Silent hang after tool_result: no assistant turn emitted, queued messages dropped on exit

Summary

Claude Code stalled silently after a Bash tool_result arrived. No subsequent assistant turn was generated — no error, no thinking block, no text output. The user queued four follow-up messages over ~3 minutes, then /exit'd, and the queued messages were dropped.

Environment

• Version: 2.1.104
• Model: claude-opus-4-6
• Platform: darwin 24.6.0
• Session: 68cfea3c-d99d-4218-b389-ed4e782587b6

Timeline (from JSONL session log)

• 16:36:06 assistant text: \"Pushed. Origin/main is now at 9f680c5d.\"
• 16:36:07 assistant tool_use: Bash (git reset --hard main && git push --force-with-lease)
• 16:36:11 tool_result returned successfully (PostToolUse hook OK, exitCode 0)
• No further assistant message ever appears in the JSONL.
• 16:36:48 user enqueue: \"I'm the plugin author. Fix the script and push to the submodule\"
• 16:38:32 user enqueue: \"Did you get that?\"
• 16:39:16 user enqueue: \"Testing\"
• 16:39:24 user enqueue: \"/clear\" → then /exit

Expected

After the tool_result, the model should either:

1. Emit another turn (text and/or tool_use), or
2. Surface an error if the inference call failed

Actual

Silent stall. No visible indicator to the user that the turn never completed. Queued messages were never dispatched to a new turn, and were lost on exit.

Impact

• User sent 4 messages, received 0 responses
• Session was unrecoverable via queue — only /exit worked
• No error logged to failures channel

Asks

1. Surface an error or timeout UI when an inference call doesn't return after a tool_result
2. Flush queued user messages into the next turn (or at least persist them across /exit)
3. Consider a watchdog that emits a heartbeat if the model call exceeds N seconds post-tool-result