Thesys has released OpenUI 1.0, its open-source framework that lets agents create working interfaces inside apps.
On Thesys' own benchmark of 46 interface briefs across six models, OpenUI used 58% fewer output tokens than Vercel's json-render and 52% fewer than Google's A2UI.
OpenUI allows models to write a compact UI language that renders on screen while the answer is still being generated.
It works with any model, including open-weight ones running on a team's own hardware.
Version 1.0 adds custom actions, allowing buttons inside a generated answer to activate an app's own code.