improvement(mothership): abort path race preventing persistence

[icecrasher321]

Summary

Fixes stopped copilot streams so partial assistant responses are persisted reliably even if the abort path clears the active stream marker first.

Type of Change

• Bug fix

Testing

Tested manually

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		May 17, 2026 10:23pm

[cursor]

PR Summary

Medium Risk
Touches chat persistence/finalization logic and introduces row-locking + new cancellation paths, which could affect chat message ordering and stream-marker clearing under concurrency.

Overview
Ensures stopped / cancelled Copilot streams reliably persist partial assistant output and emit the completed status even when the chat’s conversationId stream marker was cleared before the stop handler runs.

Refactors stop/finalization to use a transactional, FOR UPDATE-locked finalizeAssistantTurn that can optionally operate when the marker is already cleared (streamMarkerPolicy: 'active-or-cleared') and returns a structured outcome used to drive publishing and tracing.

Adds withStoppedContentBlock to consistently append a canonical complete: cancelled block, updates unified chat onComplete to persist cancelled results (instead of delegating solely to /chat/stop), and hardens the lifecycle runner to invoke onComplete(cancelled) even when abort-triggered exceptions occur; tests were expanded accordingly.

^{Reviewed by Cursor Bugbot for commit 05830df. Configure here.}

[greptile-apps]

Greptile Summary

This PR fixes a race condition where stopping a copilot stream could silently drop partial assistant responses. Previously, the abort-exception catch path called onError (which cleared conversationId), racing with the /chat/stop endpoint's UPDATE that filtered on conversationId = streamId, so whichever ran first could invalidate the other's write.

• terminal-state.ts wraps the SELECT + UPDATE in a db.transaction with SELECT … FOR UPDATE, adds a streamMarkerPolicy parameter (active-only | active-or-cleared) so the cleared-marker scenario can still own the turn, and returns a structured FinalizeAssistantTurnResult for downstream idempotency decisions.
• run.ts adds an onCompleteStarted guard and routes throw-after-abort through onComplete(cancelled) instead of onError, forwarding accumulated content and blocks so the finaliser has something to persist.
• post.ts removes the early return on result.cancelled and instead calls finalizeAssistantTurn with the new policy; route.ts delegates its own inline SELECT/UPDATE to the same finaliser, passing userId for row-level ownership.

Confidence Score: 5/5

Safe to merge; the core race is correctly closed by the FOR UPDATE transaction and the active-or-cleared policy handles both orderings of concurrent writes idempotently.

The transaction + row-lock approach is sound for PostgreSQL, the two writer paths (stop route and cancelled lifecycle) are both serialised through the same finaliser, and the AssistantAlreadyPersisted outcome prevents double-writes. New tests cover the key race scenarios. The only gap is a defence-in-depth omission (no userId on the cancelled path in post.ts), which is not immediately exploitable given session-scoped chatIds.

apps/sim/lib/copilot/chat/post.ts — the buildOnComplete cancelled path omits userId when calling finalizeAssistantTurn, while the stop route passes it; worth aligning for consistency.

Important Files Changed

Filename	Overview
apps/sim/lib/copilot/chat/terminal-state.ts	Core fix: adds db.transaction + SELECT ... FOR UPDATE row lock so concurrent stop calls are serialised; introduces streamMarkerPolicy to allow writes when the marker was already cleared by a racing finaliser; returns a structured FinalizeAssistantTurnResult instead of void
apps/sim/lib/copilot/request/lifecycle/run.ts	Adds onCompleteStarted guard to prevent double-invocation of onComplete; cancelled-path catch block now calls onComplete (not onError) with accumulated partial content, forwarding content blocks and tool call summaries correctly
apps/sim/lib/copilot/chat/post.ts	Cancelled path now calls finalizeAssistantTurn with active-or-cleared instead of returning early; userId is not forwarded to finalizeAssistantTurn, asymmetric with the stop route which does pass userId
apps/sim/app/api/copilot/chat/stop/route.ts	Delegates to finalizeAssistantTurn with active-or-cleared; correctly passes userId: session.user.id; stop outcome and pub-sub notification logic updated to handle AssistantAlreadyPersisted idempotency
apps/sim/lib/copilot/chat/persisted-message.ts	New withStoppedContentBlock helper appends a cancelled completion block to a message, guarding against double-adding one if already present; logic is correct

Sequence Diagram

sequenceDiagram
    participant Client
    participant StopRoute as StopRoute
    participant Lifecycle as Lifecycle
    participant Finalizer as Finalizer
    participant DB as PostgreSQL

    Client->>StopRoute: POST /chat/stop
    Client->>Lifecycle: AbortSignal fires

    Lifecycle->>Lifecycle: runStreamLoop throws
    Lifecycle->>Finalizer: finalizeAssistantTurn active-or-cleared
    Finalizer->>DB: BEGIN SELECT FOR UPDATE
    DB-->>Finalizer: row locked
    Finalizer->>DB: UPDATE append assistant clear marker
    Finalizer-->>Lifecycle: "updated=true AppendedAssistant COMMIT"

    StopRoute->>Finalizer: finalizeAssistantTurn active-or-cleared with userId
    Finalizer->>DB: BEGIN SELECT FOR UPDATE
    DB-->>Finalizer: row assistant already present marker null
    Finalizer-->>StopRoute: "updated=false AssistantAlreadyPersisted"
    StopRoute->>StopRoute: publishStatusChanged completed idempotent

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^{Reviewed by Cursor Bugbot for commit 05830df. Configure here.}