Copilotkit+ag-ui+sse cause severe disconnection and message loss issues. | CopilotKit | Page 1

solemn inlet Aug 4, 2025, 8:33 AM

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My agent webapp using copilotkit+ag-ui(crewai), about 20% of conversions disconnected when user uses it. This has seriously affected normal use. Some Info:

frontend deployed on vercel and backend deployed on aws
long-term task above 1 min is easy to disconnect
The network is good, when disconnection happened, backend is still running, but frontend disconnected
I checked the source code of copilotkit, seems that you are not following the standard SSE protocol. The frontend only uses fetch to establish a connection with the backend service, but there is no disconnection retry mechanism or other means to ensure that the frontend can receive messages correctly.

How to solve this issue?

raven mulchBOT Aug 4, 2025, 10:05 AM

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Hi @solemn inlet ,
Could you please ensure you are using the latest CopilotKit and ag-ui versions.

If the issue continues after updating, it might be worth examining your Vercel deployment configuration for any platform-specific settings related to connection timeouts or proxy configurations that could affect long-lived SSE connections. These platform considerations can sometimes impact connection stability in ways that are independent of the application-level retry logic.
CopilotKit and ag-ui implement built-in retry mechanisms to handle SSE disconnections and prevent message loss. The retry logic is present in both core CopilotKit and ag-ui integrations, including LangGraph connections. During reconnections, application state is preserved to avoid message loss.

Additionally, the following resources may provide helpful insights:

Let me know if you are facing issues, even after trying all these steps.