ABOUT

A focused debugger for agent event streams.

AG-UI Event Lab is an independent, free developer project that helps teams inspect AG-UI events before they reach a frontend. It accepts raw SSE, JSONL, JSON arrays and single events, then reports field and cross-event lifecycle problems.

Why it exists

A general JSON formatter can tell you whether braces match. It cannot tell you that a message delta arrived before its start, a tool result precedes the call end, or a run finished with mismatched identifiers. The validator keeps an in-browser model of the stream to make those protocol relationships visible.

Editorial approach

Every rule is tied to an observable protocol invariant and described in plain English. Supporting pages explain why a finding matters, how SSE framing works and why event order changes frontend behavior. The site follows the public AG-UI TypeScript schemas and flags deprecated THINKING events.

Independence and limitations

This project is not affiliated with AG-UI or CopilotKit. It is not a certification service. Client SDKs may transform convenience chunk events or enforce application-specific rules that this general validator cannot infer. Always test with the exact SDK and transport used in production.

Open source

Source code and issue tracking are available on GitHub. Corrections that improve specification accuracy, accessibility or safe debugging practice are welcome.