Vercel lets Chat SDK agents stream generative UI with json-render

Vercel added json-render support to its Chat SDK, so agents can stream generative UI into chat messages. The agent writes a JSON spec against a typed catalog of components such as tables, charts and buttons; json-render converts that spec into a Chat SDK card, and each adapter posts the card in the platform's native format, like Block Kit on Slack or Adaptive Cards on Teams. The streamCard helper posts a card once its root element has content and updates the message as further elements arrive, sending edits at most once every 500 ms by default. toCard checks element props against their component schemas and throws CardSpecError for specs that fail, so the issues can be sent back to the model. Documentation and a playground are available now for developers building on Chat SDK.