fix(server): settled and idle-released threads no longer stay Waiting

[t3dotgg]

After Settle stopped a thread's background server, the thread still showed "Waiting" with a Stop button. Idle release of a provider session had the same problem. In both cases the process was gone, but the background-task list it had saved on its provider threads stayed until someone pressed Stop.

Fix

Settle, archive, and idle release all go through releaseEntry in ProviderSessionManager. That is now the one place that clears the list:

• As soon as the session leaves the live session map, it records the task ids on the released session's provider threads. This includes the thread whose detach caused the release, because detach removes that thread from the attached set first.
• After the process has closed, it removes those ids from the list. The write commits through a new compare-and-set (EventSink.writeIfProviderThreadUnchanged), so a provider update that lands between the read and the write is not overwritten. The guard compares the whole stored row, not only updatedAt, because some writers (for example ACP's idle update) do not move updatedAt. A conflict is retried.
• Tasks that a same-id replacement session reports in the meantime have new ids, so they stay.
• Server shutdown keeps the lists. Startup recovery already clears them and records the cancelled work.
• PR-watch monitors are not touched. They come from pull request links, not from this list.

Which adapters get the cleanup

The cleanup is only correct when a released session's background tasks die with its process. Each adapter that writes the list was checked:

Adapter	Tasks end with the session process?	Cleanup
Claude	Yes. One CLI per session; the adapter already clears its own list when the CLI exits.	On
Muse	Yes. Workflows and subagents run in the session's own muse host, which the session scope closes.	On
Pi	Only ever writes an empty list.	Not needed
OpenCode	No. Background subagents run on the opencode serve shared by sessions, and can keep running after a session closes.	Off

So this is opt-in: a runtime sets backgroundTasksEndWithProcess (Claude and Muse do). Any other adapter keeps its list, which is the old behavior.

Proof

Five new tests in ProviderSessionManager.test.ts:

• Detach (the Settle/archive path) clears the released session's list and leaves another session's list alone. Fails on main.
• Idle release clears it. Fails on main.
• A runtime whose tasks can outlive it (like OpenCode) keeps its list. Fails without the opt-in.
• A replacement session reports a new task while the old process closes. Only the dead task is removed. Fails on main and on an earlier "clear everything" version of this fix.
• A provider update that does not move updatedAt lands between the cleanup's read and write. It survives. Fails with an updatedAt-only guard.

vp test run passes all 64 tests in the file. tsc-rs --noEmit passes for apps/server, packages/provider-core, and packages/provider-muse. Lint and format are clean on changed files.

Follow-up (not in this PR)

• An old-process roster event that is still queued when the session is released can still add a dead task back. The result is the same stale "Waiting" as before this fix, never a new failure. A full fix needs cleanup ordered after the event consumer drains.
• main's Stop path (settleBackgroundWork) still reads and writes the provider thread without the compare-and-set. It could use the new method.
• OpenCode sessions still keep a stale list if the shared server's subagent ends while no session is listening.

Thanks to @tannerpolley for tracing the release path in the issue.

Fixes #15239

Reviewed with sol-loop: 6 rounds plus 1 follow-up review with GPT-6.1 Sol on high.

Model and harness: Claude Opus 5.5 in Claude Code via T3 Code.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This production fix changes the provider-session release path and enables background-task cleanup by default for Claude and Muse, affecting when released threads leave the Waiting state. The shared orchestration and concurrency changes warrant human review before merging.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	5.0 KiB	4.9 KiB	−30 B (−0.6%)	6.8 KiB	✅
Codex	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.2 KiB	1.2 KiB	−30 B (−2.5%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	20.9 KiB	20.8 KiB	−41 B (−0.2%)	29.3 KiB	✅
Codex	Live turn messages	2	1	−1 (−50.0%)	8	✅
Claude	Total thread wire	5.0 KiB	5.0 KiB	−24 B (−0.5%)	6.8 KiB	✅
Claude	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Claude	Live turn WebSocket wire	1.2 KiB	1.2 KiB	−24 B (−2.0%)	2.0 KiB	✅
Claude	Live turn WebSocket decoded	21.2 KiB	21.2 KiB	−41 B (−0.2%)	29.3 KiB	✅
Claude	Live turn messages	2	1	−1 (−50.0%)	8	✅

Baseline: adb0420 · PR result: f224853 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[coderabbitai]

📝 Walkthrough

Provider session release now captures pending background-task IDs and removes them from provider-thread rosters. Conditional writes preserve tasks added by replacement sessions. Tests cover detach, idle release, and updates racing with release cleanup.

Changes: Provider session release

Layer / File(s)	Summary
Conditional provider-thread writes apps/server/src/orchestration-v2/EventSink.ts	The event sink adds a write that commits events only when the provider-thread update timestamp matches the expected timestamp.
Capture and clean released-session tasks apps/server/src/orchestration-v2/ProviderSessionManager.ts, apps/server/src/orchestration-v2/ProviderSessionManager.test.ts	Release handling captures pending task IDs and clears them with conditional writes. Tests cover detach, idle release, and replacement-session updates during release and write races.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge

Merge Risk: 🔵 Low · up to a6b19

A released thread can occasionally remain Waiting despite this fix. The risk is bounded and recoverable, but owners should be aware of the unresolved late-event race when merging.

Pre-merge checks: 3 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Linked Issues check		Issue [#15239] requires Settle to remove the Waiting strip and Stop button after the provider process stops. releaseEntry now captures and conditionally removes released task IDs, includes the detac…	Order roster cleanup after the old-process event consumer drains, or prevent queued old-process roster events from restoring released task IDs. Add a regression test for this race.

Passed checks: 3 passed

Check name	Status	Explanation
Out of Scope Changes check		The changes remain in the provider-session release path for [#15239]. Idle-release handling, replacement-task preservation, compare-and-set writes, and focused tests support the same stale background-…
Title check		The title clearly identifies the server fix for settled and idle-released threads that incorrectly remain in the Waiting state. It is concise and uses conventional commit format.
Description check		The description explains the problem, fix, scope, verification results, known follow-ups, linked issue, and agent details. It uses "Fix" and "Proof" instead of the template headings "Change" and "Veri…

Full details: Linked Issues check

Explanation

Issue [#15239] requires Settle to remove the Waiting strip and Stop button after the provider process stops. releaseEntry now captures and conditionally removes released task IDs, includes the detached thread, preserves replacement tasks, and covers these paths with tests. However, the PR documents that a queued roster event from the old process can add a dead task after cleanup. That race can still leave the thread in the reported Waiting state.

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[coderabbitai]

Actionable comments posted: 1

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🤖 Prompt to fix review comments

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Inline comments:
Review comments at @apps/server/src/orchestration-v2/ProviderSessionManager.ts:
- Around line 839-870: Add a warning after the three-attempt cleanup loop in the
provider-thread roster cleanup flow when every `writeIfProviderThreadUnchanged`
attempt fails to commit. Include `providerSessionId` and `providerThreadId` in
the warning, while preserving the existing early returns for completed or
unnecessary cleanup.

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📒 Files selected for processing: 3

• apps/server/src/orchestration-v2/EventSink.ts
• apps/server/src/orchestration-v2/ProviderSessionManager.test.ts
• apps/server/src/orchestration-v2/ProviderSessionManager.ts

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