Chat SDK agents can now stream generative UI with json-render

With a typed catalog of components, the agent writes a JSON spec that json-render converts into a Chat SDK card. Each adapter then posts the card in its platform’s native format, such as Block Kit on Slack and Adaptive Cards on Teams. The catalog covers tables, charts, buttons, and more, so there’s no separate tool to build and maintain for each message shape.

Stream cards as the model writes streamCard posts the card once its root element has content and updates the message as new elements stream in. Edits go out at most once every 500 ms by default, which matches Chat SDK’s streaming interval. Once the stream ends, the message shows the final, validated card.

Validate specs and enforce platform limits toCard checks every element’s props against its component schema and throws CardSpecError for an invalid spec. Each problem gets its own readable issue, so you can send the list back to the model for a corrected spec. Platforms cap what a single message can hold, and Chat SDK adapters degrade content past those caps.