debug-notes.md

Bug Analysis - Chat Message Flow

Bug 1: Auth fails on /api/chat/stream (FIXED)

• getAuthUser() in chat-endpoint.ts used SDK auth which requires JWT cookie
• In dev mode, no cookie is set → returns null → 401 Unauthorized
• Fix: Added dev-mode bypass matching tRPC context.ts

Bug 2: Race condition in Home.tsx session creation

• When user sends first message with no session:
  1. handleSend() calls createSession.mutate() with inline onSuccess that calls sendMessage(content, session.id)
  2. But createSession also has a global onSuccess that calls clearMessages()
  3. Race: sendMessage adds user msg + assistant placeholder → clearMessages() wipes them
• Fix: Remove clearMessages() from global createSession.onSuccess when it's triggered by handleSend

Bug 3: sessionMessages useEffect overwrites optimistic state

• When currentSessionId changes, trpc.messages.list.useQuery fires
• The useEffect unconditionally calls setMessages(mapped)
• This can overwrite the optimistic user message added by useChat before the DB message is visible
• Fix: Don't overwrite messages during streaming

Bug 4: "done" SSE event with empty data gets skipped

• Line 123 in useChat.ts: if (!dataStr || dataStr === "{}") continue;
• The "done" event sends data: {} which gets skipped - this is fine
• But the "done" event should trigger cleanup

Action items:

1. ✅ Fix auth bypass in chat-endpoint.ts
2. Fix race condition in Home.tsx
3. Guard sessionMessages effect during streaming
4. Test end-to-end