fix(browser): prevent window.close guest crashes (#11910)

* fix(browser): prevent window.close guest crashes

* fix(browser): guard close before inline scripts

* fix(browser): preserve explicit window close policy

electron.vite.config.ts

@@ -206,6 +206,8 @@ export const electronViteConfig: UserConfig = {
         external: isExternalMainModule,
         input: {
           index: resolve('src/main/index.ts'),
+          // Why: sandboxed webview preloads cannot load Rollup helper chunks.
+          'browser-window-close-preload': resolve('src/preload/browser-window-close.ts'),
           'daemon-entry': resolve('src/main/daemon/daemon-entry.ts'),
           'plugin-host-entry': resolve('src/main/plugins/plugin-host-entry.ts'),
           'computer-sidecar': resolve('src/main/computer/sidecar-entry.ts'),

src/main/browser/browser-manager.test.ts

@@ -1512,6 +1512,38 @@ describe('browserManager', () => {
     expect(browserManager.getGuestWebContentsId('browser-destroyed-before-register')).toBeNull()
   })
 
+  it('removes a destroyed primary guest from its tab registration maps', () => {
+    const guest = {
+      id: 306,
+      isDestroyed: vi.fn(() => false),
+      getType: vi.fn(() => 'webview'),
+      setBackgroundThrottling: guestSetBackgroundThrottlingMock,
+      setWindowOpenHandler: guestSetWindowOpenHandlerMock,
+      on: guestOnMock,
+      off: guestOffMock,
+      openDevTools: guestOpenDevToolsMock
+    }
+    webContentsFromIdMock.mockReturnValue(guest)
+
+    browserManager.attachGuestPolicies(guest as never)
+    browserManager.registerGuest({
+      browserPageId: 'browser-destroyed-after-register',
+      webContentsId: guest.id,
+      rendererWebContentsId
+    })
+
+    const destroyedHandler = guestOnMock.mock.calls.find(
+      ([event]) => event === 'destroyed'
+    )?.[1] as (() => void) | undefined
+    destroyedHandler?.()
+
+    expect(browserManager.getGuestWebContentsId('browser-destroyed-after-register')).toBeNull()
+    const managerState = browserManager as unknown as {
+      tabIdByWebContentsId: Map<number, string>
+    }
+    expect(managerState.tabIdByWebContentsId.has(guest.id)).toBe(false)
+  })
+
   it('fully unregisters stale guests discovered during authorization', () => {
     const guest = {
       id: 305,

src/main/browser/browser-manager.ts

@@ -640,7 +640,6 @@ export class BrowserManager {
 
     // Why: bot detectors probe APIs that differ in Electron webviews; inject overrides each load so manual browsing passes.
     const disposeAntiDetection = this.injectAntiDetection(guest)
-
     // Why: disable throttling so background screenshots still get frames; else the compositor stalls and capture returns empty.
     guest.setBackgroundThrottling(false)
     const installClickedLinkRouting = (): void => {
@@ -940,11 +939,15 @@ export class BrowserManager {
   private retireStaleGuestWebContents(previousWebContentsId: number): void {
     // Why: after a renderer-process swap, stop the dead guest id resolving to the live page so stale callbacks don't hit the wrong session.
     this.cleanupGuestPolicyAttachment(previousWebContentsId)
-    this.tabIdByWebContentsId.delete(previousWebContentsId)
   }
 
   private cleanupGuestPolicyAttachment(guestWebContentsId: number): void {
-    const isPrimaryGuest = this.tabIdByWebContentsId.has(guestWebContentsId)
+    const browserTabId = this.tabIdByWebContentsId.get(guestWebContentsId)
+    const isPrimaryGuest = browserTabId !== undefined
+    if (browserTabId && this.webContentsIdByTabId.get(browserTabId) === guestWebContentsId) {
+      this.webContentsIdByTabId.delete(browserTabId)
+    }
+    this.tabIdByWebContentsId.delete(guestWebContentsId)
     this.certificateTrustController?.onGuestRetired(guestWebContentsId)
     const policyCleanup = this.policyCleanupByGuestId.get(guestWebContentsId)
     if (policyCleanup) {

src/main/window/createMainWindow.test.ts

@@ -74,6 +74,8 @@ import {
 } from './createMainWindow'
 import { ipcMain } from 'electron'
 import { shouldRecoverRendererAfterProcessGone } from '../crash-reporting/process-gone-classification'
+import { BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD } from '../../shared/browser-window-close-policy'
+import { fileURLToPath } from 'node:url'
 
 function withPlatform<T>(platform: NodeJS.Platform, run: () => T): T {
   const original = process.platform
@@ -248,6 +250,7 @@ describe('createMainWindow', () => {
     expect(allowBlankPrefs).toMatchObject({
       disableHtmlFullscreenWindowResize: true,
       partition: 'persist:orca-browser',
+      preload: expect.stringMatching(/browser-window-close-preload\.js$/),
       sandbox: true
     })
 
@@ -262,6 +265,36 @@ describe('createMainWindow', () => {
     const guest = { marker: 'guest' }
     windowHandlers['did-attach-webview']({} as never, guest as never)
     expect(attachGuestPoliciesMock).toHaveBeenCalledWith(guest)
+
+    const allowWindowCloseEvent = { preventDefault: vi.fn() }
+    const allowWindowCloseParams = {
+      src: 'data:text/html,',
+      preload: BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD
+    }
+    const allowWindowClosePrefs = { partition: 'persist:orca-browser' }
+    windowHandlers['will-attach-webview'](
+      allowWindowCloseEvent as never,
+      allowWindowClosePrefs as never,
+      allowWindowCloseParams as never
+    )
+    expect(allowWindowCloseEvent.preventDefault).not.toHaveBeenCalled()
+    expect(allowWindowCloseParams.preload).toBeUndefined()
+    expect(allowWindowClosePrefs).not.toHaveProperty('preload')
+
+    const allowWindowClosePathPrefs = {
+      partition: 'persist:orca-browser',
+      preload: fileURLToPath(BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD)
+    }
+    windowHandlers['will-attach-webview'](
+      { preventDefault: vi.fn() } as never,
+      allowWindowClosePathPrefs as never,
+      { src: 'data:text/html,', preload: '' } as never
+    )
+    expect(allowWindowClosePathPrefs).not.toHaveProperty('preload')
+
+    const cliGuest = { marker: 'cli-guest' }
+    windowHandlers['did-attach-webview']({} as never, cliGuest as never)
+    expect(attachGuestPoliciesMock).toHaveBeenLastCalledWith(cliGuest)
   })
 
   it('sets platform-specific titlebar and frame options for every desktop platform', () => {

src/main/window/createMainWindow.ts

@@ -10,6 +10,7 @@ import {
   screen
 } from 'electron'
 import { join } from 'node:path'
+import { fileURLToPath } from 'node:url'
 import { is } from '@electron-toolkit/utils'
 import type { Store } from '../persistence'
 import { getAppIconPath } from '../app-icon'
@@ -18,6 +19,7 @@ import { browserSessionRegistry } from '../browser/browser-session-registry'
 import { translateMain } from '../i18n/main-i18n'
 import { normalizeBrowserNavigationUrl } from '../../shared/browser-url'
 import { ORCA_BROWSER_GUEST_WEB_PREFERENCES } from '../../shared/browser-guest-web-preferences'
+import { BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD } from '../../shared/browser-window-close-policy'
 import { isCrashReportReason } from '../../shared/crash-reporting'
 import {
   DEFAULT_RENDERER_RECOVERY_MAX_RECOVERIES,
@@ -441,6 +443,8 @@ export function createMainWindow(
   // so register it with the window's other navigation policy.
   registerPluginPanelNavigationGuard(mainWindow.webContents)
 
+  const browserWindowClosePreload = join(__dirname, 'browser-window-close-preload.js')
+  const browserWindowCloseAllowedPreloadPath = fileURLToPath(BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD)
   mainWindow.webContents.on('will-attach-webview', (event, webPreferences, params) => {
     const src = typeof params.src === 'string' ? params.src : ''
     const normalizedSrc = normalizeBrowserNavigationUrl(src)
@@ -452,7 +456,18 @@ export function createMainWindow(
       return
     }
 
-    delete webPreferences.preload
+    const allowWindowClose = [params.preload, webPreferences.preload].some(
+      (preload) =>
+        preload === BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD ||
+        preload === browserWindowCloseAllowedPreloadPath
+    )
+    delete params.preload
+    if (allowWindowClose) {
+      delete webPreferences.preload
+    } else {
+      // Why: preload runs in the page's main world before inline scripts can call window.close().
+      webPreferences.preload = browserWindowClosePreload
+    }
     // Why: older Electron builds expose preloadURL alongside preload; delete both so the guest can't inherit the main preload bridge.
     delete (webPreferences as Record<string, unknown>).preloadURL
     webPreferences.nodeIntegration = false

src/preload/browser-window-close-installation.ts

@@ -0,0 +1,15 @@
+export function installBrowserWindowCloseGuard(): void {
+  const ignoreWindowClose = (): void => {}
+  try {
+    Object.defineProperty(window, 'close', {
+      configurable: false,
+      enumerable: false,
+      writable: false,
+      value: ignoreWindowClose
+    })
+  } catch {
+    try {
+      window.close = ignoreWindowClose
+    } catch {}
+  }
+}

src/preload/browser-window-close.test.ts

@@ -0,0 +1,20 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+
+import { installBrowserWindowCloseGuard } from './browser-window-close-installation'
+
+describe('browser window close preload', () => {
+  afterEach(() => {
+    vi.unstubAllGlobals()
+  })
+
+  it('installs a non-replaceable window.close no-op in the page world', () => {
+    const nativeClose = vi.fn()
+    vi.stubGlobal('window', { close: nativeClose })
+
+    installBrowserWindowCloseGuard()
+
+    expect(window.close()).toBeUndefined()
+    expect(window.close).not.toBe(nativeClose)
+    expect(Reflect.set(window, 'close', nativeClose)).toBe(false)
+  })
+})

src/preload/browser-window-close.ts

@@ -0,0 +1,7 @@
+import { installBrowserWindowCloseGuard } from './browser-window-close-installation'
+import type { ContextBridge } from 'electron'
+
+// Why: raw require keeps the sandboxed preload standalone in the main-process CJS build.
+const { contextBridge } = require('electron') as { contextBridge: ContextBridge }
+
+contextBridge.executeInMainWorld({ func: installBrowserWindowCloseGuard })

src/renderer/src/components/browser-pane/BrowserPane.tsx

@@ -3693,6 +3693,7 @@ function BrowserPagePane({
       container,
       inputLocked: inputLockedRef.current,
       webviewPartition,
+      allowWindowClose: browserTab.allowWindowClose === true,
       resolveContainer: () =>
         ensureBrowserPageViewport(browserTab.id, workspaceId)?.container ?? null
     })

src/renderer/src/components/browser-pane/BrowserPane.webview-preferences.test.ts

@@ -1,6 +1,7 @@
 // @vitest-environment happy-dom
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { ORCA_BROWSER_GUEST_WEB_PREFERENCES_ATTRIBUTE } from '../../../../shared/browser-guest-web-preferences'
+import { BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD } from '../../../../shared/browser-window-close-policy'
 
 const registryMocks = vi.hoisted(() => ({
   destroyPersistentWebview: vi.fn(),
@@ -103,4 +104,22 @@ describe('BrowserPane webview preferences', () => {
     expect(ensuredWebview?.webview.style.pointerEvents).toBe('none')
     expect(refreshedContainer.lastElementChild).toBe(ensuredWebview?.webview as unknown as Element)
   })
+
+  it('marks explicitly allowed CLI pages before the guest attaches', () => {
+    const container = createContainer('cli-page')
+
+    const ensuredWebview = ensureBrowserPageWebview({
+      browserTabId: 'browser-page-cli',
+      container,
+      inputLocked: false,
+      webviewPartition: 'persist:orca-browser',
+      allowWindowClose: true,
+      resolveContainer: () => container
+    })
+
+    expect(ensuredWebview?.webview.getAttribute('preload')).toBe(
+      BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD
+    )
+    expect(BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD).toMatch(/^file:/)
+  })
 })

src/renderer/src/components/browser-pane/browser-page-webview.ts

@@ -1,4 +1,5 @@
 import { ORCA_BROWSER_GUEST_WEB_PREFERENCES_ATTRIBUTE } from '../../../../shared/browser-guest-web-preferences'
+import { BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD } from '../../../../shared/browser-window-close-policy'
 import {
   destroyPersistentWebview,
   registerPersistentWebview,
@@ -10,12 +11,14 @@ export function ensureBrowserPageWebview({
   container,
   inputLocked,
   webviewPartition,
+  allowWindowClose,
   resolveContainer
 }: {
   browserTabId: string
   container: HTMLDivElement
   inputLocked: boolean
   webviewPartition: string
+  allowWindowClose?: boolean
   resolveContainer: () => HTMLDivElement | null
 }): { container: HTMLDivElement; created: boolean; webview: Electron.WebviewTag } | null {
   let webview = webviewRegistry.get(browserTabId)
@@ -46,6 +49,10 @@ export function ensureBrowserPageWebview({
 
   webview = document.createElement('webview') as Electron.WebviewTag
   webview.setAttribute('partition', webviewPartition)
+  if (allowWindowClose) {
+    // Why: main consumes and removes this marker in will-attach-webview before the guest sees any preload.
+    webview.setAttribute('preload', BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD)
+  }
   webview.setAttribute('allowpopups', '')
   // Why: Electron spreads the webpreferences keys verbatim, so the shared
   // camelCase attribute must stay intact for fullscreen containment to work.

src/renderer/src/hooks/useIpcEvents.test.ts

@@ -1077,6 +1077,11 @@ describe('useIpcEvents browser tab create routing', () => {
 
     expect(acquireBrowserAutomationVisibility).toHaveBeenCalledWith('page-new')
     expect(acquireBrowserAutomationVisibility).not.toHaveBeenCalledWith('page-active')
+    expect(state.createBrowserTab).toHaveBeenCalledWith(
+      'wt-1',
+      'https://example.com',
+      expect.objectContaining({ allowWindowClose: true })
+    )
     expect(replyTabCreate).toHaveBeenCalledWith({
       requestId: 'req-create',
       browserPageId: 'page-new'

src/renderer/src/hooks/useIpcEvents.ts

@@ -2266,6 +2266,7 @@ export function useIpcEvents(): void {
           // Agent/automation opens stay in the background (activate:false) in the active browser group.
           const workspace = store.createBrowserTab(worktreeId, data.url, {
             title: data.url,
+            allowWindowClose: true,
             targetGroupId: data.activate ? undefined : activeBrowserUnifiedTab?.groupId,
             sessionProfileId: data.sessionProfileId,
             sessionPartition: data.sessionPartition,

src/renderer/src/store/slices/browser.ts

@@ -57,6 +57,7 @@ import { buildValidWorktreeIdsForSessionHydration } from './degraded-repo-worktr
 type CreateBrowserTabOptions = {
   activate?: boolean
   title?: string
+  allowWindowClose?: boolean
   sessionProfileId?: string | null
   sessionPartition?: string | null
   // Place the new tab in a specific group (e.g. "Open Preview to the Side"); defaults to the worktree's active group.
@@ -69,6 +70,7 @@ type CreateBrowserTabOptions = {
 type CreateBrowserPageOptions = {
   activate?: boolean
   title?: string
+  allowWindowClose?: boolean
   browserRuntimeEnvironmentId?: string | null
 }
 
@@ -341,7 +343,8 @@ function buildBrowserPage(
   worktreeId: string,
   url: string,
   title?: string,
-  browserRuntimeEnvironmentId?: string | null
+  browserRuntimeEnvironmentId?: string | null,
+  allowWindowClose?: boolean
 ): BrowserPage {
   const normalizedUrl = normalizeUrl(url)
   return {
@@ -357,6 +360,7 @@ function buildBrowserPage(
     canGoForward: false,
     loadError: null,
     createdAt: Date.now(),
+    ...(allowWindowClose !== undefined ? { allowWindowClose } : {}),
     ...(browserRuntimeEnvironmentId !== undefined ? { browserRuntimeEnvironmentId } : {})
   }
 }
@@ -554,7 +558,8 @@ export const createBrowserSlice: StateCreator<AppState, [], [], BrowserSlice> =
       worktreeId,
       url,
       options?.title,
-      options?.browserRuntimeEnvironmentId
+      options?.browserRuntimeEnvironmentId,
+      options?.allowWindowClose
     )
     // Why: with no explicit profile, inherit the user's default so a Settings preference applies to new tabs.
     const sessionProfileId =
@@ -902,13 +907,15 @@ export const createBrowserSlice: StateCreator<AppState, [], [], BrowserSlice> =
       activate: true,
       sessionProfileId,
       sessionPartition,
-      browserRuntimeEnvironmentId: firstPage.browserRuntimeEnvironmentId
+      browserRuntimeEnvironmentId: firstPage.browserRuntimeEnvironmentId,
+      allowWindowClose: firstPage.allowWindowClose
     })
 
     for (const p of restPages) {
       get().createBrowserPage(restored.id, p.url, {
         activate: false,
         title: p.title,
+        allowWindowClose: p.allowWindowClose,
         browserRuntimeEnvironmentId: p.browserRuntimeEnvironmentId
       })
     }
@@ -987,7 +994,8 @@ export const createBrowserSlice: StateCreator<AppState, [], [], BrowserSlice> =
       workspace.worktreeId,
       url,
       options?.title,
-      options?.browserRuntimeEnvironmentId
+      options?.browserRuntimeEnvironmentId,
+      options?.allowWindowClose
     )
 
     set((s) => {
@@ -1169,6 +1177,7 @@ export const createBrowserSlice: StateCreator<AppState, [], [], BrowserSlice> =
     return get().createBrowserPage(workspaceId, pageToRestore.url, {
       title: pageToRestore.title,
       activate: true,
+      allowWindowClose: pageToRestore.allowWindowClose,
       browserRuntimeEnvironmentId: pageToRestore.browserRuntimeEnvironmentId
     })
   },

src/shared/browser-window-close-policy.ts

@@ -0,0 +1,2 @@
+// Why: this marker carries the CLI's explicit close policy across <webview> attach before the guest exists.
+export const BROWSER_WINDOW_CLOSE_ALLOWED_PRELOAD = 'file:///__orca_window_close_allowed__'

src/shared/types.ts

@@ -982,6 +982,8 @@ export type BrowserPage = {
   canGoForward: boolean
   loadError: BrowserLoadError | null
   createdAt: number
+  // Why: CLI-created pages retain Chromium's native window.close behavior; ordinary embedded pages are guarded.
+  allowWindowClose?: boolean
   // Why: remote-owned worktrees can still host client-local fallback browser
   // pages until headless remote runtimes support real browser panes.
   browserRuntimeEnvironmentId?: string | null

src/shared/workspace-session-schema.ts

@@ -225,6 +225,7 @@ const browserPageSchema = z.object({
   canGoForward: z.boolean(),
   loadError: browserLoadErrorSchema.nullable(),
   createdAt: z.number(),
+  allowWindowClose: z.boolean().optional(),
   // Why: explicit null marks a browser page as client-local even when its
   // worktree is remote-owned; older sessions omit it and keep inferred runtime.
   browserRuntimeEnvironmentId: z.string().nullable().optional(),

tests/e2e/browser-tab.spec.ts

@@ -29,10 +29,11 @@ async function createBrowserTab(
   page: Parameters<typeof getActiveWorktreeId>[0],
   worktreeId: string,
   url?: string,
-  title = 'New Browser Tab'
+  title = 'New Browser Tab',
+  allowWindowClose?: boolean
 ): Promise<CreatedBrowserTab | null> {
   return page.evaluate(
-    ({ targetWorktreeId, targetUrl, targetTitle }) => {
+    ({ targetWorktreeId, targetUrl, targetTitle, allowClose }) => {
       const store = window.__store
       if (!store) {
         return null
@@ -44,12 +45,18 @@ async function createBrowserTab(
         targetUrl ?? state.browserDefaultUrl ?? 'about:blank',
         {
           title: targetTitle,
-          activate: true
+          activate: true,
+          allowWindowClose: allowClose
         }
       )
       return { id: tab.id, pageId: tab.activePageId ?? null }
     },
-    { targetWorktreeId: worktreeId, targetUrl: url, targetTitle: title }
+    {
+      targetWorktreeId: worktreeId,
+      targetUrl: url,
+      targetTitle: title,
+      allowClose: allowWindowClose
+    }
   )
 }
 
@@ -199,6 +206,71 @@ async function startBrowserLinkServer(): Promise<{
   }
 }
 
+async function startBrowserWindowCloseServer(): Promise<{
+  url: string
+  sourceUrl: string
+  close: () => Promise<void>
+}> {
+  const server = createServer((request, response) => {
+    const origin = `http://127.0.0.1:${(server.address() as AddressInfo).port}`
+    const pathname = new URL(request.url ?? '/', origin).pathname
+    response.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' })
+    if (pathname === '/source') {
+      response.end(`
+        <!doctype html>
+        <html>
+          <head><title>Close link source</title></head>
+          <body><a id="window-close-link" href="${origin}/window-close" target="_blank">Open close page</a></body>
+        </html>
+      `)
+      return
+    }
+    response.end(`
+      <!doctype html>
+      <html>
+        <head><title>Window close repro</title></head>
+        <body>
+          <p id="s">Attempting close…</p>
+          <script>
+            window.close()
+            setTimeout(() => {
+              document.getElementById('s').textContent =
+                'window.close() was blocked (expected).'
+            }, 200)
+          </script>
+        </body>
+      </html>
+    `)
+  })
+  await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve))
+  const port = (server.address() as AddressInfo).port
+  return {
+    url: `http://127.0.0.1:${port}/window-close`,
+    sourceUrl: `http://127.0.0.1:${port}/source`,
+    close: () => closeServer(server)
+  }
+}
+
+async function readBrowserWindowCloseStatus(
+  page: Parameters<typeof getActiveWorktreeId>[0],
+  browserTabId: string
+): Promise<string> {
+  return page.evaluate(async (targetBrowserTabId) => {
+    const slot = document.querySelector(`[data-browser-overlay-tab-id="${targetBrowserTabId}"]`)
+    const webview = slot?.querySelector('webview') as Electron.WebviewTag | null
+    if (!webview) {
+      return 'webview missing'
+    }
+    try {
+      return (await webview.executeJavaScript(
+        'document.querySelector("#s")?.textContent ?? "status missing"'
+      )) as string
+    } catch {
+      return 'guest lost'
+    }
+  }, browserTabId)
+}
+
 async function closeServer(server: Server): Promise<void> {
   await new Promise<void>((resolve, reject) =>
     server.close((error) => {
@@ -689,6 +761,88 @@ test.describe('Browser Tab', () => {
     }
   })
 
+  test('blocked window.close in a link-created tab does not break tab switching', async ({
+    orcaPage
+  }) => {
+    const closeServer = await startBrowserWindowCloseServer()
+    try {
+      const worktreeId = (await getActiveWorktreeId(orcaPage))!
+      const neighboringTab = await createBrowserTab(
+        orcaPage,
+        worktreeId,
+        'about:blank',
+        'Neighboring tab'
+      )
+      const sourceTab = await createBrowserTab(
+        orcaPage,
+        worktreeId,
+        closeServer.sourceUrl,
+        'Close link source'
+      )
+      expect(neighboringTab?.id).toBeTruthy()
+      expect(sourceTab?.id).toBeTruthy()
+
+      await clickBrowserLink(orcaPage, sourceTab!.id, '#window-close-link')
+      let closeTabId: string | null = null
+      await expect
+        .poll(async () => {
+          const tabs = await getBrowserTabs(orcaPage, worktreeId)
+          closeTabId = tabs.find((tab) => tab.url === closeServer.url)?.id ?? null
+          return closeTabId
+        })
+        .not.toBeNull()
+
+      await orcaPage.locator(`[data-tab-id="${neighboringTab!.id}"]`).click()
+      await expect.poll(async () => getActiveTabType(orcaPage), { timeout: 5_000 }).toBe('browser')
+      await expect
+        .poll(() => readBrowserWindowCloseStatus(orcaPage, closeTabId!), { timeout: 5_000 })
+        .toContain('window.close() was blocked')
+    } finally {
+      await closeServer.close()
+    }
+  })
+
+  test('explicitly allowed browser tabs retain replaceable window.close', async ({ orcaPage }) => {
+    const closeServer = await startBrowserWindowCloseServer()
+    try {
+      const worktreeId = (await getActiveWorktreeId(orcaPage))!
+      const allowedTab = await createBrowserTab(
+        orcaPage,
+        worktreeId,
+        closeServer.sourceUrl,
+        'Allowed close tab',
+        true
+      )
+      expect(allowedTab?.id).toBeTruthy()
+
+      await expect
+        .poll(
+          () =>
+            orcaPage.evaluate(async (targetBrowserTabId) => {
+              const slot = document.querySelector(
+                `[data-browser-overlay-tab-id="${targetBrowserTabId}"]`
+              )
+              const webview = slot?.querySelector('webview') as Electron.WebviewTag | null
+              if (!webview) {
+                return 'webview missing'
+              }
+              try {
+                return (await webview.executeJavaScript(`(() => {
+                  window.close = () => 'replacement-called'
+                  return window.close() === 'replacement-called' ? 'replacement-called' : 'blocked'
+                })()`)) as string
+              } catch {
+                return 'guest unavailable'
+              }
+            }, allowedTab!.id),
+          { timeout: 5_000 }
+        )
+        .toBe('replacement-called')
+    } finally {
+      await closeServer.close()
+    }
+  })
+
   /**
    * User Prompt:
    * - Browser works and also retains state when switching tabs etc.