[omartelo]

Summary

A JavaScript dialog froze the session browser. Measured before (Chromium 155, live test): a click on a button that calls alert('hi') failed with context deadline exceeded after 30.0 s, and every read after it hung another 30.0 s. Nothing handled Page.javascriptDialogOpening.

Now a dialog the page opens (alert, confirm, prompt, beforeunload) stays open until the agent or the person answers it:

• Agent: the call that opened it answers at once (about 0.16 s) with the page as it stood and a dialog open: line. Any other call on that page fails, naming the dialog. The new browser_dialog tool (lich browser dialog accept|dismiss, text for a prompt) answers it and returns the page after.
• Person: the pane shows the dialog as a card over the top of the page (option B of the mockup), naming the site, with OK/Cancel (Stay/Leave on a beforeunload) and a field for a prompt. Enter is OK/Leave and Esc is Cancel/Stay. A dialog the person answered reaches the agent's next page answer once, as dialog answered: confirm "Delete?" -> dismissed.
• Cursor: when the agent answers, the window plays its cursor pressing the card's button, as it does for back and forward. The card stays until that press has played.
• Whoever answers first wins. The other side's answer is refused, and the window ignores that refusal without logging it.

beforeunload

Accepting a beforeunload sooner than about 450 ms after it opened makes Chromium abort the navigation it held (net::ERR_ABORTED about a second in), reload the page and ask again. Measured on Chrome for Testing 155 and Helium 0.19.2.1: 3 of 3 aborted at 300 ms, 3 of 6 at 400 ms, none of 30 from 500 ms on. An accept is therefore held until one second after the dialog opened. An agent's or a person's answer already takes longer than that.

Page answer language

The prose of a page answer now comes from the prompt catalog in all seven languages: the element-list legend, the filled and checked marks, the more-below note, a running download, a timed-out wait, the count of further console errors, and what an open dialog asks of the agent. The line tags the tool descriptions name (url:, text:, downloaded:, console error:, dialog open: and the rest) stay English. pageText takes the language. That is why the existing pageText tests gained a prompt.English argument; no assertion changed.

Notes

• New API: browser.AnswerDialog (agent, returns the page) and browser.Answer (window); BrowserState.Dialog, BrowserPageInfo.Dialog and Dialogs; agent acts accept and dismiss. contract.golden is updated.
• The chromePage gate: run now fails with errDialogOpen at once while a dialog is open, and as soon as one opens during a call. Calls that do not touch the page's script (screencast acks, resize, cookies, focus, the answer itself) go through runFree.
• TestMCPListsEveryTool gained browser_dialog, because the tool list is the contract.
• A page holding a dialog cannot lay out: Emulation.setDeviceMetricsOverride and Page.captureScreenshot wait on the dialog (measured on both browsers). A pane opened during a dialog therefore starts its screencast at the page's current size, which still draws, and lays the page out once the dialog closes. Before, the pane stayed black. Screenshots fail until the dialog is answered.
• The window's own calls on a held page do nothing instead of failing, and the person answering a dialog the agent already answered is not an error, so the window does not match error text.
• The agent cursor's queue never drops an answer to the dialog, so the card always waits for its press. The UI gallery shows the new Lit button state.
• Ceilings: a dialog nobody answers holds the page; a pane opened meanwhile shows it at its old size; the accept hold on beforeunload.

Test plan

• TestChromeADialogWaitsForTheAgentsAnswer (live): alert, confirm (dismiss), prompt (custom text) and leaving through a beforeunload. 5 of 5 runs on Helium and on Chrome for Testing 155.
• Unit tests: a click that opens a dialog, a call on a held page, the agent's and the person's answers, the prompt default, the answered cap, the gate; pageText in every language; the CLI verb and the MCP tool.
• TestChromeAPaneOpenedOnADialogShowsThePage (live): a screencast started on a held page delivers a frame at once, and the page takes the pane's width after the answer. 5 of 5 on both browsers.
• Native: card from the store, keep-until-pressed, button per type and act, key mapping, the cursor queue keeping a dialog answer.
• Rig (Xvfb, slice backend): the confirm and prompt cards in the light and dark themes; the agent's accept and dismiss light the OK and Cancel buttons, show the press ring, and the card goes.
• gofmt, go vet ./..., go test ./... green for the backend and for native/.