remote-session: detect stale resume sessions reported via JSON error events

[gcsecsey]

Related issues

• Fixes STU-1711

How AI was used in this PR

Claude Code investigated the daemon log together with me, traced the regression to PR #3360, and drafted the fix and tests. I drove the diagnosis and reviewed the diff before committing.

Proposed Changes

After #3360, the session ID stored by the remote-session bridge from a previous build can no longer be resolved by the new SessionManager. studio code --resume-session <id> now fails immediately with error No AI session found for resume ID: .... The poll loop already has a recovery path, gated on outcome.staleSession. That detection was bypassed because of where the failure surfaces:

• The new pi runtime reports the resume failure as a JSON error event on stdout, not on stderr.
• detectStaleSession() in apps/cli/remote-session/turn-runner.ts only inspected stderrTail and replyText, so the stale-session pattern (/no ai session found for resume id/i) never had a chance to match.
• Result: the poll loop fell through to the generic non-zero-exit branch and posted Local agent error (no output). to Telegram. The stale ID stayed in the remote-session state, so every subsequent turn hit the same error.

This PR:

• Captures the message from JSON error events into a local lastErrorEventMessage in runTurn().
• Feeds it into detectStaleSession() alongside stderrTail and replyText. Cleaned up dead code in that function while there (the previous isError short-circuit had no effect on the result).
• Adds a stale-resume-error-event scenario to the studio-code mock that emits the failure as a JSON error event (matching the real production behavior we observed in the log).
• Adds a unit test asserting outcome.staleSession === true when the failure arrives via error event with empty stderr.

Once staleSession is correctly detected, the existing recovery path in poll-loop.ts:143-160 clears the saved session, retries without --resume-session, and the new sessionId from the retry's turn.completed is persisted at poll-loop.ts:170-172. The stuck-on-stale-ID loop self-heals on the next turn.

Testing Instructions

• npm test -- apps/cli/remote-session should report 112 passing tests (was 111).
• npm run typecheck should be clean.
• Manual:
  • npm run cli:build && node apps/cli/dist/cli/main.mjs code remote-session start --detach (with a configured bot/chat).
  • In a second terminal: node apps/cli/dist/cli/main.mjs code remote-session attach.
  • Pre-populate the remote-session state file under ~/.studio/ with a non-existent session_id (or just have a session_id from before AI sessions: adopt pi-coding-agent SessionManager end-to-end #3360).
  • Send a message from Telegram. Expected before this PR: Local agent error (no output). Expected after: an info Resume failed; retrying without session_id line in the log, a Session expired; started a new one. message in Telegram, and the agent's actual reply right after.
  • The next turn should resume cleanly against the new sessionId.

State	Telegram	Daemon log
Before fix (stale resume)
After fix (auto-recovery)

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[Copilot]

Pull request overview

This PR fixes a regression in the CLI remote-session “resume” flow by detecting stale --resume-session IDs when the underlying runtime reports the failure as a JSON error event on stdout (instead of stderr), enabling the existing recovery path to clear the stale ID and retry.

Changes:

• Capture the message from JSON error events during runTurn() and include it in stale-session detection.
• Simplify detectStaleSession() to scan a combined haystack of stderrTail, last reply text, and the last JSON error message.
• Add a new mock scenario plus a unit test covering stale resume failures emitted via JSON error events (with empty stderr).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
apps/cli/remote-session/turn-runner.ts	Track JSON error messages and use them to detect stale resume sessions.
apps/cli/remote-session/tests/turn-runner.test.ts	Add a unit test asserting staleSession is detected via JSON error events.
apps/cli/remote-session/tests/fixtures/mock-studio-code.mjs	Add a mock scenario that emits the stale-resume failure as a JSON error event.

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[wpmobilebot]

📊 Performance Test Results

Comparing a72f5e4 vs trunk

app-size

Metric	trunk	a72f5e4	Diff	Change
App Size (Mac)	1404.70 MB	1404.70 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	a72f5e4	Diff	Change
load	1493 ms	1469 ms	24 ms	⚪ 0.0%

site-startup

Metric	trunk	a72f5e4	Diff	Change
siteCreation	8586 ms	8567 ms	19 ms	⚪ 0.0%
siteStartup	4925 ms	4938 ms	+13 ms	⚪ 0.0%

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Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)

[epeicher]

Thanks @gcsecsey, this is working as expected. Changes also LGTM!