ABOUT

A small tool for a new UI protocol.

A2UI Stream Lab is an independent, free developer project that helps teams inspect agent-generated interface messages before they reach a renderer. It accepts A2UI v0.9 JSON and JSONL and looks for both message-level structure problems and cross-message lifecycle errors.

Why it exists

A general JSON formatter can tell you whether braces match. It cannot tell you that a surface update arrived before creation, a child ID never resolved, or a component graph contains a cycle. 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 and how progressive rendering changes the timing of validation. The site links to primary A2UI documentation and distinguishes stable v0.9 behavior from the evolving v1.0 candidate.

Independence and limitations

This project is not affiliated with Google or the A2UI maintainers. It is not a certification service. Custom catalogs may define additional component properties, templates, functions and theme rules that this general validator cannot infer. Always test with the exact renderer and catalog 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.