Keep desktop browser tabs stable across focus and automation (#2907)

* fix(desktop): preserve browser tabs across focus changes

Electron can replace a guest WebContents when a webview is reparented, which reloads the page and can race automation against a destroyed target. Keep each browser guest on one permanent paintable surface and make user and agent resizing share one canonical viewport.

* fix(desktop): recover browser surfaces after lifecycle changes

* fix(desktop): preserve resident browser lifecycle state

* fix(desktop): seed inactive browser viewport

packages/desktop/src/features/browser-automation/ipc.test.ts

@@ -20,11 +20,14 @@ class FakeDebugger {
   public blockCommands = false;
   public readonly blockedCommandNames = new Set<string>();
   public readonly failedCommandNames = new Set<string>();
+  public readonly failedCommandErrors = new Map<string, Error>();
   public readonly promptDialogs: unknown[] = [];
   public failPromptDrain = false;
+  public beforeCommand: ((command: string) => void) | null = null;
   private messageListener:
     | ((event: unknown, method: string, params?: Record<string, unknown>) => void)
     | null = null;
+  private detachListener: (() => void) | null = null;
   private readonly blockedCommands: Array<() => void> = [];
 
   public isAttached(): boolean {
@@ -37,6 +40,11 @@ class FakeDebugger {
 
   public async sendCommand(command: string, params?: Record<string, unknown>): Promise<unknown> {
     this.commands.push({ command, params: params ?? {} });
+    this.beforeCommand?.(command);
+    const commandError = this.failedCommandErrors.get(command);
+    if (commandError) {
+      throw commandError;
+    }
     if (this.failedCommandNames.has(command)) {
       throw new Error(`${command} failed`);
     }
@@ -58,10 +66,15 @@ class FakeDebugger {
   }
 
   public on(
-    event: "message",
-    listener: (event: unknown, method: string, params?: Record<string, unknown>) => void,
+    event: "message" | "detach",
+    listener:
+      | ((event: unknown, method: string, params?: Record<string, unknown>) => void)
+      | (() => void),
   ): void {
-    expect(event).toBe("message");
+    if (event === "detach") {
+      this.detachListener = listener;
+      return;
+    }
     this.messageListener = listener;
   }
 
@@ -72,6 +85,11 @@ class FakeDebugger {
     this.messageListener({}, method, params);
   }
 
+  public emitDetach(): void {
+    this.attachedProtocolVersions.length = 0;
+    this.detachListener?.();
+  }
+
   public finishNextCommand(): void {
     const resolve = this.blockedCommands.shift();
     if (!resolve) {
@@ -92,6 +110,7 @@ type ConsoleMessageListener = (
 class FakeWebContents {
   public readonly debugger = new FakeDebugger();
   public readonly inputEvents: IsolatedKeyboardInputEvent[] = [];
+  public readonly loadedUrls: string[] = [];
   public readonly captures: Array<{
     rect: Rectangle | undefined;
     options: { stayHidden?: boolean } | undefined;
@@ -138,7 +157,9 @@ class FakeWebContents {
     return null;
   }
 
-  public async loadURL(): Promise<void> {}
+  public async loadURL(url: string): Promise<void> {
+    this.loadedUrls.push(url);
+  }
 
   public goBack(): void {}
 
@@ -186,6 +207,7 @@ class FakeWebContents {
 
   public destroy(): void {
     this.destroyed = true;
+    this.debugger.emitDetach();
     this.destroyedListener?.();
   }
 }
@@ -571,6 +593,54 @@ describe("browser automation IPC adapter", () => {
     );
     warn.mockRestore();
   });
+
+  test("does not run the command after the debugger target closes during setup", async () => {
+    const contents = new FakeWebContents(31);
+    contents.debugger.beforeCommand = (command) => {
+      if (command === "Page.enable") {
+        contents.destroy();
+      }
+    };
+    contents.debugger.failedCommandErrors.set(
+      "Page.enable",
+      new Error("target closed while handling command"),
+    );
+    const tab = adaptWebContents(contents);
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+
+    await expect(
+      tab.captureDialogs?.(() => tab.loadURL("https://replacement.example.com")),
+    ).rejects.toThrow("target closed while handling command");
+    expect(contents.loadedUrls).toEqual([]);
+    expect(warn).not.toHaveBeenCalled();
+
+    warn.mockRestore();
+  });
+
+  test("runs without dialog capture after a live debugger session detaches", async () => {
+    const contents = new FakeWebContents(32);
+    const tab = adaptWebContents(contents);
+
+    await expect(tab.captureDialogs?.(async () => "captured")).resolves.toEqual({
+      result: "captured",
+      dialogs: [],
+    });
+    contents.debugger.emitDetach();
+    contents.debugger.failedCommandNames.add("Page.enable");
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+
+    await expect(
+      tab.captureDialogs?.(() => tab.loadURL("https://replacement.example.com")),
+    ).resolves.toEqual({ result: undefined, dialogs: [] });
+    expect(contents.loadedUrls).toEqual(["https://replacement.example.com"]);
+    expect(contents.debugger.attachedProtocolVersions).toEqual(["1.3"]);
+    expect(warn).toHaveBeenCalledWith(
+      "[browser-automation] Dialog capture unavailable; running command without it",
+      { contentsId: 32, error: expect.any(Error) },
+    );
+
+    warn.mockRestore();
+  });
 });
 
 class FakeHostWebContents {

packages/desktop/src/features/browser-automation/ipc.ts

@@ -74,6 +74,7 @@ interface WebContentsDebugger {
     event: "message",
     listener: (event: unknown, method: string, params?: Record<string, unknown>) => void,
   ): void;
+  on?(event: "detach", listener: () => void): void;
 }
 
 interface ConsoleMessageEmitter {
@@ -188,6 +189,7 @@ function getDialogMonitor(
 class DialogMonitor {
   private enabled = false;
   private listenerRegistered = false;
+  private detachGeneration = 0;
   private readonly activeCollectors: DialogCollector[] = [];
 
   public constructor(
@@ -200,10 +202,14 @@ class DialogMonitor {
     task: () => Promise<T>,
   ): Promise<{ result: T; dialogs: BrowserAutomationDialogEvent[] }> {
     const collector: DialogCollector = { dialogs: [] };
+    const setupDetachGeneration = this.detachGeneration;
     try {
       await this.enable();
       await this.installPromptShim();
     } catch (error) {
+      if (this.contents.isDestroyed() || this.detachGeneration !== setupDetachGeneration) {
+        throw error;
+      }
       console.warn("[browser-automation] Dialog capture unavailable; running command without it", {
         contentsId: this.contentsId,
         error,
@@ -244,6 +250,10 @@ class DialogMonitor {
         }
         void this.handleOpening(params ?? {});
       });
+      this.contents.debugger.on("detach", () => {
+        this.enabled = false;
+        this.detachGeneration += 1;
+      });
     }
     await this.sendDebugCommand("Page.enable");
     this.enabled = true;