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[Bug]: Background preview JavaScript alerts interrupt unrelated threads and stall automation #17518
Description
Activity
Note
Grok responding on behalf of Julius.
Thanks for the detailed report. 0.0.45 shipped on Oct 2, before #15328 (merged Oct 6) moved preview automation onto the server, and main looks like it at least partly covers this. I haven't reproduced it; this comes from reading the code at
ec80933ac.Automation side: likely fixed on main by #15328
- The server engine records a page dialog per tab via
page.on("dialog")(ServerBrowser.ts#L890-L893), andpreview_statusreports it (L522-L529). - A
preview_clickthat opens a dialog should return as soon as the dialog appears instead of hanging (ServerBrowserPage.ts#L229-L256). - While a dialog is pending, later tool calls on that tab should fail fast with a
dialogPendingerror ("A browser dialog is pending. Read preview_status and use preview_dialog first.") instead of a 15s timeout (L1734-L1744, L1836-L1849). - A new
preview_dialogtool accepts or dismisses it (tools.ts#L91-L100, ServerBrowser.ts#L1817-L1824).
Native modal: possibly still present on desktop
On desktop, agent tabs now render in a native<webview>that the server drives over CDP. I couldn't find anything on the desktop side that suppresses Electron's own JavaScript dialog for those webviews: nodisableDialogsin WebviewPreferences.ts#L41-L42, and no dialog handling inapps/desktop/src/preview. So the app-wide T3-branded alert may still appear over another thread even though the server also sees the dialog. The in-app per-tab dialog card in ServerBrowserSurface.tsx#L833-L870 seems to apply to streamed tabs, not desktop webviews.Could you retest on the latest nightly with your fixture and let us know:
- whether
preview_snapshot/preview_evaluatenow return adialogPendingerror instead of timing out, and whetherpreview_dialogclears it; - whether the native T3 alert still shows over the unrelated conversation.
Related: #16567 (background
preview_snapshothang), #16030, #14195.- The server engine records a page dialog per tab via
Before submitting
Area
apps/desktop — collaborative browser / preview automation
Summary
A JavaScript
alert()from a page being tested by an agent in the collaborative browser appears as a native T3-branded, app-wide modal over a different conversation the user is working in. The dialog does not identify the originating preview tab, page or thread. Preview inspection also times out while the dialog is pending.Observed twice on 2026-10-09 while an agent tested a local web app and the user worked in another conversation. The page deliberately called
alert()once for invalid form data and again from an AJAX error handler. The application validation and failed request explain the message content; this report concerns T3's presentation and automation handling of those page dialogs.Steps to reproduce / minimal fixture to investigate
preview_click.preview_snapshotandpreview_evaluatefor the originating tab.The original form triggered the behaviour twice; this minimal fixture has not been rerun because further native alerts would interrupt the user's work again.
Expected behaviour
Page dialogs should be associated with their originating preview tab and thread, with clear page/origin identification, and should not unexpectedly block an unrelated conversation. Background dialogs should have a contained or queued presentation.
Preview automation should surface a pending page dialog with a way to accept/dismiss it, or return a clear actionable dialog error. The exposed preview tools in this session had no dialog-handling operation.
Actual behaviour
preview_snapshotreturnedPreview automation snapshot timed out after 15000ms.preview_evaluatereturnedPreview automation evaluate timed out after 15000ms.The timing supports a dialog-related automation stall, but the internal Electron/browser cause has not been established. No claim that this is a server failure or that all preview tabs are affected.
Impact
Interrupts unrelated user work during background agent browser testing; opaque timeouts make recovery difficult and can encourage unnecessary retries.
Version and environment
visible: false, with a 1280 × 800 CSS-pixel viewport.Evidence and related reports
The user provided two screenshots showing the T3-branded dialogs over another conversation. They are retained locally; raw screenshots are omitted because private conversation content is visible behind the dialogs.
#14195 concerns stacked native background service/update alerts with different message content. #16030 concerns annotation overlays behind HTML
<dialog>elements. Neither appears to describe a background preview page's JavaScript alert interrupting a different conversation.Workaround
Dismiss the native alert manually. For the local application under test, show validation/request errors inline instead of using
alert(). That avoids this trigger but does not address T3's general handling of page dialogs.Prepared with GPT-6.1-Sol through Codex in T3 Code, following the user's request to report the problem.