GitHub · by Vercel Labs

json-render

Vercel Labs’ generative UI framework, with a Jev composer behind a flag.

json-render is Vercel Labs’ framework for generative user interfaces: a model returns a JSON spec and the framework renders it from your own component catalogue. Its Jev path is experimental and unreleased — `experimental_composeSpec` and `experimental_createEvaluator`, or the Jev option in the playground — and it composes the spec with typed decisions instead of free text.

The reason a Jev path exists here at all is the failure mode of generative UI. A language model asked to emit a component tree can invent a component that does not exist, a prop that is not in the catalogue, or a shape that will not parse. A typed decision cannot: every choice is made from the options the catalogue actually offers, so the spec is valid by construction rather than by retry.

This is the largest repository on this site by stars and the only one where Jev is a flag rather than the point. It is listed because the composition guide is the clearest published example of putting a System One model in front of a component catalogue, and because it is built by the team whose framework most of the other builds here deploy on. Follow the docs at json-render.dev/docs/jev; the guide notes the Jev path needs a source build.