* fix(task): prevent subagent silent failures in session resolution and polling lifecycle
Two failure points fixed:
1. Fallback session resolution window too narrow (3s):
- resolveFallbackTaskSessionId now accepts hasRetried boolean
- First attempt uses 3s window (avoids binding wrong sessions)
- Subsequent attempts widen to 8s (handles late-appearing child sessions)
- Uses useState + useEffect instead of side effects in Zustand selector
2. Polling stops before child results are captured:
- When child session goes idle before parent sees it active, polling
would stop without fetching results
- Added final-fetch-before-stop: a one-shot delayed fetch that runs
after the settle grace period, ensuring child results are captured
- Uses taskFinalFetchDoneRef to guarantee exactly one final fetch
- Preserves existing happy path (active child → normal settle timer)
* fix(task): serialize final fetch after polling stops
Move the subagent final-fetch into a dedicated effect that runs only after
polling has stopped, avoiding races between polling writes and final-fetch
writes to the child sync store.
Also retry safely on final-fetch failure by reopening polling instead of
marking the final fetch as done before the request succeeds.
* feat(task): distinguish child session errors from normal idle
When a subagent terminates with an error, abort, timeout, or failure,
the parent session could not tell it apart from a normal completion.
Changes:
- event-reducer.ts: session.error now stores { type: 'error' } instead of
{ type: 'idle' }, so consumers can distinguish failed from completed sessions
- useSessionActivity.ts: add 'error' phase to SessionActivityPhase and
isError flag to SessionActivityResult; error phase is non-active (like idle)
but distinguishable via isError
- ToolPart.tsx: pass childSessionError to TaskToolSummary and show
'Subagent session ended with an error.' instead of the generic
'No subagent session id on task metadata.' when the child errored
Other consumers of session_status that only check 'busy'/'idle' are
unaffected — 'error' falls through to existing idle-like behavior.
* Revert "feat(task): distinguish child session errors from normal idle"
This reverts commit b3cc749bde16ed8fc55e4f304dcc455484335fba.
* fix(task): delay fallback retry window widening
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Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>
