Closing the QuickChat browser tab mid-response left the backend agent
running with no listener. The `activeGenerations` slot persisted and the
next message's freshly-opened CLI SessionManager raced against the
lingering agent on the same session file, so the model produced no
output for the new prompt.
- POST /chat/sessions/:id/messages now calls cancelGeneration on
req.on("close") if the response hasn't ended yet, so disconnects stop
the agent promptly.
- beginGeneration only aborts the prior controller; it no longer
disposes the prior agent. Disposing pre-emptively could yank the CLI
process out from under the new generation's session opened on the
same file.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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