fix(mothership): re-attach at once when the user returns to a recovered stream by waleedlatif1 · Pull Request #8675 · simstudioai/sim

waleedlatif1 · 2026-10-06T15:56:33Z

Summary

After the user leaves a running chat and comes back, the return recovery owns the stream for the rest of the turn, and every later online / visible / pageshow event just joined that in-flight recovery.
So a later network drop waited out whatever the recovery was doing: a tail that went silent held the stream until the 45s idle timeout, and a tail that failed slept out a reconnect backoff of up to 30s. The same drop on a stream the send still owned re-attached immediately.
A return signal now supersedes an in-flight recovery the same way it supersedes the send's reader, and the new recovery re-attaches from the cursor.

Type of Change

Bug fix

Testing

New DOM regression in use-chat.dom.test.tsx covering both a stalled tail and a failed tail in backoff; both fail on staging.
Browser E2E on a local Sim + worker stack (tab hidden and returned, then 90s offline): streaming resumed under 1s after the network came back, versus ~48s before.

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)

…ed stream Once the user left a running chat and came back, the return recovery owned the stream for the rest of the turn, and every later online/visible/pageshow event just joined it. So a network drop after that waited out whatever the recovery was doing: a tail that went silent held the stream until the 45s idle timeout, and a tail that failed slept out a reconnect backoff of up to 30s. The same drop on a stream the send still owned re-attached immediately, because the return signal supersedes the send's reader. On the local QA stack the stream resumed 48s after the network came back. A return signal now supersedes an in-flight recovery the same way, and the new recovery re-attaches from the cursor.

vercel · 2026-10-06T15:56:40Z

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1 Skipped Deployment

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waleedlatif1 · 2026-10-06T15:56:45Z

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waleedlatif1 · 2026-10-06T15:56:46Z

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cubic-dev-ai · 2026-10-06T15:56:51Z

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All reported issues were addressed across 2 files

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greptile-apps · 2026-10-06T16:01:39Z

Confidence Score: 5/5

[Medium risk] Changes stream recovery logic when user returns to chat.

The PR appears safe to merge; no outstanding findings remain.

Summary

The PR lets a browser-return signal supersede an in-flight stream recovery and reattach from the current cursor. It also resolves a locally running turn after the server has finished it, including when the POST response was lost, while leaving a not-yet-admitted send alone.

Adds DOM regressions for stalled and failed recovery tails, completed turns, and pending POST admission.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Browser return signal] --> B[Abort prior recovery]
  B --> C[Load chat history]
  C --> D{Active server stream?}
  D -->|Yes| E[Reattach from cursor]
  D -->|No| F{Local turn admitted?}
  F -->|Yes| G[Resolve terminal stream and finalize]
  F -->|No| H[Leave pending POST alone]

_{Reviews (4) · Last reviewed commit: "fix(mothership): finish an admitted turn..."}

A return recovery used the chat history's `activeStreamId` to decide what to re-attach to. When the turn had ended while this surface was not listening (its reader stalled, or a later return superseded the recovery that held it), the history listed no running turn, so recovery returned without touching the stream this surface still showed as running, and the chat stayed on Stop until an idle timeout or backoff happened to run into the terminal state. When the history lists no running turn but this surface is still sending, recovery now resolves that stream: its terminal status replays the remaining events and finalizes.

waleedlatif1 · 2026-10-06T16:23:56Z

@greptile

waleedlatif1 · 2026-10-06T16:23:58Z

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cubic-dev-ai · 2026-10-06T16:24:05Z

@cubic-dev-ai review this PR

@waleedlatif1 I have started the AI code review. It will take a few minutes to complete.

cubic-dev-ai

All reported issues were addressed across 2 files

_{Reply with feedback, questions, or to request a fix.

Fix all with cubic | Turn on auto-fix | Re-trigger cubic}

A send shows as running before its POST is admitted, but the chat cannot list it yet. Resolving that stream on a return event read it as ended and aborted the POST. Recovery now resolves only a locally running stream whose POST was admitted.

waleedlatif1 · 2026-10-06T17:28:18Z

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waleedlatif1 · 2026-10-06T17:28:19Z

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cubic-dev-ai · 2026-10-06T17:28:25Z

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cubic-dev-ai

No issues found across 2 files

Confidence score: 5/5

Automated review surfaced no issues in the provided summaries.
No files require special attention.

_{Turn on auto-fix | Re-trigger cubic}

… return Recovery left a send alone while its POST had not answered, so a turn the server admitted and finished, whose answer never reached the client, kept the chat on Stop with nothing to clear it. The send now counts as admitted once the loaded chat holds its message, and recovery resolves its stream as any other.

waleedlatif1 · 2026-10-06T18:05:58Z

@greptile

waleedlatif1 · 2026-10-06T18:05:59Z

@cubic-dev-ai review this PR

cubic-dev-ai · 2026-10-06T18:06:05Z

@cubic-dev-ai review this PR

@waleedlatif1 I have started the AI code review. It will take a few minutes to complete.

cubic-dev-ai

No issues found across 2 files

Confidence score: 5/5

Automated review surfaced no issues in the provided summaries.
No files require special attention.

_{Turn on auto-fix | Re-trigger cubic}

cubic-dev-ai Bot reviewed Oct 6, 2026

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Comment thread apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts

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waleedlatif1 merged commit 662bd70 into staging Oct 6, 2026
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waleedlatif1 mentioned this pull request Oct 6, 2026

fix(mothership): close the remaining ways a chat send is lost, resent hot, or polled after unmount #8695

Merged

6 tasks done

waleedlatif1 deleted the fix/mothership-reattach-on-return branch October 6, 2026 21:19

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waleedlatif1 commented Oct 6, 2026

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