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
Launching today
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
21st
@21st @serafimcloud I've been working on the other end of this — getting agent instances to discover and talk to each other across machines, not embedding them into apps. So it's cool to see someone tackling the deployment side. One thing I keep running into though: once you have multiple agents across different deployments, how do they find each other? Does your SDK handle any of that coordination, or is that out of scope?
Had a few shadcn installs turn into local forks fast. 21st pulling components, blocks, and hooks into one stack feels useful, and a really clear diff or version flow would make that npx shadcn path hold up once teams start customizing.