h1:FvV19lu9rQ9NcbczN5y8pbWecURRRbWa8tbfFARBDa0=
+github.com/GopeedLab/webview_go v0.0.0-20260915010614-2567e492369a h1:Vzz+8aMVX9ZPPpkxgxa7mCorrAgdXCZL5EunOpOBvao=
+github.com/GopeedLab/webview_go v0.0.0-20260915010614-2567e492369a/go.mod h1:FvV19lu9rQ9NcbczN5y8pbWecURRRbWa8tbfFARBDa0=
+github.com/GopeedLab/webview_go v0.0.0-20260917153919-dcf00737f32a h1:nz1bC6TGwQ1kv/OVLahNZ0EEtb7v5LHfceAkW4MvS6I=
+github.com/GopeedLab/webview_go v0.0.0-20260917153919-dcf00737f32a/go.mod h1:FvV19lu9rQ9NcbczN5y8pbWecURRRbWa8tbfFARBDa0=
+github.com/GopeedLab/webview_go v0.0.0-20260917155039-1ee7ffb4169a h1:yudcfXpipKLnMaaw1losn6YeOBjvj2rAFicfjqYJexY=
+github.com/GopeedLab/webview_go v0.0.0-20260917155039-1ee7ffb4169a/go.mod h1:FvV19lu9rQ9NcbczN5y8pbWecURRRbWa8tbfFARBDa0=
+github.com/GopeedLab/webview_go v0.0.0-20260917155218-bd16da0d6f53 h1:nMSHKhbrEaWPE/x3mYl/270GPjswbUmS+E7yYjly4xk=
+github.com/GopeedLab/webview_go v0.0.0-20260917155218-bd16da0d6f53/go.mod h1:oNO07SCX8xgoHLds2OBwML8TU4xils88vMQ4gadKUHQ=
+github.com/GopeedLab/webview_go v0.0.0-20260917161756-2a4f989dcb1d h1:4fjlhJpBWa6IcdKVPkEMMIDd6Xo9JM09dJHdKU+1V7k=
+github.com/GopeedLab/webview_go v0.0.0-20260917161756-2a4f989dcb1d/go.mod h1:oNO07SCX8xgoHLds2OBwML8TU4xils88vMQ4gadKUHQ=
+github.com/GopeedLab/webview_go v0.0.0-20260917163929-ca26c3e6bcfa h1:VkdBMcNHYTqCMwOOCimA7b3xZKV/qFIGrhh3+vm9n3s=
+github.com/GopeedLab/webview_go v0.0.0-20260917163929-ca26c3e6bcfa/go.mod h1:oNO07SCX8xgoHLds2OBwML8TU4xils88vMQ4gadKUHQ=
+github.com/GopeedLab/webview_go v0.0.0-20260918010912-0d4c27bb7914 h1:9VJQZIZ1R6T4m+4vlNQYNXSPNUv2gf2PiTfIXiQ3MTw=
+github.com/GopeedLab/webview_go v0.0.0-20260918010912-0d4c27bb7914/go.mod h1:oNO07SCX8xgoHLds2OBwML8TU4xils88vMQ4gadKUHQ=
 github.com/Masterminds/semver/v3 v3.2.1 h1:RN9w6+7QoMeJVGyfmbcgs28Br8cvmnucEXnY0rYXWg0=
 github.com/Masterminds/semver/v3 v3.2.1/go.mod h1:qvl/7zhW3nngYb5+80sSMF+FG2BjYrf8m9wsX0PNOMQ=
 github.com/Microsoft/go-winio v0.5.2/go.mod h1:WpS1mjBmmwHBEWmogvA2mj8546UReBk4v8QkMxJ6pZY=
@@ -552,6 +566,8 @@ 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/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=
 github.com/tidwall/btree v1.8.1/go.mod h1:jBbTdUWhSZClZWoDg54VnvV7/54modSOzDN7VXftj1A=
 github.com/tinylib/msgp v1.0.2/go.mod h1:+d+yLhGm8mzTaHzB+wgMYrodPfmZrzkirds8fDWklFE=
@@ -732,6 +748,8 @@ golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
 golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/sys v0.44.0 h1:ildZl3J4uzeKP07r2F++Op7E9B29JRUy+a27EibtBTQ=
+golang.org/x/sys v0.44.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.2.0/go.mod h1:TVmDHMZPmdnySmBfhjOoOdhjzdE1h4u1VwSiw2l1Nuc=

internal/blob/registry.go

@@ -7,6 +7,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"github.com/GopeedLab/gopeed/internal/production"
 	"io"
 	"net"
 	"net/http"
@@ -61,6 +62,7 @@ type Metadata struct {
 }
 
 type Source struct {
+	producer    production.Reader
 	ID          string
 	URL         string
 	ContentType string
@@ -359,11 +361,35 @@ func (r *Registry) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 	defer reader.Close()
+	if producer, ok := reader.(production.Reader); ok {
+		src.mu.Lock()
+		src.producer = producer
+		src.mu.Unlock()
+		if err := producer.WaitProduction(req.Context()); err != nil {
+			return
+		}
+		if producer.Production() != nil {
+			meta.Size = 0
+			meta.Range = false
+			start = 0
+			end = -1
+			ranged = false
+			src.mu.Lock()
+			src.size = 0
+			src.rangeEnabled = false
+			src.mu.Unlock()
+		}
+	}
 
 	writeHeaders(w, meta, start, end, ranged)
 	if ranged {
 		w.WriteHeader(http.StatusPartialContent)
 	}
+	if producer, ok := reader.(production.Reader); ok && producer.Production() != nil {
+		if flusher, ok := w.(http.Flusher); ok {
+			flusher.Flush()
+		}
+	}
 	limit := int64(-1)
 	if end >= start {
 		limit = end - start + 1
@@ -675,3 +701,21 @@ func randomID(size int) (string, error) {
 	}
 	return hex.EncodeToString(buf), nil
 }
+
+// Production returns the active opener's input counter, if it generates output.
+func (r *Registry) Production(raw string) production.Source {
+	if r == nil {
+		return nil
+	}
+	src, err := r.get(raw)
+	if err != nil {
+		return nil
+	}
+	src.mu.Lock()
+	reader := src.producer
+	src.mu.Unlock()
+	if reader == nil {
+		return nil
+	}
+	return reader.Production()
+}

internal/controller/controller.go

@@ -1,6 +1,7 @@
 package controller
 
 import (
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
 	"github.com/GopeedLab/gopeed/pkg/base"
 	"net/http"
 	"net/url"
@@ -9,8 +10,11 @@ import (
 )
 
 type Controller struct {
-	GetConfig func(v any)
-	GetProxy  func(requestProxy *base.RequestProxy) func(*http.Request) (*url.URL, error)
+	TempFiles         *tempfiles.Scope
+	ManagedProduction func(string) bool
+	TempDir           string
+	GetConfig         func(v any)
+	GetProxy          func(requestProxy *base.RequestProxy) func(*http.Request) (*url.URL, error)
 	FileController
 	//ContextDialer() (proxy.Dialer, error)
 }

internal/fetcher/fetcher.go

@@ -106,7 +106,13 @@ func (s *SchemeFilter) Match(uri string) bool {
 	case FilterTypeUrl:
 		return strings.HasPrefix(uriUpper, patternUpper+":")
 	case FilterTypeFile:
-		return strings.HasSuffix(uriUpper, "."+patternUpper)
+		// Strip query and fragment before matching so URLs like
+		// https://example.com/video.m3u8?sign=abc still route by extension.
+		clean := uri
+		if idx := strings.IndexAny(clean, "?#"); idx >= 0 {
+			clean = clean[:idx]
+		}
+		return strings.HasSuffix(strings.ToUpper(clean), "."+patternUpper)
 	case FilterTypeBase64:
 		return strings.HasPrefix(uriUpper, "DATA:"+patternUpper+";BASE64,")
 	}

internal/production/progress.go

@@ -0,0 +1,35 @@
+// Package production associates generated resources with their input progress.
+package production
+
+import (
+	"context"
+	"sync"
+)
+
+// Source counts unique input bytes and total received bytes (including refetches).
+// Implementations must support concurrent snapshots.
+type Source interface {
+	Progress() (downloaded, received int64)
+}
+
+// Reader resolves its optional producer before response headers are sent.
+// A nil producer preserves ordinary Blob behavior.
+type Reader interface {
+	Production() Source
+	WaitProduction(context.Context) error
+}
+type Registry struct {
+	mu      sync.Mutex
+	sources map[string]Source
+}
+
+func (r *Registry) Set(id string, source Source) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.sources == nil {
+		r.sources = make(map[string]Source)
+	}
+	r.sources[id] = source
+}
+func (r *Registry) Get(id string) Source { r.mu.Lock(); defer r.mu.Unlock(); return r.sources[id] }
+func (r *Registry) Remove(id string)     { r.mu.Lock(); defer r.mu.Unlock(); delete(r.sources, id) }

internal/protocol/bt/fetcher.go

@@ -399,7 +399,10 @@ func (f *Fetcher) Wait() (err error) {
 							}
 						}
 						if !selected {
-							util.SafeRemove(filepath.Join(f.meta.Opts.Path, f.meta.Res.Name, file.Path()))
+							root, name := torrentFileLayout(f.torrent.Info(), file.FileInfo())
+							if err := removeUnselectedFile(f.meta.Opts.Path, root, name); err != nil {
+								return err
+							}
 						}
 					}
 					return
@@ -409,6 +412,62 @@ func (f *Fetcher) Wait() (err error) {
 	}
 }
 
+// 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) {
+	parts := file.BestPath()
+	if info.BestName() != metainfo.NoName {
+		if len(parts) > 0 {
+			root = info.BestName()
+		}
+		parts = append([]string{info.BestName()}, parts...)
+	}
+	// A v2 file tree can itself have a named root without an extra name wrapper.
+	if root == "" && info.HasV2() && len(info.FileTree.Dir) == 1 {
+		for dir, tree := range info.FileTree.Dir {
+			if tree.IsDir() {
+				root = dir
+			}
+		}
+	}
+	return root, filepath.Join(parts...)
+}
+
+// Preserve the actual torrent root, or the download directory for rootless
+// torrents. Only prune empty directories strictly below that boundary.
+func removeUnselectedFile(downloadDir, torrentRoot, torrentPath string) error {
+	if !filepath.IsLocal(torrentPath) || (torrentRoot != "" && !filepath.IsLocal(torrentRoot)) {
+		return fmt.Errorf("invalid torrent file path %q", torrentPath)
+	}
+	root := filepath.Join(downloadDir, torrentRoot)
+	name := filepath.Join(downloadDir, torrentPath)
+	rel, err := filepath.Rel(root, name)
+	if err != nil || rel == "." || !filepath.IsLocal(rel) {
+		return fmt.Errorf("torrent file %q is outside cleanup root %q", name, root)
+	}
+	for _, candidate := range []string{name, name + ".part"} {
+		if err := util.SafeRemove(candidate); err != nil {
+			return fmt.Errorf("remove unselected torrent file %q: %w", candidate, err)
+		}
+	}
+	for dir := filepath.Dir(name); dir != root && dir != filepath.Dir(dir); dir = filepath.Dir(dir) {
+		entries, err := os.ReadDir(dir)
+		if os.IsNotExist(err) {
+			continue
+		}
+		if err != nil {
+			return fmt.Errorf("read torrent directory %q: %w", dir, err)
+		}
+		if len(entries) != 0 {
+			break
+		}
+		if err := util.SafeRemove(dir); err != nil {
+			return fmt.Errorf("remove empty torrent directory %q: %w", dir, err)
+		}
+	}
+	return nil
+}
+
 func (f *Fetcher) isDone() bool {
 	if f.meta.Opts == nil {
 		return false
@@ -638,6 +697,10 @@ func (f *Fetcher) addTorrent(req *base.Request, fromUpload bool) (err error) {
 	}
 	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
 		},

internal/protocol/bt/selection_test.go

@@ -0,0 +1,307 @@
+package bt
+
+import (
+	"context"
+	"crypto/sha1"
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/anacrolix/torrent"
+	"github.com/anacrolix/torrent/bencode"
+	"github.com/anacrolix/torrent/metainfo"
+	"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)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	tor, err := c.AddTorrentFromFile("testdata/test.torrent")
+	if err != nil {
+		t.Fatal(err)
+	}
+	f := &Fetcher{torrent: tor, meta: &fetcher.FetcherMeta{Opts: &base.Options{}}, data: &fetcherData{}}
+	f.torrentReady.Store(true)
+	f.updateRes()
+	// Resolve initializes all files; creation replaces the selection before Start.
+	f.meta.Opts = &base.Options{SelectFiles: []int{2}}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	for i, file := range tor.Files() {
+		want := torrent.PiecePriorityNone
+		if i == 2 {
+			want = torrent.PiecePriorityNormal
+		}
+		if file.Priority() != want {
+			t.Errorf("file %d priority = %v, want %v", i, file.Priority(), want)
+		}
+	}
+	if len(f.data.Progress) != 1 {
+		t.Fatalf("progress tracks %d files, want 1", len(f.data.Progress))
+	}
+	if err := f.Pause(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if tor.Files()[0].Priority() != torrent.PiecePriorityNone {
+		t.Fatal("resume selected an unselected file")
+	}
+}
+
+func TestWaitCleansUnselectedFilesFromSharedPiece(t *testing.T) {
+	for _, mode := range []string{"partial", "part only", "both paths", "all", "already removed", "remove error"} {
+		t.Run(mode, func(t *testing.T) {
+			dir := t.TempDir()
+			keepPath := filepath.Join(dir, "bundle", "keep.txt")
+			skipPath := filepath.Join(dir, "bundle", "nested", "skip.txt")
+			if err := os.MkdirAll(filepath.Dir(skipPath), 0755); err != nil {
+				t.Fatal(err)
+			}
+			if err := os.WriteFile(keepPath, []byte("keep"), 0644); err != nil {
+				t.Fatal(err)
+			}
+			if err := os.WriteFile(skipPath, []byte("skip"), 0644); err != nil {
+				t.Fatal(err)
+			}
+			// Both files occupy the same piece, so downloading keep.txt also writes skip.txt.
+			hash := sha1.Sum([]byte("keepskip"))
+			info := metainfo.Info{Name: "bundle", PieceLength: 16, Pieces: hash[:], Files: []metainfo.FileInfo{
+				{Length: 4, Path: []string{"keep.txt"}},
+				{Length: 4, Path: []string{"nested", "skip.txt"}},
+			}}
+			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
+			config.DisableUTP = true
+			c, err := torrent.NewClient(config)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer c.Close()
+			spec, err := torrent.TorrentSpecFromMetaInfoErr(&metainfo.MetaInfo{InfoBytes: bencode.MustMarshal(&info)})
+			if err != nil {
+				t.Fatal(err)
+			}
+			spec.Storage = store
+			tor, _, err := c.AddTorrentSpec(spec)
+			if err != nil {
+				t.Fatal(err)
+			}
+			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+			defer cancel()
+			if err := tor.VerifyDataContext(ctx); err != nil {
+				t.Fatal(err)
+			}
+			f := &Fetcher{torrent: tor, meta: &fetcher.FetcherMeta{Opts: &base.Options{Path: dir, SelectFiles: []int{0}}}, data: &fetcherData{}, torrentDropCtx: ctx}
+			f.torrentReady.Store(true)
+			f.updateRes()
+			if mode == "all" {
+				f.meta.Opts.SelectFiles = []int{0, 1}
+			}
+			if !f.isDone() {
+				t.Fatal("selected file is not complete")
+			}
+			if mode == "part only" || mode == "both paths" || mode == "all" {
+				if err := os.WriteFile(skipPath+".part", []byte("skip"), 0644); err != nil {
+					t.Fatal(err)
+				}
+			}
+			if mode == "part only" || mode == "already removed" || mode == "remove error" {
+				if err := os.Remove(skipPath); err != nil {
+					t.Fatal(err)
+				}
+			}
+			if mode == "remove error" {
+				if err := os.Mkdir(skipPath, 0755); err != nil {
+					t.Fatal(err)
+				}
+				if err := os.WriteFile(filepath.Join(skipPath, "child"), []byte("preserve"), 0644); err != nil {
+					t.Fatal(err)
+				}
+			}
+			err = f.Wait()
+			if ctx.Err() != nil {
+				t.Fatal(ctx.Err())
+			}
+			if mode == "remove error" {
+				if err == nil {
+					t.Fatal("cleanup failure was silently ignored")
+				}
+			} else if err != nil {
+				t.Fatal(err)
+			}
+			data, err := os.ReadFile(keepPath)
+			if err != nil || string(data) != "keep" {
+				t.Fatalf("selected file changed: %q, %v", data, err)
+			}
+			if mode == "all" {
+				if _, err := os.Stat(skipPath + ".part"); err != nil {
+					t.Fatalf("selected part file was removed: %v", err)
+				}
+				data, err := os.ReadFile(skipPath)
+				if err != nil || string(data) != "skip" {
+					t.Fatalf("selected file changed: %q, %v", data, err)
+				}
+			} else if mode != "remove error" {
+				for _, removed := range []string{skipPath, skipPath + ".part", filepath.Dir(skipPath)} {
+					if _, err := os.Stat(removed); !os.IsNotExist(err) {
+						t.Fatalf("unselected file or empty directory remains: %s: %v", removed, err)
+					}
+				}
+			}
+		})
+	}
+}
+
+func TestRemoveUnselectedFilePrunesOnlyEmptyParents(t *testing.T) {
+	for _, preserveSibling := range []bool{false, true} {
+		t.Run(fmt.Sprint(preserveSibling), func(t *testing.T) {
+			root := t.TempDir()
+			relative := filepath.Join("bundle", "nested", "deep", "skip.txt")
+			name := filepath.Join(root, relative)
+			if err := os.MkdirAll(filepath.Dir(name), 0755); err != nil {
+				t.Fatal(err)
+			}
+			if err := os.WriteFile(name+".part", []byte("partial"), 0644); err != nil {
+				t.Fatal(err)
+			}
+			sibling := filepath.Join(root, "bundle", "keep.txt")
+			if preserveSibling {
+				if err := os.WriteFile(sibling, []byte("keep"), 0644); err != nil {
+					t.Fatal(err)
+				}
+			}
+			if err := removeUnselectedFile(root, "bundle", relative); err != nil {
+				t.Fatal(err)
+			}
+			if _, err := os.Stat(filepath.Join(root, "bundle", "nested")); !os.IsNotExist(err) {
+				t.Fatalf("empty ancestors remain: %v", err)
+			}
+			if preserveSibling {
+				data, err := os.ReadFile(sibling)
+				if err != nil || string(data) != "keep" {
+					t.Fatalf("sibling changed: %q, %v", data, err)
+				}
+			}
+			if info, err := os.Stat(filepath.Join(root, "bundle")); err != nil || !info.IsDir() {
+				t.Fatalf("torrent root directory was removed: %v", err)
+			}
+			if _, err := os.Stat(root); err != nil {
+				t.Fatalf("download directory was removed: %v", err)
+			}
+			// A file directly inside the torrent root must not cause that root to be pruned.
+			rootFile := filepath.Join("bundle", "root.txt")
+			if err := os.WriteFile(filepath.Join(root, rootFile)+".part", []byte("partial"), 0644); err != nil {
+				t.Fatal(err)
+			}
+			if err := removeUnselectedFile(root, "bundle", rootFile); err != nil {
+				t.Fatal(err)
+			}
+			if _, err := os.Stat(filepath.Join(root, "bundle")); err != nil {
+				t.Fatalf("torrent root directory was removed after root-level cleanup: %v", err)
+			}
+			// Repeating cleanup after the file and its subdirectories are gone is harmless.
+			if err := removeUnselectedFile(root, "bundle", relative); err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}
+
+func TestCleanupMatchesNamedAndRootlessStorage(t *testing.T) {
+	for _, version := range []int64{1, 2} {
+		for _, layout := range []string{"rootless", "wrapped", "file-tree-root"} {
+			if version == 1 && layout == "file-tree-root" {
+				continue
+			}
+			t.Run(fmt.Sprintf("v%d/%s", version, layout), func(t *testing.T) {
+				dir := t.TempDir()
+				info := metainfo.Info{Name: metainfo.NoName, PieceLength: 16384}
+				root := dir
+				if layout == "wrapped" {
+					info.Name = "bundle"
+					root = filepath.Join(dir, "bundle")
+				}
+				if version == 1 {
+					info.Files = []metainfo.FileInfo{{Path: []string{"keep.txt"}}, {Path: []string{"nested", "deep", "skip.txt"}}}
+				} else {
+					info.MetaVersion = 2
+					info.FileTree = metainfo.FileTree{Dir: map[string]metainfo.FileTree{
+						"keep.txt": {},
+						"nested":   {Dir: map[string]metainfo.FileTree{"deep": {Dir: map[string]metainfo.FileTree{"skip.txt": {}}}}},
+					}}
+				}
+				if layout == "file-tree-root" {
+					info.FileTree = metainfo.FileTree{Dir: map[string]metainfo.FileTree{"tree-root": info.FileTree}}
+					root = filepath.Join(dir, "tree-root")
+				}
+				// Keep the library's default FilePathMaker here to independently verify
+				// that cleanup agrees with its real disk layout, including NoName.
+				store := storage.NewFileOpts(storage.NewFileClientOpts{
+					ClientBaseDir:   dir,
+					TorrentDirMaker: func(baseDir string, _ *metainfo.Info, _ metainfo.Hash) string { return baseDir },
+				})
+				defer store.Close()
+				torrentStorage, err := store.OpenTorrent(context.Background(), &info, metainfo.Hash{1})
+				if err != nil {
+					t.Fatal(err)
+				}
+				defer torrentStorage.Close()
+				skip := filepath.Join(root, "nested", "deep", "skip.txt")
+				if _, err := os.Stat(skip); err != nil {
+					t.Fatalf("unexpected storage layout: %v", err)
+				}
+				if err := os.WriteFile(skip+".part", []byte("partial"), 0644); err != nil {
+					t.Fatal(err)
+				}
+				files := info.UpvertedFiles()
+				boundary, name := torrentFileLayout(&info, files[1])
+				if err := removeUnselectedFile(dir, boundary, name); err != nil {
+					t.Fatal(err)
+				}
+				if _, err := os.Stat(filepath.Join(root, "nested")); !os.IsNotExist(err) {
+					t.Fatalf("empty subtree remains: %v", err)
+				}
+				if _, err := os.Stat(filepath.Join(root, "keep.txt")); err != nil {
+					t.Fatalf("selected file removed: %v", err)
+				}
+				// Also verify the boundary when the protected directory becomes empty.
+				if err := os.Remove(filepath.Join(root, "keep.txt")); err != nil {
+					t.Fatal(err)
+				}
+				for _, file := range files {
+					boundary, name := torrentFileLayout(&info, file)
+					if err := removeUnselectedFile(dir, boundary, name); err != nil {
+						t.Fatal(err)
+					}
+				}
+				if stat, err := os.Stat(root); err != nil || !stat.IsDir() {
+					t.Fatalf("cleanup boundary was removed: %v", err)
+				}
+			})
+		}
+	}
+}

internal/protocol/hls/config.go

@@ -0,0 +1,30 @@
+package hls
+
+const (
+	defaultSegmentConnections = 8
+	defaultMaxRetries         = 5
+	defaultTimeoutSeconds     = 30
+
+	// maxPrefetchSizeSegments caps the HEAD probing done at resolve time.
+	// Playlists larger than this skip size prefetch entirely.
+	maxPrefetchSizeSegments = 500
+)
+
+type config struct {
+	SegmentConnections    int  `json:"segmentConnections"`
+	MaxRetries            int  `json:"maxRetries"`
+	TimeoutSeconds        int  `json:"timeoutSeconds"`
+	PrefetchContentLength bool `json:"prefetchContentLength"`
+}
+
+func (c *config) normalize() {
+	if c.SegmentConnections <= 0 {
+		c.SegmentConnections = defaultSegmentConnections
+	}
+	if c.MaxRetries < 0 {
+		c.MaxRetries = defaultMaxRetries
+	}
+	if c.TimeoutSeconds <= 0 {
+		c.TimeoutSeconds = defaultTimeoutSeconds
+	}
+}

internal/protocol/hls/crypto.go

@@ -0,0 +1,59 @@
+package hls
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"fmt"
+)
+
+// decryptAES128 decrypts an AES-128-CBC encrypted segment and strips PKCS7
+// padding. data length must be a multiple of the AES block size.
+func decryptAES128(data, key, iv []byte) ([]byte, error) {
+	if len(key) != 16 {
+		return nil, fmt.Errorf("invalid AES-128 key size %d", len(key))
+	}
+	if len(iv) != 16 {
+		return nil, fmt.Errorf("invalid AES-128 IV size %d", len(iv))
+	}
+	if len(data) == 0 || len(data)%aes.BlockSize != 0 {
+		return nil, fmt.Errorf("invalid AES-128 data size %d", len(data))
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	plain := make([]byte, len(data))
+	cipher.NewCBCDecrypter(block, iv).CryptBlocks(plain, data)
+	return pkcs7Unpad(plain, aes.BlockSize)
+}
+
+func pkcs7Unpad(data []byte, blockSize int) ([]byte, error) {
+	if len(data) == 0 {
+		return nil, fmt.Errorf("empty plaintext")
+	}
+	pad := int(data[len(data)-1])
+	if pad == 0 || pad > blockSize || pad > len(data) {
+		return nil, fmt.Errorf("invalid PKCS7 padding")
+	}
+	for _, b := range data[len(data)-pad:] {
+		if int(b) != pad {
+			return nil, fmt.Errorf("invalid PKCS7 padding")
+		}
+	}
+	return data[:len(data)-pad], nil
+}
+
+// sequenceIV derives the default per-segment IV mandated by RFC 8216: the
+// segment media sequence number as a 16-byte big-endian integer.
+func sequenceIV(sequence int64) []byte {
+	iv := make([]byte, 16)
+	iv[8] = byte(sequence >> 56)
+	iv[9] = byte(sequence >> 48)
+	iv[10] = byte(sequence >> 40)
+	iv[11] = byte(sequence >> 32)
+	iv[12] = byte(sequence >> 24)
+	iv[13] = byte(sequence >> 16)
+	iv[14] = byte(sequence >> 8)
+	iv[15] = byte(sequence)
+	return iv
+}

internal/protocol/hls/crypto_test.go

@@ -0,0 +1,66 @@
+package hls
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"testing"
+)
+
+func pkcs7Pad(data []byte, blockSize int) []byte {
+	pad := blockSize - len(data)%blockSize
+	return append(data, bytes.Repeat([]byte{byte(pad)}, pad)...)
+}
+
+func TestDecryptAES128Roundtrip(t *testing.T) {
+	key := make([]byte, 16)
+	iv := make([]byte, 16)
+	if _, err := rand.Read(key); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := rand.Read(iv); err != nil {
+		t.Fatal(err)
+	}
+	plain := []byte("hello hls segment payload, padded to block size!")
+	padded := pkcs7Pad(plain, aes.BlockSize)
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	encrypted := make([]byte, len(padded))
+	cipher.NewCBCEncrypter(block, iv).CryptBlocks(encrypted, padded)
+
+	got, err := decryptAES128(encrypted, key, iv)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(got, plain) {
+		t.Errorf("roundtrip mismatch: %q", got)
+	}
+}
+
+func TestDecryptAES128InvalidInput(t *testing.T) {
+	if _, err := decryptAES128([]byte{1, 2, 3}, make([]byte, 16), make([]byte, 16)); err == nil {
+		t.Error("non-block-aligned data should fail")
+	}
+	if _, err := decryptAES128(make([]byte, 16), make([]byte, 15), make([]byte, 16)); err == nil {
+		t.Error("short key should fail")
+	}
+	if _, err := decryptAES128(make([]byte, 16), make([]byte, 16), make([]byte, 16)); err == nil {
+		t.Error("all-zero block has invalid padding and should fail")
+	}
+}
+
+func TestSequenceIV(t *testing.T) {
+	iv := sequenceIV(1)
+	if len(iv) != 16 || iv[15] != 1 {
+		t.Errorf("sequence 1 IV wrong: %v", iv)
+	}
+	iv = sequenceIV(0x0102030405060708)
+	for i, want := range []byte{1, 2, 3, 4, 5, 6, 7, 8} {
+		if iv[8+i] != want {
+			t.Errorf("sequence IV byte %d: want %d got %d", i, want, iv[8+i])
+		}
+	}
+}

internal/protocol/hls/doc.go

@@ -0,0 +1,24 @@
+// Package hls implements native HTTP Live Streaming downloads for m3u8
+// playlists. A task produces exactly one merged, playable output file:
+// MPEG-2 TS segments are concatenated as-is, fMP4 streams are merged as
+// init section followed by the media fragments, and AES-128 encrypted
+// segments are decrypted before they are stored.
+//
+// Supported subset:
+//   - VOD media playlists (EXT-X-ENDLIST present) and master playlists whose
+//     selected variant carries its own audio
+//   - AES-128 with the identity KEYFORMAT, explicit IV or media-sequence
+//     derived IV, including key rotation mid-playlist
+//   - EXT-X-BYTERANGE (including offset inheritance) and fMP4 init sections
+//     via a single, constant EXT-X-MAP
+//
+// Everything the merge pipeline cannot reproduce faithfully is rejected with
+// an explicit error instead of silently producing a broken output file:
+//   - live streams (no EXT-X-ENDLIST) and SAMPLE-AES / DRM encryption
+//   - EXT-X-GAP (would leave a hole) and EXT-X-DISCONTINUITY (broken timeline)
+//   - changing init sections (a repeated EXT-X-MAP is compared by all its
+//     attributes, not just the URI) and encrypted EXT-X-MAP without an
+//     explicit IV
+//   - separate audio renditions referenced by the selected variant (the
+//     merged output would have no audio) and non-identity KEYFORMATs
+package hls

internal/protocol/hls/fetcher_manager.go

@@ -0,0 +1,100 @@
+package hls
+
+import (
+	"net/url"
+	"path"
+	"strings"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+)
+
+type FetcherManager struct {
+}
+
+func (fm *FetcherManager) Name() string {
+	return "hls"
+}
+
+// Filters registers the .m3u8 extension. The manager must be registered BEFORE
+// the http manager in the downloader config: protocol routing picks the first
+// manager whose filter matches, and the http filter claims every http(s) URL.
+func (fm *FetcherManager) Filters() []*fetcher.SchemeFilter {
+	return []*fetcher.SchemeFilter{
+		{
+			Type:    fetcher.FilterTypeFile,
+			Pattern: "M3U8",
+		},
+	}
+}
+
+func (fm *FetcherManager) Build() fetcher.Fetcher {
+	return &Fetcher{}
+}
+
+func (fm *FetcherManager) ParseName(u string) string {
+	parsed, err := url.Parse(u)
+	if err != nil {
+		return ""
+	}
+	name := path.Base(parsed.Path)
+	name = strings.TrimSuffix(name, path.Ext(name))
+	if name == "" || name == "/" || name == "." {
+		name = parsed.Hostname()
+	}
+	return name
+}
+
+func (fm *FetcherManager) AutoRename() bool {
+	return true
+}
+
+func (fm *FetcherManager) DefaultConfig() any {
+	return &config{
+		SegmentConnections:    defaultSegmentConnections,
+		MaxRetries:            defaultMaxRetries,
+		TimeoutSeconds:        defaultTimeoutSeconds,
+		PrefetchContentLength: true,
+	}
+}
+
+func (fm *FetcherManager) Store(f fetcher.Fetcher) (data any, err error) {
+	_f := f.(*Fetcher)
+	_f.mu.Lock()
+	defer _f.mu.Unlock()
+	if _f.state == nil {
+		return nil, nil
+	}
+	// The engine's periodic checkpoint calls Store without holding the task
+	// lock and serializes the returned value afterwards, while Resolve/Patch/
+	// Start mutate the live state under the fetcher mutex: return a snapshot
+	// copy taken under that mutex, mirroring the HTTP protocol's Store.
+	return cloneState(_f.state), nil
+}
+
+func cloneState(state *fetcherState) *fetcherState {
+	cloned := *state
+	cloned.Segments = make([]*Segment, len(state.Segments))
+	for i, seg := range state.Segments {
+		s := *seg
+		cloned.Segments[i] = &s
+	}
+	return &cloned
+}
+
+func (fm *FetcherManager) Restore() (v any, f func(meta *fetcher.FetcherMeta, v any) fetcher.Fetcher) {
+	return &fetcherState{}, func(meta *fetcher.FetcherMeta, v any) fetcher.Fetcher {
+		fb := &FetcherManager{}
+		restored := fb.Build().(*Fetcher)
+		restored.meta = meta
+		if state, ok := v.(*fetcherState); ok && state.MediaURL != "" {
+			restored.state = state
+		}
+		// Setup is invoked by the engine (restoreFetcher) after this builder
+		// returns; ReqExtra parsing happens there as well.
+		return restored
+	}
+}
+
+func (fm *FetcherManager) Close() error {
+	return nil
+}

internal/protocol/hls/fetcher_test.go

@@ -0,0 +1,857 @@
+package hls
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/controller"
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+func pkcs7PadForTest(data []byte, blockSize int) []byte {
+	pad := blockSize - len(data)%blockSize
+	return append(data, bytes.Repeat([]byte{byte(pad)}, pad)...)
+}
+
+func encryptSegment(plain, key, iv []byte) []byte {
+	padded := pkcs7PadForTest(plain, aes.BlockSize)
+	block, _ := aes.NewCipher(key)
+	encrypted := make([]byte, len(padded))
+	cipher.NewCBCEncrypter(block, iv).CryptBlocks(encrypted, padded)
+	return encrypted
+}
+
+// serveContentWithReferer is a helper handler that enforces an optional
+// Referer requirement and reports request counts.
+type cdnHandler struct {
+	mux            *http.ServeMux
+	requireReferer string
+	requests       atomic.Int64
+}
+
+func (h *cdnHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	h.requests.Add(1)
+	if h.requireReferer != "" && r.Header.Get("Referer") != h.requireReferer {
+		w.WriteHeader(http.StatusForbidden)
+		return
+	}
+	h.mux.ServeHTTP(w, r)
+}
+
+func newTestFetcher(t *testing.T, cfg config) *Fetcher {
+	t.Helper()
+	fm := &FetcherManager{}
+	f := fm.Build().(*Fetcher)
+	ctl := controller.NewController()
+	ctl.GetConfig = func(v any) {
+		if c, ok := v.(*config); ok {
+			*c = cfg
+		}
+	}
+	f.Setup(ctl)
+	return f
+}
+
+func testConfig() config {
+	return config{
+		SegmentConnections:    4,
+		MaxRetries:            2,
+		TimeoutSeconds:        5,
+		PrefetchContentLength: true,
+	}
+}
+
+func mustResolve(t *testing.T, f *Fetcher, playlistURL, referer string) {
+	t.Helper()
+	req := &base.Request{URL: playlistURL}
+	if referer != "" {
+		req.Extra = &ReqExtra{Header: map[string]string{"Referer": referer}}
+	}
+	if err := f.Resolve(req, &base.Options{Path: t.TempDir()}); err != nil {
+		t.Fatalf("resolve: %v", err)
+	}
+}
+
+func mustRun(t *testing.T, f *Fetcher) {
+	t.Helper()
+	if err := f.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("wait: %v", err)
+	}
+}
+
+func statsOf(t *testing.T, f *Fetcher) Stats {
+	t.Helper()
+	s, ok := f.Stats().Snapshot.(*Stats)
+	if !ok {
+		t.Fatalf("unexpected stats snapshot type %T", f.Stats().Snapshot)
+	}
+	return *s
+}
+
+func readOutput(t *testing.T, f *Fetcher) []byte {
+	t.Helper()
+	data, err := os.ReadFile(f.meta.SingleFilepath())
+	if err != nil {
+		t.Fatal(err)
+	}
+	return data
+}
+
+func TestFetcherE2E_MasterTS(t *testing.T) {
+	seg := func(i int) []byte {
+		return []byte(fmt.Sprintf("SEGMENT-%02d-PAYLOAD", i))
+	}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/master.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("#EXTM3U\n" +
+			"#EXT-X-STREAM-INF:BANDWIDTH=800000\nv1/index.m3u8\n" +
+			"#EXT-X-STREAM-INF:BANDWIDTH=2000000\nv2/index.m3u8\n"))
+	})
+	mux.HandleFunc("/v1/index.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("#EXTM3U\n#EXTINF:4,\nlow-0.ts\n#EXT-X-ENDLIST\n"))
+	})
+	mux.HandleFunc("/v2/index.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		var b strings.Builder
+		b.WriteString("#EXTM3U\n")
+		for i := 0; i < 5; i++ {
+			b.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+		}
+		b.WriteString("#EXT-X-ENDLIST\n")
+		w.Write([]byte(b.String()))
+	})
+	for i := 0; i < 5; i++ {
+		content := seg(i)
+		path := "/v2/seg-" + strconv.Itoa(i) + ".ts"
+		mux.HandleFunc(path, func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("Content-Length", strconv.Itoa(len(content)))
+			w.Write(content)
+		})
+	}
+	server := httptest.NewServer(&cdnHandler{mux: mux})
+	defer server.Close()
+
+	f := newTestFetcher(t, testConfig())
+	mustResolve(t, f, server.URL+"/master.m3u8", "")
+	// Master resolution picked the 2000000 variant.
+	if f.state.MediaURL != server.URL+"/v2/index.m3u8" {
+		t.Fatalf("wrong variant picked: %s", f.state.MediaURL)
+	}
+	// HEAD prefetch should have computed the exact total size.
+	if f.meta.Res.Size != int64(5*len(seg(0))) {
+		t.Fatalf("prefetched size wrong: %d", f.meta.Res.Size)
+	}
+	mustRun(t, f)
+
+	var want []byte
+	for i := 0; i < 5; i++ {
+		want = append(want, seg(i)...)
+	}
+	got := readOutput(t, f)
+	if !bytes.Equal(got, want) {
+		t.Errorf("merged output mismatch: %q", got)
+	}
+	// The staging folder must be cleaned up after a successful merge; only
+	// the output file remains in the task directory.
+	if entries, _ := os.ReadDir(filepath.Dir(f.meta.SingleFilepath())); len(entries) != 1 {
+		for _, e := range entries {
+			t.Logf("leftover entry: %s", e.Name())
+		}
+		t.Errorf("staging dir should be cleaned up after merge")
+	}
+	if f.meta.Res.Size != int64(len(want)) {
+		t.Errorf("final size wrong: %d", f.meta.Res.Size)
+	}
+}
+
+func TestFetcherE2E_RefererEnforced(t *testing.T) {
+	page := "https://player.example.com/watch/123"
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	segments := make(map[string][]byte)
+	for i := 0; i < 3; i++ {
+		name := fmt.Sprintf("seg-%d.ts", i)
+		segments["/"+name] = []byte(fmt.Sprintf("DATA-%d", i))
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\n%s\n", name))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	for path, content := range segments {
+		c := content
+		mux.HandleFunc(path, func(w http.ResponseWriter, r *http.Request) {
+			w.Write(c)
+		})
+	}
+	server := httptest.NewServer(&cdnHandler{mux: mux, requireReferer: page})
+	defer server.Close()
+
+	// 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 {
+		t.Fatal("resolve without Referer should fail")
+	}
+
+	// With the Referer set through the task extra headers it must succeed.
+	allowed := newTestFetcher(t, testConfig())
+	allowedReq := &base.Request{
+		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 {
+		t.Fatal(err)
+	}
+	mustRun(t, allowed)
+	want := []byte("DATA-0DATA-1DATA-2")
+	if !bytes.Equal(readOutput(t, allowed), want) {
+		t.Error("output mismatch with Referer download")
+	}
+}
+
+func TestFetcherE2E_AES128KeyRotation(t *testing.T) {
+	key1 := []byte("0123456789abcdef")
+	key2 := []byte("fedcba9876543210")
+	iv1 := []byte("aaaaaaaaaaaaaaaa")
+	plain1 := []byte("ENCRYPTED-SEGMENT-ONE!!") // padded on encrypt
+	plain2 := []byte("ENCRYPTED-SEGMENT-TWO!!")
+	// seg-2 has no explicit IV: derived from media sequence 1.
+	enc1 := encryptSegment(plain1, key1, iv1)
+	enc2 := encryptSegment(plain2, key2, sequenceIV(1))
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("#EXTM3U\n" +
+			"#EXT-X-MEDIA-SEQUENCE:0\n" +
+			"#EXT-X-KEY:METHOD=AES-128,URI=\"key-1.bin\",IV=0x" + hexEncode(iv1) + "\n" +
+			"#EXTINF:5,\nseg-1.ts\n" +
+			"#EXT-X-KEY:METHOD=AES-128,URI=\"key-2.bin\"\n" +
+			"#EXTINF:5,\nseg-2.ts\n" +
+			"#EXT-X-ENDLIST\n"))
+	})
+	mux.HandleFunc("/key-1.bin", func(w http.ResponseWriter, r *http.Request) {
+		w.Write(key1)
+	})
+	mux.HandleFunc("/key-2.bin", func(w http.ResponseWriter, r *http.Request) {
+		w.Write(key2)
+	})
+	mux.HandleFunc("/seg-1.ts", func(w http.ResponseWriter, r *http.Request) {
+		w.Write(enc1)
+	})
+	mux.HandleFunc("/seg-2.ts", func(w http.ResponseWriter, r *http.Request) {
+		w.Write(enc2)
+	})
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	f := newTestFetcher(t, testConfig())
+	mustResolve(t, f, server.URL+"/video.m3u8", "")
+	// Ciphertext sizes overstate the final output after decryption, so an
+	// encrypted plan must report an indeterminate size.
+	if f.meta.Res.Size != 0 {
+		t.Errorf("encrypted plan should report size 0, got %d", f.meta.Res.Size)
+	}
+	mustRun(t, f)
+
+	want := append(append([]byte{}, plain1...), plain2...)
+	if !bytes.Equal(readOutput(t, f), want) {
+		t.Errorf("decrypted output mismatch: %q", readOutput(t, f))
+	}
+}
+
+func TestFetcherE2E_ByteRange(t *testing.T) {
+	data := []byte("0123456789ABCDEFGHIJ") // 20 bytes
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("#EXTM3U\n" +
+			"#EXT-X-BYTERANGE:10@0\nblob.bin\n" +
+			"#EXT-X-BYTERANGE:10\nblob.bin\n" +
+			"#EXT-X-ENDLIST\n"))
+	})
+	mux.HandleFunc("/blob.bin", func(w http.ResponseWriter, r *http.Request) {
+		rng := r.Header.Get("Range")
+		if rng == "" {
+			w.Write(data)
+			return
+		}
+		// bytes=start-end
+		var start, end int
+		fmt.Sscanf(rng, "bytes=%d-%d", &start, &end)
+		w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, len(data)))
+		w.WriteHeader(http.StatusPartialContent)
+		w.Write(data[start : end+1])
+	})
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	f := newTestFetcher(t, testConfig())
+	mustResolve(t, f, server.URL+"/video.m3u8", "")
+	if f.meta.Res.Size != 20 {
+		t.Fatalf("byterange sizes should be known from the playlist, got %d", f.meta.Res.Size)
+	}
+	mustRun(t, f)
+	if !bytes.Equal(readOutput(t, f), data) {
+		t.Errorf("byterange merge mismatch: %q", readOutput(t, f))
+	}
+}
+
+func TestFetcherE2E_PauseResume(t *testing.T) {
+	const total = 8
+	var served atomic.Int64
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		var b strings.Builder
+		b.WriteString("#EXTM3U\n")
+		for i := 0; i < total; i++ {
+			b.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+		}
+		b.WriteString("#EXT-X-ENDLIST\n")
+		w.Write([]byte(b.String()))
+	})
+	segments := make(map[int][]byte)
+	for i := 0; i < total; i++ {
+		segments[i] = []byte(fmt.Sprintf("SLOW-SEGMENT-%02d", i))
+	}
+	for i := 0; i < total; i++ {
+		idx := i
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", i), func(w http.ResponseWriter, r *http.Request) {
+			time.Sleep(150 * time.Millisecond)
+			served.Add(1)
+			w.Write(segments[idx])
+		})
+	}
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	cfg := testConfig()
+	cfg.SegmentConnections = 2
+	cfg.PrefetchContentLength = false
+	f := newTestFetcher(t, cfg)
+	mustResolve(t, f, server.URL+"/video.m3u8", "")
+
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	// Let a couple of segments finish, then pause.
+	time.Sleep(400 * time.Millisecond)
+	if err := f.Pause(); err != nil {
+		t.Fatal(err)
+	}
+	doneBefore := statsOf(t, f).SegmentsDone
+	if doneBefore == 0 {
+		t.Fatal("expected some segments to complete before pause")
+	}
+	if doneBefore == total {
+		t.Fatal("all segments finished before pause, test is not exercising resume")
+	}
+
+	// Resume must finish the rest and produce the full output.
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	var want []byte
+	for i := 0; i < total; i++ {
+		want = append(want, segments[i]...)
+	}
+	if !bytes.Equal(readOutput(t, f), want) {
+		t.Errorf("resumed output mismatch: %q", readOutput(t, f))
+	}
+}
+
+func TestFetcherE2E_StoreRestoreResume(t *testing.T) {
+	const total = 6
+	var served atomic.Int64
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		var b strings.Builder
+		b.WriteString("#EXTM3U\n")
+		for i := 0; i < total; i++ {
+			b.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+		}
+		b.WriteString("#EXT-X-ENDLIST\n")
+		w.Write([]byte(b.String()))
+	})
+	segments := make(map[int][]byte)
+	for i := 0; i < total; i++ {
+		segments[i] = []byte(fmt.Sprintf("RESTORE-SEGMENT-%02d", i))
+	}
+	for i := 0; i < total; i++ {
+		idx := i
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", i), func(w http.ResponseWriter, r *http.Request) {
+			time.Sleep(120 * time.Millisecond)
+			served.Add(1)
+			w.Write(segments[idx])
+		})
+	}
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	cfg := testConfig()
+	cfg.SegmentConnections = 2
+	cfg.PrefetchContentLength = false
+
+	f := newTestFetcher(t, cfg)
+	mustResolve(t, f, server.URL+"/video.m3u8", "")
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(350 * time.Millisecond)
+	if err := f.Pause(); err != nil {
+		t.Fatal(err)
+	}
+	doneBefore := statsOf(t, f).SegmentsDone
+	if doneBefore == 0 {
+		t.Fatal("expected some segments to finish before simulated restart")
+	}
+
+	// Simulate an app restart: persist, then restore into a fresh fetcher.
+	fm := &FetcherManager{}
+	state, err := fm.Store(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if state == nil {
+		t.Fatal("state should be persisted")
+	}
+	ctl := controller.NewController()
+	ctl.GetConfig = func(v any) {
+		if c, ok := v.(*config); ok {
+			*c = cfg
+		}
+	}
+	holder := fm.Build().(*Fetcher)
+	holder.Setup(ctl)
+	holder.meta = &fetcher.FetcherMeta{
+		Req:  f.meta.Req,
+		Opts: f.meta.Opts,
+		Res:  f.meta.Res,
+	}
+	_, builder := fm.Restore()
+	rf := builder(holder.meta, state).(*Fetcher)
+	// The engine calls Setup on the builder result (restoreFetcher).
+	rf.Setup(ctl)
+	if rf.state == nil || len(rf.state.Segments) != total {
+		t.Fatal("restored state missing segment plan")
+	}
+
+	if err := rf.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := rf.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	if done := statsOf(t, rf).SegmentsDone; done != total {
+		t.Errorf("want %d done, got %d", total, done)
+	}
+	var want []byte
+	for i := 0; i < total; i++ {
+		want = append(want, segments[i]...)
+	}
+	if !bytes.Equal(readOutput(t, rf), want) {
+		t.Errorf("restored output mismatch: %q", readOutput(t, rf))
+	}
+}
+
+func hexEncode(b []byte) string {
+	const digits = "0123456789abcdef"
+	out := make([]byte, 0, len(b)*2)
+	for _, v := range b {
+		out = append(out, digits[v>>4], digits[v&0x0f])
+	}
+	return string(out)
+}
+
+// restoreLikeEngine round-trips the persisted state and the task meta through
+// JSON the way the engine storage does, then builds a fresh fetcher. This is
+// the path that historically lost the request extra headers.
+func restoreLikeEngine(t *testing.T, f *Fetcher, cfg config) *Fetcher {
+	t.Helper()
+	fm := &FetcherManager{}
+	stateAny, err := fm.Store(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rawState, err := json.Marshal(stateAny)
+	if err != nil {
+		t.Fatal(err)
+	}
+	storedState := &fetcherState{}
+	if err := json.Unmarshal(rawState, storedState); err != nil {
+		t.Fatal(err)
+	}
+	rawMeta, err := json.Marshal(f.meta)
+	if err != nil {
+		t.Fatal(err)
+	}
+	restoredMeta := &fetcher.FetcherMeta{}
+	if err := json.Unmarshal(rawMeta, restoredMeta); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := restoredMeta.Req.Extra.(*ReqExtra); ok {
+		t.Fatal("storage round trip should yield a map-shaped extra, like the engine")
+	}
+	ctl := controller.NewController()
+	ctl.GetConfig = func(v any) {
+		if c, ok := v.(*config); ok {
+			*c = cfg
+		}
+	}
+	_, builder := fm.Restore()
+	rf := builder(restoredMeta, storedState).(*Fetcher)
+	// The engine calls Setup on the builder result (restoreFetcher).
+	rf.Setup(ctl)
+	return rf
+}
+
+func TestFetcherE2E_StoreRestoreAuthenticated(t *testing.T) {
+	const total = 4
+	page := "https://player.example.com/watch/42"
+	var served atomic.Int64
+	mux := http.NewServeMux()
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	for i := 0; i < total; i++ {
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	segments := make(map[int][]byte)
+	for i := 0; i < total; i++ {
+		segments[i] = []byte(fmt.Sprintf("AUTH-SEGMENT-%02d", i))
+		idx := i
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", idx), func(w http.ResponseWriter, r *http.Request) {
+			time.Sleep(80 * time.Millisecond)
+			served.Add(1)
+			w.Write(segments[idx])
+		})
+	}
+	server := httptest.NewServer(&cdnHandler{mux: mux, requireReferer: page})
+	defer server.Close()
+
+	cfg := testConfig()
+	cfg.SegmentConnections = 2
+	cfg.PrefetchContentLength = false
+
+	f := newTestFetcher(t, cfg)
+	req := &base.Request{
+		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 {
+		t.Fatal(err)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(150 * time.Millisecond)
+	if err := f.Pause(); err != nil {
+		t.Fatal(err)
+	}
+
+	rf := restoreLikeEngine(t, f, cfg)
+	if rf.extra == nil || rf.extra.Header["Referer"] != page {
+		t.Fatalf("restored fetcher lost the request extra headers: %+v", rf.extra)
+	}
+	if err := rf.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := rf.Wait(); err != nil {
+		t.Fatalf("resumed download failed (request headers lost?): %v", err)
+	}
+	var want []byte
+	for i := 0; i < total; i++ {
+		want = append(want, segments[i]...)
+	}
+	if !bytes.Equal(readOutput(t, rf), want) {
+		t.Errorf("restored output mismatch: %q", readOutput(t, rf))
+	}
+}
+
+func TestFetcherE2E_PatchPartialUpdate(t *testing.T) {
+	page := "https://player.example.com/watch/7"
+	var requiredReferer atomic.Value // string
+	requiredReferer.Store(page)
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	segments := make(map[string][]byte)
+	for i := 0; i < 3; i++ {
+		segments[fmt.Sprintf("/s%d.ts", i)] = []byte(fmt.Sprintf("PATCH-%d", i))
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\ns%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	for path, content := range segments {
+		c := content
+		mux.HandleFunc(path, func(w http.ResponseWriter, r *http.Request) {
+			w.Write(c)
+		})
+	}
+	// The Referer requirement can be flipped mid-test to prove that a patched
+	// header is actually sent by the next run.
+	dyn := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if want, _ := requiredReferer.Load().(string); want != "" && r.Header.Get("Referer") != want {
+			w.WriteHeader(http.StatusForbidden)
+			return
+		}
+		mux.ServeHTTP(w, r)
+	})
+	server := httptest.NewServer(dyn)
+	defer server.Close()
+
+	f := newTestFetcher(t, testConfig())
+	req := &base.Request{
+		URL:   server.URL + "/video.m3u8",
+		Extra: &ReqExtra{Header: map[string]string{"Referer": page}},
+	}
+	opts := &base.Options{Path: t.TempDir()}
+	if err := f.Resolve(req, opts); err != nil {
+		t.Fatal(err)
+	}
+
+	// A nil/nil patch must be a no-op, not a panic.
+	if err := f.Patch(nil, nil); err != nil {
+		t.Fatalf("nil patch should be accepted: %v", err)
+	}
+
+	// Header-only patch: the resolved plan and output options are retained
+	// while the new header takes effect on the next run.
+	newReferer := "https://player.example.com/watch/9"
+	if err := f.Patch(&base.Request{
+		URL:   server.URL + "/video.m3u8",
+		Extra: &ReqExtra{Header: map[string]string{"Referer": newReferer}},
+	}, nil); err != nil {
+		t.Fatal(err)
+	}
+	if f.state == nil || f.meta.Res == nil {
+		t.Fatal("header-only patch must keep the resolved plan")
+	}
+	if f.meta.Opts.Path != opts.Path {
+		t.Fatalf("header-only patch must keep the output path: %s", f.meta.Opts.Path)
+	}
+	if f.extra.Header["Referer"] != newReferer {
+		t.Fatalf("patched header not applied: %+v", f.extra.Header)
+	}
+	requiredReferer.Store(newReferer)
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("run with patched header failed: %v", err)
+	}
+	if got := readOutput(t, f); string(got) != "PATCH-0PATCH-1PATCH-2" {
+		t.Errorf("output mismatch after header patch: %q", got)
+	}
+
+	// Options-only patch: renaming the task keeps the resolved plan.
+	if err := f.Patch(nil, &base.Options{Name: "renamed.ts"}); err != nil {
+		t.Fatal(err)
+	}
+	if f.state == nil {
+		t.Fatal("options-only patch must keep the resolved plan")
+	}
+	if f.meta.Opts.Name != "renamed.ts" || f.meta.Opts.Path != opts.Path {
+		t.Fatalf("options patch misapplied: %+v", f.meta.Opts)
+	}
+
+	// URL-only patch: the plan is dropped for a re-resolve but the output
+	// path and renamed file survive.
+	if err := f.Patch(&base.Request{URL: server.URL + "/refreshed.m3u8"}, nil); err != nil {
+		t.Fatal(err)
+	}
+	if f.state != nil || f.meta.Res != nil {
+		t.Fatal("URL patch must drop the resolved plan")
+	}
+	if f.meta.Opts.Path != opts.Path || f.meta.Opts.Name != "renamed.ts" {
+		t.Fatal("URL patch must keep the output options")
+	}
+}
+
+func TestFetcherE2E_PatchWhileRunningRejected(t *testing.T) {
+	mux := http.NewServeMux()
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	for i := 0; i < 6; i++ {
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	for i := 0; i < 6; i++ {
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", i), func(w http.ResponseWriter, r *http.Request) {
+			time.Sleep(150 * time.Millisecond)
+			w.Write([]byte("X"))
+		})
+	}
+	server := httptest.NewServer(mux)
+	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 {
+		t.Fatal(err)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Patch(&base.Request{URL: server.URL + "/other.m3u8"}, nil); err == nil {
+		t.Fatal("patching a running task must be rejected")
+	}
+	if err := f.Pause(); err != nil {
+		t.Fatal(err)
+	}
+	// After the pause the patch goes through and only then drops the plan.
+	if err := f.Patch(&base.Request{URL: server.URL + "/other.m3u8"}, nil); err != nil {
+		t.Fatal(err)
+	}
+	if f.state != nil {
+		t.Fatal("URL patch after pause must drop the plan")
+	}
+}
+
+func TestFetcherE2E_RetryAfterFailure(t *testing.T) {
+	const total = 4
+	var healthy atomic.Bool
+	mux := http.NewServeMux()
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	for i := 0; i < total; i++ {
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	segments := make(map[int][]byte)
+	for i := 0; i < total; i++ {
+		segments[i] = []byte(fmt.Sprintf("RETRY-SEGMENT-%02d", i))
+		idx := i
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", idx), func(w http.ResponseWriter, r *http.Request) {
+			if idx == 1 && !healthy.Load() {
+				w.WriteHeader(http.StatusInternalServerError)
+				return
+			}
+			time.Sleep(60 * time.Millisecond)
+			w.Write(segments[idx])
+		})
+	}
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	cfg := testConfig()
+	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 {
+		t.Fatal(err)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err == nil {
+		t.Fatal("first run should fail while the segment endpoint is down")
+	}
+	if got := statsOf(t, f).SegmentsFailed; got == 0 {
+		t.Fatal("failed segments should be reported in stats")
+	}
+
+	// Server recovered: a fresh run must succeed and report zero failures.
+	healthy.Store(true)
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("retry run failed: %v", err)
+	}
+	stats := statsOf(t, f)
+	if stats.SegmentsFailed != 0 {
+		t.Errorf("failures must reset per run, got %d", stats.SegmentsFailed)
+	}
+	if stats.SegmentsDone != total {
+		t.Errorf("want %d done, got %d", total, stats.SegmentsDone)
+	}
+	var want []byte
+	for i := 0; i < total; i++ {
+		want = append(want, segments[i]...)
+	}
+	if !bytes.Equal(readOutput(t, f), want) {
+		t.Errorf("retry output mismatch: %q", readOutput(t, f))
+	}
+}
+
+func TestFetcherE2E_StateMissingSelfHeal(t *testing.T) {
+	const total = 3
+	mux := http.NewServeMux()
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	for i := 0; i < total; i++ {
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	segments := make(map[int][]byte)
+	for i := 0; i < total; i++ {
+		segments[i] = []byte(fmt.Sprintf("SELFHEAL-%02d", i))
+		idx := i
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", idx), func(w http.ResponseWriter, r *http.Request) {
+			w.Write(segments[idx])
+		})
+	}
+	server := httptest.NewServer(mux)
+	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 {
+		t.Fatal(err)
+	}
+	// Simulate the crash window where the engine persisted the task with its
+	// resource but the HLS plan was never checkpointed.
+	f.state = nil
+	outputName := f.meta.Res.Files[0].Name
+	if err := f.Start(); err != nil {
+		t.Fatalf("start should self-heal a missing plan: %v", err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("self-healed run failed: %v", err)
+	}
+	if f.state == nil || len(f.state.Segments) != total {
+		t.Fatal("self-heal should rebuild the segment plan")
+	}
+	if f.meta.Res.Files[0].Name != outputName {
+		t.Fatalf("self-heal renamed the output: %s", f.meta.Res.Files[0].Name)
+	}
+	var want []byte
+	for i := 0; i < total; i++ {
+		want = append(want, segments[i]...)
+	}
+	if !bytes.Equal(readOutput(t, f), want) {
+		t.Errorf("self-healed output mismatch: %q", readOutput(t, f))
+	}
+}

internal/protocol/hls/helper.go

@@ -0,0 +1,100 @@
+package hls
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/http/cookiejar"
+	"time"
+
+	"github.com/GopeedLab/gopeed/internal/httpclient"
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+const defaultUserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36"
+
+const maxPlaylistSize = 10 << 20 // 10MB, playlists are small text files
+
+func (f *Fetcher) timeout() time.Duration {
+	return time.Duration(f.config.TimeoutSeconds) * time.Second
+}
+
+// buildClient builds an HTTP client honoring the task proxy and TLS settings.
+// The client has no total timeout on purpose: large segments over slow links
+// must not be aborted; body stalls are handled by stallReader instead. It is
+// only called while the fetcher is quiescent (Resolve/Start), never from
+// inside running worker goroutines.
+func (f *Fetcher) buildClient() *http.Client {
+	var proxy *base.RequestProxy
+	skipVerify := false
+	if req := f.meta.Req; req != nil {
+		proxy = req.Proxy
+		skipVerify = req.SkipVerifyCert
+	}
+	jar, _ := cookiejar.New(nil)
+	client, err := httpclient.NewClient(httpclient.Options{
+		Client: httpclient.ClientOptions{
+			Jar: jar,
+		},
+		Transport: httpclient.TransportOptions{
+			DialContext: (&net.Dialer{
+				Timeout: f.timeout(),
+			}).DialContext,
+			Proxy: f.Ctl.GetProxy(proxy),
+			TLSClientConfig: &tls.Config{
+				InsecureSkipVerify: skipVerify,
+			},
+			TLSHandshakeTimeout: f.timeout(),
+		},
+		Impersonation: httpclient.ImpersonationOptions{
+			Mode:    httpclient.ImpersonationAuto,
+			Session: f.impSession,
+		},
+	})
+	if err != nil {
+		panic(fmt.Sprintf("build HTTP client: %v", err))
+	}
+	return client
+}
+
+// buildRequest builds a request with task extra headers, the default user
+// agent and an optional byte range. extra may be nil.
+func buildRequest(ctx context.Context, extra *ReqExtra, method, u string, body io.Reader, byterange *ByteRange) (*http.Request, error) {
+	req, err := http.NewRequestWithContext(ctx, method, u, body)
+	if err != nil {
+		return nil, err
+	}
+	if extra != nil {
+		for key, value := range extra.Header {
+			req.Header.Set(key, value)
+		}
+	}
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", defaultUserAgent)
+	}
+	if byterange != nil {
+		req.Header.Set("Range", fmt.Sprintf("bytes=%d-%d", byterange.Offset, byterange.Offset+byterange.Length-1))
+	}
+	return req, nil
+}
+
+// stallReader aborts reads that see no data for the configured timeout.
+type stallReader struct {
+	rc      io.ReadCloser
+	timeout time.Duration
+}
+
+func (r *stallReader) Read(p []byte) (int, error) {
+	timer := time.AfterFunc(r.timeout, func() {
+		r.rc.Close()
+	})
+	defer timer.Stop()
+	return r.rc.Read(p)
+}
+
+func (r *stallReader) Close() error {
+	return r.rc.Close()
+}

internal/protocol/hls/journal.go

@@ -0,0 +1,112 @@
+package hls
+
+import (
+	"crypto/rand"
+	"crypto/sha1"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+)
+
+// journalFile is the persisted completed-segment ledger. It is bound to the
+// exact download plan: a journal whose fingerprint does not match the current
+// plan is discarded instead of being applied to the wrong segments.
+type journalFile struct {
+	StagingID    string           `json:"stagingID"`
+	PlanHash     string           `json:"planHash"`
+	SegmentCount int              `json:"segmentCount"`
+	Sizes        map[string]int64 `json:"sizes"`
+}
+
+// randomStagingID returns a random identifier used to give every task its own
+// staging folder, stable across app restarts through the persisted state.
+func randomStagingID() string {
+	buf := make([]byte, 6)
+	if _, err := rand.Read(buf); err != nil {
+		// crypto/rand failing is catastrophic anyway; fall back to address
+		// entropy rather than crashing the fetch.
+		return fmt.Sprintf("%x", sha1.Sum([]byte(fmt.Sprintf("%p", buf))))[:12]
+	}
+	return hex.EncodeToString(buf)
+}
+
+// planFingerprint hashes everything that defines the download plan: the media
+// URL, the ordered segments with their sequence numbers, byte ranges, keys
+// and init markers. Two tasks resolve to different fingerprints even when
+// they point at the same playlist URL.
+func planFingerprint(state *fetcherState) string {
+	h := sha1.New()
+	io.WriteString(h, state.MediaURL+"\n")
+	io.WriteString(h, strconv.Itoa(len(state.Segments))+"\n")
+	for _, seg := range state.Segments {
+		fmt.Fprintf(h, "%d|%s|", seg.Sequence, seg.URI)
+		if seg.Byterange != nil {
+			fmt.Fprintf(h, "%d@%d|", seg.Byterange.Offset, seg.Byterange.Length)
+		}
+		if seg.Key != nil {
+			// The IV is part of the plan: same URI with a rotated IV would
+			// silently decrypt to garbage if the journal were reused.
+			fmt.Fprintf(h, "key=%s iv=%x|", seg.Key.URI, seg.Key.IV)
+		}
+		if seg.IsInit {
+			io.WriteString(h, "init|")
+		}
+		io.WriteString(h, "\n")
+	}
+	return hex.EncodeToString(h.Sum(nil))[:16]
+}
+
+// loadJournal reads the journal of a run, discarding anything that cannot be
+// proven to belong to the current plan: foreign or legacy journals, corrupted
+// files, and entries whose recorded size no longer matches the plan.
+func loadJournal(run *hlsRun) error {
+	data, err := os.ReadFile(run.journalPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	var file journalFile
+	if err := json.Unmarshal(data, &file); err != nil {
+		// A broken or legacy journal must not kill a restartable download.
+		return nil
+	}
+	if file.StagingID != run.stagingID || file.PlanHash != run.planHash || file.SegmentCount != len(run.segs) {
+		return nil
+	}
+	for key, size := range file.Sizes {
+		idx, err := strconv.ParseInt(key, 10, 64)
+		if err != nil || idx < 0 || idx >= int64(len(run.segs)) || size <= 0 {
+			continue
+		}
+		run.journal[idx] = size
+	}
+	return nil
+}
+
+// saveJournal atomically rewrites the journal through a temp file + rename so
+// a crash never leaves a half-written ledger behind.
+func saveJournal(run *hlsRun) error {
+	file := journalFile{
+		StagingID:    run.stagingID,
+		PlanHash:     run.planHash,
+		SegmentCount: len(run.segs),
+		Sizes:        make(map[string]int64, len(run.journal)),
+	}
+	for idx, size := range run.journal {
+		file.Sizes[strconv.FormatInt(idx, 10)] = size
+	}
+	data, err := json.Marshal(file)
+	if err != nil {
+		return err
+	}
+	tmp := run.journalPath + ".tmp"
+	if err := os.WriteFile(tmp, data, 0666); err != nil {
+		return err
+	}
+	return os.Rename(tmp, run.journalPath)
+}

internal/protocol/hls/media_validate_test.go

@@ -0,0 +1,297 @@
+package hls
+
+import (
+	"bytes"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+// The validators below check real media structure, not just byte
+// concatenation: TS packets are verified on the 188 byte grid with
+// continuity-counter rules, PAT/PMT presence and PES start codes; fMP4
+// output is verified by walking the ISO-BMFF box hierarchy.
+
+func be32(b []byte) int {
+	return int(b[0])<<24 | int(b[1])<<16 | int(b[2])<<8 | int(b[3])
+}
+
+// validateTS asserts structural validity of a merged MPEG-2 TS stream.
+func validateTS(t *testing.T, data []byte) {
+	t.Helper()
+	if len(data) == 0 || len(data)%188 != 0 {
+		t.Fatalf("TS size %d is not a positive multiple of 188", len(data))
+	}
+	type pidState struct{ cc int }
+	ccByPID := map[int]int{}
+	patSeen, pmtSeen, pesSeen := false, false, false
+	for off := 0; off < len(data); off += 188 {
+		pkt := data[off : off+188]
+		if pkt[0] != 0x47 {
+			t.Fatalf("bad TS sync byte at offset %d", off)
+		}
+		pid := (int(pkt[1]&0x1F) << 8) | int(pkt[2])
+		pusi := pkt[1]&0x40 != 0
+		afc := (pkt[3] >> 4) & 0x3
+		if afc == 0 {
+			continue // reserved
+		}
+		idx := 4
+		if afc&0x2 != 0 { // adaptation field present
+			afLen := int(pkt[4])
+			if afLen > 0 && pkt[5]&0x80 != 0 {
+				// discontinuity_indicator: restart the CC expectation
+				delete(ccByPID, pid)
+			}
+			idx += 1 + afLen
+			if afc == 2 {
+				continue // adaptation only, no payload: no CC rule
+			}
+		}
+		if idx > 188 {
+			t.Fatalf("adaptation field overruns packet at offset %d", off)
+		}
+		if pid == 0x1FFF {
+			continue // null packet
+		}
+		payload := pkt[idx:]
+		if pusi && len(payload) >= 3 && pid != 0 && payload[0] == 0 && payload[1] == 0 && payload[2] == 1 {
+			pesSeen = true
+		}
+		if pid == 0 {
+			if ptr := int(payload[0]); 1+ptr < len(payload) && payload[1+ptr] == 0x00 {
+				patSeen = true // program_association_section table_id
+			}
+		} else if pusi && len(payload) >= 2 && payload[0] == 0 && payload[1] == 0x02 {
+			pmtSeen = true // program_map_section table_id
+		}
+		cc := int(pkt[3] & 0x0F)
+		prev, ok := ccByPID[pid]
+		if !ok {
+			ccByPID[pid] = cc
+			continue
+		}
+		// CC increments by one per payload-bearing packet; a repeated value
+		// models the single legal duplicate packet.
+		if cc != (prev+1)%16 && cc != prev {
+			t.Fatalf("continuity error on PID %d: %d after %d at offset %d", pid, cc, prev, off)
+		}
+		ccByPID[pid] = cc
+	}
+	if !patSeen {
+		t.Error("no PAT found in merged TS")
+	}
+	if !pmtSeen {
+		t.Error("no PMT found in merged TS")
+	}
+	if !pesSeen {
+		t.Error("no PES start code found in merged TS")
+	}
+}
+
+// walkBoxes iterates the top-level ISO-BMFF boxes of data[off:end].
+func walkBoxes(t *testing.T, data []byte, off, end int) []string {
+	t.Helper()
+	var types []string
+	for off+8 <= end {
+		size := be32(data[off:])
+		typ := string(data[off+4 : off+8])
+		if size < 8 || off+size > end {
+			t.Fatalf("invalid box %q at offset %d (size %d)", typ, off, size)
+		}
+		types = append(types, typ)
+		off += size
+	}
+	return types
+}
+
+// validateFMP4 asserts the merged fMP4 output is init section followed by
+// well-formed moof+mdat fragments.
+func validateFMP4(t *testing.T, merged []byte, wantFragments int) {
+	t.Helper()
+	types := walkBoxes(t, merged, 0, len(merged))
+	hasFtyp, hasMoov := false, false
+	fragments := 0
+	expectFragment := false
+	for i, typ := range types {
+		switch typ {
+		case "ftyp":
+			if i != 0 {
+				t.Errorf("ftyp not at stream start")
+			}
+			hasFtyp = true
+		case "moov":
+			if i != 1 {
+				t.Errorf("moov must follow ftyp, found at index %d", i)
+			}
+			hasMoov = true
+		case "styp":
+			expectFragment = true
+		case "moof":
+			if !hasMoov {
+				t.Errorf("fragment before moov")
+			}
+			expectFragment = true
+		case "mdat":
+			if !expectFragment {
+				t.Errorf("mdat outside of a fragment at index %d", i)
+			}
+			expectFragment = false
+			fragments++
+		case "mfra":
+			// optional trailer
+		default:
+			t.Errorf("unexpected top-level box %q", typ)
+		}
+	}
+	if !hasFtyp || !hasMoov {
+		t.Error("merged fMP4 missing ftyp/moov init section")
+	}
+	if fragments != wantFragments {
+		t.Errorf("want %d fragments in merged fMP4, got %d", wantFragments, fragments)
+	}
+}
+
+func mediaFixture(t *testing.T, name string) []byte {
+	t.Helper()
+	data, err := os.ReadFile("testdata/media/" + name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return data
+}
+
+func serveFixtureServer(t *testing.T) *httptest.Server {
+	t.Helper()
+	mux := http.NewServeMux()
+	fs := http.FileServer(http.Dir("testdata/media"))
+	mux.Handle("/", fs)
+	return httptest.NewServer(mux)
+}
+
+func TestHLSRealMedia_TS(t *testing.T) {
+	seg0 := mediaFixture(t, "sample-00.ts")
+	seg1 := mediaFixture(t, "sample-01.ts")
+	playlist := "#EXTM3U\n" +
+		"#EXTINF:0.5,\nsample-00.ts\n" +
+		"#EXTINF:0.5,\nsample-01.ts\n" +
+		"#EXT-X-ENDLIST\n"
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist))
+	})
+	mux.Handle("/", http.FileServer(http.Dir("testdata/media")))
+	server := httptest.NewServer(mux)
+	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 {
+		t.Fatal(err)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	got := readOutput(t, f)
+	if !bytes.Equal(got, append(append([]byte{}, seg0...), seg1...)) {
+		t.Fatal("merged TS is not the exact concatenation of the segments")
+	}
+	validateTS(t, got)
+}
+
+func TestHLSRealMedia_FMP4(t *testing.T) {
+	init := mediaFixture(t, "fmp4-init.mp4")
+	frag1 := mediaFixture(t, "fmp4-seg1.m4s")
+	frag2 := mediaFixture(t, "fmp4-seg2.m4s")
+	frag3 := mediaFixture(t, "fmp4-seg3.m4s")
+	playlist := "#EXTM3U\n" +
+		"#EXT-X-MAP:URI=\"fmp4-init.mp4\"\n" +
+		"#EXTINF:0.5,\nfmp4-seg1.m4s\n" +
+		"#EXTINF:0.5,\nfmp4-seg2.m4s\n" +
+		"#EXTINF:0.5,\nfmp4-seg3.m4s\n" +
+		"#EXT-X-ENDLIST\n"
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist))
+	})
+	mux.Handle("/", http.FileServer(http.Dir("testdata/media")))
+	server := httptest.NewServer(mux)
+	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 {
+		t.Fatal(err)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	got := readOutput(t, f)
+	want := append(append(append(append([]byte{}, init...), frag1...), frag2...), frag3...)
+	if !bytes.Equal(got, want) {
+		t.Fatal("merged fMP4 is not the exact concatenation of init + fragments")
+	}
+	validateFMP4(t, got, 3)
+}
+
+func TestHLSRealMedia_AES128(t *testing.T) {
+	keys := [][]byte{[]byte("key-A-0123456789"), []byte("key-B-9876543210")}
+	iv := []byte("iv-1337-01234567")
+	plain := [][]byte{mediaFixture(t, "sample-00.ts"), mediaFixture(t, "sample-01.ts")}
+
+	playlist := "#EXTM3U\n" +
+		"#EXT-X-MEDIA-SEQUENCE:0\n" +
+		"#EXT-X-KEY:METHOD=AES-128,URI=\"key-0.bin\",IV=0x" + hexEncode(iv) + "\n" +
+		"#EXTINF:0.5,\nenc-0.ts\n" +
+		"#EXT-X-KEY:METHOD=AES-128,URI=\"key-1.bin\"\n" +
+		"#EXTINF:0.5,\nenc-1.ts\n" +
+		"#EXT-X-ENDLIST\n"
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist))
+	})
+	for i, key := range keys {
+		k := key
+		mux.HandleFunc(fmt.Sprintf("/key-%d.bin", i), func(w http.ResponseWriter, r *http.Request) {
+			w.Write(k)
+		})
+		// Segment 0 has an explicit IV, segment 1 derives it from its media
+		// sequence number (1).
+		enc := encryptSegment(plain[i], k, map[bool][]byte{true: iv, false: sequenceIV(int64(i))}[i == 0])
+		mux.HandleFunc(fmt.Sprintf("/enc-%d.ts", i), func(w http.ResponseWriter, r *http.Request) {
+			w.Write(enc)
+		})
+	}
+	server := httptest.NewServer(mux)
+	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 {
+		t.Fatal(err)
+	}
+	if f.meta.Res.Size != 0 {
+		t.Errorf("encrypted plan must report indeterminate size, got %d", f.meta.Res.Size)
+	}
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	got := readOutput(t, f)
+	if !bytes.Equal(got, append(append([]byte{}, plain[0]...), plain[1]...)) {
+		t.Fatal("decrypted output mismatch")
+	}
+	validateTS(t, got)
+	if p := f.Progress(); p.TotalDownloaded() != int64(len(got)) {
+		t.Errorf("final progress %d != merged size %d", p.TotalDownloaded(), len(got))
+	}
+}

internal/protocol/hls/playlist.go

@@ -0,0 +1,479 @@
+package hls
+
+import (
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"net/url"
+	"path"
+	"strconv"
+	"strings"
+)
+
+// Variant is one rendition entry of a master playlist.
+type Variant struct {
+	URI          string
+	Bandwidth    int64
+	AvgBandwidth int64
+	Resolution   string
+	Codecs       string
+	Name         string
+	AudioGroup   string // AUDIO attribute: group id of the audio renditions
+}
+
+// MediaRendition is one EXT-X-MEDIA entry of a master playlist. Only the
+// fields needed to detect unsupported track layouts are kept.
+type MediaRendition struct {
+	Type    string
+	GroupID string
+	URI     string
+}
+
+// MasterPlaylist is a parsed master playlist with its rendition groups.
+type MasterPlaylist struct {
+	Variants  []*Variant
+	Rendition map[string][]*MediaRendition // group id -> all EXT-X-MEDIA members
+}
+
+// Key is the decryption key applied to the segments that follow its tag, until
+// the next EXT-X-KEY tag or the end of the playlist.
+type Key struct {
+	Method string
+	URI    string // absolute URI
+	IV     []byte // explicit IV; nil means derive from the media sequence number
+}
+
+// ByteRange is an EXT-X-BYTERANGE sub range of the segment resource.
+type ByteRange struct {
+	Length int64
+	Offset int64
+}
+
+// Segment is one downloadable piece of a media playlist. The init section of
+// an fMP4 stream is represented as a segment with IsInit set.
+type Segment struct {
+	URI       string
+	Sequence  int64 // media sequence number, used to derive the default AES IV
+	Byterange *ByteRange
+	Key       *Key // nil means unencrypted
+	IsInit    bool
+	Gap       bool
+	Duration  float64
+	Size      int64 // exact size in bytes when known (byterange / HEAD probe), 0 when unknown
+}
+
+// Media is a parsed media playlist.
+type Media struct {
+	Segments      []*Segment
+	Version       int
+	Live          bool // no EXT-X-ENDLIST tag
+	IsFMP4        bool // playlist declares an init section via EXT-X-MAP
+	Discontinuity bool // playlist contains EXT-X-DISCONTINUITY
+}
+
+const (
+	keyMethodNone      = "NONE"
+	keyMethodAES128    = "AES-128"
+	keyMethodSampleAES = "SAMPLE-AES"
+)
+
+// IsMasterPlaylist reports whether the content looks like a master playlist.
+func IsMasterPlaylist(content string) bool {
+	return strings.Contains(content, "#EXT-X-STREAM-INF")
+}
+
+func validateM3U8Header(content string) error {
+	for _, line := range strings.Split(content, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		if line != "#EXTM3U" {
+			return errors.New("content is not a valid m3u8 playlist")
+		}
+		return nil
+	}
+	return errors.New("empty m3u8 playlist")
+}
+
+// ParseMaster parses a master playlist and returns all variants.
+func ParseMaster(content string, baseURL *url.URL) ([]*Variant, error) {
+	master, err := ParseMasterPlaylist(content, baseURL)
+	if err != nil {
+		return nil, err
+	}
+	return master.Variants, nil
+}
+
+// ParseMasterPlaylist parses a master playlist including its EXT-X-MEDIA
+// rendition groups.
+func ParseMasterPlaylist(content string, baseURL *url.URL) (*MasterPlaylist, error) {
+	if err := validateM3U8Header(content); err != nil {
+		return nil, err
+	}
+	master := &MasterPlaylist{Rendition: make(map[string][]*MediaRendition)}
+	var pending *Variant
+	for _, line := range strings.Split(content, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		if strings.HasPrefix(line, "#EXT-X-STREAM-INF:") {
+			attrs := parseAttributes(line[len("#EXT-X-STREAM-INF:"):])
+			pending = &Variant{
+				Bandwidth:    parseInt64(attrs["BANDWIDTH"]),
+				AvgBandwidth: parseInt64(attrs["AVERAGE-BANDWIDTH"]),
+				Resolution:   attrs["RESOLUTION"],
+				Codecs:       unquote(attrs["CODECS"]),
+				Name:         unquote(attrs["NAME"]),
+				AudioGroup:   unquote(attrs["AUDIO"]),
+			}
+			continue
+		}
+		if strings.HasPrefix(line, "#EXT-X-MEDIA:") {
+			attrs := parseAttributes(line[len("#EXT-X-MEDIA:"):])
+			rendition := &MediaRendition{
+				Type:    strings.ToUpper(attrs["TYPE"]),
+				GroupID: unquote(attrs["GROUP-ID"]),
+			}
+			// Only an explicit URI means a separate track; resolving an empty
+			// reference would fabricate one out of the playlist URL.
+			if uri := unquote(attrs["URI"]); uri != "" {
+				rendition.URI = resolveURL(baseURL, uri)
+			}
+			if rendition.GroupID != "" {
+				// Keep every member: a group is unsupported as a whole when
+				// ANY of its members carries its own URI.
+				master.Rendition[rendition.GroupID] = append(master.Rendition[rendition.GroupID], rendition)
+			}
+			continue
+		}
+		if pending != nil {
+			if line[0] != '#' {
+				pending.URI = resolveURL(baseURL, line)
+				master.Variants = append(master.Variants, pending)
+			}
+			pending = nil
+		}
+	}
+	if len(master.Variants) == 0 {
+		return nil, errors.New("master playlist has no variants")
+	}
+	return master, nil
+}
+
+// checkAudioRendition rejects the selected variant when its AUDIO group
+// carries a separate audio track: downloading only the video variant would
+// silently produce a silent file. Groups the variant does not reference are
+// ignored (variants without an AUDIO attribute are assumed self-contained).
+func checkAudioRendition(master *MasterPlaylist, best *Variant) error {
+	if best == nil || best.AudioGroup == "" {
+		return nil
+	}
+	for _, rendition := range master.Rendition[best.AudioGroup] {
+		if rendition == nil || rendition.Type != "AUDIO" || rendition.URI == "" {
+			continue
+		}
+		return fmt.Errorf(
+			"selected variant uses a separate audio rendition (group %q), which is not supported: the merged output would have no audio",
+			best.AudioGroup)
+	}
+	return nil
+}
+
+// PickBestVariant selects the highest-bandwidth variant.
+func PickBestVariant(variants []*Variant) *Variant {
+	var best *Variant
+	for _, v := range variants {
+		if best == nil || v.Bandwidth > best.Bandwidth {
+			best = v
+		}
+	}
+	return best
+}
+
+// ParseMedia parses a media playlist into an ordered segment plan.
+func ParseMedia(content string, baseURL *url.URL) (*Media, error) {
+	if err := validateM3U8Header(content); err != nil {
+		return nil, err
+	}
+
+	media := &Media{Live: true}
+	var currentKey *Key
+	var pendingByterange *ByteRange
+	var pendingGap bool
+	var pendingDuration float64
+	var lastRangeEnd int64
+	var sequence int64
+	var mapIdentity string // normalized identity of the current EXT-X-MAP
+
+	for _, line := range strings.Split(content, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		if line[0] != '#' {
+			// Every non-comment line in a media playlist is a segment URI.
+			seg := &Segment{
+				URI:       resolveURL(baseURL, line),
+				Sequence:  sequence,
+				Byterange: pendingByterange,
+				Key:       currentKey,
+				Gap:       pendingGap,
+				Duration:  pendingDuration,
+			}
+			if pendingByterange != nil {
+				// Byterange segments have exact sizes straight from the playlist.
+				seg.Size = pendingByterange.Length
+			}
+			sequence++
+			pendingByterange = nil
+			pendingGap = false
+			pendingDuration = 0
+			media.Segments = append(media.Segments, seg)
+			continue
+		}
+
+		switch {
+		case strings.HasPrefix(line, "#EXTINF:"):
+			value := line[len("#EXTINF:"):]
+			if idx := strings.Index(value, ","); idx >= 0 {
+				value = value[:idx]
+			}
+			pendingDuration = parseFloat(value)
+		case strings.HasPrefix(line, "#EXT-X-KEY:"):
+			key, err := parseKey(line[len("#EXT-X-KEY:"):], baseURL)
+			if err != nil {
+				return nil, err
+			}
+			currentKey = key
+		case strings.HasPrefix(line, "#EXT-X-MAP:"):
+			attrs := parseAttributes(line[len("#EXT-X-MAP:"):])
+			uriAttr := unquote(attrs["URI"])
+			if uriAttr == "" {
+				return nil, errors.New("EXT-X-MAP without URI is not supported")
+			}
+			resolved := resolveURL(baseURL, uriAttr)
+			// The init section identity covers every attribute, not just the
+			// URI: a repeated tag with a different BYTERANGE addresses
+			// different bytes and changes the init section. NUL keeps the
+			// two parts unambiguously separated.
+			identity := resolved + "\x00" + attrs["BYTERANGE"]
+			if mapIdentity != "" {
+				if mapIdentity != identity {
+					return nil, errors.New("changing init sections are not supported")
+				}
+				media.IsFMP4 = true
+				continue
+			}
+			mapIdentity = identity
+			init := &Segment{
+				URI:      resolved,
+				Sequence: sequence,
+				IsInit:   true,
+				Key:      currentKey,
+			}
+			if attrs["BYTERANGE"] != "" {
+				init.Byterange = parseByteRange(attrs["BYTERANGE"], 0)
+				if init.Byterange == nil {
+					return nil, fmt.Errorf("invalid EXT-X-MAP BYTERANGE: %s", attrs["BYTERANGE"])
+				}
+			}
+			if init.Key != nil && init.Key.IV == nil {
+				// RFC 8216 only defines sequence-derived IVs for media
+				// segments; guessing one for the init section produces
+				// corrupt output, so require the playlist to be explicit.
+				return nil, errors.New("encrypted EXT-X-MAP without an explicit IV is not supported")
+			}
+			// The init section is prepended to the segment plan, it takes
+			// the media sequence number of the playlist for IV derivation.
+			media.Segments = append(media.Segments, init)
+			media.IsFMP4 = true
+		case strings.HasPrefix(line, "#EXT-X-BYTERANGE:"):
+			pendingByterange = parseByteRange(line[len("#EXT-X-BYTERANGE:"):], lastRangeEnd)
+			if pendingByterange == nil {
+				return nil, fmt.Errorf("invalid EXT-X-BYTERANGE: %s", line)
+			}
+		case line == "#EXT-X-GAP":
+			pendingGap = true
+		case line == "#EXT-X-DISCONTINUITY":
+			media.Discontinuity = true
+		case line == "#EXT-X-ENDLIST":
+			media.Live = false
+		case strings.HasPrefix(line, "#EXT-X-MEDIA-SEQUENCE:"):
+			sequence = parseInt64(line[len("#EXT-X-MEDIA-SEQUENCE:"):])
+		case strings.HasPrefix(line, "#EXT-X-VERSION:"):
+			media.Version = int(parseInt64(line[len("#EXT-X-VERSION:"):]))
+		}
+
+		if pendingByterange != nil {
+			// Non-segment tags between BYTERANGE and its URI must not reset the
+			// running offset, so it is tracked here after each parse.
+			lastRangeEnd = pendingByterange.Offset + pendingByterange.Length
+		}
+	}
+
+	if len(media.Segments) == 0 {
+		return nil, errors.New("media playlist has no segments")
+	}
+	return media, nil
+}
+
+// validateSupported rejects playlist features the byte-concatenation merge
+// cannot reproduce faithfully. Skipping such features silently would report
+// success while producing a broken file.
+func validateSupported(media *Media) error {
+	if media.Live {
+		return errors.New("live streams are not supported yet")
+	}
+	if media.Discontinuity {
+		return errors.New("EXT-X-DISCONTINUITY is not supported: the merged output would have a broken timeline")
+	}
+	for _, seg := range media.Segments {
+		if seg.Gap {
+			return errors.New("EXT-X-GAP is not supported: the missing segment would leave a hole in the merged output")
+		}
+	}
+	return nil
+}
+
+func parseKey(attrs string, baseURL *url.URL) (*Key, error) {
+	parsed := parseAttributes(attrs)
+	switch method := parsed["METHOD"]; method {
+	case keyMethodNone:
+		return nil, nil
+	case keyMethodAES128:
+		uri := unquote(parsed["URI"])
+		if uri == "" {
+			return nil, errors.New("AES-128 EXT-X-KEY without URI")
+		}
+		if format := unquote(parsed["KEYFORMAT"]); format != "" && format != "identity" {
+			return nil, fmt.Errorf("unsupported EXT-X-KEY KEYFORMAT: %s", format)
+		}
+		key := &Key{Method: keyMethodAES128, URI: resolveURL(baseURL, uri)}
+		if iv, ok := parsed["IV"]; ok {
+			value := strings.TrimPrefix(strings.ToLower(iv), "0x")
+			decoded, err := hex.DecodeString(value)
+			if err != nil || len(decoded) != 16 {
+				return nil, fmt.Errorf("invalid EXT-X-KEY IV: %s", iv)
+			}
+			key.IV = decoded
+		}
+		return key, nil
+	case keyMethodSampleAES:
+		return nil, errors.New("SAMPLE-AES encryption is not supported")
+	default:
+		return nil, fmt.Errorf("unsupported encryption method: %s", method)
+	}
+}
+
+func parseByteRange(value string, defaultOffset int64) *ByteRange {
+	lengthPart := value
+	offsetPart := ""
+	if idx := strings.Index(value, "@"); idx >= 0 {
+		lengthPart = value[:idx]
+		offsetPart = value[idx+1:]
+	}
+	length := parseInt64(lengthPart)
+	if length <= 0 {
+		return nil
+	}
+	offset := defaultOffset
+	if offsetPart != "" {
+		offset = parseInt64(offsetPart)
+		if offset < 0 {
+			return nil
+		}
+	}
+	return &ByteRange{Length: length, Offset: offset}
+}
+
+// resolveURL resolves a playlist URI reference against the playlist URL
+// following RFC 3986.
+func resolveURL(baseURL *url.URL, ref string) string {
+	refURL, err := url.Parse(ref)
+	if err != nil {
+		return ref
+	}
+	return baseURL.ResolveReference(refURL).String()
+}
+
+// parseAttributes parses an HLS attribute list like FOO="bar",NUM=42.
+func parseAttributes(s string) map[string]string {
+	attrs := make(map[string]string)
+	var key, val strings.Builder
+	inKey := true
+	inQuote := false
+	flush := func() {
+		name := strings.ToUpper(strings.TrimSpace(key.String()))
+		if name != "" {
+			attrs[name] = strings.TrimSpace(val.String())
+		}
+		key.Reset()
+		val.Reset()
+		inKey = true
+	}
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if inKey {
+			if c == '=' {
+				inKey = false
+			} else {
+				key.WriteByte(c)
+			}
+			continue
+		}
+		if c == '"' {
+			inQuote = !inQuote
+			continue
+		}
+		if c == ',' && !inQuote {
+			flush()
+			continue
+		}
+		val.WriteByte(c)
+	}
+	flush()
+	return attrs
+}
+
+func unquote(s string) string {
+	s = strings.TrimSpace(s)
+	if len(s) >= 2 && strings.HasPrefix(s, "\"") && strings.HasSuffix(s, "\"") {
+		return s[1 : len(s)-1]
+	}
+	return s
+}
+
+func parseInt64(s string) int64 {
+	value, _ := strconv.ParseInt(strings.TrimSpace(s), 10, 64)
+	return value
+}
+
+func parseFloat(s string) float64 {
+	value, _ := strconv.ParseFloat(strings.TrimSpace(s), 64)
+	return value
+}
+
+// OutputExtension returns the container file extension for the playlist.
+func (m *Media) OutputExtension() string {
+	if m.IsFMP4 {
+		return ".mp4"
+	}
+	return ".ts"
+}
+
+// DeriveOutputName builds the merged output file name from a playlist URL.
+func DeriveOutputName(playlistURL string, media *Media) string {
+	name := ""
+	if u, err := url.Parse(playlistURL); err == nil {
+		name = path.Base(u.Path)
+		name = strings.TrimSuffix(name, path.Ext(name))
+	}
+	if name == "" || name == "/" || name == "." {
+		if u, err := url.Parse(playlistURL); err == nil {
+			name = u.Hostname()
+		}
+	}
+	return name + media.OutputExtension()
+}

internal/protocol/hls/playlist_realworld_test.go

@@ -0,0 +1,39 @@
+package hls
+
+import (
+	_ "embed"
+	"net/url"
+	"testing"
+)
+
+//go:embed testdata/olemovienews.m3u8
+var realWorldPlaylist string
+
+// TestParseMediaRealWorld guards parsing against a real site playlist
+// (olemovienews.com VOD, 138 TS segments).
+func TestParseMediaRealWorld(t *testing.T) {
+	base, err := url.Parse("https://europe.olemovienews.com/ts2/20230125/afAxfjit/mp4/afAxfjit.mp4/index-v1-a1.m3u8")
+	if err != nil {
+		t.Fatal(err)
+	}
+	media, err := ParseMedia(realWorldPlaylist, base)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if media.Live {
+		t.Error("real VOD playlist should not be live")
+	}
+	if media.IsFMP4 {
+		t.Error("playlist should be detected as TS")
+	}
+	if len(media.Segments) != 138 {
+		t.Errorf("want 138 segments, got %d", len(media.Segments))
+	}
+	first := media.Segments[0]
+	if first.URI != "https://europe.olemovienews.com/ts2/20230125/afAxfjit/mp4/afAxfjit.mp4/seg-1-v1-a1.ts" {
+		t.Errorf("segment URI resolution wrong: %s", first.URI)
+	}
+	if media.Segments[0].Sequence != 1 {
+		t.Errorf("first sequence = %d, want 1", media.Segments[0].Sequence)
+	}
+}

internal/protocol/hls/playlist_test.go

@@ -0,0 +1,252 @@
+package hls
+
+import (
+	"net/url"
+	"testing"
+)
+
+func mustURL(t *testing.T, raw string) *url.URL {
+	t.Helper()
+	u, err := url.Parse(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return u
+}
+
+func TestParseMediaTS(t *testing.T) {
+	content := "#EXTM3U\n" +
+		"#EXT-X-TARGETDURATION:20\n" +
+		"#EXT-X-VERSION:3\n" +
+		"#EXT-X-MEDIA-SEQUENCE:1\n" +
+		"#EXTINF:20.000,\n" +
+		"seg-1.ts\n" +
+		"#EXTINF:20.000,\n" +
+		"seg-2.ts\n" +
+		"#EXT-X-ENDLIST\n"
+	media, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/vod/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if media.Live {
+		t.Error("VOD playlist should not be live")
+	}
+	if media.IsFMP4 {
+		t.Error("TS playlist should not be fMP4")
+	}
+	if len(media.Segments) != 2 {
+		t.Fatalf("want 2 segments, got %d", len(media.Segments))
+	}
+	want := "https://cdn.example.com/vod/seg-1.ts"
+	if media.Segments[0].URI != want {
+		t.Errorf("want uri %s, got %s", want, media.Segments[0].URI)
+	}
+	if media.Segments[0].Sequence != 1 {
+		t.Errorf("want sequence 1, got %d", media.Segments[0].Sequence)
+	}
+	if media.Segments[0].Key != nil {
+		t.Error("segment should be unencrypted")
+	}
+}
+
+func TestParseMediaWithoutExtinf(t *testing.T) {
+	// Some playlists list segment URIs without EXTINF lines.
+	content := "#EXTM3U\nseg-1.ts\nseg-2.ts\n#EXT-X-ENDLIST\n"
+	media, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/a/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(media.Segments) != 2 {
+		t.Fatalf("want 2 segments, got %d", len(media.Segments))
+	}
+}
+
+func TestParseMediaLive(t *testing.T) {
+	content := "#EXTM3U\n#EXT-X-TARGETDURATION:6\n#EXTINF:6.0,\nseg-1.ts\n"
+	media, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/live/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !media.Live {
+		t.Error("playlist without ENDLIST should be live")
+	}
+}
+
+func TestParseMediaFMP4(t *testing.T) {
+	content := "#EXTM3U\n" +
+		"#EXT-X-VERSION:6\n" +
+		"#EXT-X-MAP:URI=\"init.mp4\"\n" +
+		"#EXTINF:5.0,\n" +
+		"seg-1.m4s\n" +
+		"#EXT-X-ENDLIST\n"
+	media, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/vod/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !media.IsFMP4 {
+		t.Error("playlist with MAP should be fMP4")
+	}
+	if len(media.Segments) != 2 {
+		t.Fatalf("want 2 segments (init + 1), got %d", len(media.Segments))
+	}
+	if !media.Segments[0].IsInit {
+		t.Error("first segment should be the init section")
+	}
+	if media.Segments[0].URI != "https://cdn.example.com/vod/init.mp4" {
+		t.Errorf("init uri wrong: %s", media.Segments[0].URI)
+	}
+	if media.OutputExtension() != ".mp4" {
+		t.Errorf("want .mp4, got %s", media.OutputExtension())
+	}
+}
+
+func TestParseMediaMultiMapError(t *testing.T) {
+	content := "#EXTM3U\n" +
+		"#EXT-X-MAP:URI=\"init1.mp4\"\n" +
+		"#EXTINF:5.0,\nseg-1.m4s\n" +
+		"#EXT-X-DISCONTINUITY\n" +
+		"#EXT-X-MAP:URI=\"init2.mp4\"\n" +
+		"#EXTINF:5.0,\nseg-2.m4s\n" +
+		"#EXT-X-ENDLIST\n"
+	if _, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/vod/index.m3u8")); err == nil {
+		t.Error("multi-period fMP4 should be rejected")
+	}
+}
+
+func TestParseMediaKeyRotation(t *testing.T) {
+	content := "#EXTM3U\n" +
+		"#EXT-X-KEY:METHOD=AES-128,URI=\"key1.bin\",IV=0x00000000000000000000000000000001\n" +
+		"#EXTINF:5.0,\nseg-1.ts\n" +
+		"#EXT-X-KEY:METHOD=AES-128,URI=\"key2.bin\"\n" +
+		"#EXTINF:5.0,\nseg-2.ts\n" +
+		"#EXT-X-KEY:METHOD=NONE\n" +
+		"#EXTINF:5.0,\nseg-3.ts\n" +
+		"#EXT-X-ENDLIST\n"
+	media, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/vod/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if media.Segments[0].Key == nil || media.Segments[0].Key.URI != "https://cdn.example.com/vod/key1.bin" {
+		t.Fatalf("segment 1 key wrong: %+v", media.Segments[0].Key)
+	}
+	if len(media.Segments[0].Key.IV) != 16 || media.Segments[0].Key.IV[15] != 1 {
+		t.Error("explicit IV not parsed")
+	}
+	if media.Segments[1].Key == nil || media.Segments[1].Key.URI != "https://cdn.example.com/vod/key2.bin" {
+		t.Fatalf("segment 2 key wrong: %+v", media.Segments[1].Key)
+	}
+	if media.Segments[1].Key.IV != nil {
+		t.Error("key without IV should leave IV nil (sequence-derived)")
+	}
+	if media.Segments[2].Key != nil {
+		t.Error("segment 3 should be unencrypted after METHOD=NONE")
+	}
+}
+
+func TestParseMediaSampleAESError(t *testing.T) {
+	content := "#EXTM3U\n#EXT-X-KEY:METHOD=SAMPLE-AES,URI=\"skd://key\"\n#EXTINF:5.0,\nseg-1.ts\n"
+	if _, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/vod/index.m3u8")); err == nil {
+		t.Error("SAMPLE-AES should be rejected")
+	}
+}
+
+func TestParseMediaByterange(t *testing.T) {
+	content := "#EXTM3U\n" +
+		"#EXT-X-BYTERANGE:1000@0\nseg.ts\n" +
+		"#EXT-X-BYTERANGE:2000\nseg.ts\n" +
+		"#EXT-X-BYTERANGE:3000\nseg.ts\n" +
+		"#EXT-X-ENDLIST\n"
+	media, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/vod/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	ranges := [][2]int64{{0, 1000}, {1000, 2000}, {3000, 3000}}
+	for i, want := range ranges {
+		br := media.Segments[i].Byterange
+		if br == nil {
+			t.Fatalf("segment %d byterange missing", i)
+		}
+		if br.Offset != want[0] || br.Length != want[1] {
+			t.Errorf("segment %d: want offset %d length %d, got %d/%d", i, want[0], want[1], br.Offset, br.Length)
+		}
+	}
+}
+
+func TestParseMediaGap(t *testing.T) {
+	content := "#EXTM3U\n#EXTINF:5.0,\nseg-1.ts\n#EXT-X-GAP\n#EXTINF:5.0,\nseg-2.ts\n#EXT-X-ENDLIST\n"
+	media, err := ParseMedia(content, mustURL(t, "https://cdn.example.com/vod/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if media.Segments[0].Gap || !media.Segments[1].Gap {
+		t.Error("gap flags wrong")
+	}
+}
+
+func TestParseMediaInvalidHeader(t *testing.T) {
+	if _, err := ParseMedia("not a playlist", mustURL(t, "https://cdn.example.com/a.m3u8")); err == nil {
+		t.Error("invalid content should be rejected")
+	}
+}
+
+func TestParseMasterPickBest(t *testing.T) {
+	content := "#EXTM3U\n" +
+		"#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID=\"aud\",NAME=\"en\",DEFAULT=YES,URI=\"audio/index.m3u8\"\n" +
+		"#EXT-X-STREAM-INF:BANDWIDTH=800000,RESOLUTION=640x360\n" +
+		"360p/index.m3u8\n" +
+		"#EXT-X-STREAM-INF:BANDWIDTH=2500000,RESOLUTION=1920x1080,CODECS=\"avc1.640028,mp4a.40.2\"\n" +
+		"1080p/index.m3u8?sign=abc\n" +
+		"#EXT-X-ENDLIST\n"
+	variants, err := ParseMaster(content, mustURL(t, "https://cdn.example.com/vod/master.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(variants) != 2 {
+		t.Fatalf("want 2 variants, got %d", len(variants))
+	}
+	best := PickBestVariant(variants)
+	if best.Bandwidth != 2500000 {
+		t.Errorf("want highest bandwidth variant, got %d", best.Bandwidth)
+	}
+	if best.URI != "https://cdn.example.com/vod/1080p/index.m3u8?sign=abc" {
+		t.Errorf("variant uri wrong: %s", best.URI)
+	}
+}
+
+func TestResolveURLQueryNotInherited(t *testing.T) {
+	base := mustURL(t, "https://cdn.example.com/vod/index.m3u8?sign=abc")
+	got := resolveURL(base, "seg-1.ts")
+	if got != "https://cdn.example.com/vod/seg-1.ts" {
+		t.Errorf("relative resolution should follow RFC3986 (no query inheritance), got %s", got)
+	}
+}
+
+func TestDeriveOutputName(t *testing.T) {
+	media := &Media{}
+	if got := DeriveOutputName("https://cdn.example.com/ts2/a/index-v1-a1.m3u8", media); got != "index-v1-a1.ts" {
+		t.Errorf("want index-v1-a1.ts, got %s", got)
+	}
+	fmp4 := &Media{IsFMP4: true}
+	if got := DeriveOutputName("https://cdn.example.com/ts2/a/index.m3u8", fmp4); got != "index.mp4" {
+		t.Errorf("want index.mp4, got %s", got)
+	}
+	if got := DeriveOutputName("https://cdn.example.com/play?token=x", media); got != "play.ts" {
+		t.Errorf("want play.ts, got %s", got)
+	}
+	if got := DeriveOutputName("https://cdn.example.com/", media); got != "cdn.example.com.ts" {
+		t.Errorf("want host fallback, got %s", got)
+	}
+}
+
+func TestParseAttributesQuotedComma(t *testing.T) {
+	attrs := parseAttributes(`URI="a,b.ts",IV=0xABCDEF00000000000000000000000001,NAME="x"`)
+	if attrs["URI"] != "a,b.ts" {
+		t.Errorf("quoted comma value wrong: %q", attrs["URI"])
+	}
+	if attrs["IV"] != "0xABCDEF00000000000000000000000001" {
+		t.Errorf("hex value wrong: %q", attrs["IV"])
+	}
+	if attrs["NAME"] != "x" {
+		t.Errorf("quoted value wrong: %q", attrs["NAME"])
+	}
+}

internal/protocol/hls/staging_test.go

@@ -0,0 +1,296 @@
+package hls
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+)
+
+func TestFetcherE2E_SameURLTwoTasks(t *testing.T) {
+	const total = 6
+	mux := http.NewServeMux()
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	for i := 0; i < total; i++ {
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	segments := make(map[int][]byte)
+	for i := 0; i < total; i++ {
+		segments[i] = []byte(fmt.Sprintf("SHARED-SEGMENT-%02d", i))
+		idx := i
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", idx), func(w http.ResponseWriter, r *http.Request) {
+			time.Sleep(120 * time.Millisecond)
+			w.Write(segments[idx])
+		})
+	}
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	cfg := testConfig()
+	cfg.SegmentConnections = 2
+	cfg.PrefetchContentLength = false
+	dir := t.TempDir()
+
+	// Two tasks for the same playlist URL into the same directory, like a
+	// 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 {
+		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 {
+		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)
+	}
+
+	// Start task 1, let it stage some segments, then pause it.
+	if err := f1.Start(); err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(250 * time.Millisecond)
+	if err := f1.Pause(); err != nil {
+		t.Fatal(err)
+	}
+	staged1, err := os.ReadDir(f1.state.StagingDir)
+	if err != nil || len(staged1) == 0 {
+		t.Fatalf("task 1 should have staged segments, dir: %s", f1.state.StagingDir)
+	}
+
+	// Task 2 must complete without touching task 1's staging data...
+	if err := f2.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f2.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	stillThere, err := os.ReadDir(f1.state.StagingDir)
+	if err != nil || len(stillThere) != len(staged1) {
+		t.Fatalf("task 2 disturbed task 1 staging: had %d entries, now %d", len(staged1), len(stillThere))
+	}
+
+	// ...and task 1 resumes to a complete, correct output of its own.
+	if err := f1.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f1.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	var want []byte
+	for i := 0; i < total; i++ {
+		want = append(want, segments[i]...)
+	}
+	if !bytes.Equal(readOutput(t, f1), want) || !bytes.Equal(readOutput(t, f2), want) {
+		t.Error("same-URL task outputs mismatch")
+	}
+	entries, _ := os.ReadDir(dir)
+	if len(entries) != 2 {
+		names := make([]string, 0, len(entries))
+		for _, e := range entries {
+			names = append(names, e.Name())
+		}
+		t.Errorf("expected only the two outputs to remain, got %v", names)
+	}
+}
+
+func TestFetcherE2E_ForeignJournalDiscarded(t *testing.T) {
+	const total = 3
+	var served atomic.Int64
+	mux := http.NewServeMux()
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	for i := 0; i < total; i++ {
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	for i := 0; i < total; i++ {
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", i), func(w http.ResponseWriter, r *http.Request) {
+			served.Add(1)
+			w.Write([]byte("DATA"))
+		})
+	}
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	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 {
+		t.Fatal(err)
+	}
+	// Plant a journal that does not belong to this plan (wrong fingerprint).
+	tempDir := f.resolveStagingDirLocked()
+	if err := os.MkdirAll(tempDir, 0777); err != nil {
+		t.Fatal(err)
+	}
+	foreign := journalFile{
+		StagingID:    "some-other-task",
+		PlanHash:     "deadbeef",
+		SegmentCount: total,
+		Sizes:        map[string]int64{"0": 4, "1": 4, "2": 4},
+	}
+	data, _ := json.Marshal(foreign)
+	if err := os.WriteFile(filepath.Join(tempDir, "journal.json"), data, 0666); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	if got := served.Load(); got != total {
+		t.Errorf("foreign journal must be discarded, want %d downloads, got %d", total, got)
+	}
+}
+
+func TestFetcherE2E_MergeFailurePreservesStaging(t *testing.T) {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("#EXTM3U\n#EXTINF:4,\na.ts\n#EXTINF:4,\nb.ts\n#EXT-X-ENDLIST\n"))
+	})
+	mux.HandleFunc("/a.ts", func(w http.ResponseWriter, r *http.Request) { w.Write([]byte("AAAA")) })
+	mux.HandleFunc("/b.ts", func(w http.ResponseWriter, r *http.Request) { w.Write([]byte("BBBB")) })
+	server := httptest.NewServer(mux)
+	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 {
+		t.Fatal(err)
+	}
+	run := &hlsRun{
+		ctx:        context.Background(),
+		cancel:     func() {},
+		done:       make(chan struct{}),
+		segs:       f.state.Segments,
+		outputPath: f.meta.SingleFilepath(),
+		stagingID:  f.state.StagingID,
+		planHash:   planFingerprint(f.state),
+		tempDir:    f.resolveStagingDirLocked(),
+		keyCache:   make(map[string][]byte),
+		journal:    make(map[int64]int64),
+	}
+	run.journalPath = filepath.Join(run.tempDir, "journal.json")
+	if err := os.MkdirAll(run.tempDir, 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(segmentPath(run.tempDir, 0), []byte("AAAA"), 0666); err != nil {
+		t.Fatal(err)
+	}
+	// Segment 1 is missing on disk: the merge must fail without deleting the
+	// staged data or leaving a partial output behind.
+	if err := f.merge(run); err == nil {
+		t.Fatal("merge with a missing segment should fail")
+	}
+	if _, err := os.Stat(segmentPath(run.tempDir, 0)); err != nil {
+		t.Fatal("merge failure must preserve staged segments")
+	}
+	entries, _ := os.ReadDir(filepath.Dir(run.outputPath))
+	for _, e := range entries {
+		if strings.HasSuffix(e.Name(), ".part") {
+			t.Errorf("failed merge left a partial output behind: %s", e.Name())
+		}
+	}
+
+	// Recover the segment: the retried merge succeeds.
+	if err := os.WriteFile(segmentPath(run.tempDir, 1), []byte("BBBB"), 0666); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.merge(run); err != nil {
+		t.Fatalf("retried merge failed: %v", err)
+	}
+	got, err := os.ReadFile(run.outputPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "AAAABBBB" {
+		t.Errorf("retried merge output mismatch: %q", got)
+	}
+}
+
+func TestFetcherE2E_ReMergeOverExistingOutput(t *testing.T) {
+	const total = 2
+	mux := http.NewServeMux()
+	var playlist strings.Builder
+	playlist.WriteString("#EXTM3U\n")
+	for i := 0; i < total; i++ {
+		playlist.WriteString(fmt.Sprintf("#EXTINF:4,\nseg-%d.ts\n", i))
+	}
+	playlist.WriteString("#EXT-X-ENDLIST\n")
+	mux.HandleFunc("/video.m3u8", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(playlist.String()))
+	})
+	for i := 0; i < total; i++ {
+		mux.HandleFunc(fmt.Sprintf("/seg-%d.ts", i), func(w http.ResponseWriter, r *http.Request) {
+			w.Write([]byte("DATA"))
+		})
+	}
+	server := httptest.NewServer(mux)
+	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 {
+		t.Fatal(err)
+	}
+	tempDir := f.resolveStagingDirLocked()
+	if err := os.MkdirAll(tempDir, 0777); err != nil {
+		t.Fatal(err)
+	}
+	// Simulate the crash window after a completed rename but before the task
+	// was marked done: a stale output file, a complete journal and all
+	// segments staged.
+	stale := filepath.Join(filepath.Dir(f.meta.SingleFilepath()), f.state.OutputName)
+	if err := os.WriteFile(stale, []byte("STALE-OUTPUT"), 0666); err != nil {
+		t.Fatal(err)
+	}
+	jr := &hlsRun{
+		segs:        f.state.Segments,
+		stagingID:   f.state.StagingID,
+		planHash:    planFingerprint(f.state),
+		journalPath: filepath.Join(tempDir, "journal.json"),
+		journal:     map[int64]int64{0: 4, 1: 4},
+	}
+	if err := saveJournal(jr); err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < total; i++ {
+		if err := os.WriteFile(segmentPath(tempDir, int64(i)), []byte("DATA"), 0666); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	if err := f.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Wait(); err != nil {
+		t.Fatalf("re-merge over an existing output failed: %v", err)
+	}
+	got, err := os.ReadFile(stale)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "DATADATA" {
+		t.Errorf("stale output was not replaced: %q", got)
+	}
+}

internal/protocol/hls/subset_test.go

@@ -0,0 +1,146 @@
+package hls
+
+import (
+	"net/url"
+	"strings"
+	"testing"
+)
+
+func mustParseURL(t *testing.T, raw string) *url.URL {
+	t.Helper()
+	u, err := url.Parse(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return u
+}
+
+// subsetCase is a media playlist plus the error substring the pipeline must
+// reject it with; wantOK playlists must parse AND validate cleanly.
+type subsetCase struct {
+	name     string
+	playlist string
+	wantErr  string
+}
+
+func TestSubsetRejections(t *testing.T) {
+	cases := []subsetCase{
+		{
+			name:     "gap",
+			playlist: "#EXTM3U\n#EXTINF:4,\na.ts\n#EXT-X-GAP\n#EXTINF:4,\nb.ts\n#EXT-X-ENDLIST\n",
+			wantErr:  "EXT-X-GAP",
+		},
+		{
+			name:     "gap-before-first-segment",
+			playlist: "#EXTM3U\n#EXT-X-GAP\n#EXTINF:4,\na.ts\n#EXT-X-ENDLIST\n",
+			wantErr:  "EXT-X-GAP",
+		},
+		{
+			name:     "discontinuity",
+			playlist: "#EXTM3U\n#EXTINF:4,\na.ts\n#EXT-X-DISCONTINUITY\n#EXTINF:4,\nb.ts\n#EXT-X-ENDLIST\n",
+			wantErr:  "EXT-X-DISCONTINUITY",
+		},
+		{
+			name:     "live",
+			playlist: "#EXTM3U\n#EXTINF:4,\na.ts\n",
+			wantErr:  "live",
+		},
+		{
+			name:     "keyformat",
+			playlist: "#EXTM3U\n#EXT-X-KEY:METHOD=AES-128,URI=\"k\",KEYFORMAT=\"com.apple.streamingkeydelivery\"\n#EXTINF:4,\na.ts\n#EXT-X-ENDLIST\n",
+			wantErr:  "KEYFORMAT",
+		},
+		{
+			name:     "encrypted-map-without-iv",
+			playlist: "#EXTM3U\n#EXT-X-KEY:METHOD=AES-128,URI=\"k\"\n#EXT-X-MAP:URI=\"init.mp4\"\n#EXTINF:4,\na.m4s\n#EXT-X-ENDLIST\n",
+			wantErr:  "explicit IV",
+		},
+		{
+			name:     "map-change-byterange",
+			playlist: "#EXTM3U\n#EXT-X-MAP:URI=\"init.mp4\",BYTERANGE=\"100@0\"\n#EXTINF:4,\na.m4s\n#EXT-X-MAP:URI=\"init.mp4\",BYTERANGE=\"100@100\"\n#EXTINF:4,\nb.m4s\n#EXT-X-ENDLIST\n",
+			wantErr:  "changing init sections",
+		},
+		{
+			name:     "map-change-uri",
+			playlist: "#EXTM3U\n#EXT-X-MAP:URI=\"init1.mp4\"\n#EXTINF:4,\na.m4s\n#EXT-X-MAP:URI=\"init2.mp4\"\n#EXTINF:4,\nb.m4s\n#EXT-X-ENDLIST\n",
+			wantErr:  "changing init sections",
+		},
+	}
+	baseURL := mustParseURL(t, "https://cdn.example.com/vod/index.m3u8")
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			media, parseErr := ParseMedia(tc.playlist, baseURL)
+			if parseErr != nil {
+				if !strings.Contains(parseErr.Error(), tc.wantErr) {
+					t.Fatalf("parse error %q does not mention %q", parseErr, tc.wantErr)
+				}
+				return
+			}
+			err := validateSupported(media)
+			if err == nil {
+				t.Fatalf("playlist should be rejected with %q", tc.wantErr)
+			}
+			if !strings.Contains(err.Error(), tc.wantErr) {
+				t.Fatalf("error %q does not mention %q", err, tc.wantErr)
+			}
+		})
+	}
+}
+
+func TestSubsetRepeatedSameMapAllowed(t *testing.T) {
+	playlist := "#EXTM3U\n" +
+		"#EXT-X-MAP:URI=\"init.mp4\",BYTERANGE=\"100@0\"\n" +
+		"#EXTINF:4,\na.m4s\n" +
+		"#EXT-X-MAP:URI=\"init.mp4\",BYTERANGE=\"100@0\"\n" +
+		"#EXTINF:4,\nb.m4s\n" +
+		"#EXT-X-ENDLIST\n"
+	media, err := ParseMedia(playlist, mustParseURL(t, "https://cdn.example.com/vod/index.m3u8"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := validateSupported(media); err != nil {
+		t.Fatalf("identical repeated MAP must be allowed: %v", err)
+	}
+	if len(media.Segments) != 3 { // init + 2 segments, no duplicate init
+		t.Fatalf("want 3 segments (init + 2), got %d", len(media.Segments))
+	}
+}
+
+func TestMasterAudioRenditionDetection(t *testing.T) {
+	masterURL := mustParseURL(t, "https://cdn.example.com/master.m3u8")
+
+	separateAudio := "#EXTM3U\n" +
+		"#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID=\"aud\",NAME=\"en\",DEFAULT=YES,URI=\"audio/index.m3u8\"\n" +
+		"#EXT-X-STREAM-INF:BANDWIDTH=1000000,AUDIO=\"aud\"\nvideo/index.m3u8\n"
+	master, err := ParseMasterPlaylist(separateAudio, masterURL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := checkAudioRendition(master, PickBestVariant(master.Variants)); err == nil {
+		t.Fatal("selected variant with a separate audio rendition must be rejected")
+	}
+
+	// A group the variant does not reference must not cause a false positive.
+	unrelatedGroup := "#EXTM3U\n" +
+		"#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID=\"aud\",NAME=\"en\",DEFAULT=YES,URI=\"audio/index.m3u8\"\n" +
+		"#EXT-X-STREAM-INF:BANDWIDTH=1000000\nvideo/index.m3u8\n"
+	master, err = ParseMasterPlaylist(unrelatedGroup, masterURL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := checkAudioRendition(master, PickBestVariant(master.Variants)); err != nil {
+		t.Fatalf("unreferenced audio group must not be rejected: %v", err)
+	}
+
+	// A rendition group without URIs (muxed tracks) is fine.
+	groupWithoutURI := "#EXTM3U\n" +
+		"#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID=\"aud\",NAME=\"en\",DEFAULT=YES\n" +
+		"#EXT-X-STREAM-INF:BANDWIDTH=1000000,AUDIO=\"aud\"\nvideo/index.m3u8\n"
+	master, err = ParseMasterPlaylist(groupWithoutURI, masterURL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := checkAudioRendition(master, PickBestVariant(master.Variants)); err != nil {
+		t.Fatalf("audio group without URI must not be rejected: %v", err)
+	}
+}

internal/protocol/hls/testdata/media/README.md

@@ -0,0 +1,10 @@
+Media fixtures generated locally with FFmpeg 7.0.2 (testsrc + sine sources,
+no third-party content):
+
+- sample-00.ts / sample-01.ts: one continuous MPEG-2 TS encode split at a
+  packet boundary, so continuity counters and PCR are consistent across the
+  segment join exactly like segments cut from a single real-time stream.
+- fmp4-init.mp4: ftyp+moov init section of a fragmented MP4.
+- fmp4-seg1.m4s .. fmp4-seg3.m4s: moof+mdat media fragments (styp omitted by
+  the muxer, which is legal) split at moof boundaries from one fragmented MP4
+  (-movflags +frag_keyframe+empty_moov+default_base_moof -frag_duration 500000).

internal/protocol/hls/testdata/olemovienews.m3u8

@@ -0,0 +1,283 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:20
+#EXT-X-ALLOW-CACHE:YES
+#EXT-X-PLAYLIST-TYPE:VOD
+#EXT-X-VERSION:3
+#EXT-X-MEDIA-SEQUENCE:1
+#EXTINF:20.000,
+seg-1-v1-a1.ts
+#EXTINF:20.000,
+seg-2-v1-a1.ts
+#EXTINF:20.000,
+seg-3-v1-a1.ts
+#EXTINF:20.000,
+seg-4-v1-a1.ts
+#EXTINF:20.000,
+seg-5-v1-a1.ts
+#EXTINF:20.000,
+seg-6-v1-a1.ts
+#EXTINF:20.000,
+seg-7-v1-a1.ts
+#EXTINF:20.000,
+seg-8-v1-a1.ts
+#EXTINF:20.000,
+seg-9-v1-a1.ts
+#EXTINF:20.000,
+seg-10-v1-a1.ts
+#EXTINF:20.000,
+seg-11-v1-a1.ts
+#EXTINF:20.000,
+seg-12-v1-a1.ts
+#EXTINF:20.000,
+seg-13-v1-a1.ts
+#EXTINF:20.000,
+seg-14-v1-a1.ts
+#EXTINF:20.000,
+seg-15-v1-a1.ts
+#EXTINF:20.000,
+seg-16-v1-a1.ts
+#EXTINF:20.000,
+seg-17-v1-a1.ts
+#EXTINF:20.000,
+seg-18-v1-a1.ts
+#EXTINF:20.000,
+seg-19-v1-a1.ts
+#EXTINF:20.000,
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internal/protocol/http/config.go

@@ -1,5 +1,8 @@
 package http
 
+// DefaultUserAgent is shared by HTTP downloads and extension HTTP requests.
+const DefaultUserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36"
+
 type config struct {
 	UserAgent      string `json:"userAgent"`
 	Connections    int    `json:"connections"`

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"
@@ -150,7 +155,7 @@ type slowStartController struct {
 	totalLaunched  int
 	batchPending   int           // Connections in current batch waiting for HTTP response
 	batchReady     int           // Connections in current batch that succeeded
-	nextBatchSize  int           // Next batch size: 1, 2, 4, 8...
+	nextBatchSize  int           // Next batch size: 1, 2, 4, 16, 256... (capped)
 	expansionCh    chan struct{} // Signal to trigger next expansion
 	paused         bool          // Pause expansion (e.g., on 429)
 }
@@ -229,7 +234,15 @@ func (s *slowStartController) commitBatch(count int) {
 	defer s.mu.Unlock()
 
 	s.totalLaunched += count
-	s.nextBatchSize = s.nextBatchSize * 2 // Exponential growth: 1, 2, 4, 8...
+	if s.nextBatchSize == 1 {
+		// Bootstrap growth: squaring one would never increase the batch size.
+		s.nextBatchSize = min(2, s.maxConnections)
+	} else if s.nextBatchSize > s.maxConnections/s.nextBatchSize {
+		// Cap before multiplying to avoid integer overflow.
+		s.nextBatchSize = s.maxConnections
+	} else {
+		s.nextBatchSize *= s.nextBatchSize
+	}
 	s.batchPending = count
 	s.batchReady = 0
 }
@@ -272,6 +285,12 @@ 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
@@ -363,20 +382,9 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 		f.meta.Opts = &base.Options{}
 	}
 
-	// Parse options
-	if err := base.ParseOptExtra[fhttp.OptsExtra](opts); err != nil {
+	if err := f.initOptions(); err != nil {
 		return err
 	}
-	if opts.Extra == nil {
-		opts.Extra = &fhttp.OptsExtra{}
-	}
-	extra := opts.Extra.(*fhttp.OptsExtra)
-	if extra.Connections <= 0 {
-		extra.Connections = f.config.Connections
-		if extra.Connections <= 0 {
-			extra.Connections = 1
-		}
-	}
 
 	f.setState(stateResolving)
 
@@ -420,12 +428,26 @@ 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()
+			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
+			}
 		}
 	}
 
@@ -459,6 +481,7 @@ func (f *Fetcher) Resolve(req *base.Request, opts *base.Options) error {
 	if file.Name == "" || file.Name == "/" || file.Name == "." {
 		file.Name = httpReq.URL.Hostname()
 	}
+	file.Name = appendFilenameExtension(file.Name, resp.Header.Get("Content-Type"))
 
 	res.Files = append(res.Files, file)
 	f.meta.Res = res
@@ -469,7 +492,12 @@ 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
+	} else {
+		resp.Body.Close()
+		f.prefetchDone.Store(true)
+	}
 	f.resolveRespLock.Unlock()
 
 	f.setState(stateResolved)
@@ -481,7 +509,7 @@ 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()
@@ -511,17 +539,9 @@ func (f *Fetcher) asyncPrefetch() {
 		return
 	}
 
-	// Create temporary file for prefetch data
-	tmpFile, err := os.CreateTemp("", "gopeed-prefetch-*")
-	if err != nil {
-		f.prefetchErr = err
-		return
-	}
-	f.prefetchFile = tmpFile
-	f.prefetchFilePath = tmpFile.Name()
-
 	defer func() {
-		// Close response body when prefetch stops
+		// 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()
@@ -530,8 +550,33 @@ func (f *Fetcher) asyncPrefetch() {
 		f.resolveRespLock.Unlock()
 	}()
 
+	// Create temporary file for prefetch data
+	tempDir := ""
+	if f.ctl != nil && f.ctl.TempDir != "" {
+		tempDir = f.ctl.TempDir
+		if err := os.MkdirAll(tempDir, 0700); err != nil {
+			f.prefetchErr = err
+			return
+		}
+	}
+	tmpFile, err := os.CreateTemp(tempDir, "gopeed-prefetch-*")
+	if err != nil {
+		f.prefetchErr = err
+		return
+	}
+	if f.ctl != nil {
+		if err := f.ctl.TempFiles.Track(tmpFile.Name()); err != nil {
+			tmpFile.Close()
+			os.Remove(tmpFile.Name())
+			f.prefetchErr = err
+			return
+		}
+	}
+	f.prefetchFile = tmpFile
+	f.prefetchFilePath = tmpFile.Name()
+
 	buf := make([]byte, 32*1024) // 32KB buffer
-	reader := NewTimeoutReader(resp.Body, readTimeout)
+	reader := f.responseReader(resp)
 
 	for {
 		select {
@@ -616,7 +661,11 @@ func (f *Fetcher) cleanupPrefetchFile() {
 		f.prefetchFile = nil
 	}
 	if f.prefetchFilePath != "" {
-		os.Remove(f.prefetchFilePath)
+		if f.ctl != nil {
+			f.ctl.TempFiles.Remove(f.prefetchFilePath)
+		} else {
+			os.Remove(f.prefetchFilePath)
+		}
 		f.prefetchFilePath = ""
 	}
 	// The byte count is only reusable while the backing prefetch file exists.
@@ -626,7 +675,31 @@ func (f *Fetcher) cleanupPrefetchFile() {
 	f.resolveFallback.Store(false)
 }
 
+// Options may be replaced between Resolve and Start when creating a resolved task.
+func (f *Fetcher) initOptions() error {
+	opts := f.meta.Opts
+	// Parse options
+	if err := base.ParseOptExtra[fhttp.OptsExtra](opts); err != nil {
+		return err
+	}
+	if opts.Extra == nil {
+		opts.Extra = &fhttp.OptsExtra{}
+	}
+	extra := opts.Extra.(*fhttp.OptsExtra)
+	if extra.Connections <= 0 {
+		extra.Connections = f.config.Connections
+		if extra.Connections <= 0 {
+			extra.Connections = 1
+		}
+	}
+
+	return nil
+}
+
 func (f *Fetcher) Start() error {
+	if err := f.initOptions(); err != nil {
+		return err
+	}
 	state := f.getState()
 
 	switch state {
@@ -673,12 +746,26 @@ func (f *Fetcher) doStart() error {
 
 	// If retrying after error, reset connection states for retry
 	if state == stateError {
+		forceFullReset := f.checksumFailed.Swap(false)
+		if forceFullReset {
+			// 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.connMu.Lock()
 		for _, conn := range f.connections {
-			// Reset connections that can be retried
-			if !conn.Completed && conn.State != connCompleted {
+			// 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 := forceFullReset || (!conn.Completed && conn.State != connCompleted)
+			if shouldReset {
 				if !f.hasSequentialPrefixLocked(conn) {
-					f.resetConnectionForRestart(conn)
+					f.resetConnectionForRestart(conn, forceFullReset)
 				}
 				conn.State = connNotStarted
 				conn.failed = false
@@ -908,8 +995,14 @@ 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
 		}
 
@@ -1045,7 +1138,7 @@ func (f *Fetcher) runConnection(conn *connection) {
 			// it only when no safe validator exists or If-Range returns a full 200.
 			f.connMu.Lock()
 			if !f.hasSequentialPrefixLocked(conn) {
-				f.resetConnectionForRestart(conn)
+				f.resetConnectionForRestart(conn, false)
 			}
 			f.connMu.Unlock()
 		}
@@ -1152,7 +1245,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 	resumeProbe := f.canProbeSequentialResumeLocked(conn)
 	intentionalRestart := sequentialSizeUnknown
 	if sequentialSizeUnknown || (hasSequentialPrefix && !resumeProbe) {
-		f.resetConnectionForRestart(conn)
+		f.resetConnectionForRestart(conn, false)
 		f.resolveDataPos.Store(0)
 		f.rangeValidatorPinned = false
 		intentionalRestart = true
@@ -1328,7 +1421,7 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 		f.slowStart.onConnectSuccess()
 	}
 
-	reader := NewTimeoutReader(resp.Body, readTimeout)
+	reader := f.responseReader(resp)
 	var responseBytesRead int64
 	for {
 		if conn.ctx.Err() != nil {
@@ -1501,27 +1594,41 @@ 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)
@@ -1530,11 +1637,7 @@ 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 {
@@ -1587,7 +1690,7 @@ func (f *Fetcher) fallbackToSequentialDownload(conn *connection, ifRange string)
 	f.rangeReprobeEligible = true
 	f.rangeValidatorPinned = false
 	f.ifRange = ifRange
-	f.resetConnectionForRestart(conn)
+	f.resetConnectionForRestart(conn, false)
 	f.resolveDataPos.Store(0)
 	return nil
 }
@@ -1603,7 +1706,7 @@ func (f *Fetcher) restartSequentialDownload(conn *connection, ifRange string) {
 	f.rangeReprobeEligible = true
 	f.rangeValidatorPinned = false
 	f.ifRange = ifRange
-	f.resetConnectionForRestart(conn)
+	f.resetConnectionForRestart(conn, false)
 	f.resolveDataPos.Store(0)
 }
 
@@ -1710,7 +1813,7 @@ func (f *Fetcher) runConnectionWithResolveResp(conn *connection) {
 	}
 
 	// Download data from resolve response
-	reader := NewTimeoutReader(resp.Body, readTimeout)
+	reader := f.responseReader(resp)
 	for {
 		if conn.ctx.Err() != nil {
 			return
@@ -1827,7 +1930,7 @@ func (f *Fetcher) runConnectionFallback(conn *connection) {
 				f.slowStart.onConnectSuccess()
 			}
 
-			reader := NewTimeoutReader(resp.Body, readTimeout)
+			reader := f.responseReader(resp)
 			for {
 				if conn.ctx.Err() != nil {
 					return conn.ctx.Err()
@@ -1986,16 +2089,25 @@ func (f *Fetcher) helpOtherConnection(helper *connection) bool {
 	return true
 }
 
-func (f *Fetcher) resetConnectionForRestart(conn *connection) {
-	if f.meta.Res.Range {
+func (f *Fetcher) resetConnectionForRestart(conn *connection, force bool) {
+	if f.meta.Res.Range && !force {
 		return
 	}
+	if f.meta.Res.Range && force {
+		// Checksum mismatch: the on-disk content for this chunk is
+		// confirmed wrong, so its bytes must be re-fetched from the
+		// origin server even though range support would normally let
+		// us just resume from the existing Downloaded position.
+		if conn.Chunk != nil {
+			conn.Chunk.Downloaded = 0
+		}
+	}
 
 	// Without range support a new request always starts from byte 0,
 	// 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
@@ -2059,7 +2171,7 @@ func (f *Fetcher) resumeConnections() {
 			}
 		}
 		if !f.hasSequentialPrefixLocked(conn) {
-			f.resetConnectionForRestart(conn)
+			f.resetConnectionForRestart(conn, false)
 		}
 		// Reset the connection state for resume
 		conn.ctx, conn.cancel = context.WithCancel(f.ctx)
@@ -2166,10 +2278,15 @@ 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 {
@@ -2178,6 +2295,51 @@ 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()
@@ -2450,3 +2612,12 @@ func (f *Fetcher) Progress() fetcher.Progress {
 func (f *Fetcher) Wait() error {
 	return <-f.doneCh
 }
+
+// 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 {
+	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)
+}

internal/protocol/http/fetcher_checksum_retry_test.go

@@ -0,0 +1,122 @@
+package http
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	gohttp "net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/GopeedLab/gopeed/pkg/base"
+	"github.com/GopeedLab/gopeed/pkg/protocol/http"
+)
+
+func TestFetcher_ChecksumMismatch_Retry(t *testing.T) {
+	corruptContent := []byte("Corrupt Initial Download Data!")
+	correctContent := []byte("Correct Retried Download Data!")
+
+	correctSha256Hasher := sha256.New()
+	correctSha256Hasher.Write(correctContent)
+	correctSha256 := hex.EncodeToString(correctSha256Hasher.Sum(nil))
+
+	var reqCount atomic.Int32
+	server := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+		count := reqCount.Add(1)
+		var served []byte
+		if count == 1 {
+			// First request: serve corrupted content
+			served = corruptContent
+		} else {
+			// Second / subsequent request: serve correct content
+			served = correctContent
+		}
+		w.Header().Set(base.HttpHeaderContentLength, fmt.Sprintf("%d", len(served)))
+		w.Header().Set(base.HttpHeaderAcceptRanges, base.HttpHeaderBytes)
+		w.WriteHeader(gohttp.StatusOK)
+		_, _ = w.Write(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"}, opts); err != nil {
+		t.Fatalf("Resolve error: %v", err)
+	}
+	// Ensure the reusable resolve response has been fully prefetched so the
+	// first attempt deterministically verifies the corrupt initial payload.
+	deadline := time.NewTimer(5 * time.Second)
+	defer deadline.Stop()
+	ticker := time.NewTicker(10 * time.Millisecond)
+	defer ticker.Stop()
+	for !f.prefetchDone.Load() {
+		select {
+		case <-deadline.C:
+			t.Fatal("timed out waiting for checksum test prefetch")
+		case <-ticker.C:
+		}
+	}
+	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())
+	}
+
+	// 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)
+	}
+}

internal/protocol/http/fetcher_checksum_test.go

@@ -0,0 +1,307 @@
+package http
+
+import (
+	"crypto/md5"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	gohttp "net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/internal/fetcher"
+	"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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		err := f.Wait()
+		if err == nil {
+			t.Fatal("Wait 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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		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"}, opts); err != nil {
+			t.Fatalf("Resolve error: %v", err)
+		}
+		if err := f.Start(); err != nil {
+			t.Fatalf("Start error: %v", err)
+		}
+		if err := f.Wait(); err != nil {
+			t.Fatalf("Wait error: %v", err)
+		}
+	})
+}
+
+func TestResetConnectionForRestart_ForceOnRangeDownload(t *testing.T) {
+	f := buildFetcher()
+	f.meta = &fetcher.FetcherMeta{
+		Res: &base.Resource{
+			Range: true,
+		},
+	}
+	conn := &connection{
+		Chunk:      newChunk(0, 1024),
+		Downloaded: 512,
+		Completed:  true,
+	}
+	conn.Chunk.Downloaded = 512
+
+	// Non-forced reset on range-supported download does not reset Chunk.Downloaded
+	f.resetConnectionForRestart(conn, false)
+	if conn.Chunk.Downloaded != 512 {
+		t.Fatalf("expected Chunk.Downloaded to remain 512 when force is false, got %d", conn.Chunk.Downloaded)
+	}
+
+	// Forced reset on range-supported download resets Chunk.Downloaded to 0
+	f.resetConnectionForRestart(conn, true)
+	if conn.Chunk.Downloaded != 0 {
+		t.Fatalf("expected Chunk.Downloaded to be reset to 0 when force is true, got %d", conn.Chunk.Downloaded)
+	}
+	if conn.Completed {
+		t.Fatal("expected Completed to be false after reset")
+	}
+}

internal/protocol/http/fetcher_manager.go

@@ -72,7 +72,7 @@ func (fm *FetcherManager) AutoRename() bool {
 
 func (fm *FetcherManager) DefaultConfig() any {
 	return &config{
-		UserAgent:   "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36",
+		UserAgent:   DefaultUserAgent,
 		Connections: 16,
 	}
 }

internal/protocol/http/fetcher_test.go

@@ -13,6 +13,7 @@ import (
 	"net/url"
 	"os"
 	"strings"
+	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -221,6 +222,30 @@ func TestFetcher_Resolve(t *testing.T) {
 	})
 }
 
+func TestFetcher_ResolveFilenameFromContentType(t *testing.T) {
+	server := httptest.NewServer(gohttp.HandlerFunc(func(w gohttp.ResponseWriter, r *gohttp.Request) {
+		w.Header().Set("Content-Type", "image/webp")
+		w.WriteHeader(gohttp.StatusOK)
+	}))
+	defer server.Close()
+
+	fetcher := buildFetcher()
+	defer fetcher.Pause()
+
+	const opaqueName = "OIP-C.u5nEXTXND3PJF0gNTgw5YgHaFP"
+	err := fetcher.Resolve(&base.Request{URL: server.URL + "/" + opaqueName}, &base.Options{
+		Name: test.DownloadName,
+		Path: test.Dir,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if got := fetcher.meta.Res.Files[0].Name; got != opaqueName+".webp" {
+		t.Fatalf("resolved filename = %q, want %q", got, opaqueName+".webp")
+	}
+}
+
 func TestFetcher_ResolveWithHostHeader(t *testing.T) {
 	listener := test.StartTestHostHeaderServer()
 	defer listener.Close()
@@ -829,22 +854,34 @@ 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{

internal/protocol/http/filename_parse_test.go

@@ -136,3 +136,52 @@ func TestUnescapeHTMLEntities(t *testing.T) {
 		})
 	}
 }
+
+func TestAppendFilenameExtension(t *testing.T) {
+	tests := []struct {
+		name        string
+		filename    string
+		contentType string
+		want        string
+	}{
+		{
+			name:        "adds extension from content type",
+			filename:    "download",
+			contentType: "image/png",
+			want:        "download.png",
+		},
+		{
+			name:        "parses MIME parameters",
+			filename:    "download",
+			contentType: "image/png; charset=binary",
+			want:        "download.png",
+		},
+		{
+			name:        "preserves existing extension",
+			filename:    "download.zip",
+			contentType: "application/zip",
+			want:        "download.zip",
+		},
+		{
+			name:        "ignores invalid content type",
+			filename:    "download",
+			contentType: "not a content type",
+			want:        "download",
+		},
+		{
+			name:        "ignores unknown content type",
+			filename:    "download",
+			contentType: "application/x-gopeed-unknown",
+			want:        "download",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := appendFilenameExtension(tt.filename, tt.contentType)
+			if got != tt.want {
+				t.Errorf("appendFilenameExtension() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}

internal/protocol/http/helper.go

@@ -12,6 +12,7 @@ import (
 	"net/http"
 	"net/http/cookiejar"
 	"net/url"
+	"path"
 	"strings"
 	"time"
 	"unicode/utf8"
@@ -314,6 +315,28 @@ func parseFilename(contentDisposition string) string {
 	return parseFilenameFallback(contentDisposition)
 }
 
+// appendFilenameExtension adds a MIME-derived extension when the resolved
+// filename has no usable extension. Some image hosts use opaque path segments
+// that look like extensions, even though the response Content-Type is the
+// only reliable source for the file type.
+func appendFilenameExtension(filename, contentType string) string {
+	mediaType, _, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return filename
+	}
+
+	extensions, err := mime.ExtensionsByType(mediaType)
+	if err != nil || len(extensions) == 0 {
+		return filename
+	}
+
+	ext := path.Ext(filename)
+	if len(ext) > 1 && len(ext) <= 20 {
+		return filename
+	}
+	return filename + extensions[0]
+}
+
 // parseFilenameExtended handles RFC 5987 extended notation (filename*=)
 // Format: filename*=charset'language'value (e.g., UTF-8”%E6%B5%8B%E8%AF%95.zip)
 func parseFilenameExtended(cd string) string {

internal/protocol/http/prefetch_setup_test.go

@@ -0,0 +1,74 @@
+package http
+
+import (
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/GopeedLab/gopeed/internal/controller"
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
+)
+
+type prefetchSetupBody struct {
+	io.Reader
+	closed bool
+}
+
+func (b *prefetchSetupBody) Close() error {
+	b.closed = true
+	return nil
+}
+
+func TestPrefetchSetupFailureClosesResponse(t *testing.T) {
+	for _, closedScope := range []bool{false, true} {
+		name := "invalid_temp_directory"
+		if closedScope {
+			name = "downloader_already_closed"
+		}
+		t.Run(name, func(t *testing.T) {
+			root := t.TempDir()
+			scope := &tempfiles.Scope{}
+			dir := root
+			if closedScope {
+				if err := scope.Close(); err != nil {
+					t.Fatal(err)
+				}
+			} else {
+				dir = filepath.Join(root, "file")
+				if err := os.WriteFile(dir, nil, 0600); err != nil {
+					t.Fatal(err)
+				}
+			}
+			body := &prefetchSetupBody{Reader: strings.NewReader("unused response")}
+			f := &Fetcher{
+				ctl:         &controller.Controller{TempDir: dir, TempFiles: scope},
+				resolveResp: &http.Response{Body: body},
+			}
+			f.asyncPrefetch()
+			if f.prefetchErr == nil {
+				t.Fatal("expected temporary-file initialization to fail")
+			}
+			if !body.closed {
+				t.Error("prefetch setup failure left the response body open")
+			}
+			if f.resolveResp != nil {
+				t.Error("prefetch retained its failed resolve response")
+			}
+			if !f.prefetchDone.Load() {
+				t.Error("prefetch did not report completion")
+			}
+			if closedScope {
+				entries, err := os.ReadDir(root)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if len(entries) != 0 {
+					t.Errorf("late prefetch left temporary files: %v", entries)
+				}
+			}
+		})
+	}
+}

internal/protocol/http/resolve_range_test.go

@@ -0,0 +1,119 @@
+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()
+			err := f.Resolve(&base.Request{URL: server.URL + "/file"}, &base.Options{Path: t.TempDir()})
+			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()
+				if err := f.Resolve(&base.Request{URL: server.URL + "/file"}, &base.Options{Path: t.TempDir(), Name: "file", Extra: &fhttp.OptsExtra{Connections: connections}}); 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/tempfiles/scope.go

@@ -0,0 +1,63 @@
+// Package tempfiles tracks temporary paths owned by one downloader, without
+// requiring a private parent directory or scanning the shared system temp root.
+package tempfiles
+
+import (
+	"errors"
+	"io"
+	"os"
+	"sync"
+)
+
+type Scope struct {
+	mu     sync.Mutex
+	paths  map[string]struct{}
+	closed bool
+}
+
+// Track adopts a newly created unique path. Late creations are removed when
+// shutdown has already begun. A nil scope leaves cleanup to the resource owner.
+func (s *Scope) Track(path string) error {
+	if s == nil {
+		return nil
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return errors.Join(io.ErrClosedPipe, os.RemoveAll(path))
+	}
+	if s.paths == nil {
+		s.paths = make(map[string]struct{})
+	}
+	s.paths[path] = struct{}{}
+	return nil
+}
+func (s *Scope) Remove(path string) error {
+	if s == nil {
+		return os.RemoveAll(path)
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if err := os.RemoveAll(path); err != nil {
+		return err
+	}
+	delete(s.paths, path)
+	return nil
+}
+func (s *Scope) Close() error {
+	if s == nil {
+		return nil
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.closed = true
+	var result error
+	for path := range s.paths {
+		if err := os.RemoveAll(path); err != nil {
+			result = errors.Join(result, err)
+		} else {
+			delete(s.paths, path)
+		}
+	}
+	return result
+}

internal/tempfiles/scope_test.go

@@ -0,0 +1,76 @@
+package tempfiles
+
+import (
+	"errors"
+	"io"
+	"os"
+	"sync"
+	"testing"
+)
+
+func TestSharedDirectoryOwnersAndLateCreation(t *testing.T) {
+	root := t.TempDir()
+	a, b := &Scope{}, &Scope{}
+	own := func(scope *Scope) string {
+		t.Helper()
+		dir, err := os.MkdirTemp(root, "gopeed-media-")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := scope.Track(dir); err != nil {
+			t.Fatal(err)
+		}
+		return dir
+	}
+	first, second := own(a), own(b)
+	if err := a.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(first); !os.IsNotExist(err) {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(second); err != nil {
+		t.Fatal("removed other owner's path", err)
+	}
+	late, err := os.MkdirTemp(root, "gopeed-media-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := a.Track(late); !errors.Is(err, io.ErrClosedPipe) {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(late); !os.IsNotExist(err) {
+		t.Fatal("late creation leaked", err)
+	}
+	if err := b.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestConcurrentCreationAndShutdown(t *testing.T) {
+	root := t.TempDir()
+	scope := &Scope{}
+	var wg sync.WaitGroup
+	for i := 0; i < 20; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			dir, err := os.MkdirTemp(root, "gopeed-media-")
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			if err := scope.Track(dir); err != nil && !errors.Is(err, io.ErrClosedPipe) {
+				t.Error(err)
+			}
+		}()
+	}
+	if err := scope.Close(); err != nil {
+		t.Fatal(err)
+	}
+	wg.Wait()
+	entries, err := os.ReadDir(root)
+	if err != nil || len(entries) != 0 {
+		t.Fatal("shutdown leaked paths", entries, err)
+	}
+}

internal/webview/README.md

@@ -0,0 +1,109 @@
+# Extension browser host configuration
+
+The downloader wraps each provider with the extension's stable identity before
+constructing the runtime. `OpenOptions.ProfileID`, `DataPath`, and `ProxyURL` are
+host-only fields. `parseOpenOptions` never reads them from extension JavaScript.
+The extension API is unchanged. The Flutter host uses the fork's public
+`WebViewProfile`, `InAppWebViewSettings.profileId`, and profile-scoped
+`CookieManager` APIs; the library has no Gopeed-specific method-channel bridge.
+Only the Gopeed extension JavaScript boundary keeps these options host-only.
+
+Profiles are persistent and shared across invocations/pages of the same extension.
+Different identities use different native stores. Go providers use a SHA-256-based
+path under `<StorageDir>/webview`; Apple RPC hosts use a stable UUID data store;
+Android uses a named WebView profile. Cookie operations select that same store,
+including `clearCookies`. Closing an execution closes its pages, not its profile.
+Uninstall closes the extension's pages, prevents its old runtimes from opening
+new pages, and removes its native profile before deleting the extension record.
+Cleanup failures abort uninstall and can be retried. Reinstallation starts with
+empty browser data; an ordinary extension update keeps the existing profile.
+Windows/Linux delete the profile directory; Apple removes the named WebKit store.
+Android cannot delete a profile already loaded by the current process: when
+DELETE_BROWSING_DATA is supported it clears all site data immediately, and records
+an empty-profile deletion in SharedPreferences for the next process start. A
+reinstallation may reuse that cleared profile and cancels the pending deletion.
+If the full-data clearing API is unavailable, uninstall fails with a restart
+instruction; the pending profile is deleted at startup before it can be loaded.
+No removal operation is exposed through extension JavaScript.
+
+Existing shared browser data is not copied into every extension's new profile.
+
+The downloader lazily owns one loopback forward proxy with HTTP and SOCKS5
+listeners. Windows/Linux/Android use HTTP; Apple uses SOCKS5 because its HTTP
+CONNECT configuration may bypass plain HTTP. The forwarder reads the current
+Gopeed proxy config for each new request/tunnel and supports direct, system,
+HTTP(S) upstream proxies with Basic authentication, and authenticated SOCKS5.
+Credentials remain in Go and are never sent over the WebView RPC.
+
+Changes affect new requests/connections. Existing CONNECT/SOCKS tunnels keep their
+route until closed; opening another page in the same profile does not reset it.
+SOCKS carries host/port rather than a full URL: system proxy/PAC selection for
+Apple is host-based, with port 80 treated as HTTP and other ports as HTTPS.
+Path-dependent PAC rules cannot be reproduced from a SOCKS connection.
+
+Apple requires macOS 14 / iOS 17. Android checks MULTI_PROFILE and PROXY_OVERRIDE.
+Unsupported hosts fail explicitly instead of silently sharing browser storage or
+ignoring the proxy.
+
+## Validation
+
+- `go test -race ./internal/webview/proxy ./pkg/download/engine/webview`
+- `go test ./pkg/download -run 'TestWebViewProfileBound|TestDownloader_ExtensionRuntimeWebView'`
+- Windows/Linux: `go test -tags webview -v ./internal/webview/goprovider` (Linux: run under `xvfb-run -a`).
+- macOS: start the normal Flutter app, then run `go test -tags webview -v ./internal/webview/rpcprovider` with its socket address. See `rpcprovider/README.md`.
+- In webview_go: `go test -tags webview_integration -v -count=1 .` (Linux: run under `xvfb-run -a`).
+
+The shared provider contract covers HTTP/HTTPS proxy routing, concurrent pages,
+HttpOnly cookies, LocalStorage, IndexedDB, profile-scoped clearing, reopening,
+and removal without affecting another profile. HTTPS routing is checked with a
+rejecting upstream tunnel; no test-only certificate bypass is added to the app.
+Go proxy unit tests separately cover successful TLS forwarding and authentication.
+These cases run in the existing `test.yml` WebView jobs; existing mobile build jobs
+compile the Android/iOS bridge. No separate Flutter test application is required.
+
+## Extension events and host environment
+
+`gopeed.host.env.version` is the host's build version (`dev` for development
+builds). `gopeed.info.version` continues to identify the extension's own version.
+`gopeed.host.env.os` and `gopeed.host.env.arch` match the REST info endpoint's `os` and
+`arch`: the host's Go `runtime.GOOS` and `runtime.GOARCH` values (for example,
+`windows` / `amd64` or `darwin` / `arm64`).
+See [extension-api.d.ts](extension-api.d.ts) for the event payloads.
+
+```js
+const page = await gopeed.runtime.webview.open();
+const unsubscribe = await page.on("url-changed", ({ url, sameDocument }) => {
+  gopeed.logger.info(url, sameDocument);
+});
+await page.on("closed", ({ reason }) => gopeed.logger.info(reason));
+await page.addInitScript("globalThis.extensionReady = true");
+await page.goto("https://example.com");
+unsubscribe();
+await page.close();
+```
+
+Registration resolves only after the listener is installed; it does not replay
+current state. `url-changed` reports actual address changes, including hash,
+pushState, replaceState and history navigation. `load` follows the main document's
+`window.load`, including reloads, and does not wait for business-level async work.
+Iframe loads and subresource failures do not become main-page notifications.
+`closed` distinguishes the user's close action from API closure and is terminal.
+Unsubscribe is idempotent. Notifications cannot block navigation; the engine does
+not await promises returned by handlers. Catch async errors inside the handler.
+
+`addInitScript` applies to future document contexts only. Use `execute` to run
+code on the current page. Executable functions are serialized and cannot capture
+extension-side lexical variables; pass values explicitly as arguments.
+
+The RPC host uses an NDJSON `page.events` response whose first record is
+`{"ready":true}`. Subsequent records are `{event,data}`. Closing a page sends the
+terminal record before ending the stream. The native backend uses document-start
+notifications for main-document URL/load events and native callbacks for
+navigation failures and user closure.
+
+Additional validation:
+
+- `go test -race ./pkg/download/engine/webview ./internal/webview/rpcprovider`
+- `go test ./pkg/download -run 'TestExtension(WebViewEvents|InfoHostVersion)'`
+- macOS native: `go test -tags webview_native ./internal/webview/goprovider -run TestProviderEvents`
+- Running Flutter host: `go test -tags webview ./internal/webview/rpcprovider -run TestProviderEvents`

internal/webview/extension-api.d.ts

@@ -0,0 +1,60 @@
+/** Public extension API additions. info.version remains the extension version. */
+export interface ExtensionInfo {
+  identity: string;
+  name: string;
+  author: string;
+  title: string;
+  version: string;
+}
+
+/** Available as gopeed.host. */
+export interface Host {
+  env: HostEnv;
+}
+
+export interface HostEnv {
+  /** Host build version; "dev" for development builds. */
+  version: string;
+  /** Host OS and architecture, matching the REST info endpoint (Go GOOS/GOARCH). */
+  os: string;
+  arch: string;
+}
+
+/** Functions are serialized; they cannot capture extension-side variables. */
+export type WebviewExecutable<T = unknown> =
+  | string
+  | ((...args: unknown[]) => T | Promise<T>);
+
+export type WebviewUnsubscribe = () => void;
+
+/** Navigation and load notifications are for the main document only. */
+export interface WebviewEventMap {
+  "url-changed": { url: string; sameDocument: boolean };
+  /** window.load, including reloads, excluding hash/History API navigation. */
+  "load": { url: string };
+  "load-error": { url: string; message: string };
+  "closed": { reason: "user" | "api" };
+}
+
+export interface WebviewGotoOptions {
+  timeoutMs?: number;
+  waitUntil?: "load" | "domcontentloaded";
+}
+
+/** These members extend the existing WebviewPage API. */
+export interface WebviewPage {
+  /**
+   * Resolves when listening is ready. Does not replay current state.
+   * Register before goto() to observe navigation. Unsubscribe is idempotent.
+   * Closed is delivered once, then listeners are released automatically.
+   * Callbacks cannot cancel navigation; returned promises are not awaited.
+   * Callers handle errors in asynchronous callbacks.
+   */
+  on<K extends keyof WebviewEventMap>(
+    event: K,
+    handler: (data: WebviewEventMap[K]) => void,
+  ): Promise<WebviewUnsubscribe>;
+  /** Runs at document creation on future navigations, never immediately. */
+  addInitScript(script: string): Promise<void>;
+  goto(url: string, opts?: WebviewGotoOptions): Promise<void>;
+}

internal/webview/goprovider/events_darwin_test.go

@@ -0,0 +1,12 @@
+//go:build cgo && darwin && webview_native
+
+package goprovider
+
+import (
+	"github.com/GopeedLab/gopeed/internal/webview/integrationtest"
+	"os"
+	"testing"
+)
+
+func TestMain(m *testing.M)           { os.Exit(RunMainThreadLoop(m.Run)) }
+func TestProviderEvents(t *testing.T) { integrationtest.RunEventContract(t, New()) }

internal/webview/goprovider/events_script_test.go

@@ -0,0 +1,49 @@
+//go:build cgo
+
+package goprovider
+
+import (
+	enginewebview "github.com/GopeedLab/gopeed/pkg/download/engine/webview"
+	webview "github.com/GopeedLab/webview_go"
+	"github.com/dop251/goja"
+	"testing"
+	"time"
+)
+
+func TestInternalErrorDocumentDoesNotReportPageEvents(t *testing.T) {
+	vm := goja.New()
+	if _, err := vm.RunString(`
+  var window = globalThis;
+  window.top = window;
+  var location = {protocol: "chrome-error:", href: "chrome-error://chromewebdata/"};
+  var notifications = [];
+  var listeners = [];
+  function notify(payload) { notifications.push(payload); }
+  window.addEventListener = (name) => listeners.push(name);
+ `); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := vm.RunString(buildLoadNotifyScript("notify")); err != nil {
+		t.Fatal(err)
+	}
+	for _, name := range []string{"notifications", "listeners"} {
+		value, err := vm.RunString(name + ".length")
+		if err != nil || value.ToInteger() != 0 {
+			t.Fatalf("internal error page registered %s: %v (%v)", name, value, err)
+		}
+	}
+	// The provider must wait for the native failure, preserving the failed URL.
+	page := newPageWrapper(enginewebview.OpenOptions{})
+	got := make(chan string, 1)
+	_, err := page.On("load-error", func(e enginewebview.Event) { got <- e.Data["url"].(string) })
+	if err != nil {
+		t.Fatal(err)
+	}
+	page.handleNativeEvent(webview.Event{Name: "load-error", URL: "https://example.test/failure", Message: "TLS handshake failed"})
+	if err := page.waitForNavigation(time.Second, "load"); err == nil {
+		t.Fatal("native failure completed navigation successfully")
+	}
+	if url := <-got; url != "https://example.test/failure" {
+		t.Fatal(url)
+	}
+}

internal/webview/goprovider/mainthread_linux.go

@@ -0,0 +1,47 @@
+//go:build linux && cgo
+
+package goprovider
+
+/*
+#cgo pkg-config: gtk+-3.0
+#include <gtk/gtk.h>
+static void pumpGTK(void) {
+  // Bound each batch so Go creation/removal requests cannot be starved.
+  for (int i = 0; i < 64 && g_main_context_pending(NULL); ++i)
+    g_main_context_iteration(NULL, FALSE);
+}
+*/
+import "C"
+
+import (
+	"runtime"
+	"sync"
+	"time"
+)
+
+var gtkThreadOnce sync.Once
+var gtkThreadTasks = make(chan func())
+
+func RunMainThreadLoop(run func() int) int { return run() }
+
+func postMainThreadTask(task func()) bool {
+	gtkThreadOnce.Do(func() {
+		go func() {
+			runtime.LockOSThread()
+			// WebKit must always use its original UI thread, including after
+			// the last page closes. A page cannot stop this shared event loop.
+			ticker := time.NewTicker(10 * time.Millisecond)
+			defer ticker.Stop()
+			for {
+				select {
+				case task := <-gtkThreadTasks:
+					task()
+				case <-ticker.C:
+				}
+				C.pumpGTK()
+			}
+		}()
+	})
+	gtkThreadTasks <- task
+	return true
+}

internal/webview/goprovider/mainthread_other.go

@@ -1,4 +1,4 @@
-//go:build !darwin
+//go:build !darwin && (!linux || !cgo)
 
 package goprovider
 

internal/webview/goprovider/provider.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"net/url"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -37,7 +36,9 @@ func (p *Provider) Open(opts enginewebview.OpenOptions) (enginewebview.Page, err
 }
 
 type pageWrapper struct {
-	opts enginewebview.OpenOptions
+	opts             enginewebview.OpenOptions
+	events           enginewebview.EventHub
+	navigationErrors chan error
 
 	callbackName string
 	readyID      string
@@ -49,19 +50,23 @@ type pageWrapper struct {
 	url     string
 	closed  bool
 
-	ready chan error
-	done  chan struct{}
-	loads chan string
+	ready        chan error
+	done         chan struct{}
+	loads        chan string
+	domReady     chan struct{}
+	sameDocument chan struct{}
 }
 
 type evalMessage struct {
-	ID    string `json:"id"`
-	Ready bool   `json:"ready,omitempty"`
-	Load  bool   `json:"load,omitempty"`
-	URL   string `json:"url,omitempty"`
-	OK    bool   `json:"ok,omitempty"`
-	Value any    `json:"value,omitempty"`
-	Error string `json:"error,omitempty"`
+	Event        string `json:"event,omitempty"`
+	SameDocument bool   `json:"sameDocument,omitempty"`
+	ID           string `json:"id"`
+	Ready        bool   `json:"ready,omitempty"`
+	Load         bool   `json:"load,omitempty"`
+	URL          string `json:"url,omitempty"`
+	OK           bool   `json:"ok,omitempty"`
+	Value        any    `json:"value,omitempty"`
+	Error        string `json:"error,omitempty"`
 }
 
 type evalResult struct {
@@ -88,13 +93,16 @@ const startupTimeout = time.Minute
 func newPageWrapper(opts enginewebview.OpenOptions) *pageWrapper {
 	seq := providerSeq.Add(1)
 	return &pageWrapper{
-		opts:         opts,
-		callbackName: fmt.Sprintf("__gopeedWebViewCallback_%d", seq),
-		readyID:      fmt.Sprintf("__ready__%d", seq),
-		pending:      make(map[string]chan evalResult),
-		ready:        make(chan error, 1),
-		done:         make(chan struct{}),
-		loads:        make(chan string, 8),
+		opts:             opts,
+		navigationErrors: make(chan error, 8),
+		callbackName:     fmt.Sprintf("__gopeedWebViewCallback_%d", seq),
+		readyID:          fmt.Sprintf("__ready__%d", seq),
+		pending:          make(map[string]chan evalResult),
+		ready:            make(chan error, 1),
+		done:             make(chan struct{}),
+		loads:            make(chan string, 8),
+		domReady:         make(chan struct{}, 8),
+		sameDocument:     make(chan struct{}, 8),
 	}
 }
 
@@ -105,12 +113,21 @@ func (p *pageWrapper) start() error {
 		defer runtimepkg.UnlockOSThread()
 
 		var w webview.WebView
-		if p.opts.Headless {
+		if p.opts.DataPath != "" {
+			var err error
+			w, err = webview.NewWithOptions(webview.Options{Debug: p.opts.Debug, Headless: p.opts.Headless, DataPath: p.opts.DataPath, ProxyURL: p.opts.ProxyURL})
+			if err != nil {
+				p.ready <- err
+				close(p.done)
+				return
+			}
+		} else if p.opts.Headless {
 			w = webview.NewHeadless(p.opts.Debug)
 		} else {
 			w = webview.New(p.opts.Debug)
 		}
 		p.view = w
+		w.SetEventHandler(p.handleNativeEvent)
 		w.SetTitle(firstNonEmpty(p.opts.Title, "Gopeed WebView"))
 		w.SetSize(defaultWindowDimension(p.opts.Width, 1280), defaultWindowDimension(p.opts.Height, 800), webview.HintNone)
 
@@ -122,18 +139,25 @@ func (p *pageWrapper) start() error {
 				setter.SetUserAgent(p.opts.UserAgent)
 			}
 		}
-		w.Init(buildLoadNotifyScript(p.callbackName))
 
 		if err := w.Bind(p.callbackName, func(payload string) error {
 			return p.handleCallback(payload)
 		}); err != nil {
+			w.Destroy()
 			p.ready <- err
+			close(p.done)
 			return
 		}
 
+		w.Init(buildLoadNotifyScript(p.callbackName))
 		applyWindowOptions(w, p.opts)
 		w.SetHtml(buildBootstrapHTML(p.callbackName, p.readyID))
+		if runtimepkg.GOOS == "linux" {
+			// All GTK pages share the process-wide event loop below.
+			return
+		}
 		w.Run()
+		p.handleNativeEvent(webview.Event{Name: "closed"})
 		w.Destroy()
 		close(p.done)
 	}
@@ -162,10 +186,15 @@ func (p *pageWrapper) AddInitScript(script string) error {
 func (p *pageWrapper) Goto(url string, opts enginewebview.GotoOptions) error {
 	startedAt := time.Now()
 	p.drainLoads()
+	for {
+		select {
+		case <-p.navigationErrors:
+			continue
+		default:
+		}
+		break
+	}
 	if err := p.dispatch(func(w webview.WebView) error {
-		p.mu.Lock()
-		p.url = url
-		p.mu.Unlock()
 		w.Navigate(url)
 		return nil
 	}); err != nil {
@@ -179,7 +208,7 @@ func (p *pageWrapper) Goto(url string, opts enginewebview.GotoOptions) error {
 	if waitUntil == "" {
 		waitUntil = "load"
 	}
-	err := p.waitForNavigation(url, timeout, waitUntil)
+	err := p.waitForNavigation(timeout, waitUntil)
 	if err != nil {
 		p.tracef("goto failed %dms url=%s err=%v", time.Since(startedAt).Milliseconds(), url, err)
 		return err
@@ -219,7 +248,12 @@ func (p *pageWrapper) Execute(expression string, args ...any) (any, error) {
 		return nil, err
 	}
 
-	result := <-ch
+	var result evalResult
+	select {
+	case result = <-ch:
+	case <-p.done:
+		return nil, fmt.Errorf("webview page is closed")
+	}
 	if result.err != nil {
 		p.tracef("execute failed %dms err=%v", time.Since(startedAt).Milliseconds(), result.err)
 		return result.value, result.err
@@ -307,6 +341,7 @@ func (p *pageWrapper) Close() error {
 		return nil
 	}
 	p.closed = true
+	p.failPendingLocked()
 	w := p.view
 	wait := p.done
 	p.mu.Unlock()
@@ -318,12 +353,18 @@ func (p *pageWrapper) Close() error {
 		// the quit message lands on the correct queue.
 		terminateDone := make(chan struct{})
 		w.Dispatch(func() {
-			w.Terminate()
+			if runtimepkg.GOOS == "linux" {
+				w.Destroy()
+				close(p.done)
+			} else {
+				w.Terminate()
+			}
 			close(terminateDone)
 		})
 		<-terminateDone
 	}
 	<-wait
+	p.events.Emit(enginewebview.Event{Name: "closed", Data: map[string]any{"reason": "api"}})
 	return nil
 }
 
@@ -334,94 +375,29 @@ func (p *pageWrapper) tracef(format string, args ...any) {
 	fmt.Printf("goprovider "+format+"\n", args...)
 }
 
-func (p *pageWrapper) waitForNavigation(targetURL string, timeout time.Duration, waitUntil string) error {
-	deadline := time.Now().Add(timeout)
-	ticker := time.NewTicker(100 * time.Millisecond)
-	defer ticker.Stop()
-
+func (p *pageWrapper) waitForNavigation(timeout time.Duration, waitUntil string) error {
+	timer := time.NewTimer(timeout)
+	defer timer.Stop()
 	for {
 		select {
+		case <-p.done:
+			return fmt.Errorf("webview page is closed")
+		case err := <-p.navigationErrors:
+			return err
+		case <-timer.C:
+			return fmt.Errorf("webview navigation timeout")
+		case <-p.sameDocument:
+			return nil
+		case <-p.domReady:
+			if waitUntil == "domcontentloaded" {
+				return nil
+			}
 		case <-p.loads:
-			if waitUntil == "load" {
-				return nil
-			}
-		case <-ticker.C:
-			state, err := p.navigationState()
-			if err == nil && state.ready(targetURL, waitUntil) {
-				return nil
-			}
-			if time.Now().After(deadline) {
-				return fmt.Errorf("webview navigation timeout")
-			}
+			return nil
 		}
 	}
 }
 
-type navigationState struct {
-	URL        string `json:"url"`
-	ReadyState string `json:"readyState"`
-}
-
-func (s navigationState) ready(targetURL string, waitUntil string) bool {
-	if s.URL == "" || s.URL == "about:blank" {
-		return false
-	}
-	switch waitUntil {
-	case "domcontentloaded":
-		if s.ReadyState == "loading" || s.ReadyState == "" {
-			return false
-		}
-	default:
-		if s.ReadyState != "complete" {
-			return false
-		}
-	}
-	if targetURL == "" {
-		return true
-	}
-	if s.URL == targetURL {
-		return true
-	}
-	target, err := parseURL(targetURL)
-	if err != nil {
-		return true
-	}
-	current, err := parseURL(s.URL)
-	if err != nil {
-		return true
-	}
-	if current.Scheme == target.Scheme && current.Host == target.Host && current.Path == target.Path {
-		return true
-	}
-	return false
-}
-
-func parseURL(raw string) (*url.URL, error) {
-	return url.Parse(raw)
-}
-
-func (p *pageWrapper) navigationState() (navigationState, error) {
-	value, err := p.Execute(`() => ({
-		url: String(location.href || ""),
-		readyState: document.readyState || "",
-	})`)
-	if err != nil {
-		return navigationState{}, err
-	}
-	stateMap, ok := value.(map[string]any)
-	if !ok {
-		return navigationState{}, fmt.Errorf("invalid navigation state")
-	}
-	state := navigationState{}
-	if urlValue, ok := stateMap["url"].(string); ok {
-		state.URL = urlValue
-	}
-	if readyValue, ok := stateMap["readyState"].(string); ok {
-		state.ReadyState = readyValue
-	}
-	return state, nil
-}
-
 func (p *pageWrapper) dispatch(fn func(w webview.WebView) error) error {
 	p.mu.Lock()
 	if p.closed {
@@ -438,7 +414,12 @@ func (p *pageWrapper) dispatch(fn func(w webview.WebView) error) error {
 	w.Dispatch(func() {
 		done <- fn(w)
 	})
-	return <-done
+	select {
+	case err := <-done:
+		return err
+	case <-p.done:
+		return fmt.Errorf("webview page is closed")
+	}
 }
 
 func (p *pageWrapper) nativeCookies() ([]nativeCookieJSON, error) {
@@ -496,7 +477,31 @@ func (p *pageWrapper) handleCallback(payload string) error {
 		}
 		return nil
 	}
+	if msg.Event == "domcontentloaded" {
+		select {
+		case p.domReady <- struct{}{}:
+		default:
+		}
+		return nil
+	}
+	if msg.Event == "url-changed" {
+		if msg.SameDocument {
+			select {
+			case p.sameDocument <- struct{}{}:
+			default:
+			}
+		}
+		p.mu.Lock()
+		changed := p.url != msg.URL
+		p.url = msg.URL
+		p.mu.Unlock()
+		if changed {
+			p.events.Emit(enginewebview.Event{Name: "url-changed", Data: map[string]any{"url": msg.URL, "sameDocument": msg.SameDocument}})
+		}
+		return nil
+	}
 	if msg.Load {
+		p.events.Emit(enginewebview.Event{Name: "load", Data: map[string]any{"url": msg.URL}})
 		select {
 		case p.loads <- msg.URL:
 		default:
@@ -521,6 +526,22 @@ func (p *pageWrapper) handleCallback(payload string) error {
 }
 
 func (p *pageWrapper) drainLoads() {
+	for {
+		select {
+		case <-p.domReady:
+			continue
+		default:
+		}
+		break
+	}
+	for {
+		select {
+		case <-p.sameDocument:
+			continue
+		default:
+		}
+		break
+	}
 	for {
 		select {
 		case <-p.loads:
@@ -582,19 +603,77 @@ func buildExecuteScript(callbackName string, reqID string, expression string, ar
 func buildLoadNotifyScript(callbackName string) string {
 	callbackJSON, _ := json.Marshal(callbackName)
 	return fmt.Sprintf(`(() => {
-  window.addEventListener("load", () => {
-    const __cb = globalThis[%s];
-    if (typeof __cb !== "function") {
-      return;
-    }
-    __cb(JSON.stringify({
-      load: true,
-      url: String(location.href || ""),
-    }));
-  }, { once: true });
+  if (window !== window.top) return;
+  // WebView2 runs init scripts in its internal error document too. Its load
+  // must not complete goto() before the native NavigationCompleted failure.
+  if (location.protocol === "chrome-error:") return;
+  const send = (message) => {
+    const cb = globalThis[%s];
+    if (typeof cb === "function") cb(JSON.stringify(message));
+  };
+  let lastURL = String(location.href);
+  const changed = () => {
+    const url = String(location.href);
+    if (url === lastURL) return;
+    lastURL = url;
+    send({event: "url-changed", url, sameDocument: true});
+  };
+  send({event: "url-changed", url: lastURL, sameDocument: false});
+  for (const name of ["pushState", "replaceState"]) {
+    const original = history[name];
+    history[name] = function(...args) {
+      const result = Reflect.apply(original, this, args);
+      changed();
+      return result;
+    };
+  }
+  window.addEventListener("hashchange", changed);
+  window.addEventListener("popstate", changed);
+  window.addEventListener("pageshow", (event) => {
+    if (event.persisted) send({event: "url-changed", url: String(location.href), sameDocument: false});
+    else changed();
+  });
+  window.addEventListener("DOMContentLoaded", () => send({event: "domcontentloaded"}), {once:true});
+  window.addEventListener("load", () => send({load: true, url: String(location.href)}), {once: true});
 })();`, string(callbackJSON))
 }
 
+func (p *pageWrapper) On(name string, handler func(enginewebview.Event)) (func(), error) {
+	return p.events.On(name, handler)
+}
+
+func (p *pageWrapper) failPendingLocked() {
+	for id, ch := range p.pending {
+		ch <- evalResult{err: fmt.Errorf("webview page is closed")}
+		delete(p.pending, id)
+	}
+}
+
+func (p *pageWrapper) handleNativeEvent(event webview.Event) {
+	switch event.Name {
+	case "load-error":
+		p.events.Emit(enginewebview.Event{Name: "load-error", Data: map[string]any{"url": event.URL, "message": event.Message}})
+		select {
+		case p.navigationErrors <- errors.New(event.Message):
+		default:
+		}
+	case "closed":
+		p.mu.Lock()
+		api := p.closed
+		p.closed = true
+		p.failPendingLocked()
+		p.mu.Unlock()
+		reason := "user"
+		if api {
+			reason = "api"
+		}
+		p.events.Emit(enginewebview.Event{Name: "closed", Data: map[string]any{"reason": reason}})
+		if runtimepkg.GOOS == "linux" && !api {
+			p.view.Dispatch(func() { p.view.Destroy(); close(p.done) })
+		}
+	}
+}
+
 func defaultWindowDimension(value int, fallback int) int {
 	if value > 0 {
 		return value
@@ -610,3 +689,12 @@ func firstNonEmpty(values ...string) string {
 	}
 	return ""
 }
+
+func (p *Provider) RemoveProfile(profileID, dataPath string) error {
+	done := make(chan error, 1)
+	run := func() { done <- webview.RemoveProfile(dataPath) }
+	if !postMainThreadTask(run) {
+		run()
+	}
+	return <-done
+}

internal/webview/goprovider/provider_integration_test.go

@@ -13,3 +13,7 @@ func TestProviderContract(t *testing.T) {
 		CookieDomainMode: integrationtest.CookieDomainModeRequired,
 	})
 }
+
+func TestProviderProfiles(t *testing.T) { integrationtest.RunProfileContract(t, New()) }
+
+func TestProviderEvents(t *testing.T) { integrationtest.RunEventContract(t, New()) }

internal/webview/integrationtest/contract.go

@@ -1,10 +1,14 @@
 package integrationtest
 
 import (
+	"crypto/sha256"
 	"fmt"
+	webviewproxy "github.com/GopeedLab/gopeed/internal/webview/proxy"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -104,8 +108,10 @@ func RunProviderContract(t *testing.T, provider enginewebview.Provider, opts Con
 		t.Fatalf("expected click count to be 1, got %v", clickCount)
 	}
 
+	// Hidden WebViews can throttle timers on shared CI runners. Keep the
+	// positive asynchronous waits within the same budget as navigation.
 	found, err := page.WaitForSelector("#delayed", map[string]any{
-		"timeoutMs":      5000,
+		"timeoutMs":      10000,
 		"pollIntervalMs": 25,
 		"visible":        true,
 	})
@@ -113,11 +119,18 @@ func RunProviderContract(t *testing.T, provider enginewebview.Provider, opts Con
 		t.Fatalf("waitForSelector failed: %v", err)
 	}
 	if !found {
-		t.Fatal("expected delayed selector to appear")
+		diagnostic, diagnosticErr := page.Execute(`() => {
+			const element = document.querySelector('#delayed');
+			const rect = element && element.getBoundingClientRect();
+			return {url: location.href, readyState: document.readyState,
+				visibility: document.visibilityState, exists: !!element,
+				width: rect && rect.width, height: rect && rect.height};
+		}`)
+		t.Fatalf("expected delayed selector to appear: state=%v, diagnostic error=%v", diagnostic, diagnosticErr)
 	}
 
 	value, err := page.WaitForFunction(`() => window.__readyValue`, map[string]any{
-		"timeoutMs":      5000,
+		"timeoutMs":      10000,
 		"pollIntervalMs": 25,
 	})
 	if err != nil {
@@ -219,7 +232,19 @@ func openTestPage(t *testing.T, provider enginewebview.Provider, opts enginewebv
 	}))
 	t.Cleanup(server.Close)
 
-	runtime := enginewebview.NewRuntime(provider, true)
+	proxy, err := webviewproxy.New(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { proxy.Close() })
+	path := filepath.Join(t.TempDir(), "profile")
+	sum := sha256.Sum256([]byte(path))
+	profileID := fmt.Sprintf("%x-%x-%x-%x-%x", sum[:4], sum[4:6], sum[6:8], sum[8:10], sum[10:16])
+	proxyURL := proxy.URL()
+	if runtime.GOOS == "darwin" {
+		proxyURL = proxy.SOCKSURL()
+	}
+	runtime := enginewebview.NewRuntime(&configuredOpener{provider: provider, profileID: profileID, dataPath: path, proxyURL: proxyURL}, true)
 	page, err := runtime.Open(map[string]any{
 		"headless":  opts.Headless,
 		"debug":     opts.Debug,
@@ -232,7 +257,14 @@ func openTestPage(t *testing.T, provider enginewebview.Provider, opts enginewebv
 		t.Fatalf("failed to open webview: %v", err)
 	}
 	t.Cleanup(func() {
-		_ = runtime.Close()
+		if err := runtime.Close(); err != nil {
+			t.Errorf("close contract page: %v", err)
+		}
+		if remover, ok := provider.(enginewebview.ProfileRemover); ok {
+			if err := remover.RemoveProfile(profileID, path); err != nil {
+				t.Errorf("remove contract profile: %v", err)
+			}
+		}
 	})
 
 	return page, server, server.URL
@@ -380,3 +412,15 @@ func hasCookie(cookies []enginewebview.Cookie, name string, value string) bool {
 	}
 	return false
 }
+
+type configuredOpener struct {
+	provider                      enginewebview.Provider
+	profileID, dataPath, proxyURL string
+}
+
+func (o *configuredOpener) Open(opts enginewebview.OpenOptions) (enginewebview.Page, error) {
+	opts.ProfileID = o.profileID
+	opts.DataPath = o.dataPath
+	opts.ProxyURL = o.proxyURL
+	return o.provider.Open(opts)
+}

internal/webview/integrationtest/events.go

@@ -0,0 +1,110 @@
+package integrationtest
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+
+	wv "github.com/GopeedLab/gopeed/pkg/download/engine/webview"
+)
+
+// RunEventContract exercises the same public semantics on native and RPC hosts.
+func RunEventContract(t *testing.T, provider wv.Provider) {
+	t.Helper()
+	page, _, url := openTestPage(t, provider, wv.OpenOptions{Headless: true, Title: "WebView event contract"})
+	events := make(chan wv.Event, 100)
+	for _, name := range []string{"url-changed", "load", "load-error", "closed"} {
+		if _, err := page.On(name, func(e wv.Event) { events <- e }); err != nil {
+			t.Fatal(err)
+		}
+	}
+	next := func(name string) wv.Event {
+		t.Helper()
+		select {
+		case event := <-events:
+			if event.Name != name {
+				t.Fatalf("got event %s (%v), want %s", event.Name, event.Data, name)
+			}
+			return event
+		case <-time.After(10 * time.Second):
+			t.Fatalf("timed out waiting for %s", name)
+		}
+		return wv.Event{}
+	}
+	quiet := func() {
+		t.Helper()
+		select {
+		case e := <-events:
+			t.Fatalf("unexpected event: %+v", e)
+		case <-time.After(150 * time.Millisecond):
+		}
+	}
+	quiet()
+	if err := page.AddInitScript(`globalThis.__initBeforePage = document.readyState`); err != nil {
+		t.Fatal(err)
+	}
+	if err := page.Goto(url, map[string]any{"timeoutMs": 10000}); err != nil {
+		t.Fatal(err)
+	}
+	e := next("url-changed")
+	if strings.TrimRight(fmt.Sprint(e.Data["url"]), "/") != strings.TrimRight(url, "/") || e.Data["sameDocument"] != false {
+		t.Fatal(e)
+	}
+	next("load")
+	if result, err := page.Execute(`() => globalThis.__initBeforePage`); err != nil || result != "loading" {
+		t.Fatalf("init script: %v %v", result, err)
+	}
+	if err := page.AddInitScript(`globalThis.__onlyNext = true`); err != nil {
+		t.Fatal(err)
+	}
+	if result, err := page.Execute(`() => typeof globalThis.__onlyNext`); err != nil || result != "undefined" {
+		t.Fatalf("init ran in current page: %v %v", result, err)
+	}
+	for _, expression := range []string{
+		`() => { history.pushState({}, '', '#push'); }`,
+		`() => { history.replaceState({}, '', '#replace'); }`,
+		`() => { location.hash = 'hash'; }`,
+	} {
+		if _, err := page.Execute(expression); err != nil {
+			t.Fatal(err)
+		}
+		e := next("url-changed")
+		if e.Data["sameDocument"] != true {
+			t.Fatal(e)
+		}
+		quiet()
+	}
+	if _, err := page.Execute(`() => { location.reload(); }`); err != nil {
+		t.Fatal(err)
+	}
+	next("load") // Same address on refresh is not a URL change.
+	if result, err := page.Execute(`() => globalThis.__onlyNext`); err != nil || result != true {
+		t.Fatalf("next init: %v %v", result, err)
+	}
+	if _, err := page.Execute(`() => { const f=document.createElement('iframe'); f.src='/next'; document.body.append(f); }`); err != nil {
+		t.Fatal(err)
+	}
+	quiet()
+	// The fixture serves plain HTTP. Attempting TLS against it produces a
+	// real navigation failure through both HTTP CONNECT and SOCKS proxies.
+	// An unreachable HTTP origin would instead become a valid 502 document
+	// when the host's HTTP proxy handles the connection error.
+	failedURL := strings.Replace(url, "http://", "https://", 1) + "/failure"
+	if err := page.Goto(failedURL, map[string]any{"timeoutMs": 3000}); err == nil {
+		t.Fatal("failed navigation succeeded")
+	}
+	e = next("load-error")
+	if e.Data["message"] == "" || !strings.Contains(fmt.Sprint(e.Data["url"]), "/failure") {
+		t.Fatal(e)
+	}
+	quiet() // A handled failure must not load a browser-generated fallback page.
+	if err := page.Close(); err != nil {
+		t.Fatal(err)
+	}
+	e = next("closed")
+	if e.Data["reason"] != "api" {
+		t.Fatal(e)
+	}
+	quiet()
+}

internal/webview/integrationtest/profiles.go

@@ -0,0 +1,247 @@
+package integrationtest
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"path/filepath"
+	"reflect"
+	"runtime"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	webviewproxy "github.com/GopeedLab/gopeed/internal/webview/proxy"
+	webview "github.com/GopeedLab/gopeed/pkg/download/engine/webview"
+)
+
+// RunProfileContract exercises the same host API through both native and RPC
+// providers. It never bypasses the host bridge with direct Flutter plugin calls.
+func RunProfileContract(t *testing.T, provider webview.Provider) {
+	t.Helper()
+	waitForProviderAvailable(t, provider, defaultAvailabilityTimeout)
+	remover, ok := provider.(webview.ProfileRemover)
+	if !ok {
+		t.Fatal("provider does not implement host profile removal")
+	}
+	proxyURL, secureHits := profileProxy(t)
+	a := newContractProfile(t, provider, remover, proxyURL)
+	b := newContractProfile(t, provider, remover, proxyURL)
+	first := a.open(t)
+	assertProfileValue(t, first, `async () => { localStorage.setItem('owner','a'); return 'a'; }`, "a")
+	assertProfileValue(t, first, profileDatabaseScript(true), "saved")
+	if err := first.SetCookie(webview.Cookie{Name: "session", Value: "a", Domain: "profiles.invalid", Path: "/", HTTPOnly: true, Expires: time.Now().Add(time.Hour)}); err != nil {
+		t.Fatal(err)
+	}
+	second := b.open(t)
+	assertProfileValue(t, second, `() => localStorage.getItem('owner')`, nil)
+	assertProfileValue(t, second, profileDatabaseScript(false), nil)
+	assertProfileCookies(t, second, "", "new profile B")
+	assertProfileValue(t, second, `() => { localStorage.setItem('owner','b'); return 'b'; }`, "b")
+	if err := second.SetCookie(webview.Cookie{Name: "session", Value: "b", Domain: "profiles.invalid", Path: "/", HTTPOnly: true}); err != nil {
+		t.Fatal(err)
+	}
+	shared := a.open(t)
+	assertProfileValue(t, shared, `() => localStorage.getItem('owner')`, "a")
+	assertProfileValue(t, shared, profileDatabaseScript(false), "saved")
+	assertProfileCookies(t, shared, "a", "shared profile A")
+	storedCookies, err := shared.GetCookies()
+	if err != nil || len(storedCookies) != 1 || storedCookies[0].Expires.Before(time.Now()) {
+		t.Fatalf("persistent cookie lost its expiration: %#v, error %v", storedCookies, err)
+	}
+	assertProfileValue(t, shared, `() => document.cookie`, "") // HttpOnly stays hidden.
+	if err := second.ClearCookies(); err != nil {
+		t.Fatal(err)
+	}
+	assertProfileCookies(t, first, "a", "clearing B leaves A intact")
+	if err := second.SetCookie(webview.Cookie{Name: "session", Value: "b", Domain: "profiles.invalid", Path: "/", HTTPOnly: true}); err != nil {
+		t.Fatal(err)
+	}
+	a.close(t)
+	reopened := a.open(t)
+	assertProfileValue(t, reopened, `() => localStorage.getItem('owner')`, "a")
+	assertProfileValue(t, reopened, profileDatabaseScript(false), "saved")
+	assertProfileCookies(t, reopened, "a", "reopened profile A")
+	// Include a session cookie immediately before deletion to catch stale
+	// in-process CookieStore caches when the same profile is recreated.
+	if err := reopened.SetCookie(webview.Cookie{Name: "session", Value: "remove-me", Domain: "profiles.invalid", Path: "/", HTTPOnly: true}); err != nil {
+		t.Fatal(err)
+	}
+	a.close(t)
+	a.remove(t)
+	a.remove(t) // Retrying a successful uninstall is harmless.
+	reinstalled := a.open(t)
+	assertProfileValue(t, reinstalled, `() => localStorage.getItem('owner')`, nil)
+	assertProfileValue(t, reinstalled, profileDatabaseScript(false), nil)
+	assertProfileCookies(t, reinstalled, "", "reinstalled profile A")
+	assertProfileValue(t, second, `() => localStorage.getItem('owner')`, "b")
+	assertProfileCookies(t, second, "b", "B after removing A")
+	// Refuse the HTTPS tunnel deliberately. Seeing it at our proxy proves HTTPS
+	// routing without adding a certificate-validation bypass to the test host.
+	// WebView2 may commit its built-in error page and report navigation as
+	// complete. The invariant here is that the HTTPS tunnel reaches the proxy.
+	_ = reinstalled.Goto("https://profiles.invalid/", webview.GotoOptions{TimeoutMS: 5000})
+	deadline := time.Now().Add(5 * time.Second)
+	for secureHits.Load() == 0 && time.Now().Before(deadline) {
+		time.Sleep(10 * time.Millisecond)
+	}
+	if secureHits.Load() == 0 {
+		t.Fatal("HTTPS bypassed the host proxy")
+	}
+}
+
+type contractProfile struct {
+	provider webview.Provider
+	remover  webview.ProfileRemover
+	options  webview.OpenOptions
+	pages    []webview.Page
+}
+
+func newContractProfile(t *testing.T, provider webview.Provider, remover webview.ProfileRemover, proxyURL string) *contractProfile {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "profile")
+	hash := sha256.Sum256([]byte(path))
+	id := fmt.Sprintf("%x-%x-%x-%x-%x", hash[:4], hash[4:6], hash[6:8], hash[8:10], hash[10:16])
+	p := &contractProfile{provider: provider, remover: remover, options: webview.OpenOptions{ProfileID: id, DataPath: path, ProxyURL: proxyURL, Headless: true, Title: "Gopeed profile contract"}}
+	t.Cleanup(func() { p.close(t); p.remove(t) })
+	return p
+}
+func (p *contractProfile) open(t *testing.T) webview.Page {
+	t.Helper()
+	page, err := p.provider.Open(p.options)
+	if err != nil {
+		t.Fatal(err)
+	}
+	p.pages = append(p.pages, page)
+	if err := page.Goto("http://profiles.invalid/", webview.GotoOptions{TimeoutMS: 10000}); err != nil {
+		t.Fatal(err)
+	}
+	return page
+}
+func (p *contractProfile) close(t *testing.T) {
+	t.Helper()
+	for _, page := range p.pages {
+		if err := page.Close(); err != nil {
+			t.Errorf("close profile page: %v", err)
+		}
+	}
+	p.pages = nil
+}
+func (p *contractProfile) remove(t *testing.T) {
+	t.Helper()
+	if err := p.remover.RemoveProfile(p.options.ProfileID, p.options.DataPath); err != nil {
+		t.Errorf("remove profile: %v", err)
+	}
+}
+func assertProfileValue(t *testing.T, page webview.Page, script string, want any) {
+	t.Helper()
+	got, err := page.Execute(script)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("script %s: got %#v, want %#v", script, got, want)
+	}
+}
+func assertProfileCookies(t *testing.T, page webview.Page, want, stage string) {
+	t.Helper()
+	// Native cookie managers propagate updates across browser processes
+	// asynchronously. Wait for the expected state rather than assuming the
+	// first IPC read already includes the preceding write.
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		cookies, err := page.GetCookies()
+		if err != nil {
+			t.Fatalf("%s: %v", stage, err)
+		}
+		matches := len(cookies) == 0 && want == "" || len(cookies) == 1 && want != "" && cookies[0].Name == "session" && cookies[0].Value == want && cookies[0].HTTPOnly
+		if matches {
+			return
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("%s: cookies %#v, want %q", stage, cookies, want)
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+}
+func profileDatabaseScript(write bool) string {
+	operation := "store.get('owner')"
+	if write {
+		operation = "store.put('saved','owner')"
+	}
+	return fmt.Sprintf(`async () => await new Promise((resolve,reject)=>{
+ const request=indexedDB.open('profile-contract',1);
+ request.onupgradeneeded=()=>request.result.createObjectStore('state');
+ request.onerror=()=>reject(String(request.error));
+ request.onsuccess=()=>{
+  const db=request.result, tx=db.transaction('state','readwrite'), store=tx.objectStore('state');
+  const op=%s; let value;
+  op.onsuccess=()=>value=%s;
+  tx.oncomplete=()=>{db.close();resolve(value===undefined?null:value)};
+  tx.onerror=()=>{db.close();reject(String(tx.error))};
+ };
+})`, operation, map[bool]string{true: "'saved'", false: "op.result"}[write])
+}
+
+func profileProxy(t *testing.T) (string, *atomic.Int32) {
+	t.Helper()
+	origin := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/html")
+		w.Header().Set("Cache-Control", "no-store")
+		fmt.Fprint(w, "<!doctype html><title>Profile contract</title>")
+	}))
+	t.Cleanup(origin.Close)
+	secureHits := &atomic.Int32{}
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodConnect {
+			origin.Config.Handler.ServeHTTP(w, r)
+			return
+		}
+		if r.Host == "profiles.invalid:443" {
+			secureHits.Add(1)
+			http.Error(w, "HTTPS routing fixture rejects tunnels", http.StatusBadGateway)
+			return
+		}
+		if r.Host != "profiles.invalid:80" {
+			http.Error(w, "unexpected target", http.StatusBadGateway)
+			return
+		}
+		remote, err := net.DialTimeout("tcp", origin.Listener.Addr().String(), 5*time.Second)
+		if err != nil {
+			http.Error(w, "origin unavailable", http.StatusBadGateway)
+			return
+		}
+		defer remote.Close()
+		client, buffer, err := w.(http.Hijacker).Hijack()
+		if err != nil {
+			return
+		}
+		defer client.Close()
+		if _, err := buffer.WriteString("HTTP/1.1 200 Connection Established\r\n\r\n"); err != nil {
+			return
+		}
+		if err := buffer.Flush(); err != nil {
+			return
+		}
+		go func() { io.Copy(remote, buffer); remote.Close() }()
+		io.Copy(client, remote)
+	}))
+	t.Cleanup(upstream.Close)
+	upstreamURL, err := url.Parse(upstream.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	proxy, err := webviewproxy.New(func(*http.Request) (*url.URL, error) { return upstreamURL, nil })
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { proxy.Close() })
+	if runtime.GOOS == "darwin" {
+		return proxy.SOCKSURL(), secureHits
+	}
+	return proxy.URL(), secureHits
+}

internal/webview/proxy/server.go

@@ -0,0 +1,341 @@
+// Package proxy provides the host-owned WebView forward proxy. Browser engines
+// always use this endpoint; Gopeed decides the upstream route for each request.
+package proxy
+
+import (
+	"bufio"
+	"context"
+	"crypto/tls"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/armon/go-socks5"
+	xproxy "golang.org/x/net/proxy"
+)
+
+type Selector func(*http.Request) (*url.URL, error)
+
+type Server struct {
+	listener      net.Listener
+	socksListener net.Listener
+	server        *http.Server
+	transport     *http.Transport
+	selectProxy   Selector
+	mu            sync.Mutex
+	connections   map[io.Closer]struct{}
+	closed        bool
+}
+
+func New(selectProxy Selector) (*Server, error) {
+	if selectProxy == nil {
+		selectProxy = func(*http.Request) (*url.URL, error) { return nil, nil }
+	}
+	listener, err := net.Listen("tcp4", "127.0.0.1:0")
+	if err != nil {
+		return nil, err
+	}
+	s := &Server{listener: listener, selectProxy: selectProxy, connections: make(map[io.Closer]struct{})}
+	s.transport = &http.Transport{Proxy: selectProxy, DisableKeepAlives: true, TLSHandshakeTimeout: 15 * time.Second, ResponseHeaderTimeout: 30 * time.Second}
+	s.server = &http.Server{Handler: s, ReadHeaderTimeout: 15 * time.Second}
+	s.socksListener, err = net.Listen("tcp4", "127.0.0.1:0")
+	if err != nil {
+		listener.Close()
+		return nil, err
+	}
+	socks, err := socks5.New(&socks5.Config{Logger: log.New(io.Discard, "", 0), Resolver: unresolvedDNS{}, Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+		_, port, _ := net.SplitHostPort(address)
+		scheme := "https"
+		if port == "80" {
+			scheme = "http"
+		}
+		request := &http.Request{URL: &url.URL{Scheme: scheme, Host: address}, Header: make(http.Header)}
+		upstream, err := selectProxy(request)
+		if err != nil {
+			return nil, err
+		}
+		timed, cancel := context.WithTimeout(ctx, 30*time.Second)
+		defer cancel()
+		conn, err := dialTunnel(timed, address, upstream)
+		if err != nil {
+			return nil, err
+		}
+		return s.track(conn)
+	}})
+	if err != nil {
+		listener.Close()
+		s.socksListener.Close()
+		return nil, err
+	}
+	go s.server.Serve(listener)
+	go socks.Serve(&trackedListener{Listener: s.socksListener, server: s})
+	return s, nil
+}
+
+func (s *Server) URL() string { return "http://" + s.listener.Addr().String() }
+
+func (s *Server) SOCKSURL() string { return "socks5://" + s.socksListener.Addr().String() }
+
+func (s *Server) Close() error {
+	s.mu.Lock()
+	s.closed = true
+	connections := make([]io.Closer, 0, len(s.connections))
+	for c := range s.connections {
+		connections = append(connections, c)
+	}
+	s.mu.Unlock()
+	for _, c := range connections {
+		c.Close()
+	}
+	s.socksListener.Close()
+	s.transport.CloseIdleConnections()
+	return s.server.Close()
+}
+
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method == http.MethodConnect {
+		s.connect(w, r)
+		return
+	}
+	if !r.URL.IsAbs() || (r.URL.Scheme != "http" && r.URL.Scheme != "https") {
+		http.Error(w, "absolute HTTP URL required", http.StatusBadRequest)
+		return
+	}
+	out := r.Clone(r.Context())
+	out.RequestURI = ""
+	upgrade := out.Header.Get("Upgrade")
+	stripHopHeaders(out.Header)
+	if upgrade != "" {
+		out.Header.Set("Connection", "Upgrade")
+		out.Header.Set("Upgrade", upgrade)
+	}
+	resp, err := s.transport.RoundTrip(out)
+	if err != nil {
+		http.Error(w, "upstream request failed", http.StatusBadGateway)
+		return
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode == http.StatusSwitchingProtocols {
+		remote, ok := resp.Body.(io.ReadWriteCloser)
+		if !ok {
+			http.Error(w, "invalid upstream upgrade", 502)
+			return
+		}
+		client, buffer, err := w.(http.Hijacker).Hijack()
+		if err != nil {
+			return
+		}
+		defer client.Close()
+		resp.Body = nil
+		if err := resp.Write(buffer); err != nil {
+			return
+		}
+		if err := buffer.Flush(); err != nil {
+			return
+		}
+		s.bridge(client, buffer, remote)
+		return
+	}
+	stripHopHeaders(resp.Header)
+	for k, v := range resp.Header {
+		w.Header()[k] = v
+	}
+	w.WriteHeader(resp.StatusCode)
+	io.Copy(w, resp.Body)
+}
+
+func stripHopHeaders(h http.Header) {
+	for _, key := range strings.Split(h.Get("Connection"), ",") {
+		h.Del(strings.TrimSpace(key))
+	}
+	for _, key := range []string{"Connection", "Proxy-Connection", "Proxy-Authorization", "Proxy-Authenticate", "Keep-Alive", "TE", "Trailer", "Transfer-Encoding", "Upgrade"} {
+		h.Del(key)
+	}
+}
+
+func (s *Server) connect(w http.ResponseWriter, r *http.Request) {
+	if _, _, err := net.SplitHostPort(r.Host); err != nil {
+		http.Error(w, "invalid tunnel destination", 400)
+		return
+	}
+	target := r.Clone(r.Context())
+	target.URL = &url.URL{Scheme: "https", Host: r.Host}
+	upstream, err := s.selectProxy(target)
+	if err != nil {
+		http.Error(w, "proxy selection failed", 502)
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 30*time.Second)
+	defer cancel()
+	remote, err := dialTunnel(ctx, r.Host, upstream)
+	if err != nil {
+		http.Error(w, "upstream connection failed", 502)
+		return
+	}
+	defer remote.Close()
+	client, buffer, err := w.(http.Hijacker).Hijack()
+	if err != nil {
+		return
+	}
+	defer client.Close()
+	if _, err := buffer.WriteString("HTTP/1.1 200 Connection Established\r\n\r\n"); err != nil {
+		return
+	}
+	if err := buffer.Flush(); err != nil {
+		return
+	}
+	s.bridge(client, buffer, remote)
+}
+
+func (s *Server) bridge(client net.Conn, buffer *bufio.ReadWriter, remote io.ReadWriteCloser) {
+	s.mu.Lock()
+	if s.closed {
+		s.mu.Unlock()
+		return
+	}
+	s.connections[client] = struct{}{}
+	s.connections[remote] = struct{}{}
+	s.mu.Unlock()
+	defer func() { s.mu.Lock(); delete(s.connections, client); delete(s.connections, remote); s.mu.Unlock() }()
+
+	done := make(chan struct{})
+	go func() { io.Copy(remote, buffer); remote.Close(); close(done) }()
+	io.Copy(client, remote)
+	client.Close()
+	<-done
+}
+
+type bufferedConn struct {
+	net.Conn
+	reader *bufio.Reader
+}
+
+func (c *bufferedConn) Read(p []byte) (int, error) { return c.reader.Read(p) }
+
+func dialTunnel(ctx context.Context, target string, upstream *url.URL) (net.Conn, error) {
+	dialer := &net.Dialer{}
+	if upstream == nil {
+		return dialer.DialContext(ctx, "tcp", target)
+	}
+	if upstream.Scheme == "socks5" || upstream.Scheme == "socks5h" {
+		u := *upstream
+		u.Scheme = "socks5"
+		d, err := xproxy.FromURL(&u, dialer)
+		if err != nil {
+			return nil, err
+		}
+		return d.(xproxy.ContextDialer).DialContext(ctx, "tcp", target)
+	}
+	if upstream.Scheme != "http" && upstream.Scheme != "https" {
+		return nil, errors.New("unsupported proxy scheme")
+	}
+	host := upstream.Host
+	if upstream.Port() == "" {
+		port := "80"
+		if upstream.Scheme == "https" {
+			port = "443"
+		}
+		host = net.JoinHostPort(upstream.Hostname(), port)
+	}
+	conn, err := dialer.DialContext(ctx, "tcp", host)
+	if err != nil {
+		return nil, err
+	}
+	ok := false
+	defer func() {
+		if !ok {
+			conn.Close()
+		}
+	}()
+	if deadline, exists := ctx.Deadline(); exists {
+		conn.SetDeadline(deadline)
+	}
+	if upstream.Scheme == "https" {
+		secure := tls.Client(conn, &tls.Config{ServerName: upstream.Hostname(), MinVersion: tls.VersionTLS12})
+		if err := secure.HandshakeContext(ctx); err != nil {
+			return nil, err
+		}
+		conn = secure
+	}
+	request := &http.Request{Method: http.MethodConnect, URL: &url.URL{Opaque: target}, Host: target, Header: make(http.Header)}
+	if upstream.User != nil {
+		password, _ := upstream.User.Password()
+		request.Header.Set("Proxy-Authorization", "Basic "+base64.StdEncoding.EncodeToString([]byte(upstream.User.Username()+":"+password)))
+	}
+	if err := request.Write(conn); err != nil {
+		return nil, err
+	}
+	reader := bufio.NewReader(conn)
+	response, err := http.ReadResponse(reader, request)
+	if err != nil {
+		return nil, err
+	}
+	if response.StatusCode != 200 {
+		response.Body.Close()
+		return nil, fmt.Errorf("upstream CONNECT status %d", response.StatusCode)
+	}
+	conn.SetDeadline(time.Time{})
+	ok = true
+	return &bufferedConn{Conn: conn, reader: reader}, nil
+}
+
+// Leave hostname resolution to the selected upstream (SOCKS remote DNS / CONNECT).
+type unresolvedDNS struct{}
+
+func (unresolvedDNS) Resolve(ctx context.Context, name string) (context.Context, net.IP, error) {
+	return ctx, nil, nil
+}
+
+type trackedListener struct {
+	net.Listener
+	server *Server
+}
+
+func (l *trackedListener) Accept() (net.Conn, error) {
+	c, err := l.Listener.Accept()
+	if err != nil {
+		return nil, err
+	}
+	return l.server.track(c)
+}
+
+type trackedConn struct {
+	net.Conn
+	server *Server
+}
+
+func (c *trackedConn) Close() error {
+	err := c.Conn.Close()
+	c.server.mu.Lock()
+	delete(c.server.connections, c)
+	c.server.mu.Unlock()
+	return err
+}
+func (s *Server) track(c net.Conn) (net.Conn, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		c.Close()
+		return nil, net.ErrClosed
+	}
+	tracked := &trackedConn{Conn: c, server: s}
+	s.connections[tracked] = struct{}{}
+	return tracked, nil
+}
+
+func (c *trackedConn) CloseWrite() error  { return closeWrite(c.Conn) }
+func (c *bufferedConn) CloseWrite() error { return closeWrite(c.Conn) }
+func closeWrite(c net.Conn) error {
+	if writer, ok := c.(interface{ CloseWrite() error }); ok {
+		return writer.CloseWrite()
+	}
+	return c.Close()
+}

internal/webview/proxy/server_test.go

@@ -0,0 +1,315 @@
+package proxy
+
+import (
+	"bufio"
+	"context"
+	"crypto/tls"
+	"errors"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/armon/go-socks5"
+)
+
+func TestRejectedProxyRequests(t *testing.T) {
+	secret := "upstream-password"
+	for _, tc := range []struct {
+		name, method, target string
+		status               int
+	}{
+		{"relative URL", "GET", "/relative", 400},
+		{"unsupported URL", "GET", "ftp://example.com/file", 400},
+		{"invalid CONNECT", "CONNECT", "example.com", 400},
+		{"HTTP selection failure", "GET", "http://example.com/", 502},
+		{"CONNECT selection failure", "CONNECT", "example.com:443", 502},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			s := &Server{selectProxy: func(*http.Request) (*url.URL, error) { return nil, errors.New(secret) }}
+			s.transport = &http.Transport{Proxy: s.selectProxy}
+			defer s.transport.CloseIdleConnections()
+			response := httptest.NewRecorder()
+			s.ServeHTTP(response, httptest.NewRequest(tc.method, tc.target, nil))
+			if response.Code != tc.status || strings.Contains(response.Body.String(), secret) {
+				t.Fatalf("unexpected proxy rejection: %d %q", response.Code, response.Body.String())
+			}
+		})
+	}
+}
+
+func TestTunnelRejectsUnsafeUpstreams(t *testing.T) {
+	rejected := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "authentication required", http.StatusProxyAuthRequired)
+	}))
+	defer rejected.Close()
+	secure := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		t.Error("untrusted TLS proxy received a request")
+	}))
+	defer secure.Close()
+	for _, upstream := range []string{"ftp://127.0.0.1", rejected.URL, secure.URL} {
+		t.Run(upstream, func(t *testing.T) {
+			selected, err := url.Parse(upstream)
+			if err != nil {
+				t.Fatal(err)
+			}
+			ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+			defer cancel()
+			conn, err := dialTunnel(ctx, "example.com:443", selected)
+			if conn != nil {
+				conn.Close()
+			}
+			if err == nil {
+				t.Fatal("unsafe upstream unexpectedly accepted")
+			}
+		})
+	}
+}
+
+func TestRoutesAndAuthentication(t *testing.T) {
+	origin := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Proxy-Authorization") != "" {
+			t.Error("proxy credentials leaked to origin")
+		}
+		w.Write([]byte("origin"))
+	}))
+	defer origin.Close()
+	secure := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.Write([]byte("secure")) }))
+	defer secure.Close()
+	upstream, err := New(func(*http.Request) (*url.URL, error) { return nil, nil })
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer upstream.Close()
+	var authenticated atomic.Int32
+	authProxy := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Proxy-Authorization") != "Basic dXNlcjpwYXNz" {
+			http.Error(w, "authentication required", 407)
+			return
+		}
+		authenticated.Add(1)
+		upstream.ServeHTTP(w, r)
+	}))
+	defer authProxy.Close()
+	socks, err := socks5.New(&socks5.Config{Credentials: socks5.StaticCredentials{"user": "pass"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer listener.Close()
+	go socks.Serve(listener)
+	for _, route := range []string{"", authProxy.URL, "socks5://" + listener.Addr().String()} {
+		t.Run(route, func(t *testing.T) {
+			var selected *url.URL
+			if route != "" {
+				selected, _ = url.Parse(route)
+				selected.User = url.UserPassword("user", "pass")
+			}
+			local, err := New(func(r *http.Request) (*url.URL, error) { return selected, nil })
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer local.Close()
+			proxyURL, _ := url.Parse(local.URL())
+			transport := &http.Transport{Proxy: http.ProxyURL(proxyURL), TLSClientConfig: &tls.Config{InsecureSkipVerify: true}}
+			defer transport.CloseIdleConnections()
+			client := &http.Client{Transport: transport, Timeout: 5 * time.Second}
+			for _, test := range []struct{ url, want string }{{origin.URL, "origin"}, {secure.URL, "secure"}} {
+				response, err := client.Get(test.url)
+				if err != nil {
+					t.Fatal(err)
+				}
+				body, _ := io.ReadAll(response.Body)
+				response.Body.Close()
+				if string(body) != test.want {
+					t.Fatalf("got status %d, body %q", response.StatusCode, body)
+				}
+			}
+		})
+	}
+	if authenticated.Load() != 2 {
+		t.Fatalf("expected authenticated HTTP and CONNECT, got %d", authenticated.Load())
+	}
+}
+
+func TestRoutingChangesAndFailureDoesNotBypassProxy(t *testing.T) {
+	var hits atomic.Int32
+	origin := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { hits.Add(1); w.Write([]byte("direct")) }))
+	defer origin.Close()
+	var useProxy atomic.Bool
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.Write([]byte("proxied")) }))
+	upstreamURL, _ := url.Parse(upstream.URL)
+	local, err := New(func(*http.Request) (*url.URL, error) {
+		if useProxy.Load() {
+			return upstreamURL, nil
+		}
+		return nil, nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer local.Close()
+	endpoint, _ := url.Parse(local.URL())
+	transport := &http.Transport{Proxy: http.ProxyURL(endpoint)}
+	defer transport.CloseIdleConnections()
+	client := &http.Client{Transport: transport, Timeout: 3 * time.Second}
+	for _, want := range []string{"direct", "proxied", "upstream request failed\n"} {
+		resp, err := client.Get(origin.URL)
+		if err != nil {
+			t.Fatal(err)
+		}
+		body, _ := io.ReadAll(resp.Body)
+		resp.Body.Close()
+		if string(body) != want {
+			t.Fatalf("got %q want %q", body, want)
+		}
+		if want == "direct" {
+			useProxy.Store(true)
+		} else if want == "proxied" {
+			upstream.Close()
+		}
+	}
+	if hits.Load() != 1 {
+		t.Fatal("failed proxy must not fall back to direct")
+	}
+}
+
+func TestCloseTerminatesTunnels(t *testing.T) {
+	echo, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer echo.Close()
+	go func() {
+		c, e := echo.Accept()
+		if e == nil {
+			defer c.Close()
+			io.Copy(c, c)
+		}
+	}()
+	s, err := New(func(*http.Request) (*url.URL, error) { return nil, nil })
+	if err != nil {
+		t.Fatal(err)
+	}
+	endpoint, _ := url.Parse(s.URL())
+	c, err := dialTunnel(context.Background(), echo.Addr().String(), endpoint)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	c.SetDeadline(time.Now().Add(3 * time.Second))
+	c.Write([]byte("hello\n"))
+	line, err := bufio.NewReader(c).ReadString('\n')
+	if err != nil || line != "hello\n" {
+		t.Fatalf("echo %q %v", line, err)
+	}
+	s.Close()
+	if _, err := c.Read(make([]byte, 1)); err == nil {
+		t.Fatal("tunnel stayed open")
+	}
+}
+
+func TestSOCKSIngressPreservesRemoteDNS(t *testing.T) {
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != "CONNECT" || r.Host != "unresolved.invalid:80" {
+			t.Errorf("lost destination: %s %s", r.Method, r.Host)
+		}
+		c, b, err := w.(http.Hijacker).Hijack()
+		if err != nil {
+			return
+		}
+		defer c.Close()
+		b.WriteString("HTTP/1.1 200 Connection Established\r\n\r\n")
+		b.Flush()
+		request, err := http.ReadRequest(b.Reader)
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		request.Body.Close()
+		b.WriteString("HTTP/1.1 200 OK\r\nContent-Length: 7\r\nConnection: close\r\n\r\nproxied")
+		b.Flush()
+	}))
+	defer upstream.Close()
+	target, _ := url.Parse(upstream.URL)
+	local, err := New(func(r *http.Request) (*url.URL, error) {
+		if r.URL.Host != "unresolved.invalid:80" {
+			t.Errorf("selector lost hostname: %s", r.URL)
+		}
+		return target, nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer local.Close()
+	endpoint, _ := url.Parse(local.SOCKSURL())
+	transport := &http.Transport{Proxy: http.ProxyURL(endpoint)}
+	defer transport.CloseIdleConnections()
+	client := &http.Client{Transport: transport, Timeout: 5 * time.Second}
+	response, err := client.Get("http://unresolved.invalid/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer response.Body.Close()
+	body, _ := io.ReadAll(response.Body)
+	if string(body) != "proxied" {
+		t.Fatalf("unexpected body %q", body)
+	}
+}
+
+func TestHTTPUpgradeIsForwarded(t *testing.T) {
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Upgrade") != "fixture" {
+			http.Error(w, "upgrade lost", 400)
+			return
+		}
+		c, b, err := w.(http.Hijacker).Hijack()
+		if err != nil {
+			return
+		}
+		defer c.Close()
+		b.WriteString("HTTP/1.1 101 Switching Protocols\r\nConnection: Upgrade\r\nUpgrade: fixture\r\n\r\n")
+		b.Flush()
+		line, err := b.ReadString('\n')
+		if err != nil {
+			return
+		}
+		b.WriteString(line)
+		b.Flush()
+	}))
+	defer upstream.Close()
+	local, err := New(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer local.Close()
+	endpoint, _ := url.Parse(local.URL())
+	c, err := net.Dial("tcp", endpoint.Host)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	c.SetDeadline(time.Now().Add(3 * time.Second))
+	io.WriteString(c, "GET "+upstream.URL+"/ HTTP/1.1\r\nHost: fixture\r\nConnection: Upgrade\r\nUpgrade: fixture\r\n\r\n")
+	reader := bufio.NewReader(c)
+	response, err := http.ReadResponse(reader, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if response.StatusCode != 101 {
+		t.Fatalf("upgrade failed: %s", response.Status)
+	}
+	io.WriteString(c, "hello\n")
+	line, err := reader.ReadString('\n')
+	if err != nil || line != "hello\n" {
+		t.Fatalf("upgraded echo %q %v", line, err)
+	}
+}

internal/webview/rpcprovider/README.md

@@ -1,5 +1,11 @@
 # rpcprovider
 
+The private Flutter native profile bridge is maintained in the
+[GopeedLab flutter_inappwebview fork](https://github.com/GopeedLab/flutter_inappwebview/tree/codex/gopeed-profiles).
+All three platform overrides pin one commit in `ui/flutter/pubspec.yaml`;
+see the fork’s [GOPEED.md](https://github.com/GopeedLab/flutter_inappwebview/blob/codex/gopeed-profiles/GOPEED.md)
+for patch scope and upstream synchronization.
+
 `rpcprovider` is the RPC-backed implementation of Gopeed's `webview.Provider` interface.
 
 It is intended for environments where WebView capability is owned by another process, most notably mobile hosts. This package does not implement a WebView itself. Instead, it translates the `pkg/download/engine/webview` page API into single-request `POST + JSON` calls sent to a local host-side RPC service.

internal/webview/rpcprovider/events_test.go

@@ -0,0 +1,207 @@
+package rpcprovider
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	wv "github.com/GopeedLab/gopeed/pkg/download/engine/webview"
+)
+
+func TestPageEventStream(t *testing.T) {
+	events := make(chan wv.Event, 8)
+	disconnected := make(chan struct{})
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var request wv.RPCRequest
+		if err := json.NewDecoder(r.Body).Decode(&request); err != nil {
+			t.Error(err)
+			return
+		}
+		if request.Method != "page.events" {
+			t.Errorf("unexpected method %s", request.Method)
+			return
+		}
+		if r.Header.Get("Authorization") != "Bearer test" {
+			t.Error("missing authorization")
+		}
+		defer close(disconnected)
+		enc := json.NewEncoder(w)
+		_ = enc.Encode(map[string]any{"ready": true})
+		w.(http.Flusher).Flush()
+		for {
+			select {
+			case e := <-events:
+				_ = enc.Encode(e)
+				w.(http.Flusher).Flush()
+				if e.Name == "closed" {
+					return
+				}
+			case <-r.Context().Done():
+				return
+			}
+		}
+	}))
+	defer server.Close()
+	p := &page{client: NewClient(wv.RPCConfig{Network: "tcp", Address: strings.TrimPrefix(server.URL, "http://"), Token: "test"}), id: "page-1"}
+	got := make(chan wv.Event, 8)
+	off, err := p.On("load", func(e wv.Event) { got <- e })
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = p.On("closed", func(e wv.Event) { got <- e })
+	if err != nil {
+		t.Fatal(err)
+	}
+	events <- wv.Event{Name: "load", Data: map[string]any{"url": "https://example.test"}}
+	select {
+	case e := <-got:
+		if e.Name != "load" {
+			t.Fatal(e)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("no load event")
+	}
+	off()
+	off()
+	events <- wv.Event{Name: "load"}
+	events <- wv.Event{Name: "closed", Data: map[string]any{"reason": "user"}}
+	select {
+	case e := <-got:
+		if e.Name != "closed" || e.Data["reason"] != "user" {
+			t.Fatal(e)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("no closed event")
+	}
+	select {
+	case <-disconnected:
+	case <-time.After(time.Second):
+		t.Fatal("stream retained after close")
+	}
+	if _, err = p.On("load", func(wv.Event) {}); err == nil {
+		t.Fatal("registration after close")
+	}
+}
+
+func TestPageEventStreamHandshakeFailureCanRetry(t *testing.T) {
+	for _, tc := range []struct {
+		name   string
+		status int
+		body   string
+	}{
+		{"http_error", http.StatusUnauthorized, `{"ready":true}`},
+		{"invalid_json", http.StatusOK, `not json`},
+		{"not_ready", http.StatusOK, `{"ready":false}`},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			var requests atomic.Int32
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if requests.Add(1) == 1 {
+					w.WriteHeader(tc.status)
+					_, _ = io.WriteString(w, tc.body)
+					return
+				}
+				_, _ = io.WriteString(w, "{\"ready\":true}\n{\"event\":\"load\",\"data\":{\"url\":\"https://example.test\"}}\n")
+				w.(http.Flusher).Flush()
+				<-r.Context().Done()
+			}))
+			defer server.Close()
+			p := &page{client: NewClient(wv.RPCConfig{Network: "tcp", Address: strings.TrimPrefix(server.URL, "http://")}), id: "retry-page"}
+			if off, err := p.On("load", func(wv.Event) { t.Error("failed registration retained its listener") }); err == nil || off != nil {
+				t.Fatal("failed handshake accepted")
+			}
+			got := make(chan wv.Event, 1)
+			off, err := p.On("load", func(e wv.Event) { got <- e })
+			if err != nil {
+				t.Fatalf("retry: %v", err)
+			}
+			defer func() {
+				p.eventCancel()
+				<-p.eventDone
+			}()
+			defer off()
+			select {
+			case e := <-got:
+				if e.Data["url"] != "https://example.test" {
+					t.Fatal(e)
+				}
+			case <-time.After(time.Second):
+				t.Fatal("retry did not receive load notification")
+			}
+			if requests.Load() != 2 {
+				t.Fatalf("unexpected request count: %d", requests.Load())
+			}
+		})
+	}
+}
+
+func TestPageEventStreamDisconnectAndClose(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var request wv.RPCRequest
+		if err := json.NewDecoder(r.Body).Decode(&request); err != nil {
+			t.Error(err)
+			return
+		}
+		switch request.Method {
+		case wv.MethodPageEvents:
+			// End the stream without a terminal event, as if the host dropped it.
+			_, _ = io.WriteString(w, "{\"ready\":true}\n")
+		case wv.MethodPageClose:
+			_ = json.NewEncoder(w).Encode(wv.RPCResponse{})
+		default:
+			t.Errorf("unexpected method: %s", request.Method)
+		}
+	}))
+	defer server.Close()
+	p := &page{client: NewClient(wv.RPCConfig{Network: "tcp", Address: strings.TrimPrefix(server.URL, "http://")}), id: "disconnected-page"}
+	closed := make(chan wv.Event, 1)
+	if _, err := p.On("closed", func(e wv.Event) { closed <- e }); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case <-p.eventDone:
+	case <-time.After(time.Second):
+		t.Fatal("disconnected stream did not stop")
+	}
+	if _, err := p.On("load", func(wv.Event) {}); err == nil || !strings.Contains(err.Error(), "disconnected") {
+		t.Fatalf("registration hid stream failure: %v", err)
+	}
+	if err := p.Close(); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case event := <-closed:
+		if event.Data["reason"] != "api" {
+			t.Fatal(event)
+		}
+	default:
+		t.Fatal("API close did not release listeners after disconnect")
+	}
+	if err := p.Close(); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case event := <-closed:
+		t.Fatalf("duplicate close notification: %+v", event)
+	default:
+	}
+}
+
+func TestPageEventStreamConnectionFailureCanRetry(t *testing.T) {
+	server := httptest.NewServer(http.NotFoundHandler())
+	server.Close()
+	p := &page{client: NewClient(wv.RPCConfig{Network: "tcp", Address: strings.TrimPrefix(server.URL, "http://")}), id: "offline-page"}
+	for i := 0; i < 2; i++ {
+		if off, err := p.On("load", func(wv.Event) {}); err == nil || off != nil {
+			t.Fatal("registration to unavailable host succeeded")
+		}
+	}
+	if p.eventCancel != nil {
+		t.Fatal("failed connection retained an active stream")
+	}
+}

internal/webview/rpcprovider/provider.go

@@ -4,10 +4,13 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net"
 	"net/http"
 	"strings"
+	"sync"
+	"time"
 
 	enginewebview "github.com/GopeedLab/gopeed/pkg/download/engine/webview"
 )
@@ -48,8 +51,13 @@ func (p *Provider) Open(opts enginewebview.OpenOptions) (enginewebview.Page, err
 }
 
 type page struct {
-	client *Client
-	id     string
+	eventMu     sync.Mutex
+	events      enginewebview.EventHub
+	eventCancel context.CancelFunc
+	eventDone   chan struct{}
+	eventErr    error
+	client      *Client
+	id          string
 }
 
 func (p *page) AddInitScript(script string) error {
@@ -109,9 +117,28 @@ func (p *page) ClearCookies() error {
 }
 
 func (p *page) Close() error {
-	return p.client.Call(enginewebview.MethodPageClose, enginewebview.PageCloseParams{
-		PageID: p.id,
-	}, nil)
+	err := p.client.Call(enginewebview.MethodPageClose, enginewebview.PageCloseParams{PageID: p.id}, nil)
+	var rpcErr *enginewebview.RPCError
+	if errors.As(err, &rpcErr) && rpcErr.Code == enginewebview.ErrorCodePageNotFound {
+		err = nil
+	}
+	if err != nil {
+		return err
+	}
+	p.eventMu.Lock()
+	cancel, done := p.eventCancel, p.eventDone
+	p.eventMu.Unlock()
+	if cancel != nil {
+		// Drain the terminal notification before cancelling the transport, so
+		// already-sent navigation events keep their order before closed.
+		select {
+		case <-done:
+		case <-time.After(5 * time.Second):
+		}
+		cancel()
+	}
+	p.events.Emit(enginewebview.Event{Name: "closed", Data: map[string]any{"reason": "api"}})
+	return nil
 }
 
 type Client struct {
@@ -193,3 +220,83 @@ func (c *Client) Call(method string, params any, result any) error {
 	}
 	return json.Unmarshal(body.Result, result)
 }
+
+func (p *Provider) RemoveProfile(profileID, dataPath string) error {
+	return p.client.Call(enginewebview.MethodProfileRemove, enginewebview.ProfileRemoveParams{ProfileID: profileID}, nil)
+}
+
+// On starts one ordered notification stream per page. The ready record is sent
+// only after the host has installed its subscription.
+func (p *page) On(name string, handler func(enginewebview.Event)) (func(), error) {
+	p.eventMu.Lock()
+	defer p.eventMu.Unlock()
+	if p.eventErr != nil {
+		return nil, p.eventErr
+	}
+	unsubscribe, err := p.events.On(name, handler)
+	if err != nil {
+		return nil, err
+	}
+	if p.eventCancel != nil {
+		return unsubscribe, nil
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	payload, err := json.Marshal(enginewebview.RPCRequest{Method: enginewebview.MethodPageEvents, Params: enginewebview.PageCloseParams{PageID: p.id}})
+	if err != nil {
+		cancel()
+		unsubscribe()
+		return nil, err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, p.client.endpoint, bytes.NewReader(payload))
+	if err != nil {
+		cancel()
+		unsubscribe()
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	if p.client.token != "" {
+		req.Header.Set("Authorization", "Bearer "+p.client.token)
+	}
+	// A broken host must not leave registration pending indefinitely.
+	timer := time.AfterFunc(30*time.Second, cancel)
+	resp, err := p.client.http.Do(req)
+	if err != nil {
+		timer.Stop()
+		cancel()
+		unsubscribe()
+		return nil, err
+	}
+	decoder := json.NewDecoder(resp.Body)
+	var ready struct {
+		Ready bool `json:"ready"`
+	}
+	err = decoder.Decode(&ready)
+	timer.Stop()
+	if err != nil || !ready.Ready || resp.StatusCode != http.StatusOK {
+		resp.Body.Close()
+		cancel()
+		unsubscribe()
+		return nil, fmt.Errorf("webview event stream did not become ready: %v", err)
+	}
+	p.eventCancel = cancel
+	p.eventDone = make(chan struct{})
+	go func() {
+		defer resp.Body.Close()
+		defer cancel()
+		defer close(p.eventDone)
+		for {
+			var event enginewebview.Event
+			if err := decoder.Decode(&event); err != nil {
+				p.eventMu.Lock()
+				p.eventErr = fmt.Errorf("webview event stream disconnected: %w", err)
+				p.eventMu.Unlock()
+				return
+			}
+			p.events.Emit(event)
+			if event.Name == "closed" {
+				return
+			}
+		}
+	}()
+	return unsubscribe, nil
+}

internal/webview/rpcprovider/provider_integration_test.go

@@ -37,3 +37,12 @@ func defaultWebViewRPCAddress() string {
 	}
 	return filepath.Join(homeDir, "Library", "Application Support", "com.gopeed.gopeed", "gopeed_webview.sock")
 }
+
+func TestProviderProfiles(t *testing.T) {
+	provider := New(enginewebview.RPCConfig{Network: *webViewRPCNetwork, Address: *webViewRPCAddress, Token: *webViewRPCToken})
+	integrationtest.RunProfileContract(t, provider)
+}
+
+func TestProviderEvents(t *testing.T) {
+	integrationtest.RunEventContract(t, New(enginewebview.RPCConfig{Network: *webViewRPCNetwork, Address: *webViewRPCAddress, Token: *webViewRPCToken}))
+}

internal/webview/rpcprovider/provider_test.go

@@ -184,3 +184,29 @@ func TestPageSetCookieParamsOmitsZeroExpires(t *testing.T) {
 		t.Fatalf("expected expires in payload: %s", got)
 	}
 }
+
+func TestRemoveProfileUsesPrivateHostRPC(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var request struct {
+			Method string            `json:"method"`
+			Params map[string]string `json:"params"`
+		}
+		if err := json.NewDecoder(r.Body).Decode(&request); err != nil {
+			t.Error(err)
+		}
+		if request.Method != enginewebview.MethodProfileRemove || request.Params["profileId"] != "extension-profile" || len(request.Params) != 1 {
+			t.Errorf("unexpected profile removal request: %+v", request)
+		}
+		if r.Header.Get("Authorization") != "Bearer secret" {
+			t.Error("missing host authentication")
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.Write([]byte(`{"error":{"code":"PROFILE_REMOVE_FAILED","message":"store busy"}}`))
+	}))
+	defer server.Close()
+	provider := New(enginewebview.RPCConfig{Network: "tcp", Address: strings.TrimPrefix(server.URL, "http://"), Token: "secret"})
+	err := provider.(enginewebview.ProfileRemover).RemoveProfile("extension-profile", "/host-only/path")
+	if err == nil || err.Error() != "store busy" {
+		t.Fatalf("cleanup failure was lost: %v", err)
+	}
+}

pkg/api/events.go

@@ -10,8 +10,15 @@ import (
 type TaskEventMask uint64
 
 const (
+	// Keep these first two unchanged because Flutter already uses
+	// bit 0 for done and bit 1 for error.
 	TaskEventDone TaskEventMask = 1 << iota
 	TaskEventError
+
+	TaskEventStart
+	TaskEventProgress
+	TaskEventPause
+	TaskEventDelete
 )
 
 type TaskEvent struct {
@@ -42,11 +49,26 @@ func (s *Service) emitTaskEvent(event *download.Event) {
 	}
 
 	var mask TaskEventMask
+
 	switch event.Key {
 	case download.EventKeyDone:
 		mask = TaskEventDone
+
 	case download.EventKeyError:
 		mask = TaskEventError
+
+	case download.EventKeyStart:
+		mask = TaskEventStart
+
+	case download.EventKeyProgress:
+		mask = TaskEventProgress
+
+	case download.EventKeyPause:
+		mask = TaskEventPause
+
+	case download.EventKeyDelete:
+		mask = TaskEventDelete
+
 	default:
 		return
 	}

pkg/api/service.go

@@ -156,7 +156,7 @@ func (s *Service) createTask(ctx *Context) *Response {
 		err    error
 	)
 	if request.Rid != "" {
-		taskID, err = s.Downloader.Create(request.Rid)
+		taskID, err = s.Downloader.CreateWithOptions(request.Rid, request.Opts)
 	} else if request.Req != nil {
 		taskID, err = s.Downloader.CreateDirect(request.Req, request.Opts)
 	} else {

pkg/base/model.go

@@ -25,24 +25,6 @@ type Request struct {
 	SkipVerifyCert bool `json:"skipVerifyCert"`
 }
 
-// SetLabels replaces all labels on the request.
-func (r *Request) SetLabels(labels map[string]string) {
-	r.Labels = labels
-}
-
-// PutLabel sets a label on the request.
-func (r *Request) 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 *Request) DelLabel(key string) {
-	delete(r.Labels, key)
-}
-
 func (r *Request) Validate() error {
 	if r.URL == "" {
 		return fmt.Errorf("invalid request url")
@@ -94,9 +76,6 @@ type Resource struct {
 }
 
 func (r *Resource) Validate() error {
-	if r.Name == "" {
-		return fmt.Errorf("invalid resource name")
-	}
 	if len(r.Files) == 0 {
 		return fmt.Errorf("invalid resource files")
 	}

pkg/download/downloader.go

@@ -21,6 +21,8 @@ import (
 	"github.com/GopeedLab/gopeed/internal/controller"
 	"github.com/GopeedLab/gopeed/internal/fetcher"
 	"github.com/GopeedLab/gopeed/internal/logger"
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
+	webviewproxy "github.com/GopeedLab/gopeed/internal/webview/proxy"
 	"github.com/GopeedLab/gopeed/pkg/base"
 	"github.com/GopeedLab/gopeed/pkg/protocol/http"
 	"github.com/GopeedLab/gopeed/pkg/util"
@@ -97,8 +99,13 @@ type Progress struct {
 }
 
 type Downloader struct {
-	Logger          *logger.Logger
-	ExtensionLogger *logger.Logger
+	tempFiles           *tempfiles.Scope
+	webviewProfilesLock sync.Mutex
+	webviewProfiles     map[string]*extensionWebViewProfile
+	webviewProxyLock    sync.Mutex
+	webviewProxy        *webviewproxy.Server
+	Logger              *logger.Logger
+	ExtensionLogger     *logger.Logger
 
 	cfg          *DownloaderConfig
 	fetcherCache map[string]fetcher.Fetcher
@@ -152,6 +159,9 @@ func NewDownloader(cfg *DownloaderConfig) *Downloader {
 }
 
 func (d *Downloader) Setup() error {
+	if err := d.setupTempDir(); err != nil {
+		return err
+	}
 	d.blob = internalblob.NewRegistry("")
 
 	// setup storage
@@ -263,24 +273,45 @@ func (d *Downloader) Setup() error {
 						if d.GetTask(task.ID) == nil {
 							return
 						}
+						// Startup can replace resource metadata while resolving a Blob.
+						// Skip that short transition instead of reading half-initialized state.
+						if !task.lock.TryLock() {
+							return
+						}
 						task.statusLock.Lock()
 						if task.Status != base.DownloadStatusRunning && !task.Uploading {
 							task.statusLock.Unlock()
+							task.lock.Unlock()
 							return
 						}
 						if task.fetcher == nil {
 							task.statusLock.Unlock()
+							task.lock.Unlock()
 							return
 						}
 
 						current := task.fetcher.Progress().TotalDownloaded()
+						delta := current - task.Progress.Downloaded
+						if task.Meta != nil && task.Meta.Req != nil {
+							if producer := d.blob.Production(task.Meta.Req.URL); producer != nil {
+								downloaded, received := producer.Progress()
+								if task.producer != producer {
+									task.producer = producer
+									task.producerReceived = 0
+									task.speedArr = nil
+								}
+								current = downloaded
+								delta = max(0, received-task.producerReceived)
+								task.producerReceived = received
+							}
+						}
 						tick := float64(d.cfg.RefreshInterval) / 1000
 						downloadDataChanged := false
 						uploading := task.Uploading
 						if task.Status == base.DownloadStatusRunning {
 							downloadDataChanged = current != task.Progress.Downloaded
 							task.Progress.Used = task.timer.Used()
-							task.Progress.Speed = task.updateSpeed(current-task.Progress.Downloaded, tick)
+							task.Progress.Speed = task.updateSpeed(max(0, delta), tick)
 							task.Progress.Downloaded = current
 						}
 
@@ -299,6 +330,7 @@ func (d *Downloader) Setup() error {
 						if err := d.captureTaskStats(task, true, false); err != nil {
 							d.Logger.Warn().Err(err).Msgf("persist task stats failed, task id: %s", task.ID)
 						}
+						task.lock.Unlock()
 						// Listener callbacks may Pause/Continue and acquire statusLock.
 						d.emit(EventKeyProgress, task)
 
@@ -389,6 +421,9 @@ func (d *Downloader) parseFm(url string) (fetcher.FetcherManager, error) {
 
 func (d *Downloader) setupFetcher(fm fetcher.FetcherManager, fetcher fetcher.Fetcher) {
 	ctl := controller.NewController()
+	ctl.TempDir = d.cfg.TempDir
+	ctl.TempFiles = d.tempFiles
+	ctl.ManagedProduction = func(raw string) bool { return d.blob.Production(raw) != nil }
 	ctl.GetConfig = func(v any) {
 		d.getProtocolConfig(fm.Name(), v)
 	}
@@ -582,12 +617,36 @@ func (d *Downloader) CreateDirectBatch(req *base.CreateTaskBatch) (taskId []stri
 }
 
 func (d *Downloader) Create(rrId string) (taskId string, err error) {
+	return d.CreateWithOptions(rrId, nil)
+}
+
+// CreateWithOptions creates a resolved task using the submitted options, or the
+// resolve-time options when opts is nil.
+func (d *Downloader) CreateWithOptions(rrId string, opts *base.Options) (taskId string, err error) {
 	d.fetcherMapLock.RLock()
 	fetcher, ok := d.fetcherCache[rrId]
 	d.fetcherMapLock.RUnlock()
 	if !ok {
 		return "", errors.New("invalid resource id")
 	}
+	if opts != nil {
+		opts, err = d.initOptions(opts.Clone())
+		if err != nil {
+			return "", err
+		}
+		if res := fetcher.Meta().Res; res != nil {
+			for _, index := range opts.SelectFiles {
+				if index < 0 || index >= len(res.Files) {
+					return "", fmt.Errorf("invalid selected file index: %d", index)
+				}
+			}
+			opts.InitSelectFiles(len(res.Files))
+		}
+		fetcher.Meta().Opts = opts
+	}
+	if res := fetcher.Meta().Res; res != nil {
+		res.CalcSize(fetcher.Meta().Opts.SelectFiles)
+	}
 	defer func() {
 		d.fetcherMapLock.Lock()
 		delete(d.fetcherCache, rrId)
@@ -1114,6 +1173,11 @@ func (d *Downloader) doDelete(task *Task, force bool) (err error) {
 
 func (d *Downloader) Close() error {
 	d.closed.Store(true)
+	d.webviewProxyLock.Lock()
+	if d.webviewProxy != nil {
+		_ = d.webviewProxy.Close()
+	}
+	d.webviewProxyLock.Unlock()
 
 	closeArr := []func() error{
 		d.pauseAll,
@@ -1124,7 +1188,7 @@ func (d *Downloader) Close() error {
 	if d.blob != nil {
 		closeArr = append(closeArr, d.blob.Close)
 	}
-	closeArr = append(closeArr, d.storage.Close)
+	closeArr = append(closeArr, d.storage.Close, d.tempFiles.Close)
 	// Make sure all resources are released, if had error, return the last error
 	var lastErr error
 	for i, close := range closeArr {
@@ -1399,17 +1463,6 @@ func (d *Downloader) watch(task *Task) {
 			}
 		}
 
-		task.Progress.Used = task.timer.Used()
-		if task.Meta.Res.Size == 0 {
-			task.Meta.Res.Size = task.fetcher.Progress().TotalDownloaded()
-		}
-		used := task.Progress.Used / int64(time.Second)
-		if used == 0 {
-			used = 1
-		}
-		totalSize := task.Meta.Res.Size
-		task.Progress.Speed = totalSize / used
-		task.Progress.Downloaded = totalSize
 		if !d.markTaskDone(task) {
 			return
 		}
@@ -1808,7 +1861,9 @@ func (d *Downloader) doStart(task *Task) (err error) {
 			task.Meta.Res.CalcSize(task.Meta.Opts.SelectFiles)
 		}
 
+		task.statusLock.Lock()
 		task.Progress.Speed = 0
+		task.statusLock.Unlock()
 		if !d.taskIsRunningGeneration(task, generation) {
 			return nil
 		}
@@ -1857,6 +1912,7 @@ func (d *Downloader) doPause(task *Task) (err error) {
 	}
 	if handled {
 		d.emit(EventKeyPause, task)
+		d.triggerWebhooks(WebhookEventDownloadPause, task, nil)
 	}
 	return nil
 }
@@ -1962,11 +2018,27 @@ func (d *Downloader) markTaskDone(task *Task) bool {
 	if task == nil || task.statusLock == nil {
 		return false
 	}
+	task.lock.Lock()
+	defer task.lock.Unlock()
 	task.statusLock.Lock()
 	defer task.statusLock.Unlock()
 	if task.Status != base.DownloadStatusRunning {
 		return false
 	}
+	task.Progress.Used = task.timer.Used()
+	if task.Meta.Res.Size == 0 {
+		task.Meta.Res.Size = task.fetcher.Progress().TotalDownloaded()
+	}
+	used := task.Progress.Used / int64(time.Second)
+	if used == 0 {
+		used = 1
+	}
+	totalSize := task.Meta.Res.Size
+	task.Progress.Speed = totalSize / used
+	task.Progress.Downloaded = totalSize
+
+	task.producer = nil
+	task.producerReceived = 0
 	task.updateStatus(base.DownloadStatusDone)
 	task.runGeneration++
 	return true

pkg/download/downloader_test.go

@@ -45,6 +45,32 @@ type generationTestManager struct {
 
 func TestExtensionTaskMethodsMatchEventCapabilities(t *testing.T) {
 	taskType := reflect.TypeOf((*Task)(nil))
+	for _, typ := range []reflect.Type{taskType, reflect.TypeOf((*ExtensionTask)(nil)), reflect.TypeOf((*OnErrorExtensionTask)(nil))} {
+		for _, name := range []string{"SetUrl", "SetExtra", "PatchExtra", "PatchHeaders", "SetMethod", "SetBody", "SetHeaders", "PutHeader", "DelHeader", "SetTrackers"} {
+			if _, ok := typ.MethodByName(name); ok {
+				t.Fatalf("%v unexpectedly exposes %s", typ, name)
+			}
+		}
+	}
+	requestType := reflect.TypeOf((*ExtensionTaskRequest)(nil))
+	for _, name := range []string{"SetUrl", "SetLabels", "PutLabel", "DelLabel", "SetMethod", "SetBody", "SetHeaders", "PutHeader", "DelHeader", "SetTrackers"} {
+		if _, ok := requestType.MethodByName(name); !ok {
+			t.Fatalf("request wrapper does not expose %s", name)
+		}
+	}
+	for _, typ := range []reflect.Type{reflect.TypeOf(ExtensionTask{}), reflect.TypeOf(OnErrorExtensionTask{})} {
+		if _, ok := typ.FieldByName("Req"); ok {
+			t.Fatalf("%v exposes the removed task.req entry", typ)
+		}
+		field, ok := typ.FieldByName("Meta")
+		if !ok || field.Type != reflect.TypeOf((*ExtensionTaskMeta)(nil)) {
+			t.Fatalf("%v has no metadata wrapper", typ)
+		}
+	}
+	field, ok := reflect.TypeOf(ExtensionTaskMeta{}).FieldByName("Req")
+	if !ok || field.Type != requestType {
+		t.Fatal("meta.req has no request wrapper")
+	}
 	if _, ok := taskType.MethodByName("Continue"); ok {
 		t.Fatal("regular task unexpectedly exposes Continue")
 	}
@@ -53,17 +79,11 @@ func TestExtensionTaskMethodsMatchEventCapabilities(t *testing.T) {
 	}
 
 	extensionTaskType := reflect.TypeOf((*ExtensionTask)(nil))
-	if _, ok := extensionTaskType.MethodByName("SetUrl"); !ok {
-		t.Fatal("extension task does not expose SetUrl")
-	}
 	if _, ok := extensionTaskType.MethodByName("Continue"); ok {
 		t.Fatal("non-error extension task unexpectedly exposes Continue")
 	}
 
 	errorTaskType := reflect.TypeOf((*OnErrorExtensionTask)(nil))
-	if _, ok := errorTaskType.MethodByName("SetUrl"); !ok {
-		t.Fatal("onError task does not expose SetUrl")
-	}
 	if _, ok := errorTaskType.MethodByName("Continue"); !ok {
 		t.Fatal("onError task does not expose Continue")
 	}

pkg/download/engine/engine.go

@@ -6,9 +6,12 @@ import (
 	"fmt"
 	"sync"
 
+	"github.com/GopeedLab/gopeed/internal/production"
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
 	"github.com/GopeedLab/gopeed/pkg/base"
 	gojaerror "github.com/GopeedLab/gopeed/pkg/download/engine/inject/error"
 	fetchapi "github.com/GopeedLab/gopeed/pkg/download/engine/inject/fetch"
+	ffmpegapi "github.com/GopeedLab/gopeed/pkg/download/engine/inject/ffmpeg"
 	"github.com/GopeedLab/gopeed/pkg/download/engine/inject/file"
 	"github.com/GopeedLab/gopeed/pkg/download/engine/inject/stream"
 	"github.com/GopeedLab/gopeed/pkg/download/engine/inject/vm"
@@ -159,8 +162,12 @@ func (e *Engine) addCleanup(cleanup func()) {
 }
 
 type Config struct {
-	ProxyConfig  *base.DownloaderProxyConfig
-	StreamConfig *stream.Config
+	TempFiles *tempfiles.Scope
+	// HTTPUserAgent is a snapshot of the downloader HTTP default. Nil leaves standalone engines unchanged.
+	TempDir       string
+	HTTPUserAgent *string
+	ProxyConfig   *base.DownloaderProxyConfig
+	StreamConfig  *stream.Config
 }
 
 func NewEngine(cfg *Config) *Engine {
@@ -200,12 +207,29 @@ func NewEngine(cfg *Config) *Engine {
 		if _, err := runtime.RunString("global.location = new URL('http://localhost');"); err != nil {
 			return
 		}
-		if err := stream.Enable(runtime, loop, cfg.StreamConfig); err != nil {
+		producers := &production.Registry{}
+		streamCfg := stream.Config{}
+		if cfg.StreamConfig != nil {
+			streamCfg = *cfg.StreamConfig
+		}
+		streamCfg.Producers = producers
+		if err := stream.Enable(runtime, loop, &streamCfg); err != nil {
+			return
+		}
+		if err := ffmpegapi.Enable(runtime, loop, &ffmpegapi.Config{
+			Producers:        producers,
+			TempDir:          cfg.TempDir,
+			TempFiles:        cfg.TempFiles,
+			ProxyHandler:     cfg.ProxyConfig.ToHandler(),
+			DefaultUserAgent: cfg.HTTPUserAgent,
+			RegisterCleanup:  engine.addCleanup,
+		}); err != nil {
 			return
 		}
 		if err := fetchapi.Enable(runtime, loop, &fetchapi.Config{
-			ProxyHandler:    cfg.ProxyConfig.ToHandler(),
-			RegisterCleanup: engine.addCleanup,
+			ProxyHandler:     cfg.ProxyConfig.ToHandler(),
+			DefaultUserAgent: cfg.HTTPUserAgent,
+			RegisterCleanup:  engine.addCleanup,
 		}); err != nil {
 			return
 		}
@@ -265,3 +289,8 @@ func callExportedFunction(fn func(goja.FunctionCall) goja.Value, args ...goja.Va
 		Arguments: args,
 	}), nil
 }
+
+// Post queues a notification without waiting for its callback or returned promise.
+func (e *Engine) Post(fn func(*goja.Runtime)) bool {
+	return e.loop.RunOnLoop(fn)
+}

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

@@ -0,0 +1,160 @@
+# Extension FFmpeg runtime
+
+`gopeed.runtime.ffmpeg.merge(options)` returns a `ReadableStream<Uint8Array>`.
+It merges one video track and one audio track without re-encoding, using
+[go-ffmpreg](https://codeberg.org/gruf/go-ffmpreg)'s embedded FFmpeg 5.1.10 and
+wazero. No system FFmpeg installation is required. go-ffmpreg and its embedded
+GPL-enabled FFmpeg are distributed under GPLv3; see the pinned dependency's
+LICENSE, README and build scripts for its source and included components.
+
+## HTTP inputs and one downloadable output
+
+```js
+gopeed.events.onResolve(async (ctx) => {
+  // Resolve these URLs and headers using the site's API in your extension.
+  const video = { url: videoURL, headers: { Referer: pageURL } };
+  const audio = { url: audioURL, headers: { Referer: pageURL } };
+  const url = await gopeed.runtime.blob.createObjectURL(
+    () => gopeed.runtime.ffmpeg.merge({ video, audio }),
+    { contentType: "video/mp4" }
+  );
+  ctx.res = {
+    name: "video",
+    files: [{ name: "video.mp4", req: { url } }]
+  };
+});
+```
+
+The opener creates a new merge on each open. Output size is unknown and range
+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.
+
+## JS inputs, including SABR
+
+Stream inputs **must** be created by an `inputs({ signal })` callback. It returns
+`{ video, audio }`, each an HTTP descriptor or `ReadableStream<Uint8Array>`,
+including mixed inputs. Do not start producers before this callback. SABR/UMP decoding belongs
+to the extension: pass the resulting media streams, with initialization data,
+not the SABR protocol bytes. Keep each selected track's codec/configuration
+stable for the duration of a merge.
+
+```js
+const output = gopeed.runtime.ffmpeg.merge({
+  inputs: async ({ signal }) => {
+    const session = await prepareSession({ signal });
+    const { videoStream, audioStream, abort } = await session.openStreams();
+    if (signal.aborted) { abort(); throw new Error("Cancelled"); }
+    signal.addEventListener("abort", abort, { once: true });
+    return { video: videoStream, audio: audioStream };
+  },
+  signal: abortController.signal,
+  args: ["-shortest", "-metadata", "title=Example"]
+});
+```
+
+Creating the output does not start requests or acquire input readers until the
+output is pulled. Inputs then download to temporary disk chunks even while the
+job waits for a global FFmpeg execution slot. Only merging occupies a slot.
+The callback runs once per output; its signal aborts on cancellation, engine
+shutdown, failure, and completion. A callback must cooperate with cancellation;
+returned streams are cancelled even if the callback finishes after cancellation.
+A stream input is single-use. To retry a Blob-backed task,
+its opener must create a new SABR session and fresh input streams. Arbitrary
+output byte ranges / resumable merged output are not supported.
+
+`gopeed.runtime.ffmpeg.supportsInputFactory === true` identifies the callback API.
+`gopeed.runtime.ffmpeg.supportsProducerProgress === true` identifies disk-backed
+inputs and automatic Blob production progress. Require the latter before using
+one shared SABR session for both tracks; older bounded buffers can deadlock.
+
+## Options
+
+- `inputs`: callback returning `{ video, audio }`, synchronously or asynchronously.
+  Required for stream inputs. Cannot be combined with top-level `video`/`audio`.
+- `video`, `audio`: HTTP descriptors only when supplied at the top level; both
+  are required unless `inputs` is supplied. HTTP descriptors have `url` and optional
+  `headers` (standard `HeadersInit`). HTTP requests use Gopeed's configured
+  proxy. Supply required cookies/authorization explicitly; browser or `fetch`
+  cookie jars are not implicitly shared. When `User-Agent` is absent, requests
+  use the downloader HTTP protocol's configured UA, captured when the extension
+  engine is created, matching fetch and XHR. Explicit UA values (including an
+  empty string) take precedence.
+- `format`: defaults to `"mp4"`. MP4 output always enables fragmentation
+  (`frag_keyframe+empty_moov+default_base_moof`) for non-seekable output. The
+  other accepted muxers are `"mkv"`/`"matroska"`, `"webm"`, and `"mpegts"`.
+  Codec/container incompatibility is an error, not an automatic conversion.
+  Choose the matching filename and Blob content type in the extension.
+- `args`: optional array of **output options**, not a shell command or a full
+  FFmpeg invocation. Defaults select `0:v:0`, `1:a:0`, and `-c copy`. Additional
+  `-map` options are additive. Allowed options are listed in `outputOptions` in
+  `runtime.go`: metadata, dispositions, bitstream filters, duration/shortest,
+  fragmentation, timestamp/interleaving options and `-strict`. Codec options
+  must remain `copy`. Extra inputs, output paths, reports and arbitrary global
+  options are rejected. Required MP4 fragmentation is enforced by the host.
+- `signal`: optional `AbortSignal`. Aborting or cancelling the output stops
+  network requests and native execution, cancels input readers, and removes
+  temporary buffers. Await/consume the output inside a live engine or retain
+  it through a Blob URL; unowned work ends with the extension engine.
+
+The backend defaults to strict input errors (`-xerror`). Native errors include
+the FFmpeg exit code and a bounded stderr tail. No host directories are exposed
+to the WASM module; it can access only its two input files and standard output.
+
+## Input behavior and resource limits
+
+HTTP inputs start with a 1 MiB Range GET, reusing the bytes for media reads.
+A validated 206 response with a known total size enables seeking; a 200
+response is consumed as-is, sequentially. Subsequent ranges verify positions,
+lengths, total size and available ETag/Last-Modified validators. Without a
+server validator, same-size remote changes cannot be reliably detected.
+Content encoding is forced to identity. Authentication/status failures and
+malformed range responses are errors. There is no full-file seek fallback.
+
+HTTP and sequential JS inputs are drained into **8 MiB disk chunks** beneath
+`TempDir/gopeed-media-<random>`. Range downloads stream each response into as many chunks as
+needed, tracking valid byte intervals independently of sparse file length.
+Verified HTTP Range inputs can seek, skip missing blocks, and re-fetch deleted
+blocks. Sequential inputs cannot seek even though their bytes are on disk.
+Consumed chunks are deleted; cancellation, errors and completion remove the
+remaining input directories. Disk space is not capped; write failures stop the
+merge. Media size does not determine the size of in-memory input queues.
+
+JS writes await disk writes, and Blob output writes await bounded downstream
+capacity. Extensions must still propagate backpressure through upstream queues
+and network reads. Both tracks can share a SABR response because disk spooling
+continues independently of which track FFmpeg currently reads.
+
+When a Blob opener returns the merge stream directly, the runtime automatically
+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;
+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
+still enforce a 15-second network idle deadline.
+
+`tempDir` defaults to Go's `os.TempDir()` when omitted. Flutter only supplies
+an explicit directory on Android/iOS, using `getTemporaryDirectory()` directly;
+no extra `gopeed` parent directory is added. Desktop/server callers can override
+it via startup JSON or `--temp-dir`.
+
+Initialization never clears this directory. Media inputs, HTTP prefetch and
+extension installation staging create unique `gopeed-media-*`,
+`gopeed-prefetch-*`, and `gopeed-extension-*` paths directly beneath it. The
+downloader tracks only its own paths and removes remaining ones on normal
+shutdown, without scanning or deleting other files in a shared temporary
+directory. Resources still clean up on completion/cancellation, and consumed
+media chunks are deleted promptly. Forced process termination can leave files
+behind; the next startup does not delete them. Persistent HLS resume data and
+WebView profiles are unchanged.
+
+At most two WASM merges execute concurrently per process, with a 512 MiB
+linear-memory limit per instance. Compilation is shared and lazy; the upstream
+embedded package still decompresses its WASM at process initialization. Native
+compilation memory, host buffers and JS allocations are additional to the
+linear-memory limit. Playback support depends on the selected codecs, not just
+the `.mp4` suffix. Platform execution and performance must be tested on target
+devices, especially mobile/32-bit devices.

pkg/download/engine/ffmpeg/http_spool.go

@@ -0,0 +1,248 @@
+package ffmpeg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"sync"
+
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
+)
+
+// HTTPSpool downloads ahead independently of the FFmpeg semaphore. Range
+// sources can fetch a missing block on demand, including blocks already evicted.
+type HTTPSpool struct {
+	demand     chan int64
+	demandDone chan struct{}
+	ctx        context.Context
+	cancel     context.CancelFunc
+	source     Input
+	disk       *DiskInput
+	network    sync.Mutex
+	readMu     sync.Mutex
+	pos        int64
+	done       chan struct{}
+}
+
+func OpenSpoolingHTTP(ctx context.Context, client *http.Client, source HTTPSource, root string, owners ...*tempfiles.Scope) (Input, error) {
+	ctx, cancel := context.WithCancel(ctx)
+	in, err := OpenHTTP(ctx, client, source)
+	if err != nil {
+		cancel()
+		return nil, err
+	}
+	disk, err := NewDiskInput(ctx, root, owners...)
+	if err != nil {
+		cancel()
+		in.Close()
+		return nil, err
+	}
+	if ranged := in.(*httpInput); ranged.ranged {
+		if _, err = disk.spool.WriteAt(ranged.block, 0); err != nil {
+			cancel()
+			in.Close()
+			disk.Close()
+			return nil, err
+		}
+		ranged.block = nil
+	}
+	h := &HTTPSpool{ctx: ctx, cancel: cancel, source: in, disk: disk, done: make(chan struct{}), demand: make(chan int64, 1), demandDone: make(chan struct{})}
+	go func() {
+		defer close(h.demandDone)
+		for {
+			select {
+			case offset := <-h.demand:
+				// A prefetch may have filled this position while demand was queued.
+				var probe [1]byte
+				if n, err, _ := h.disk.spool.readAt(probe[:], offset); n > 0 || err != nil {
+					continue
+				}
+				if err := h.fetch(offset / SpoolBlockSize * SpoolBlockSize); err != nil {
+					h.disk.End(err)
+					return
+				}
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+	go func() {
+		defer close(h.done)
+		var err error
+		if !in.Seekable() {
+			_, err = io.CopyBuffer(disk, in, make([]byte, 64*1024))
+		} else {
+			for offset := int64(0); offset < in.Size(); offset += 3 * SpoolBlockSize {
+				if err = h.fetch(offset); err != nil {
+					break
+				}
+			}
+		}
+		disk.End(err)
+	}()
+	return h, nil
+}
+func (h *HTTPSpool) fetch(offset int64) error {
+	h.network.Lock()
+	defer h.network.Unlock()
+	if err := h.ctx.Err(); err != nil {
+		return err
+	}
+	source := h.source.(*httpInput)
+	end := offset + min(3*SpoolBlockSize, h.source.Size()-offset)
+	buffer := make([]byte, 64*1024)
+	for offset < end {
+		n, err, _ := h.disk.spool.readAt(buffer[:min(int64(len(buffer)), end-offset)], offset)
+		if err != nil {
+			return err
+		}
+		if n > 0 {
+			offset += int64(n)
+			continue
+		}
+		resp, err := source.request(offset, end-1)
+		if err != nil {
+			return err
+		}
+		err = func() error {
+			defer resp.Body.Close()
+			if resp.StatusCode != http.StatusPartialContent {
+				return fmt.Errorf("ffmpeg: Range request returned %d; source changed or stopped supporting Range", resp.StatusCode)
+			}
+			start, last, size, err := contentRange(resp.Header.Get("Content-Range"))
+			if err != nil || start != offset || last >= end || size != source.size {
+				return errors.New("ffmpeg: inconsistent Content-Range")
+			}
+			if source.etag != "" && resp.Header.Get("ETag") != source.etag {
+				return errors.New("ffmpeg: HTTP input ETag changed")
+			}
+			if source.etag == "" && source.modified != "" && resp.Header.Get("Last-Modified") != source.modified {
+				return errors.New("ffmpeg: HTTP input Last-Modified changed")
+			}
+			if err := identityEncoding(resp); err != nil {
+				return err
+			}
+			remaining := last - start + 1
+			if resp.ContentLength >= 0 && resp.ContentLength != remaining {
+				return errors.New("ffmpeg: Range response length mismatch")
+			}
+			for remaining > 0 {
+				n, err := resp.Body.Read(buffer[:min(int64(len(buffer)), remaining)])
+				if n > 0 {
+					if _, e := h.disk.spool.WriteAt(buffer[:n], offset); e != nil {
+						return e
+					}
+					offset += int64(n)
+					remaining -= int64(n)
+				}
+				if err != nil {
+					if err == io.EOF && remaining == 0 {
+						return nil
+					}
+					if err == io.EOF {
+						return io.ErrUnexpectedEOF
+					}
+					return err
+				}
+				if n == 0 {
+					return io.ErrNoProgress
+				}
+			}
+			n, err := resp.Body.Read(buffer[:1])
+			if n != 0 || err != io.EOF {
+				if err != nil && err != io.EOF {
+					return err
+				}
+				return errors.New("ffmpeg: oversized Range response")
+			}
+			return nil
+		}()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+func (h *HTTPSpool) Read(p []byte) (int, error) {
+	if !h.Seekable() {
+		return h.disk.Read(p)
+	}
+	h.readMu.Lock()
+	defer h.readMu.Unlock()
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if h.pos >= h.Size() {
+		if err := h.disk.spool.discard((h.Size() - 1) / SpoolBlockSize); err != nil {
+			return 0, err
+		}
+		return 0, io.EOF
+	}
+	for {
+		if err := h.ctx.Err(); err != nil {
+			return 0, err
+		}
+		n, err, wake := h.disk.spool.readAt(p, h.pos)
+		if n > 0 {
+			block := h.pos / SpoolBlockSize
+			h.pos += int64(n)
+			if h.pos/SpoolBlockSize > block {
+				if e := h.disk.spool.discard(block); err == nil {
+					err = e
+				}
+			}
+			return n, err
+		}
+		if err != nil {
+			return 0, err
+		}
+		select {
+		case h.demand <- h.pos:
+		default:
+		}
+		// Read as soon as a partial response supplies these bytes, rather than
+		// waiting for its entire multi-block Range request to finish.
+		select {
+		case <-wake:
+		case <-h.ctx.Done():
+			return 0, h.ctx.Err()
+		}
+	}
+}
+func (h *HTTPSpool) Seek(offset int64, whence int) (int64, error) {
+	if !h.Seekable() {
+		return 0, ErrSeek
+	}
+	h.readMu.Lock()
+	defer h.readMu.Unlock()
+	base := int64(0)
+	switch whence {
+	case io.SeekStart:
+	case io.SeekCurrent:
+		base = h.pos
+	case io.SeekEnd:
+		base = h.Size()
+	default:
+		return 0, errors.New("invalid seek origin")
+	}
+	next := base + offset
+	if next < 0 || (offset > 0 && next < base) {
+		return 0, errors.New("invalid seek offset")
+	}
+	h.pos = next
+	return next, nil
+}
+func (h *HTTPSpool) Size() int64              { return h.source.Size() }
+func (h *HTTPSpool) Seekable() bool           { return h.source.Seekable() }
+func (h *HTTPSpool) Progress() (int64, int64) { return h.disk.Progress() }
+func (h *HTTPSpool) Close() error {
+	h.cancel()
+	h.source.Close()
+	<-h.done
+	<-h.demandDone
+	return h.disk.Close()
+}
+
+func (h *HTTPSpool) Failures() <-chan error { return h.disk.Failures() }

pkg/download/engine/ffmpeg/http_spool_test.go

@@ -0,0 +1,198 @@
+package ffmpeg
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestHTTPSpoolRangeCrossBlocksAndRefetch(t *testing.T) {
+	data := make([]byte, 4*SpoolBlockSize+57)
+	for i := range data {
+		data[i] = byte(i*31 + i/257)
+	}
+	var large atomic.Bool
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var start, end int64
+		fmt.Sscanf(r.Header.Get("Range"), "bytes=%d-%d", &start, &end)
+		if end-start+1 > SpoolBlockSize {
+			large.Store(true)
+		}
+		w.Header().Set("ETag", `"stable"`)
+		http.ServeContent(w, r, "media", time.Time{}, bytes.NewReader(data))
+	}))
+	defer srv.Close()
+	input, err := OpenSpoolingHTTP(context.Background(), srv.Client(), HTTPSource{URL: srv.URL}, t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer input.Close()
+	h := input.(*HTTPSpool)
+	select {
+	case <-h.done:
+	case <-time.After(10 * time.Second):
+		t.Fatal("prefetch did not finish")
+	}
+	if !large.Load() {
+		t.Fatal("did not fetch multiple blocks in one response")
+	}
+	for _, offset := range []int64{3*SpoolBlockSize - 123, 0, 2*SpoolBlockSize + 41, SpoolBlockSize - 5} {
+		if _, err := h.Seek(offset, io.SeekStart); err != nil {
+			t.Fatal(err)
+		}
+		got := make([]byte, min(int64(2*SpoolBlockSize), int64(len(data))-offset))
+		if _, err := io.ReadFull(h, got); err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(got, data[offset:offset+int64(len(got))]) {
+			t.Fatal("incorrect random/cross-block read", offset)
+		}
+	}
+	unique, received := h.Progress()
+	if unique != int64(len(data)) || received <= unique {
+		t.Fatal("refetch progress must not double-count stored bytes", unique, received)
+	}
+}
+
+func TestHTTPSpoolSequentialAndCancellation(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	entered := make(chan struct{})
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("hello"))
+		w.(http.Flusher).Flush()
+		close(entered)
+		<-r.Context().Done()
+	}))
+	defer srv.Close()
+	in, err := OpenSpoolingHTTP(ctx, srv.Client(), HTTPSource{URL: srv.URL}, t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	<-entered
+	if in.Seekable() {
+		t.Fatal("200 response advertised seek")
+	}
+	got := make([]byte, 5)
+	if _, err := io.ReadFull(in, got); err != nil || string(got) != "hello" {
+		t.Fatal(string(got), err)
+	}
+	cancel()
+	if err := in.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestHTTPSpoolRejectsBadRanges(t *testing.T) {
+	for _, mode := range []string{"etag", "length", "offset", "status", "truncated", "encoding"} {
+		t.Run(mode, func(t *testing.T) {
+			var calls atomic.Int32
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				first := calls.Add(1) == 1
+				start, end := int64(0), int64(httpBlockSize-1)
+				if !first {
+					fmt.Sscanf(r.Header.Get("Range"), "bytes=%d-%d", &start, &end)
+				}
+				tag := `"stable"`
+				if !first && mode == "etag" {
+					tag = `"changed"`
+				}
+				w.Header().Set("ETag", tag)
+				if !first && mode == "status" {
+					w.WriteHeader(200)
+					return
+				}
+				if !first && mode == "offset" {
+					start++
+				}
+				if !first && mode == "encoding" {
+					w.Header().Set("Content-Encoding", "gzip")
+				}
+				w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, 2*SpoolBlockSize))
+				length := end - start + 1
+				if !first && mode == "length" {
+					length++
+				}
+				w.Header().Set("Content-Length", fmt.Sprint(length))
+				w.WriteHeader(206)
+				if !first && mode == "truncated" {
+					length /= 2
+				}
+				chunk := make([]byte, 64*1024)
+				for length > 0 {
+					n := min(int64(len(chunk)), length)
+					if _, err := w.Write(chunk[:n]); err != nil {
+						return
+					}
+					length -= n
+				}
+			}))
+			defer srv.Close()
+			in, err := OpenSpoolingHTTP(context.Background(), srv.Client(), HTTPSource{URL: srv.URL}, t.TempDir())
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer in.Close()
+			h := in.(*HTTPSpool)
+			select {
+			case err := <-h.Failures():
+				if err == nil {
+					t.Fatal("nil failure")
+				}
+			case <-time.After(5 * time.Second):
+				t.Fatal("bad range did not fail")
+			}
+		})
+	}
+}
+
+func TestHTTPSpoolReadsPartialRangeBeforeResponseFinishes(t *testing.T) {
+	ready, finish := make(chan struct{}), make(chan struct{})
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var start, end int64
+		fmt.Sscanf(r.Header.Get("Range"), "bytes=%d-%d", &start, &end)
+		end = min(end, 4*1024*1024-1)
+		w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, 4*1024*1024))
+		w.Header().Set("Content-Length", fmt.Sprint(end-start+1))
+		w.WriteHeader(206)
+		if start == 0 {
+			w.Write(make([]byte, end+1))
+			return
+		}
+		w.Write(bytes.Repeat([]byte{93}, 64*1024))
+		w.(http.Flusher).Flush()
+		close(ready)
+		select {
+		case <-finish:
+			w.Write(make([]byte, end-start+1-64*1024))
+		case <-r.Context().Done():
+		}
+	}))
+	defer srv.Close()
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	input, err := OpenSpoolingHTTP(ctx, srv.Client(), HTTPSource{URL: srv.URL}, t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer input.Close()
+	select {
+	case <-ready:
+	case <-ctx.Done():
+		t.Fatal(ctx.Err())
+	}
+	if _, err := input.Seek(1024*1024, io.SeekStart); err != nil {
+		t.Fatal(err)
+	}
+	b := make([]byte, 1)
+	if _, err := io.ReadFull(input, b); err != nil || b[0] != 93 {
+		t.Fatal("waited for complete response", b, err)
+	}
+	close(finish)
+}

pkg/download/engine/ffmpeg/input.go

@@ -0,0 +1,252 @@
+// Package ffmpeg runs an embedded FFmpeg with host-controlled media inputs.
+package ffmpeg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const httpBlockSize = 1024 * 1024
+
+// Input is a file visible to FFmpeg. Only verified HTTP Range sources seek.
+type Input interface {
+	io.ReadCloser
+	Seek(int64, int) (int64, error)
+	Size() int64
+	Seekable() bool
+}
+
+var ErrSeek = errors.New("ffmpeg: input requires seeking but source is sequential")
+
+type HTTPSource struct {
+	URL     string            `json:"url"`
+	Headers map[string]string `json:"headers"`
+}
+
+type httpInput struct {
+	ctx                   context.Context
+	client                *http.Client
+	source                HTTPSource
+	body                  io.ReadCloser
+	size, pos, blockStart int64
+	block                 []byte
+	ranged                bool
+	etag, modified        string
+}
+
+// OpenHTTP combines capability detection with the first media read. A 200
+// response remains open and is consumed sequentially without another request.
+func OpenHTTP(ctx context.Context, client *http.Client, source HTTPSource) (Input, error) {
+	u, err := url.Parse(source.URL)
+	if err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" {
+		return nil, errors.New("ffmpeg: expected an HTTP(S) input URL")
+	}
+	h := &httpInput{ctx: ctx, client: client, source: source, size: -1}
+	resp, err := h.request(0, httpBlockSize-1)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode == http.StatusOK {
+		if err = identityEncoding(resp); err != nil {
+			resp.Body.Close()
+			return nil, err
+		}
+		h.body, h.size = resp.Body, resp.ContentLength
+		return h, nil
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusPartialContent {
+		return nil, fmt.Errorf("ffmpeg: HTTP input returned %d", resp.StatusCode)
+	}
+	start, end, size, err := contentRange(resp.Header.Get("Content-Range"))
+	if err != nil || start != 0 || end >= httpBlockSize {
+		return nil, errors.New("ffmpeg: invalid initial Content-Range")
+	}
+	h.size, h.ranged = size, true
+	h.etag = resp.Header.Get("ETag")
+	if strings.HasPrefix(h.etag, "W/") {
+		h.etag = ""
+	}
+	h.modified = resp.Header.Get("Last-Modified")
+	h.block, err = readBlock(resp, end-start+1)
+	return h, err
+}
+
+func (h *httpInput) request(start, end int64) (*http.Response, error) {
+	ctx, cancel := context.WithCancel(h.ctx)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, h.source.URL, nil)
+	if err != nil {
+		cancel()
+		return nil, err
+	}
+	for k, v := range h.source.Headers {
+		req.Header.Set(k, v)
+	}
+	// Offsets must refer to the actual media bytes, not a decompressed response.
+	req.Header.Set("Accept-Encoding", "identity")
+	req.Header.Set("Range", fmt.Sprintf("bytes=%d-%d", start, end))
+	if h.etag != "" {
+		req.Header.Set("If-Range", h.etag)
+	} else if h.modified != "" {
+		req.Header.Set("If-Range", h.modified)
+	}
+	timer := time.AfterFunc(15*time.Second, cancel)
+	resp, err := h.client.Do(req)
+	timer.Stop()
+	if err != nil {
+		cancel()
+		return nil, err
+	}
+	resp.Body = &idleMediaBody{ReadCloser: resp.Body, cancel: cancel}
+	return resp, nil
+}
+
+func identityEncoding(resp *http.Response) error {
+	if enc := resp.Header.Get("Content-Encoding"); enc != "" && !strings.EqualFold(enc, "identity") {
+		return errors.New("ffmpeg: encoded HTTP responses cannot represent media byte offsets")
+	}
+	return nil
+}
+
+func contentRange(value string) (start, end, size int64, err error) {
+	err = errors.New("invalid Content-Range")
+	if !strings.HasPrefix(value, "bytes ") {
+		return
+	}
+	parts := strings.Split(strings.TrimPrefix(value, "bytes "), "/")
+	if len(parts) != 2 {
+		return
+	}
+	bounds := strings.Split(parts[0], "-")
+	if len(bounds) != 2 {
+		return
+	}
+	var e error
+	if start, e = strconv.ParseInt(bounds[0], 10, 64); e != nil {
+		return
+	}
+	if end, e = strconv.ParseInt(bounds[1], 10, 64); e != nil {
+		return
+	}
+	if size, e = strconv.ParseInt(parts[1], 10, 64); e != nil {
+		return
+	}
+	if start < 0 || end < start || size <= end {
+		return
+	}
+	err = nil
+	return
+}
+
+func readBlock(resp *http.Response, length int64) ([]byte, error) {
+	if err := identityEncoding(resp); err != nil {
+		return nil, err
+	}
+	if resp.ContentLength >= 0 && resp.ContentLength != length {
+		return nil, errors.New("ffmpeg: Range response length mismatch")
+	}
+	b, err := io.ReadAll(io.LimitReader(resp.Body, length+1))
+	if err != nil {
+		return nil, err
+	}
+	if int64(len(b)) != length {
+		return nil, errors.New("ffmpeg: truncated or oversized Range response")
+	}
+	return b, nil
+}
+
+func (h *httpInput) Read(p []byte) (int, error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if err := h.ctx.Err(); err != nil {
+		return 0, err
+	}
+	if !h.ranged {
+		return h.body.Read(p)
+	}
+	if h.pos >= h.size {
+		return 0, io.EOF
+	}
+	if h.pos < h.blockStart || h.pos >= h.blockStart+int64(len(h.block)) {
+		end := min(h.pos+httpBlockSize-1, h.size-1)
+		resp, err := h.request(h.pos, end)
+		if err != nil {
+			return 0, err
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusPartialContent {
+			return 0, fmt.Errorf("ffmpeg: Range request returned %d; source changed or stopped supporting Range", resp.StatusCode)
+		}
+		start, actualEnd, size, err := contentRange(resp.Header.Get("Content-Range"))
+		if err != nil || start != h.pos || actualEnd > end || size != h.size {
+			return 0, errors.New("ffmpeg: inconsistent Content-Range")
+		}
+		if h.etag != "" && resp.Header.Get("ETag") != h.etag {
+			return 0, errors.New("ffmpeg: HTTP input ETag changed")
+		}
+		if h.etag == "" && h.modified != "" && resp.Header.Get("Last-Modified") != h.modified {
+			return 0, errors.New("ffmpeg: HTTP input Last-Modified changed")
+		}
+		h.block, err = readBlock(resp, actualEnd-start+1)
+		if err != nil {
+			return 0, err
+		}
+		h.blockStart = start
+	}
+	n := copy(p, h.block[h.pos-h.blockStart:])
+	h.pos += int64(n)
+	return n, nil
+}
+
+func (h *httpInput) Seek(offset int64, whence int) (int64, error) {
+	if !h.ranged {
+		return 0, ErrSeek
+	}
+	base := int64(0)
+	switch whence {
+	case io.SeekStart:
+	case io.SeekCurrent:
+		base = h.pos
+	case io.SeekEnd:
+		base = h.size
+	default:
+		return 0, errors.New("invalid seek origin")
+	}
+	next := base + offset
+	if next < 0 || (offset > 0 && next < base) {
+		return 0, errors.New("invalid seek offset")
+	}
+	h.pos = next
+	return next, nil
+}
+
+func (h *httpInput) Size() int64    { return h.size }
+func (h *httpInput) Seekable() bool { return h.ranged }
+func (h *httpInput) Close() error {
+	if h.body != nil {
+		return h.body.Close()
+	}
+	return nil
+}
+
+// Only time spent waiting on the network counts toward this idle deadline.
+// Pauses between reads (disk writes or FFmpeg scheduling) do not count.
+type idleMediaBody struct {
+	io.ReadCloser
+	cancel context.CancelFunc
+}
+
+func (b *idleMediaBody) Read(p []byte) (int, error) {
+	timer := time.AfterFunc(15*time.Second, b.cancel)
+	defer timer.Stop()
+	return b.ReadCloser.Read(p)
+}
+func (b *idleMediaBody) Close() error { b.cancel(); return b.ReadCloser.Close() }

pkg/download/engine/ffmpeg/input_test.go

@@ -0,0 +1,131 @@
+package ffmpeg
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestHTTPRange(t *testing.T) {
+	data := bytes.Repeat([]byte("0123456789"), 300000)
+	var requests atomic.Int32
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		count := requests.Add(1)
+		if r.Header.Get("X-Test") != "secret" {
+			t.Error("missing headers")
+		}
+		if r.Header.Get("Accept-Encoding") != "identity" {
+			t.Error("missing identity encoding")
+		}
+		if count > 1 && r.Header.Get("If-Range") != `"v1"` {
+			t.Error("missing If-Range")
+		}
+		w.Header().Set("ETag", `"v1"`)
+		http.ServeContent(w, r, "media", time.Time{}, bytes.NewReader(data))
+	}))
+	defer srv.Close()
+	in, err := OpenHTTP(context.Background(), srv.Client(), HTTPSource{URL: srv.URL, Headers: map[string]string{"X-Test": "secret"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer in.Close()
+	if !in.Seekable() || in.Size() != int64(len(data)) {
+		t.Fatal("range not detected")
+	}
+	for _, off := range []int64{0, int64(len(data) - 16), 12, int64(httpBlockSize + 35)} {
+		if _, err = in.Seek(off, io.SeekStart); err != nil {
+			t.Fatal(err)
+		}
+		b := make([]byte, 16)
+		if _, err = io.ReadFull(in, b); err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(b, data[off:off+16]) {
+			t.Fatalf("wrong bytes at %d", off)
+		}
+	}
+}
+
+func TestHTTPSequentialAndValidation(t *testing.T) {
+	for _, kind := range []string{"sequential", "bad-range", "changed", "truncated", "unauthorized"} {
+		t.Run(kind, func(t *testing.T) {
+			var requests atomic.Int32
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				count := requests.Add(1)
+				switch kind {
+				case "sequential":
+					w.Write([]byte("media"))
+				case "unauthorized":
+					w.WriteHeader(403)
+				case "bad-range":
+					w.Header().Set("Content-Range", "bytes 2-6/10")
+					w.WriteHeader(206)
+					w.Write([]byte("media"))
+				case "truncated":
+					w.Header().Set("Content-Range", "bytes 0-9/10")
+					w.WriteHeader(206)
+					w.Write([]byte("media"))
+				case "changed":
+					if count == 1 {
+						w.Header().Set("Content-Range", "bytes 0-4/10")
+						w.Header().Set("ETag", `"v1"`)
+						w.WriteHeader(206)
+					}
+					w.Write([]byte("media"))
+				}
+			}))
+			defer srv.Close()
+			in, err := OpenHTTP(context.Background(), srv.Client(), HTTPSource{URL: srv.URL})
+			if kind == "sequential" {
+				if err != nil {
+					t.Fatal(err)
+				}
+				defer in.Close()
+				if in.Seekable() {
+					t.Fatal("unexpected seeking")
+				}
+				if _, err = in.Seek(0, 0); err != ErrSeek {
+					t.Fatal(err)
+				}
+				b, err := io.ReadAll(in)
+				if err != nil || string(b) != "media" || requests.Load() != 1 {
+					t.Fatalf("%q %v count %d", b, err, requests.Load())
+				}
+			} else if kind == "changed" {
+				if err != nil {
+					t.Fatal(err)
+				}
+				defer in.Close()
+				in.Seek(5, 0)
+				if _, err = in.Read(make([]byte, 2)); err == nil {
+					t.Fatal("accepted 200 after range")
+				}
+			} else if err == nil {
+				in.Close()
+				t.Fatal("accepted invalid response")
+			}
+		})
+	}
+}
+
+func TestOutputArguments(t *testing.T) {
+	a, err := Arguments("", []string{"-shortest", "-metadata", "title=test"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(strings.Join(a, " "), "-f mp4 pipe:1") {
+		t.Fatal(a)
+	}
+	for _, args := range [][]string{{"-i", "/etc/passwd"}, {"-report"}, {"-c:v", "libx264"}, {"-metadata"}, {"other.mp4"}} {
+		if _, err := Arguments("mp4", args); err == nil {
+			t.Fatal(fmt.Sprint(args))
+		}
+	}
+}

pkg/download/engine/ffmpeg/runtime.go

@@ -0,0 +1,255 @@
+package ffmpeg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"strings"
+	"sync"
+
+	ffembed "codeberg.org/gruf/go-ffmpreg/embed"
+	"codeberg.org/gruf/go-ffmpreg/wasm"
+	"github.com/tetratelabs/wazero"
+	expsys "github.com/tetratelabs/wazero/experimental/sys"
+	"github.com/tetratelabs/wazero/experimental/sysfs"
+	"github.com/tetratelabs/wazero/sys"
+)
+
+var shared struct {
+	once    sync.Once
+	runtime wazero.Runtime
+	module  wazero.CompiledModule
+	err     error
+}
+
+// Limit active instances independently of the number of extension engines.
+var slots = make(chan struct{}, 2)
+
+func initialize() {
+	shared.once.Do(func() {
+		defer func() {
+			if r := recover(); r != nil {
+				shared.err = fmt.Errorf("ffmpeg initialization: %v", r)
+			}
+		}()
+		cfg := wazero.NewRuntimeConfig().WithCloseOnContextDone(true).WithMemoryLimitPages(8192)
+		shared.runtime, shared.err = wasm.NewRuntime(context.Background(), cfg)
+		if shared.err != nil {
+			return
+		}
+		shared.module, shared.err = shared.runtime.CompileModule(context.Background(), ffembed.B())
+		if shared.err != nil {
+			shared.runtime.Close(context.Background())
+			return
+		}
+		ffembed.Free()
+	})
+}
+
+// Output arguments deliberately do not accept extra inputs, output paths or
+// global filesystem/logging options. The host owns all I/O and cancellation.
+var outputOptions = map[string]int{
+	"-c": 1, "-codec": 1, "-c:v": 1, "-c:a": 1, "-codec:v": 1, "-codec:a": 1,
+	"-map": 1, "-map_metadata": 1, "-map_chapters": 1, "-metadata": 1, "-metadata:s:a:0": 1, "-metadata:s:v:0": 1,
+	"-movflags": 1, "-frag_duration": 1, "-frag_size": 1, "-min_frag_duration": 1,
+	"-bsf:v": 1, "-bsf:a": 1, "-strict": 1, "-shortest": 0, "-t": 1, "-to": 1,
+	"-avoid_negative_ts": 1, "-max_interleave_delta": 1, "-flush_packets": 1,
+	"-disposition:a:0": 1, "-disposition:v:0": 1,
+}
+
+func Arguments(format string, extra []string) ([]string, error) {
+	if format == "" {
+		format = "mp4"
+	}
+	if format == "mkv" {
+		format = "matroska"
+	}
+	switch format {
+	case "mp4", "matroska", "webm", "mpegts":
+	default:
+		return nil, fmt.Errorf("ffmpeg: unsupported output format %q", format)
+	}
+	for i := 0; i < len(extra); {
+		count, ok := outputOptions[extra[i]]
+		if !ok {
+			return nil, fmt.Errorf("ffmpeg: unsupported output option %q", extra[i])
+		}
+		if i+count >= len(extra) {
+			return nil, fmt.Errorf("ffmpeg: missing value for %s", extra[i])
+		}
+		if strings.HasPrefix(extra[i], "-c") && extra[i+1] != "copy" {
+			return nil, errors.New("ffmpeg: merge only supports stream copy")
+		}
+		i += count + 1
+	}
+	args := []string{"-hide_banner", "-nostdin", "-xerror", "-loglevel", "error", "-protocol_whitelist", "file,pipe", "-i", "/inputs/video", "-protocol_whitelist", "file,pipe", "-i", "/inputs/audio", "-map", "0:v:0", "-map", "1:a:0", "-c", "copy"}
+	fragmentFlags := ""
+	for i := 0; i < len(extra); {
+		count := outputOptions[extra[i]]
+		if format == "mp4" && extra[i] == "-movflags" {
+			if strings.Contains(extra[i+1], "faststart") || strings.Contains(extra[i+1], "global_sidx") {
+				return nil, errors.New("ffmpeg: these movflags require seekable output")
+			}
+			fragmentFlags = extra[i+1]
+		} else {
+			args = append(args, extra[i:i+count+1]...)
+		}
+		i += count + 1
+	}
+	if format == "mp4" {
+		args = append(args, "-movflags", fragmentFlags+"+frag_keyframe+empty_moov+default_base_moof")
+	}
+	args = append(args, "-f", format, "pipe:1")
+	return args, nil
+}
+
+// Run shares compilation, but gives every merge its own memory and filesystem.
+// A clean stdout EOF is only delivered by the caller after this succeeds.
+func Run(ctx context.Context, video, audio Input, out io.Writer, format string, extra []string) error {
+	_, err := Arguments(format, extra)
+	if err != nil {
+		return err
+	}
+	release, err := Acquire(ctx)
+	if err != nil {
+		return err
+	}
+	defer release()
+	return RunAcquired(ctx, video, audio, out, format, extra)
+}
+
+// Acquire reserves WASM execution capacity. Disk-backed input downloads may
+// already be running while this call waits.
+func Acquire(ctx context.Context) (func(), error) {
+	select {
+	case slots <- struct{}{}:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+	var once sync.Once
+	return func() { once.Do(func() { <-slots }) }, nil
+}
+
+// RunAcquired requires a reservation held until this call returns.
+func RunAcquired(ctx context.Context, video, audio Input, out io.Writer, format string, extra []string) error {
+	args, err := Arguments(format, extra)
+	if err != nil {
+		return err
+	}
+	ready := make(chan struct{})
+	go func() { initialize(); close(ready) }()
+	select {
+	case <-ready:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+	if shared.err != nil {
+		return shared.err
+	}
+	files := &inputFS{files: map[string]Input{"video": video, "audio": audio}}
+	fsconfig := wazero.NewFSConfig().(sysfs.FSConfig).WithSysFSMount(files, "/inputs")
+	logs := &tailLog{}
+	rc, err := wasm.Run(ctx, shared.runtime, shared.module, wasm.Args{
+		Name: "ffmpeg", Args: args, Stdout: out, Stderr: logs,
+		Config: func(c wazero.ModuleConfig) wazero.ModuleConfig { return c.WithFSConfig(fsconfig) },
+	})
+	if ctx.Err() != nil {
+		return ctx.Err()
+	}
+	if files.err != nil {
+		return fmt.Errorf("ffmpeg input: %w (%s)", files.err, logs.String())
+	}
+	if err != nil {
+		return fmt.Errorf("ffmpeg runtime: %w (%s)", err, logs.String())
+	}
+	if rc != 0 {
+		return fmt.Errorf("ffmpeg exited with code %d: %s", rc, logs.String())
+	}
+	return nil
+}
+
+type tailLog struct{ data []byte }
+
+func (l *tailLog) Write(p []byte) (int, error) {
+	n := len(p)
+	if len(p) > 8192 {
+		p = p[len(p)-8192:]
+	}
+	l.data = append(l.data, p...)
+	if len(l.data) > 8192 {
+		l.data = l.data[len(l.data)-8192:]
+	}
+	return n, nil
+}
+func (l *tailLog) String() string { return strings.TrimSpace(string(l.data)) }
+
+type inputFS struct {
+	expsys.UnimplementedFS
+	files map[string]Input
+	err   error
+}
+
+func (f *inputFS) OpenFile(path string, flag expsys.Oflag, perm fs.FileMode) (expsys.File, expsys.Errno) {
+	if flag&(expsys.O_WRONLY|expsys.O_RDWR|expsys.O_CREAT|expsys.O_TRUNC) != 0 {
+		return nil, expsys.EROFS
+	}
+	path = strings.TrimPrefix(path, "/")
+	if path == "." || path == "" {
+		return &inputFile{owner: f}, 0
+	}
+	in := f.files[path]
+	if in == nil {
+		return nil, expsys.ENOENT
+	}
+	return &inputFile{owner: f, in: in}, 0
+}
+func (f *inputFS) Stat(path string) (sys.Stat_t, expsys.Errno) {
+	file, err := f.OpenFile(path, 0, 0)
+	if err != 0 {
+		return sys.Stat_t{}, err
+	}
+	return file.Stat()
+}
+
+type inputFile struct {
+	expsys.UnimplementedFile
+	owner *inputFS
+	in    Input
+}
+
+func (f *inputFile) IsDir() (bool, expsys.Errno) { return f.in == nil, 0 }
+func (f *inputFile) Stat() (sys.Stat_t, expsys.Errno) {
+	if f.in == nil {
+		return sys.Stat_t{Mode: fs.ModeDir | 0555}, 0
+	}
+	mode := fs.FileMode(0444)
+	if !f.in.Seekable() {
+		mode |= fs.ModeNamedPipe
+	}
+	return sys.Stat_t{Mode: mode, Size: max(0, f.in.Size()), Nlink: 1}, 0
+}
+func (f *inputFile) Read(p []byte) (int, expsys.Errno) {
+	if f.in == nil {
+		return 0, expsys.EISDIR
+	}
+	n, err := f.in.Read(p)
+	if err != nil && err != io.EOF {
+		f.owner.err = err
+		return n, expsys.EIO
+	}
+	return n, 0
+}
+func (f *inputFile) Seek(off int64, whence int) (int64, expsys.Errno) {
+	if f.in == nil {
+		return 0, expsys.EISDIR
+	}
+	n, err := f.in.Seek(off, whence)
+	// Capability probes may legitimately fail; a failed seek alone is not a
+	// media error. FFmpeg decides whether it can continue sequentially.
+	if err != nil {
+		return 0, expsys.ENOSYS
+	}
+	return n, 0
+}

pkg/download/engine/ffmpeg/runtime_test.go

@@ -0,0 +1,221 @@
+package ffmpeg
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"codeberg.org/gruf/go-ffmpreg/wasm"
+	"github.com/tetratelabs/wazero"
+)
+
+// Generate tiny deterministic media with the exact embedded build under test;
+// no system FFmpeg, network media or third-party fixture licensing is needed.
+func fixture(t *testing.T, audio bool) []byte {
+	t.Helper()
+	initialize()
+	if shared.err != nil {
+		t.Fatal(shared.err)
+	}
+	args := []string{"-hide_banner", "-loglevel", "error", "-f", "lavfi", "-i", "color=c=black:s=32x32:r=10", "-t", "0.3", "-c:v", "libx264", "-preset", "ultrafast", "-movflags", "frag_keyframe+empty_moov", "-f", "mp4", "pipe:1"}
+	if audio {
+		args = []string{"-hide_banner", "-loglevel", "error", "-f", "lavfi", "-i", "anullsrc=r=48000:cl=mono", "-t", "0.3", "-c:a", "aac", "-movflags", "frag_keyframe+empty_moov", "-f", "mp4", "pipe:1"}
+	}
+	var out, logs bytes.Buffer
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	rc, err := wasm.Run(ctx, shared.runtime, shared.module, wasm.Args{Name: "ffmpeg", Args: args, Stdout: &out, Stderr: &logs})
+	if err != nil || rc != 0 {
+		t.Fatalf("fixture: %d %v %s", rc, err, logs.String())
+	}
+	return out.Bytes()
+}
+
+func TestTailMoovNeedsRange(t *testing.T) {
+	initialize()
+	if shared.err != nil {
+		t.Fatal(shared.err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	dir := t.TempDir()
+	var logs bytes.Buffer
+	rc, err := wasm.Run(ctx, shared.runtime, shared.module, wasm.Args{Name: "ffmpeg", Args: []string{
+		"-v", "error", "-f", "lavfi", "-i", "color=c=black:s=32x32:r=10", "-t", "0.3", "-c:v", "libx264", "-preset", "ultrafast", "/out/video.mp4",
+	}, Stderr: &logs, Config: func(c wazero.ModuleConfig) wazero.ModuleConfig {
+		return c.WithFSConfig(wazero.NewFSConfig().WithDirMount(dir, "/out"))
+	}})
+	if rc != 0 || err != nil {
+		t.Fatalf("fixture %d %v %s", rc, err, logs.String())
+	}
+	raw, err := os.ReadFile(filepath.Join(dir, "video.mp4"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var video []byte
+	for offset := 0; offset < len(raw); {
+		length := int(binary.BigEndian.Uint32(raw[offset : offset+4]))
+		if string(raw[offset+4:offset+8]) == "moov" {
+			free := make([]byte, 2*httpBlockSize)
+			binary.BigEndian.PutUint32(free, uint32(len(free)))
+			copy(free[4:], "free")
+			video = append(video, free...)
+		}
+		video = append(video, raw[offset:offset+length]...)
+		offset += length
+	}
+	audio := fixture(t, true)
+	for _, ranged := range []bool{true, false} {
+		t.Run(fmtBool(ranged), func(t *testing.T) {
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				data := video
+				if r.URL.Path == "/audio" {
+					data = audio
+				}
+				if ranged {
+					http.ServeContent(w, r, "media", time.Time{}, bytes.NewReader(data))
+				} else {
+					w.Write(data)
+				}
+			}))
+			defer srv.Close()
+			v, err := OpenHTTP(ctx, srv.Client(), HTTPSource{URL: srv.URL})
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer v.Close()
+			a, err := OpenHTTP(ctx, srv.Client(), HTTPSource{URL: srv.URL + "/audio"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer a.Close()
+			err = Run(ctx, v, a, io.Discard, "mp4", nil)
+			if ranged && err != nil {
+				t.Fatal(err)
+			}
+			if !ranged && err == nil {
+				t.Fatal("non-seekable tail-moov input unexpectedly succeeded")
+			}
+		})
+	}
+}
+
+func fmtBool(b bool) string {
+	if b {
+		return "range"
+	}
+	return "sequential"
+}
+
+func TestWebMToMP4(t *testing.T) {
+	initialize()
+	if shared.err != nil {
+		t.Fatal(shared.err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	inputs := make([]*DiskInput, 2)
+	for i, name := range []string{"video.webm", "audio.webm"} {
+		data, err := os.ReadFile(filepath.Join("..", "testdata", "ffmpeg", name))
+		if err != nil {
+			t.Fatal(err)
+		}
+		inputs[i], err = NewDiskInput(ctx, t.TempDir())
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer inputs[i].Close()
+		if _, err = inputs[i].Write(data); err != nil {
+			t.Fatal(err)
+		}
+		inputs[i].End(nil)
+	}
+
+	var output, probe, logs bytes.Buffer
+	if err := Run(ctx, inputs[0], inputs[1], &output, "mp4", nil); err != nil {
+		t.Fatal(err)
+	}
+	rc, err := wasm.Run(ctx, shared.runtime, shared.module, wasm.Args{Name: "ffprobe", Args: []string{"-v", "error", "-show_entries", "stream=codec_name", "-of", "json", "pipe:0"}, Stdin: bytes.NewReader(output.Bytes()), Stdout: &probe, Stderr: &logs})
+	if rc != 0 || err != nil {
+		t.Fatalf("probe %d %v %s", rc, err, logs.String())
+	}
+	if !bytes.Contains(probe.Bytes(), []byte(`"vp9"`)) || !bytes.Contains(probe.Bytes(), []byte(`"opus"`)) {
+		t.Fatalf("codecs changed: %s", probe.String())
+	}
+}
+
+func TestWASMMerge(t *testing.T) {
+	video, audio := fixture(t, false), fixture(t, true)
+	for _, ranged := range []bool{false, true} {
+		t.Run(map[bool]string{false: "sequential", true: "range"}[ranged], func(t *testing.T) {
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				data := video
+				if r.URL.Path == "/audio" {
+					data = audio
+				}
+				if ranged {
+					http.ServeContent(w, r, "media", time.Time{}, bytes.NewReader(data))
+				} else {
+					w.Write(data)
+				}
+			}))
+			defer srv.Close()
+			ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+			defer cancel()
+			v, err := OpenHTTP(ctx, srv.Client(), HTTPSource{URL: srv.URL + "/video"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer v.Close()
+			a, err := OpenHTTP(ctx, srv.Client(), HTTPSource{URL: srv.URL + "/audio"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer a.Close()
+			var output bytes.Buffer
+			if err = Run(ctx, v, a, &output, "", nil); err != nil {
+				t.Fatal(err)
+			}
+			if !bytes.Contains(output.Bytes(), []byte("moof")) {
+				t.Fatal("output is not fragmented MP4")
+			}
+			// Probe the actual result, rather than just checking its filename/header.
+			var probe, logs bytes.Buffer
+			rc, err := wasm.Run(ctx, shared.runtime, shared.module, wasm.Args{Name: "ffprobe", Args: []string{"-v", "error", "-show_streams", "-of", "json", "pipe:0"}, Stdin: bytes.NewReader(output.Bytes()), Stdout: &probe, Stderr: &logs})
+			if rc != 0 || err != nil {
+				t.Fatalf("probe: %d %v %s", rc, err, logs.String())
+			}
+			var result struct {
+				Streams []struct {
+					CodecType string `json:"codec_type"`
+					CodecName string `json:"codec_name"`
+				}
+			}
+			if err = json.Unmarshal(probe.Bytes(), &result); err != nil {
+				t.Fatal(err)
+			}
+			if len(result.Streams) != 2 || result.Streams[0].CodecName != "h264" || result.Streams[1].CodecName != "aac" {
+				t.Fatalf("unexpected streams %s", probe.String())
+			}
+		})
+	}
+	// A malformed input must produce an error, not successful empty output.
+	s, err := NewDiskInput(context.Background(), t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer s.Close()
+	s.Write([]byte("invalid"))
+	s.End(nil)
+	if err := Run(context.Background(), s, s, io.Discard, "", nil); err == nil {
+		t.Fatal("accepted invalid media")
+	}
+}

pkg/download/engine/ffmpeg/spool.go

@@ -0,0 +1,284 @@
+package ffmpeg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
+)
+
+const SpoolBlockSize int64 = 8 * 1024 * 1024
+
+type byteSpan struct{ start, end int64 }
+
+// blockSpool tracks valid byte intervals separately from file length: a sparse
+// file's unwritten holes are never valid media. No file handles survive a call.
+type blockSpool struct {
+	owner                *tempfiles.Scope
+	failures             chan error
+	mu                   sync.Mutex
+	dir                  string
+	blocks               map[int64][]byteSpan
+	seen                 []byteSpan
+	wake                 chan struct{}
+	ended, closed        bool
+	err                  error
+	downloaded, received int64
+}
+
+func newBlockSpool(root string, owners ...*tempfiles.Scope) (*blockSpool, error) {
+	if root != "" {
+		if err := os.MkdirAll(root, 0700); err != nil {
+			return nil, err
+		}
+	}
+	dir, err := os.MkdirTemp(root, "gopeed-media-")
+	if err != nil {
+		return nil, err
+	}
+	var owner *tempfiles.Scope
+	if len(owners) > 0 {
+		owner = owners[0]
+	}
+	if err := owner.Track(dir); err != nil {
+		return nil, err
+	}
+	return &blockSpool{owner: owner, failures: make(chan error, 1), dir: dir, blocks: make(map[int64][]byteSpan), wake: make(chan struct{})}, nil
+}
+func (s *blockSpool) notify()                 { close(s.wake); s.wake = make(chan struct{}) }
+func (s *blockSpool) path(index int64) string { return filepath.Join(s.dir, fmt.Sprintf("%d", index)) }
+func addSpan(spans []byteSpan, next byteSpan) ([]byteSpan, int64) {
+	before := int64(0)
+	for _, span := range spans {
+		before += span.end - span.start
+	}
+	out := make([]byteSpan, 0, len(spans)+1)
+	for _, span := range spans {
+		if span.end < next.start {
+			out = append(out, span)
+		} else if next.end < span.start {
+			out = append(out, next)
+			next = span
+		} else {
+			next.start = min(next.start, span.start)
+			next.end = max(next.end, span.end)
+		}
+	}
+	out = append(out, next)
+	after := int64(0)
+	for _, span := range out {
+		after += span.end - span.start
+	}
+	return out, after - before
+}
+func (s *blockSpool) WriteAt(p []byte, offset int64) (int, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if offset < 0 {
+		return 0, errors.New("negative media offset")
+	}
+	if s.closed {
+		return 0, io.ErrClosedPipe
+	}
+	if s.err != nil {
+		return 0, s.err
+	}
+	written := 0
+	for len(p) > 0 {
+		index, local := offset/SpoolBlockSize, offset%SpoolBlockSize
+		count := int(min(int64(len(p)), SpoolBlockSize-local))
+		f, err := os.OpenFile(s.path(index), os.O_CREATE|os.O_WRONLY, 0600)
+		if err != nil {
+			s.fail(err)
+			s.notify()
+			return written, err
+		}
+		n, err := f.WriteAt(p[:count], local)
+		closeErr := f.Close()
+		if err == nil {
+			err = closeErr
+		}
+		if n > 0 {
+			s.blocks[index], _ = addSpan(s.blocks[index], byteSpan{local, local + int64(n)})
+			var added int64
+			s.seen, added = addSpan(s.seen, byteSpan{offset, offset + int64(n)})
+			s.downloaded += added
+			s.received += int64(n)
+			written += n
+			offset += int64(n)
+			p = p[n:]
+		}
+		if err == nil && n != count {
+			err = io.ErrShortWrite
+		}
+		if err != nil {
+			s.fail(err)
+			s.notify()
+			return written, err
+		}
+	}
+	s.notify()
+	return written, nil
+}
+func (s *blockSpool) readAt(p []byte, offset int64) (int, error, <-chan struct{}) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return 0, io.ErrClosedPipe, nil
+	}
+	if s.err != nil {
+		return 0, s.err, nil
+	}
+	index, local := offset/SpoolBlockSize, offset%SpoolBlockSize
+	for _, span := range s.blocks[index] {
+		if span.start <= local && local < span.end {
+			f, err := os.Open(s.path(index))
+			if err != nil {
+				return 0, err, nil
+			}
+			n, err := f.ReadAt(p[:min(int64(len(p)), span.end-local)], local)
+			f.Close()
+			return n, err, nil
+		}
+	}
+	return 0, nil, s.wake
+}
+func (s *blockSpool) discard(index int64) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if err := os.Remove(s.path(index)); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	delete(s.blocks, index)
+	return nil
+}
+func (s *blockSpool) end(err error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.ended = true
+	if s.err == nil {
+		s.fail(err)
+	}
+	s.notify()
+}
+func (s *blockSpool) Close() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.closed = true
+	clear(s.blocks)
+	s.seen = nil
+	s.notify()
+	return s.owner.Remove(s.dir)
+}
+func (s *blockSpool) progress() (int64, int64) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.downloaded, s.received
+}
+
+// DiskInput consumes a sequential producer without retaining its payload in RAM.
+// Writes acknowledge durable-to-the-OS chunks, allowing both SABR tracks to drain
+// even while FFmpeg is queued or currently reading only the other track.
+type DiskInput struct {
+	ctx             context.Context
+	spool           *blockSpool
+	writeMu, readMu sync.Mutex
+	written, read   int64
+}
+
+func NewDiskInput(ctx context.Context, root string, owners ...*tempfiles.Scope) (*DiskInput, error) {
+	spool, err := newBlockSpool(root, owners...)
+	if err != nil {
+		return nil, err
+	}
+	return &DiskInput{ctx: ctx, spool: spool}, nil
+}
+func (s *DiskInput) Write(p []byte) (int, error) {
+	s.writeMu.Lock()
+	defer s.writeMu.Unlock()
+	if err := s.ctx.Err(); err != nil {
+		return 0, err
+	}
+	s.spool.mu.Lock()
+	ended := s.spool.ended
+	s.spool.mu.Unlock()
+	if ended {
+		return 0, io.ErrClosedPipe
+	}
+	n, err := s.spool.WriteAt(p, s.written)
+	s.written += int64(n)
+	return n, err
+}
+func (s *DiskInput) End(err error) { s.writeMu.Lock(); defer s.writeMu.Unlock(); s.spool.end(err) }
+func (s *DiskInput) Read(p []byte) (int, error) {
+	s.readMu.Lock()
+	defer s.readMu.Unlock()
+	if len(p) == 0 {
+		return 0, nil
+	}
+	for {
+		if err := s.ctx.Err(); err != nil {
+			return 0, err
+		}
+		n, err, wake := s.spool.readAt(p, s.read)
+		if n > 0 {
+			previous := s.read / SpoolBlockSize
+			s.read += int64(n)
+			if s.read/SpoolBlockSize > previous {
+				if e := s.spool.discard(previous); err == nil {
+					err = e
+				}
+			}
+			return n, err
+		}
+		if err != nil {
+			return 0, err
+		}
+		s.spool.mu.Lock()
+		ended := s.spool.ended
+		s.spool.mu.Unlock()
+		// End can race the missing-data check; recheck after observing it.
+		if ended {
+			n, err, _ = s.spool.readAt(p, s.read)
+			if n > 0 {
+				// Use the regular consumption path, including block eviction.
+				continue
+			}
+			if err != nil {
+				return 0, err
+			}
+			if err := s.spool.discard(s.read / SpoolBlockSize); err != nil {
+				return 0, err
+			}
+			return 0, io.EOF
+		}
+		select {
+		case <-wake:
+		case <-s.ctx.Done():
+			return 0, s.ctx.Err()
+		}
+	}
+}
+func (s *DiskInput) Close() error                 { return s.spool.Close() }
+func (*DiskInput) Seek(int64, int) (int64, error) { return 0, ErrSeek }
+func (*DiskInput) Size() int64                    { return -1 }
+func (*DiskInput) Seekable() bool                 { return false }
+func (s *DiskInput) Progress() (int64, int64)     { return s.spool.progress() }
+
+// fail is called with mu held. The first error wakes a queued FFmpeg job.
+func (s *blockSpool) fail(err error) {
+	if err == nil || s.err != nil {
+		return
+	}
+	s.err = err
+	select {
+	case s.failures <- err:
+	default:
+	}
+}
+func (s *DiskInput) Failures() <-chan error { return s.spool.failures }

pkg/download/engine/ffmpeg/spool_test.go

@@ -0,0 +1,101 @@
+package ffmpeg
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"os"
+	"testing"
+)
+
+func TestSpoolSparseCrossBlock(t *testing.T) {
+	s, err := newBlockSpool(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer s.Close()
+	offset := 7*SpoolBlockSize + 123
+	data := bytes.Repeat([]byte{91}, int(3*SpoolBlockSize+37))
+	if n, err := s.WriteAt(data, offset); err != nil || n != len(data) {
+		t.Fatal(n, err)
+	}
+	if n, err, wake := s.readAt(make([]byte, 16), 7*SpoolBlockSize); n != 0 || err != nil || wake == nil {
+		t.Fatal("sparse hole was exposed", n, err)
+	}
+	got := make([]byte, len(data))
+	pos := 0
+	for pos < len(got) {
+		n, err, _ := s.readAt(got[pos:], offset+int64(pos))
+		if err != nil || n == 0 {
+			t.Fatal(n, err)
+		}
+		pos += n
+	}
+	if !bytes.Equal(data, got) {
+		t.Fatal("cross-block contents differ")
+	}
+	if err := s.discard(8); err != nil {
+		t.Fatal(err)
+	}
+	if n, _, wake := s.readAt(got[:1], 8*SpoolBlockSize); n != 0 || wake == nil {
+		t.Fatal("deleted block remained readable")
+	}
+	if _, err := s.WriteAt(data, offset); err != nil {
+		t.Fatal(err)
+	}
+	unique, received := s.progress()
+	if unique != int64(len(data)) || received != 2*unique {
+		t.Fatal(unique, received)
+	}
+}
+func TestDiskInputDrainAndCleanup(t *testing.T) {
+	s, err := NewDiskInput(context.Background(), t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	data := bytes.Repeat([]byte{33}, int(3*SpoolBlockSize+99))
+	if _, err := s.Write(data); err != nil {
+		t.Fatal(err)
+	}
+	s.End(nil)
+	got, err := io.ReadAll(s)
+	if err != nil || !bytes.Equal(data, got) {
+		t.Fatal("drain", err)
+	}
+	files, err := os.ReadDir(s.spool.dir)
+	if err != nil || len(files) != 0 {
+		t.Fatal("consumed blocks retained", len(files), err)
+	}
+	if err := s.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(s.spool.dir); !os.IsNotExist(err) {
+		t.Fatal("spool not removed", err)
+	}
+}
+func TestDiskInputCancelAndWriteFailure(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	s, err := NewDiskInput(ctx, t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer s.Close()
+	cancel()
+	if _, err := s.Read(make([]byte, 1)); err != context.Canceled {
+		t.Fatal(err)
+	}
+	broken, err := NewDiskInput(context.Background(), t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer broken.Close()
+	if err := os.RemoveAll(broken.spool.dir); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := broken.Write([]byte{1}); err == nil {
+		t.Fatal("missing disk error")
+	}
+	if _, err := broken.Read(make([]byte, 1)); err == nil {
+		t.Fatal("disk error not propagated")
+	}
+}

pkg/download/engine/ffmpeg_integration_test.go

@@ -0,0 +1,433 @@
+package engine
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"github.com/GopeedLab/gopeed/internal/production"
+	media "github.com/GopeedLab/gopeed/pkg/download/engine/ffmpeg"
+	"github.com/GopeedLab/gopeed/pkg/download/engine/inject/stream"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestFFmpegJSStreams(t *testing.T) {
+	video, err := os.ReadFile("testdata/ffmpeg/video.mp4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	audio, err := os.ReadFile("testdata/ffmpeg/audio.mp4")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, mode := range []string{"streams", "http", "mixed"} {
+		t.Run(mode, func(t *testing.T) {
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				b := video
+				if r.URL.Path == "/audio" {
+					b = audio
+				}
+				http.ServeContent(w, r, "media", time.Time{}, bytes.NewReader(b))
+			}))
+			defer srv.Close()
+			e := NewEngine(nil)
+			defer e.Close()
+			// Input data is deliberately interleaved through one JS producer.
+			// Native push/read operations must never block the event loop.
+			e.Runtime.Set("videoBytes", e.Runtime.NewArrayBuffer(video))
+			e.Runtime.Set("audioBytes", e.Runtime.NewArrayBuffer(audio))
+			e.Runtime.Set("sourceURL", srv.URL)
+			e.Runtime.Set("inputMode", mode)
+			result, err := e.RunString(`(async()=>{
+		  let vc, ac, offset=0;
+		  const v=new Uint8Array(videoBytes), a=new Uint8Array(audioBytes);
+		  const video=new ReadableStream({start(c){vc=c;}});
+		  const audio=new ReadableStream({start(c){ac=c;}});
+		  const timer=setInterval(()=>{
+		    if(offset<v.length)vc.enqueue(v.slice(offset,offset+97));
+		    if(offset<a.length)ac.enqueue(a.slice(offset,offset+97));
+		    offset+=97;
+		    if(offset>=Math.max(v.length,a.length)){clearInterval(timer);vc.close();ac.close();}
+		  },1);
+		  const stream=__gopeed_ffmpeg.merge({
+		    inputs: () => ({ video:inputMode==='http'?{url:sourceURL+'/video'}:video,
+		    audio:inputMode==='streams'?audio:{url:sourceURL+'/audio'} }),
+		    args:['-metadata','title=gopeed-test']
+		  });
+		  const bytes=await new Response(stream).arrayBuffer();
+		  return new Uint8Array(bytes);
+		})()`)
+			if err != nil {
+				t.Fatal(err)
+			}
+			out, ok := result.([]byte)
+			if !ok {
+				t.Fatalf("output %T", result)
+			}
+			if !bytes.Contains(out, []byte("moof")) || !bytes.Contains(out, []byte("gopeed-test")) {
+				t.Fatalf("invalid output (%d bytes)", len(out))
+			}
+		})
+	}
+}
+
+func TestFFmpegJSErrorAndCancel(t *testing.T) {
+	for _, scenario := range []string{"input-error", "abort", "output-cancel", "invalid-args"} {
+		t.Run(scenario, func(t *testing.T) {
+			e := NewEngine(nil)
+			defer e.Close()
+			e.Runtime.Set("scenario", scenario)
+			result, err := e.RunString(`(async()=>{
+		 let cancelled=0;
+		 const source=()=>new ReadableStream({
+		   pull(c){if(scenario==='input-error')c.error(new Error('upstream failed'));else return new Promise(()=>{});},
+		   cancel(){cancelled++;}
+		 });
+		 const controller=new AbortController();
+		 const output=__gopeed_ffmpeg.merge({inputs:()=>({video:source(),audio:source()}),signal:controller.signal,
+		   args:scenario==='invalid-args'?['-i','/outside']:[]});
+		 const reader=output.getReader();
+		 const pending=reader.read().then(()=>'',e=>e.message);
+		 if(scenario==='abort')setTimeout(()=>controller.abort(),20);
+		 if(scenario==='output-cancel')setTimeout(()=>reader.cancel(),20);
+		 const message=await pending;
+		 await new Promise(r=>setTimeout(r,10));
+		 return {message,cancelled};
+		})()`)
+			if err != nil {
+				t.Fatal(err)
+			}
+			m := result.(map[string]any)
+			if scenario != "output-cancel" && m["message"] == "" {
+				t.Fatalf("missing error: %v", m)
+			}
+			if scenario == "abort" || scenario == "output-cancel" {
+				if fmt.Sprint(m["cancelled"]) != "2" {
+					t.Fatalf("inputs not cancelled: %v", m)
+				}
+			}
+		})
+	}
+}
+
+func TestFFmpegMalformedMediaFails(t *testing.T) {
+	e := NewEngine(nil)
+	defer e.Close()
+	_, err := e.RunString(`(async()=>{
+	  const source=()=>new ReadableStream({start(c){c.enqueue(new Uint8Array([1,2,3]));c.close();}});
+	  return await new Response(__gopeed_ffmpeg.merge({inputs:()=>({video:source(),audio:source()})})).arrayBuffer();
+	})()`)
+	if err == nil || !strings.Contains(err.Error(), "ffmpeg") {
+		t.Fatalf("expected FFmpeg error: %v", err)
+	}
+}
+
+func TestFFmpegBlobOpener(t *testing.T) {
+	var open stream.ObjectURLOpener
+	e := NewEngine(&Config{StreamConfig: &stream.Config{CreateObjectURL: func(opts *stream.ObjectURLOptions, opener stream.ObjectURLOpener) (string, error) {
+		if opts.Range || opts.Size != 0 {
+			t.Fatal("merged output must not advertise range or a guessed size")
+		}
+		open = opener
+		return "blob:ffmpeg-test", nil
+	}}})
+	defer e.Close()
+	video, _ := os.ReadFile("testdata/ffmpeg/video.mp4")
+	audio, _ := os.ReadFile("testdata/ffmpeg/audio.mp4")
+	e.Runtime.Set("videoBytes", e.Runtime.NewArrayBuffer(video))
+	e.Runtime.Set("audioBytes", e.Runtime.NewArrayBuffer(audio))
+	_, err := e.RunString(`__gopeed_blob_create_object_url(()=>{
+	  const source=b=>new ReadableStream({start(c){c.enqueue(new Uint8Array(b));c.close();}});
+	  return __gopeed_ffmpeg.merge({inputs:()=>({video:source(videoBytes),audio:source(audioBytes)})});
+	},{contentType:'video/mp4'})`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 2; i++ {
+		ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+		r, err := open(ctx, stream.ObjectURLOpenRequest{End: -1})
+		if err != nil {
+			cancel()
+			t.Fatal(err)
+		}
+		b, err := io.ReadAll(r)
+		r.Close()
+		cancel()
+		if err != nil || !bytes.Contains(b, []byte("moof")) {
+			t.Fatalf("Blob read: %v (%d bytes)", err, len(b))
+		}
+	}
+}
+
+func TestFFmpegEngineCloseCancelsRequest(t *testing.T) {
+	started, closed := make(chan struct{}), make(chan struct{})
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		close(started)
+		<-r.Context().Done()
+		close(closed)
+	}))
+	defer srv.Close()
+	e := NewEngine(nil)
+	defer e.Close()
+	_, err := e.RunString(fmt.Sprintf(`
+	globalThis.cancelCount=0;
+	const audio=new ReadableStream({cancel(){cancelCount++;}});
+	__gopeed_ffmpeg.merge({inputs:()=>({video:{url:%q},audio})}).getReader().read().catch(()=>{});
+	"started";`, srv.URL))
+	if err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case <-started:
+	case <-time.After(5 * time.Second):
+		t.Fatal("HTTP did not start")
+	}
+	e.Close()
+	select {
+	case <-closed:
+	case <-time.After(5 * time.Second):
+		t.Fatal("HTTP leaked after engine shutdown")
+	}
+	if e.Runtime.Get("cancelCount").ToInteger() != 1 {
+		t.Fatal("JS input not cancelled on shutdown")
+	}
+}
+
+func TestFFmpegInputsStartBeforeCapacity(t *testing.T) {
+	for _, mode := range []string{"factory", "http", "cancel"} {
+		t.Run(mode, func(t *testing.T) {
+			release1, _ := media.Acquire(context.Background())
+			defer release1()
+			release2, _ := media.Acquire(context.Background())
+			defer release2()
+			var requests atomic.Int32
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { requests.Add(1); http.Error(w, "test", 500) }))
+			defer srv.Close()
+			e := NewEngine(nil)
+			defer e.Close()
+			e.Runtime.Set("mode", mode)
+			e.Runtime.Set("sourceURL", srv.URL)
+			result, err := e.RunString(`(async()=>{
+     globalThis.factoryCalls=0;
+     globalThis.abortQueue=new AbortController();
+     const options=mode==='http'?{video:{url:sourceURL},audio:{url:sourceURL}}:
+       {inputs:()=>{factoryCalls++;throw new Error('factory failed');}};
+     options.signal=abortQueue.signal;
+     globalThis.work=__gopeed_ffmpeg.merge(options).getReader().read().then(()=>'',e=>e.message);
+     await new Promise(r=>setTimeout(r,50));
+     if(mode==='cancel')abortQueue.abort();
+     return factoryCalls;
+   })()`)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if mode == "http" {
+				if requests.Load() != 1 {
+					t.Fatalf("queued HTTP did not start: %d", requests.Load())
+				}
+			} else if fmt.Sprint(result) != "1" {
+				t.Fatalf("queued factory did not start: %v", result)
+			}
+			if mode == "cancel" {
+				if _, err = e.RunString(`work`); err != nil {
+					t.Fatal(err)
+				}
+			}
+			release1()
+			if _, err = e.RunString(`work`); err != nil {
+				t.Fatal(err)
+			}
+			calls, err := e.RunString(`factoryCalls`)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if mode == "factory" && fmt.Sprint(calls) != "1" {
+				t.Fatal(calls)
+			}
+			if mode == "cancel" && fmt.Sprint(calls) != "1" {
+				t.Fatal("cancelled factory ran")
+			}
+			if mode == "http" && requests.Load() != 1 {
+				t.Fatal("HTTP was restarted unnecessarily")
+			}
+			// Failure/cancellation must return the acquired slot even with the other held.
+			ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+			defer cancel()
+			release, err := media.Acquire(ctx)
+			if err != nil {
+				t.Fatalf("slot leaked: %v", err)
+			}
+			release()
+		})
+	}
+}
+
+func TestFFmpegRequiresFactoryForStreams(t *testing.T) {
+	e := NewEngine(nil)
+	defer e.Close()
+	result, err := e.RunString(`(()=>{
+  const source=()=>new ReadableStream({});
+  let rejected=0;
+  for(const opts of [
+   {video:source(),audio:source()},
+   {video:{url:'https://example.test'},audio:source()},
+   {inputs:()=>({}),video:{url:'https://example.test'}},
+   {inputs:{video:source(),audio:source()}}
+  ]) {try{__gopeed_ffmpeg.merge(opts);}catch(e){if(e instanceof TypeError)rejected++;}}
+  return rejected;
+ })()`)
+	if err != nil || fmt.Sprint(result) != "4" {
+		t.Fatalf("validation: %v %v", result, err)
+	}
+}
+
+func TestFFmpegCancelPendingFactoryCleansLateInputs(t *testing.T) {
+	e := NewEngine(nil)
+	defer e.Close()
+	result, err := e.RunString(`(async()=>{
+   let ready,finish,cancelled=0,signal;
+   const entered=new Promise(r=>ready=r);
+   const abort=new AbortController();
+   const output=__gopeed_ffmpeg.merge({signal:abort.signal,inputs:async opts=>{
+     signal=opts.signal;ready();await new Promise(r=>finish=r);
+     const source=()=>new ReadableStream({cancel(){cancelled++;}});
+     return {video:source(),audio:source()};
+   }});
+   const work=output.getReader().read().catch(e=>e.name);
+   await entered;abort.abort();await work;finish();
+   await new Promise(r=>setTimeout(r,30));
+   return {cancelled,aborted:signal.aborted};
+ })()`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	state := result.(map[string]any)
+	if fmt.Sprint(state["cancelled"]) != "2" || state["aborted"] != true {
+		t.Fatal(state)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	first, err := media.Acquire(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer first()
+	second, err := media.Acquire(ctx)
+	if err != nil {
+		t.Fatal("factory cancellation leaked capacity")
+	}
+	second()
+}
+
+func TestQueuedMergePrefetchFailureAndCancel(t *testing.T) {
+	for _, mode := range []string{"failure", "cancel"} {
+		t.Run(mode, func(t *testing.T) {
+			release1, _ := media.Acquire(context.Background())
+			defer release1()
+			release2, _ := media.Acquire(context.Background())
+			defer release2()
+			second := make(chan struct{})
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if r.Header.Get("Range") == "bytes=0-1048575" {
+					w.Header().Set("Content-Range", "bytes 0-1048575/33554432")
+					w.Header().Set("Content-Length", "1048576")
+					w.WriteHeader(206)
+					w.Write(make([]byte, 1048576))
+					return
+				}
+				close(second)
+				if mode == "cancel" {
+					<-r.Context().Done()
+					return
+				}
+				http.Error(w, "upstream failed", 503)
+			}))
+			defer srv.Close()
+			root := t.TempDir()
+			e := NewEngine(&Config{TempDir: root})
+			defer e.Close()
+			e.Runtime.Set("sourceURL", srv.URL)
+			_, err := e.RunString(`
+   globalThis.abortJob=new AbortController();
+   globalThis.result=__gopeed_ffmpeg.merge({signal:abortJob.signal,inputs:()=>({video:{url:sourceURL},audio:new ReadableStream({start(c){c.close();}})})})
+    .getReader().read().then(()=>'',e=>String(e.message||e));
+   'started';`)
+			if err != nil {
+				t.Fatal(err)
+			}
+			select {
+			case <-second:
+			case <-time.After(3 * time.Second):
+				t.Fatal("queued input did not download")
+			}
+			if mode == "cancel" {
+				if _, err := e.RunString(`abortJob.abort()`); err != nil {
+					t.Fatal(err)
+				}
+			}
+			result, err := e.RunString(`Promise.race([result,new Promise(r=>setTimeout(()=>r('test timeout'),3000))])`)
+			if err != nil || fmt.Sprint(result) == "test timeout" || fmt.Sprint(result) == "" {
+				t.Fatal(result, err)
+			}
+			if mode == "failure" && !strings.Contains(fmt.Sprint(result), "503") {
+				t.Fatal("lost upstream failure", result)
+			}
+			deadline := time.Now().Add(3 * time.Second)
+			for {
+				entries, err := os.ReadDir(root)
+				if err == nil && len(entries) == 0 {
+					break
+				}
+				if time.Now().After(deadline) {
+					t.Fatal("queued input files leaked", entries, err)
+				}
+				time.Sleep(10 * time.Millisecond)
+			}
+		})
+	}
+}
+
+func TestFFmpegUnavailableTempDirReportsBlobError(t *testing.T) {
+	root := filepath.Join(t.TempDir(), "blocked")
+	if err := os.WriteFile(root, []byte("not a directory"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	var open stream.ObjectURLOpener
+	e := NewEngine(&Config{TempDir: root, StreamConfig: &stream.Config{CreateObjectURL: func(_ *stream.ObjectURLOptions, opener stream.ObjectURLOpener) (string, error) {
+		open = opener
+		return "blob:test", nil
+	}}})
+	defer e.Close()
+	_, err := e.RunString(`__gopeed_blob_create_object_url(()=>__gopeed_ffmpeg.merge({inputs:()=>({video:new ReadableStream(),audio:new ReadableStream()})}),{})`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	reader, err := open(ctx, stream.ObjectURLOpenRequest{End: -1})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer reader.Close()
+	produced := reader.(production.Reader)
+	if err := produced.WaitProduction(ctx); err != nil {
+		t.Fatal(err)
+	}
+	source := produced.Production()
+	if source == nil {
+		t.Fatal("missing producer")
+	}
+	if _, err := io.ReadAll(reader); err == nil || !strings.Contains(err.Error(), "blocked") {
+		t.Fatal("missing useful disk error", err)
+	}
+	if downloaded, received := source.Progress(); downloaded != 0 || received != 0 {
+		t.Fatal(downloaded, received)
+	}
+}

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

@@ -29,8 +29,9 @@ const FingerprintMagicKey = "__gopeed_fetch_fingerprint"
 var script string
 
 type Config struct {
-	ProxyHandler    func(*http.Request) (*url.URL, error)
-	RegisterCleanup func(func())
+	DefaultUserAgent *string
+	ProxyHandler     func(*http.Request) (*url.URL, error)
+	RegisterCleanup  func(func())
 }
 
 func Enable(runtime *goja.Runtime, loop *eventloop.EventLoop, cfg *Config) error {
@@ -51,6 +52,9 @@ func Enable(runtime *goja.Runtime, loop *eventloop.EventLoop, cfg *Config) error
 		if err != nil {
 			panic(runtime.NewGoError(err))
 		}
+		if cfg.DefaultUserAgent != nil && !hasHeader(request.Headers, "User-Agent") {
+			request.Headers = append(request.Headers, [2]string{"User-Agent", *cfg.DefaultUserAgent})
+		}
 		fingerprint := util.SafeGet[string](runtime, FingerprintMagicKey)
 		promise, resolve, reject := runtime.NewPromise()
 		go func() {
@@ -298,6 +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/inject/ffmpeg/ffmpeg.js

@@ -0,0 +1,144 @@
+(function () {
+  const create = __gopeed_ffmpeg_create;
+  const read = __gopeed_ffmpeg_read;
+  const start = __gopeed_ffmpeg_start;
+  const push = __gopeed_ffmpeg_push;
+  const end = __gopeed_ffmpeg_end;
+  const cancel = __gopeed_ffmpeg_cancel;
+  const active = new Set();
+  globalThis.__gopeed_ffmpeg_close_all = () => {
+    for (const stop of Array.from(active)) stop(new Error("extension engine closed"));
+  };
+
+  function input(value, name, allowStream) {
+    if (value && typeof value.getReader === "function") {
+      if (!allowStream) throw new TypeError("stream inputs must be created by the inputs callback");
+      if (value.locked) throw new TypeError(name + " stream is locked");
+      return { stream: value, request: null };
+    }
+    if (!value || typeof value.url !== "string" || !/^https?:\/\//i.test(value.url)) {
+      throw new TypeError(name + " must be an HTTP request or ReadableStream");
+    }
+    const headers = {};
+    new Headers(value.headers || {}).forEach((v, k) => { headers[k] = v; });
+    return { request: { url: value.url, headers } };
+  }
+
+  function merge(options) {
+    if (!options || typeof options !== "object") throw new TypeError("merge options are required");
+    const factory = options.inputs;
+    if (factory !== undefined && typeof factory !== "function") throw new TypeError("inputs must be a callback");
+    if (factory && (options.video !== undefined || options.audio !== undefined)) throw new TypeError("inputs cannot be combined with video/audio");
+    let video = factory ? null : input(options.video, "video", false);
+    let audio = factory ? null : input(options.audio, "audio", false);
+    const args = options.args === undefined ? [] : options.args;
+    if (!Array.isArray(args) || args.some(v => typeof v !== "string")) throw new TypeError("args must be a string array");
+    const format = options.format === undefined ? "mp4" : options.format;
+    if (typeof format !== "string") throw new TypeError("format must be a string");
+    const signal = options.signal;
+    const id = create({ format, args });
+    let controller, initialized = false, stopped = false;
+    const readers = [];
+    const lifetime = new AbortController();
+    let ownedInputs;
+    function discardInputs(inputs, reason) {
+      for (const source of new Set([inputs && inputs.video, inputs && inputs.audio])) {
+        if (source && typeof source.cancel === "function" && !source.locked) Promise.resolve(source.cancel(reason)).catch(() => {});
+      }
+    }
+
+    function stop(reason) {
+      if (stopped) return;
+      stopped = true;
+      active.delete(shutdown);
+      lifetime.abort();
+      discardInputs(ownedInputs, reason);
+      if (id) cancel(id);
+      if (signal) signal.removeEventListener("abort", abort);
+      for (const reader of readers) {
+        Promise.resolve(reader.cancel(reason)).catch(() => {}).then(() => {
+          try { reader.releaseLock(); } catch (_) {}
+        });
+      }
+    }
+    function shutdown(reason) {
+      controller.error(reason);
+      stop(reason);
+    }
+    function abort() {
+      const error = new Error("FFmpeg operation aborted");
+      error.name = "AbortError";
+      stop(error);
+      controller.error(error);
+    }
+    async function pump(reader, index) {
+      try {
+        while (!stopped) {
+          const result = await reader.read();
+          if (stopped) return;
+          if (result.done) { end(id, index, ""); return; }
+          if (!(result.value instanceof Uint8Array)) throw new TypeError("media streams must contain Uint8Array chunks");
+          // Keep individual crossings bounded, even if upstream emits a large chunk.
+          for (let offset = 0; offset < result.value.byteLength && !stopped; offset += 256 * 1024) {
+            if (!await push(id, index, result.value.subarray(offset, offset + 256 * 1024))) return;
+          }
+        }
+      } catch (error) {
+        if (!stopped) {
+          end(id, index, String(error && error.message || error));
+          controller.error(error);
+          stop(error);
+        }
+      }
+    }
+    const output = new ReadableStream({
+      start(c) {
+        controller = c;
+        active.add(shutdown);
+        if (signal) {
+          if (signal.aborted) abort();
+          else signal.addEventListener("abort", abort);
+        }
+      },
+      async pull(c) {
+        if (stopped) return;
+        try {
+          if (!initialized) {
+            initialized = true;
+            if (stopped) return;
+            if (factory) {
+              const inputs = await factory({ signal: lifetime.signal });
+              if (stopped) { discardInputs(inputs, new Error("FFmpeg operation cancelled")); return; }
+              ownedInputs = inputs;
+              video = input(inputs && inputs.video, "video", true);
+              audio = input(inputs && inputs.audio, "audio", true);
+            }
+            if (video.stream && video.stream === audio.stream) throw new TypeError("video and audio must be distinct streams");
+            for (const source of [video, audio]) {
+              if (source.stream) readers.push(source.stream.getReader());
+            }
+            start(id, { video: video.request, audio: audio.request, format, args });
+            let readerIndex = 0;
+            for (const [index, source] of [video, audio].entries()) {
+              if (source.stream) void pump(readers[readerIndex++], index);
+            }
+          }
+          const chunk = await read(id);
+          if (stopped) return;
+          if (chunk === null) { stop(); c.close(); }
+          else c.enqueue(new Uint8Array(chunk));
+        } catch (error) {
+          if (!stopped) {
+            const failure = typeof MessageError === "function" && !(error instanceof MessageError)
+              ? new MessageError(String(error && error.message || error)) : error;
+            c.error(failure); stop(failure);
+          }
+        }
+      },
+      cancel(reason) { stop(reason); }
+    }, { highWaterMark: 0 });
+    if (globalThis.__gopeed_bind_producer) globalThis.__gopeed_bind_producer(output, id);
+    return output;
+  }
+  globalThis.__gopeed_ffmpeg = Object.freeze({ merge, supportsInputFactory: true, supportsProducerProgress: true });
+})();

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

@@ -0,0 +1,337 @@
+package ffmpeg
+
+import (
+	"context"
+	_ "embed"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+	"sync/atomic"
+
+	"github.com/GopeedLab/gopeed/internal/httpclient"
+	"github.com/GopeedLab/gopeed/internal/production"
+	"github.com/GopeedLab/gopeed/internal/tempfiles"
+	media "github.com/GopeedLab/gopeed/pkg/download/engine/ffmpeg"
+	"github.com/dop251/goja"
+	"github.com/dop251/goja_nodejs/eventloop"
+)
+
+//go:embed ffmpeg.js
+var script string
+
+type Config struct {
+	TempFiles        *tempfiles.Scope
+	Producers        *production.Registry
+	TempDir          string
+	DefaultUserAgent *string
+	ProxyHandler     func(*http.Request) (*url.URL, error)
+	RegisterCleanup  func(func())
+}
+type options struct {
+	Video  *media.HTTPSource `json:"video"`
+	Audio  *media.HTTPSource `json:"audio"`
+	Format string            `json:"format"`
+	Args   []string          `json:"args"`
+}
+type job struct {
+	inputs  [2]media.Input
+	ctx     context.Context
+	cancel  context.CancelFunc
+	output  *io.PipeReader
+	streams [2]*media.DiskInput
+	mu      sync.Mutex
+	start   chan options
+	started bool
+}
+
+func (j *job) Progress() (downloaded, received int64) {
+	j.mu.Lock()
+	defer j.mu.Unlock()
+	for _, input := range j.inputs {
+		if p, ok := input.(production.Source); ok {
+			d, r := p.Progress()
+			downloaded += d
+			received += r
+		}
+	}
+	return
+}
+
+func (j *job) stop() {
+	j.cancel()
+	j.output.CloseWithError(context.Canceled)
+	j.mu.Lock()
+	defer j.mu.Unlock()
+	for _, s := range j.streams {
+		if s != nil {
+			s.Close()
+		}
+	}
+}
+
+func Enable(vm *goja.Runtime, loop *eventloop.EventLoop, cfg *Config) error {
+	if cfg == nil {
+		cfg = &Config{}
+	}
+	spoolDir := cfg.TempDir
+	if cfg.Producers == nil {
+		cfg.Producers = &production.Registry{}
+	}
+	client, err := httpclient.NewClient(httpclient.Options{Transport: httpclient.TransportOptions{Proxy: cfg.ProxyHandler}})
+	if err != nil {
+		return err
+	}
+	var mu sync.Mutex
+	jobs := map[string]*job{}
+	var next atomic.Uint64
+	get := func(id string) *job { mu.Lock(); defer mu.Unlock(); return jobs[id] }
+	remove := func(id string) {
+		mu.Lock()
+		j := jobs[id]
+		delete(jobs, id)
+		cfg.Producers.Remove(id)
+		mu.Unlock()
+		if j != nil {
+			j.stop()
+		}
+	}
+	if cfg.RegisterCleanup != nil {
+		cfg.RegisterCleanup(func() {
+			done := make(chan struct{})
+			if loop.RunOnLoop(func(vm *goja.Runtime) {
+				defer close(done)
+				if closeAll, ok := goja.AssertFunction(vm.Get("__gopeed_ffmpeg_close_all")); ok {
+					_, _ = closeAll(goja.Undefined())
+				}
+			}) {
+				<-done
+			}
+			mu.Lock()
+			old := jobs
+			jobs = map[string]*job{}
+			mu.Unlock()
+			for _, j := range old {
+				j.stop()
+			}
+			client.CloseIdleConnections()
+		})
+	}
+	if err := vm.Set("__gopeed_ffmpeg_create", func(call goja.FunctionCall) goja.Value {
+		var opts options
+		if err := vm.ExportTo(call.Argument(0), &opts); err != nil {
+			panic(vm.NewGoError(err))
+		}
+		ctx, cancelCause := context.WithCancelCause(context.Background())
+		cancel := func() { cancelCause(context.Canceled) }
+		r, w := io.Pipe()
+		j := &job{ctx: ctx, cancel: cancel, output: r, start: make(chan options, 1)}
+		id := fmt.Sprintf("ffmpeg-%d", next.Add(1))
+		mu.Lock()
+		jobs[id] = j
+		cfg.Producers.Set(id, j)
+		mu.Unlock()
+		go func() {
+			var inputs [2]media.Input
+			var runErr error
+			defer func() {
+				if v := recover(); v != nil {
+					runErr = fmt.Errorf("ffmpeg panic: %v", v)
+				}
+				if errors.Is(runErr, context.Canceled) {
+					runErr = context.Cause(ctx)
+				}
+				cancel()
+				for _, in := range inputs {
+					if in != nil {
+						in.Close()
+					}
+				}
+				w.CloseWithError(runErr)
+			}()
+			var opts options
+			select {
+			case opts = <-j.start:
+			case <-ctx.Done():
+				runErr = ctx.Err()
+				return
+			}
+			for i, source := range []*media.HTTPSource{opts.Video, opts.Audio} {
+				if source == nil {
+					inputs[i] = j.streams[i]
+				} else {
+					inputs[i], runErr = media.OpenSpoolingHTTP(ctx, client, *source, spoolDir, cfg.TempFiles)
+					if runErr != nil {
+						return
+					}
+				}
+				j.mu.Lock()
+				j.inputs[i] = inputs[i]
+				j.mu.Unlock()
+				if input, ok := inputs[i].(interface{ Failures() <-chan error }); ok {
+					go func() {
+						select {
+						case err := <-input.Failures():
+							cancelCause(err)
+						case <-ctx.Done():
+						}
+					}()
+				}
+			}
+			release, err := media.Acquire(ctx)
+			if err != nil {
+				runErr = err
+				return
+			}
+			defer release()
+			runErr = media.RunAcquired(ctx, inputs[0], inputs[1], w, opts.Format, opts.Args)
+		}()
+		return vm.ToValue(id)
+	}); err != nil {
+		return err
+	}
+	if err := vm.Set("__gopeed_ffmpeg_start", func(call goja.FunctionCall) goja.Value {
+		id := call.Argument(0).String()
+		j := get(id)
+		if j == nil {
+			panic(vm.NewGoError(io.ErrClosedPipe))
+		}
+		var opts options
+		if err := vm.ExportTo(call.Argument(1), &opts); err != nil {
+			panic(vm.NewGoError(err))
+		}
+		if _, err := media.Arguments(opts.Format, opts.Args); err != nil {
+			panic(vm.NewGoError(err))
+		}
+		for _, source := range []*media.HTTPSource{opts.Video, opts.Audio} {
+			if source == nil || cfg.DefaultUserAgent == nil {
+				continue
+			}
+			specified := false
+			for key := range source.Headers {
+				if strings.EqualFold(key, "User-Agent") {
+					specified = true
+					break
+				}
+			}
+			if !specified {
+				if source.Headers == nil {
+					source.Headers = make(map[string]string)
+				}
+				source.Headers["User-Agent"] = *cfg.DefaultUserAgent
+			}
+		}
+
+		j.mu.Lock()
+		defer j.mu.Unlock()
+		if j.started || j.ctx.Err() != nil {
+			panic(vm.NewGoError(io.ErrClosedPipe))
+		}
+		j.started = true
+		for i, source := range []*media.HTTPSource{opts.Video, opts.Audio} {
+			if source == nil {
+				var err error
+				j.streams[i], err = media.NewDiskInput(j.ctx, spoolDir, cfg.TempFiles)
+				if err != nil {
+					j.cancel()
+					panic(vm.NewGoError(err))
+				}
+				j.inputs[i] = j.streams[i]
+			}
+		}
+		j.start <- opts
+		return goja.Undefined()
+	}); err != nil {
+		return err
+	}
+	if err := vm.Set("__gopeed_ffmpeg_read", func(id string) goja.Value {
+		promise, resolve, reject := vm.NewPromise()
+		go func() {
+			var readErr error
+			buf := make([]byte, 64*1024)
+			n := 0
+			j := get(id)
+			if j == nil {
+				readErr = io.ErrClosedPipe
+			} else {
+				n, readErr = j.output.Read(buf)
+			}
+			if !loop.RunOnLoop(func(vm *goja.Runtime) {
+				if readErr != nil {
+					remove(id)
+					if readErr == io.EOF {
+						resolve(goja.Null())
+					} else {
+						reject(vm.NewGoError(readErr))
+					}
+					return
+				}
+				resolve(vm.ToValue(vm.NewArrayBuffer(buf[:n])))
+			}) {
+				remove(id)
+			}
+		}()
+		return vm.ToValue(promise)
+	}); err != nil {
+		return err
+	}
+	if err := vm.Set("__gopeed_ffmpeg_push", func(call goja.FunctionCall) goja.Value {
+		id := call.Argument(0).String()
+		index := int(call.Argument(1).ToInteger())
+		var chunk []byte
+		switch b := call.Argument(2).Export().(type) {
+		case goja.ArrayBuffer:
+			chunk = append([]byte(nil), b.Bytes()...)
+		case []byte:
+			chunk = append([]byte(nil), b...)
+		default:
+			panic(vm.NewTypeError("ffmpeg input requires bytes"))
+		}
+		promise, resolve, reject := vm.NewPromise()
+		go func() {
+			var err error
+			j := get(id)
+			if j == nil || index < 0 || index > 1 || j.streams[index] == nil {
+				err = io.ErrClosedPipe
+			} else {
+				_, err = j.streams[index].Write(chunk)
+			}
+			if err != nil && j != nil && index >= 0 && index < 2 && j.streams[index] != nil {
+				j.streams[index].End(err)
+			}
+			loop.RunOnLoop(func(vm *goja.Runtime) {
+				if j != nil && j.ctx.Err() != nil {
+					resolve(false)
+					return
+				}
+				if err != nil {
+					reject(vm.NewGoError(err))
+				} else {
+					resolve(true)
+				}
+			})
+		}()
+		return vm.ToValue(promise)
+	}); err != nil {
+		return err
+	}
+	if err := vm.Set("__gopeed_ffmpeg_end", func(id string, index int, message string) {
+		if j := get(id); j != nil && index >= 0 && index < 2 && j.streams[index] != nil {
+			var err error
+			if message != "" {
+				err = errors.New(message)
+			}
+			j.streams[index].End(err)
+		}
+	}); err != nil {
+		return err
+	}
+	if err := vm.Set("__gopeed_ffmpeg_cancel", remove); err != nil {
+		return err
+	}
+	_, err = vm.RunString(script)
+	return err
+}

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

@@ -9,6 +9,7 @@ import (
 	"sync"
 	"sync/atomic"
 
+	"github.com/GopeedLab/gopeed/internal/production"
 	"github.com/dop251/goja"
 	"github.com/dop251/goja_nodejs/eventloop"
 )
@@ -17,6 +18,7 @@ import (
 var script string
 
 type Config struct {
+	Producers       *production.Registry
 	CreateObjectURL func(opts *ObjectURLOptions, open ObjectURLOpener) (string, error)
 	RevokeObjectURL func(url string) error
 }
@@ -39,6 +41,23 @@ func Enable(runtime *goja.Runtime, loop *eventloop.EventLoop, cfg *Config) error
 		cfg = &Config{}
 	}
 	blobPipes := newBlobPipeRegistry()
+	if err := runtime.Set("__gopeed_blob_pipe_bind", func(pipeID, producerID string) {
+		var source production.Source
+		if cfg.Producers != nil {
+			source = cfg.Producers.Get(producerID)
+		}
+		blobPipes.mu.Lock()
+		pipe := blobPipes.pipes[pipeID]
+		blobPipes.mu.Unlock()
+		if pipe != nil {
+			pipe.mu.Lock()
+			pipe.producer = source
+			pipe.mu.Unlock()
+			pipe.readyOnce.Do(func() { close(pipe.ready) })
+		}
+	}); err != nil {
+		return err
+	}
 	if err := runtime.Set("__gopeed_create_blob_object_url", func(call goja.FunctionCall) goja.Value {
 		if cfg.CreateObjectURL == nil {
 			panic(runtime.NewGoError(fmt.Errorf("blob object url handler not configured")))
@@ -86,18 +105,23 @@ func Enable(runtime *goja.Runtime, loop *eventloop.EventLoop, cfg *Config) error
 	}
 	if err := runtime.Set("__gopeed_blob_pipe_chunk", func(call goja.FunctionCall) goja.Value {
 		id := call.Argument(0).String()
-		ok := blobPipes.Push(id, exportBytes(call.Argument(1)))
-		return runtime.ToValue(ok)
+		chunk := append([]byte(nil), exportBytes(call.Argument(1))...)
+		promise, resolve, _ := runtime.NewPromise()
+		go func() {
+			ok := blobPipes.Push(id, chunk)
+			loop.RunOnLoop(func(vm *goja.Runtime) { resolve(ok) })
+		}()
+		return runtime.ToValue(promise)
 	}); err != nil {
 		return err
 	}
 	if err := runtime.Set("__gopeed_blob_pipe_close", func(id string) {
-		blobPipes.Close(id, nil)
+		go blobPipes.Close(id, nil)
 	}); err != nil {
 		return err
 	}
 	if err := runtime.Set("__gopeed_blob_pipe_error", func(id string, message string) {
-		blobPipes.Close(id, errors.New(message))
+		go blobPipes.Close(id, errors.New(message))
 	}); err != nil {
 		return err
 	}
@@ -184,12 +208,15 @@ type blobPipeItem struct {
 }
 
 type blobPipe struct {
-	id       string
-	loop     *eventloop.EventLoop
-	registry *blobPipeRegistry
-	ctx      context.Context
-	cancel   context.CancelFunc
-	ch       chan blobPipeItem
+	ready     chan struct{}
+	readyOnce sync.Once
+	producer  production.Source
+	id        string
+	loop      *eventloop.EventLoop
+	registry  *blobPipeRegistry
+	ctx       context.Context
+	cancel    context.CancelFunc
+	ch        chan blobPipeItem
 
 	mu     sync.Mutex
 	buf    []byte
@@ -200,6 +227,7 @@ type blobPipe struct {
 func newBlobPipe(ctx context.Context, loop *eventloop.EventLoop, registry *blobPipeRegistry) *blobPipe {
 	pipeCtx, cancel := context.WithCancel(ctx)
 	return &blobPipe{
+		ready:    make(chan struct{}),
 		id:       registry.NewID(),
 		loop:     loop,
 		registry: registry,
@@ -223,6 +251,7 @@ func (p *blobPipe) Push(chunk []byte) bool {
 }
 
 func (p *blobPipe) CloseWithError(err error) {
+	p.readyOnce.Do(func() { close(p.ready) })
 	p.once.Do(func() {
 		p.registry.Remove(p.id)
 		select {
@@ -475,3 +504,20 @@ func exportJSError(value goja.Value) error {
 	}
 	return errors.New(stack)
 }
+
+func (p *blobPipe) Production() production.Source {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.producer
+}
+
+func (p *blobPipe) WaitProduction(ctx context.Context) error {
+	select {
+	case <-p.ready:
+		return nil
+	case <-p.ctx.Done():
+		return p.ctx.Err()
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}

pkg/download/engine/inject/stream/module_integration_test.go

@@ -269,3 +269,57 @@ func newStreamTestEngine(t *testing.T, created chan<- createdObjectURL) (*engine
 	})
 	return e, e.Close
 }
+
+// A stalled disk/network consumer must pause the producer without blocking
+// the JS event loop, so cancellation and other tracks can still run.
+func TestBlobBackpressureLeavesEventLoopResponsive(t *testing.T) {
+	created := make(chan createdObjectURL, 1)
+	e, cleanup := newStreamTestEngine(t, created)
+	defer cleanup()
+	_, err := e.RunString(`
+ globalThis.produced = 0;
+ globalThis.sourceCancelled = false;
+ __gopeed_blob_create_object_url(() => new ReadableStream({
+   pull(c) { produced++; c.enqueue(new Uint8Array(64*1024)); },
+   cancel() { sourceCancelled = true; }
+ }));
+ `)
+	if err != nil {
+		t.Fatal(err)
+	}
+	object := <-created
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	reader, err := object.open(ctx, stream.ObjectURLOpenRequest{End: -1})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer reader.Close()
+	time.Sleep(100 * time.Millisecond)
+	value, err := e.RunString("produced")
+	if err != nil {
+		t.Fatal(err)
+	}
+	before := value.(int64)
+	if before > 10 {
+		t.Fatalf("unbounded production: %d", before)
+	}
+	time.Sleep(50 * time.Millisecond)
+	after, err := e.RunString("produced")
+	if err != nil || after != value {
+		t.Fatalf("producer did not pause: %v -> %v (%v)", value, after, err)
+	}
+	if ctx.Err() != nil {
+		t.Fatal("event loop only resumed after cancellation")
+	}
+	if _, err = reader.Read(make([]byte, 64*1024)); err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(30 * time.Millisecond)
+	after, err = e.RunString("produced")
+	if err != nil || after.(int64) <= before {
+		t.Fatalf("producer did not resume: %v (%v)", after, err)
+	}
+	reader.Close()
+	waitForJSValue(t, e, "String(sourceCancelled)", "true")
+}