21st.dev is the largest React component registry for AI applications, used by 1.4M developers (200K MAU).
We provide the building blocks to create AI agents and agent-powered apps: UI components, agent templates, and an SDK with built-in UI, tools, memory, observability, and managed infrastructure.
This is the 3rd launch from 21st. View more
21st Agents SDK
Launched this week
21st Agents SDK is the fastest way to add an AI agent to your app.
Define your agent in TypeScript, deploy in one command, and embed
a production-ready chat UI with .
Built-in streaming, session management, usage billing, and observability — so you can focus on what makes your agent unique, not infrastructure.
Backed by Y Combinator (W26).
Free Options
Launch Team
Claude AI agent SDK — this is exactly what indie builders needed to skip the heavy lifting. Upvoted! What's the easiest integration path for a React + Node stack?
Congrats on the launch! The Agents SDK concept is solid. One thing landed on 21st.dev and it took me a moment to understand what the product actually does. The hero section might be losing non-developer visitors fast.
cool