chat processing with typing indicators and batching support for msgs

[whoiskatrin]

the idea is to type more than one msg at a time
want to give users 2 options:

• blast the chat and let him reply after all my messages (that's where typing indicator comes to mind)
• or say a few things, but it gets queued and replied to separately
  inspired by this ai chat agent should handle multiple inputs coming in at the same time #24

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commit: d7939b7

[claude]

Claude Code Review

Summary

Solid implementation of chat message batching and typing indicators for AIChatAgent. The core logic is sound with good test coverage. Found one potential race condition that needs attention.

Issues

1. Race condition in batch mode processing (ai-chat-agent.ts:762-764)

When processing completes and finds a new pending request, there's a window where the timer could fire while the new request is being scheduled:

} finally {
  this._isProcessingChat = false;  // Processing lock released
  // ← Race window: timer could fire here before _scheduleProcessing() resets it
  if (this._pendingChatRequest) {
    this._scheduleProcessing();    // This cancels old timer and creates new one
  }
}

If a timer from before processing started fires during this window, _processPendingRequest() could be called twice concurrently since _isProcessingChat is false but the new timer hasn't been created yet.

Fix: Set the lock before scheduling:

} finally {
  // Check for new request before releasing lock
  if (this._pendingChatRequest) {
    this._scheduleProcessing();
  }
  this._isProcessingChat = false;
}

2. Missing test coverage

Tests don't verify sequential mode works correctly. All tests use batch mode. Should add at least one test with chatProcessingMode = "sequential" to ensure both paths work.

Minor observations

• Good: Comprehensive test suite covers edge cases (cancellation, clearing, multiple connections, typing indicators)
• Good: Proper cleanup on clear/cancel operations (ai-chat-agent.ts:356-395)
• Good: Comment explaining DO eviction edge case (ai-chat-agent.ts:346-349)
• The typing throttle (500ms) in React hook is reasonable but consider making it configurable
• Example client code properly uses onInputChange (examples/resumable-stream-chat/src/client.tsx:72)

The race condition is the only blocking issue - fix the lock ordering and this is good to merge.