In the Flutter chat interface for our tkstock project, a ghost was haunting the UI. The AI's typewriter effect would freeze mid-sentence. New data wasn't appearing, but the backend hadn't stopped sending it.
Was it a network blip? A crashed thread? No—it was a silent logic error in how we handled state updates.
The Problem: Asynchronous Ambiguity
Streaming UI bugs are tricky because of the "asynchronous illusion." When the interface freezes, it's hard to tell immediately if the SSE (Server-Sent Events) stream broke or if the frontend state merge logic failed.
If we didn't fix this thoroughly, users would face truncated content during critical information retrieval. Worse, an over-aggressive fix (like showing only the first line) would break the feature entirely.
