fix: stop working timer when turn completes despite stale session status

[rdoupe]

What Changed

Two locations showed a stale "Working" state after the agent finished responding:

1. ChatView.tsx — "Working for Xm Xs" timer in the main chat area
2. Sidebar.logic.ts — "Working" pill on thread list items

Root Cause

The server's shouldApplyThreadLifecycle guard in ProviderRuntimeIngestion.ts can reject turn.completed events when turn IDs don't match. When this happens:

• session.status stays stuck on "running" indefinitely
• session.activeTurnId becomes permanently stale

However, latestTurn.completedAt is set through a separate, independent path (thread.turn.diff.complete) that bypasses this guard — so the frontend has a reliable signal that the turn is done.

Fix

Use completedAt on the latest turn as the reliable completion signal, rather than depending solely on session.status:

// ChatView.tsx
const turnDone = !!activeLatestTurn?.completedAt;
const isActivelyRunning =
  phase === "running" && pendingUserInputs.length === 0 && !turnDone;
const isWorking = isActivelyRunning || isSendBusy || isConnecting || isRevertingCheckpoint;

// Sidebar.logic.ts
const sidebarTurnDone = !!thread.latestTurn?.completedAt;
if (thread.session?.status === "running" && !sidebarTurnDone) { ... }

This also correctly suppresses the working indicator when the agent is blocked waiting for user input (pendingUserInputs.length > 0), since that check was already present.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes

Fixes #1069, closes #1335

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[sfncore]

Just made a PR related to this as well. Below is message from Claude:

Interesting — PR #1348 is a different
fix for the same root cause we
identified. They took the frontend
approach: use latestTurn.completedAt as
the reliable completion signal instead
of trusting session.status.

Their fix is a workaround (frontend
compensates for the stale session
status). Our fix (#1364) addresses the
root cause (server-side: always apply
turn.completed so session status
actually transitions to "ready").

Both fixes are complementary — theirs
makes the UI resilient even if the
server state is stale, ours prevents the
server state from getting stale in the
first place. Together they'd provide
defense in depth.

[rdoupe]

Just made a PR related to this as well. Below is message from Claude:

Interesting — PR #1348 is a different fix for the same root cause we identified. They took the frontend approach: use latestTurn.completedAt as the reliable completion signal instead of trusting session.status.

Their fix is a workaround (frontend compensates for the stale session status). Our fix (#1364) addresses the root cause (server-side: always apply turn.completed so session status actually transitions to "ready").

Both fixes are complementary — theirs makes the UI resilient even if the server state is stale, ours prevents the server state from getting stale in the first place. Together they'd provide defense in depth.

@sfncore

feel free to snag all or part of this if you want. found out this version doesn't actually start the Working text correctly in the chat or the sidebar. working on it again, lets see what else I find.

[rdoupe]

I've confirmed through human testing the backend only fix in #1364 is working correctly to my taste.

I'm going to close this issue.