21st.dev Agent Elements
registry.directory/21st-dev/agent-elements
Open-source registry of agent UI primitives — chat shell, tool-call cards (Bash, Edit, Search, Todo, Plan), clarifying questions, input bar, streaming markdown. Built on React 19, Tailwind v4, and the Vercel AI SDK.
Install
npx shadcn@latest add https://agent-elements.21st.dev/r/agent-chat.json
# works for any of the 25 items in this registry