[berry-13]

Pull Request

Before submitting, please review the Contributing Guide.

Documentation changes belong in the LibreChat documentation repository.

Summary

useResumableSSE keeps everything it knows about the attached generation in seventeen refs (the live connection, the reconnect ladder, the submission it serves, the optimistic stream ids, the frame retries waiting on a placeholder, the edit-prefix state, the epoch and run-end flags) and rebuilds the attachment's own fences, reattach timers, foreground recovery and stream route inline in a 2,600-line callback. None of that is React, and as long as it lives there no other host can run a resumable stream.

This adds two core classes in packages/chat/src/core/resumable/. ResumableRun owns the pane's run state and takes its clock and frames through an injected scheduler. ResumableSubscription is one attachment: it holds the submission as the stream revises it, the fences every late callback checks (isCurrent), the delayed and immediate re-attach, the foreground re-attach and its status check (through an injected status read and page visibility), the stream route and the connection's event routing. The hook now creates one run per pane and one subscription per attach, and the frame, failure and reconcile handlers it still holds read the subscription instead of closure variables; they move into core in the next links. StreamStatusResponse and the protocol headers move into core with it, re-exported where the client already imported them. No behavior changes. Stacked on #17112.

Type of change

• Refactor

Testing

Tested environments/configuration:

Not applicable: the lifecycle is moved, not changed; the existing hook specs exercise every path through the new classes.

Automated tests:

• Added packages/chat/src/core/__tests__/subscription.spec.ts: fences, stream route, event routing, delayed re-attach that a newer attachment supersedes, foreground re-attach for a closed connection and for an open one the status proves terminal, one foreground listener per pane, and the run's prefix and timer state, all against a fake scheduler, visibility and status read.
• npx jest src/core in packages/chat (146 pass), and in client the hooks/SSE and hooks/Chat specs plus data-provider/SSE (1148 pass, including the 6,000-line useResumableSSE.spec.ts and transport.spec.tsx unchanged).
• npx tsc --noEmit in packages/chat and client, eslint, prettier and sort-imports on the changed files: clean.

Screenshots / recordings

No user-facing change.

Risk / compatibility

Timers, animation frames and the clock now go through the run's scheduler, which defaults to the browser globals and reads them at call time, so fake timers in tests behave as before.

Checklist

• I reviewed my own changes
• Relevant tests have been added or updated
• Existing relevant tests pass
• The change does not introduce new warnings or errors

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-15T15:28:07.421601Z	c48c975	New commits
🔒 Security Review	✅ Completed 2026-10-15T06:04:09.031392Z	98dfa53	PR opened

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