feat(extension): expose host version and WebView page events

internal/webview/README.md

@@ -60,3 +60,47 @@ 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 version
+
+`gopeed.info.hostVersion` is the host's build version (`dev` for development
+builds). `gopeed.info.version` continues to identify the extension's own version.
+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 +1,48 @@
+/** Public extension API additions. info.version remains the extension version. */
+export interface ExtensionInfo {
+  identity: string;
+  name: string;
+  author: string;
+  title: string;
+  version: string;
+  hostVersion: 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/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),
 	}
 }
 
@@ -119,6 +127,7 @@ func (p *pageWrapper) start() error {
 			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)
 
@@ -130,7 +139,6 @@ 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)
@@ -141,6 +149,7 @@ func (p *pageWrapper) start() error {
 			return
 		}
 
+		w.Init(buildLoadNotifyScript(p.callbackName))
 		applyWindowOptions(w, p.opts)
 		w.SetHtml(buildBootstrapHTML(p.callbackName, p.readyID))
 		if runtimepkg.GOOS == "linux" {
@@ -148,6 +157,7 @@ func (p *pageWrapper) start() error {
 			return
 		}
 		w.Run()
+		p.handleNativeEvent(webview.Event{Name: "closed"})
 		w.Destroy()
 		close(p.done)
 	}
@@ -176,10 +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 {
@@ -193,7 +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
@@ -233,7 +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
@@ -321,6 +341,7 @@ func (p *pageWrapper) Close() error {
 		return nil
 	}
 	p.closed = true
+	p.failPendingLocked()
 	w := p.view
 	wait := p.done
 	p.mu.Unlock()
@@ -343,6 +364,7 @@ func (p *pageWrapper) Close() error {
 		<-terminateDone
 	}
 	<-wait
+	p.events.Emit(enginewebview.Event{Name: "closed", Data: map[string]any{"reason": "api"}})
 	return nil
 }
 
@@ -353,94 +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 {
@@ -457,7 +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) {
@@ -515,7 +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:
@@ -540,6 +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:
@@ -601,19 +603,74 @@ 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;
+  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

internal/webview/goprovider/provider_integration_test.go

@@ -15,3 +15,5 @@ func TestProviderContract(t *testing.T) {
 }
 
 func TestProviderProfiles(t *testing.T) { integrationtest.RunProfileContract(t, New()) }
+
+func TestProviderEvents(t *testing.T) { integrationtest.RunEventContract(t, New()) }

internal/webview/integrationtest/events.go

@@ -0,0 +1,111 @@
+package integrationtest
+
+import (
+	"fmt"
+	"net"
+	"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()
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	failedURL := "http://" + listener.Addr().String() + "/failure"
+	listener.Close()
+	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)
+	}
+	if err := page.Close(); err != nil {
+		t.Fatal(err)
+	}
+	e = next("closed")
+	if e.Data["reason"] != "api" {
+		t.Fatal(e)
+	}
+	quiet()
+}

internal/webview/rpcprovider/events_test.go

@@ -0,0 +1,87 @@
+package rpcprovider
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"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")
+	}
+}

internal/webview/rpcprovider/provider.go

@@ -9,6 +9,8 @@ import (
 	"net"
 	"net/http"
 	"strings"
+	"sync"
+	"time"
 
 	enginewebview "github.com/GopeedLab/gopeed/pkg/download/engine/webview"
 )
@@ -49,8 +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 {
@@ -110,14 +117,28 @@ func (p *page) ClearCookies() error {
 }
 
 func (p *page) Close() error {
-	err := 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 {
-		return nil
+		err = nil
 	}
-	return err
+	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 {
@@ -203,3 +224,79 @@ func (c *Client) Call(method string, params any, result any) error {
 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

@@ -42,3 +42,7 @@ 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}))
+}