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[Bug]: Browser tools don't tell agents why a page failed to load #18555
Description
Before submitting
- I searched existing issues and did not find a duplicate.
- I included enough detail to reproduce or investigate the problem.
Area
apps/server
Steps to reproduce
- In a thread, open the Browser panel and load
https://self-signed.badssl.com/(any page that fails to load: an untrusted certificate, a refused connection, a blocked port). - The panel shows Chromium's "This site can't be reached … ERR_CERT_AUTHORITY_INVALID" page.
- Ask the agent to call
preview_statusandpreview_snapshoton that tab.
Expected behavior
The browser tools tell the agent why the page did not load: the URL that failed, the browser's error code, and its description.
Actual behavior
preview_status returns only "url": "chrome-error://chromewebdata/" with an empty title, and preview_snapshot has no page text. For a tab the desktop app renders, the failure usually happens before the server connects to the page, so nothing in either result names the error. The agent has to guess (often a self-signed certificate on a LAN device) or ask the user to read the screen.
Impact
Minor bug or occasional failure
Version or commit
main @ 5fe7568
Environment
macOS, web dev server (server-rendered tabs); desktop-rendered tabs reasoned from code.
Workaround
The user reads the error page in the Browser panel and tells the agent. For server-rendered tabs, the failed request sometimes appears in preview_snapshot's networkEntries if it has not been pushed out by later requests.
Earlier attempt at a fix: #16835 (closed for incomplete verification).
Activity
juliusmarminge commentedon Oct 12, 2026
Note
Grok responding on behalf of Julius.
Confirmed on main (
bed92398): the failure details are already recorded but the agent tools never return them.LoadFailednav status withcodeanddescription(packages/contracts/src/preview.ts): desktop fromdid-fail-loadinapps/desktop/src/preview/Manager.ts, server tabs inapps/server/src/preview/ServerBrowser.ts.apps/server/src/preview/Manager.tsstores it on the session snapshot and emits afailedevent.PreviewAutomationStatus(packages/contracts/src/previewAutomation.ts) has onlyurl/title/loading, sopreview_statusreportschrome-error://chromewebdata/.chrome-error://pages, but no tool exposes one.Likely fix: add an optional
loadError { url, code, description }to the status (and snapshot) output from the session'sLoadFailednav status. Then verify it on both desktop-rendered and server-rendered tabs. That cross-host check is where #16835 fell short.Related: #17965 (one common trigger, local HTTPS certs). #7212 is a separate UI issue.
juliusmarminge commentedon Oct 22, 2026
Reproduced on main at 8acbefefc5 on Linux. The real preview broker and ServerBrowser with Chromium returned an empty error-page snapshot and no direct load diagnostic in status or snapshot for
https://self-signed.badssl.com/, a local self-signed HTTPS fixture, and Chromium's blocked port 1. Recovery to local HTTP succeeded. The error remains available only in network/action history.Existing fix #18588 covers this issue; no duplicate fix PR is needed. Live Electron verification is unavailable on this VM.