assistant-ui
assistant-ui is a YC Winter 2025 (W25) company. Based in San Francisco, CA, USA. Team of 3.
About assistant-ui
Summary
assistant-ui builds an open-source TypeScript/React library that gives frontend developers production-ready chat UI components and a runtime for AI agents. It handles streaming, tool calls, branching, and generative UI, replacing the work of building these primitives from scratch. Integrations with LangGraph, LangChain, and the Vercel AI SDK let developers connect any backend through adapters.
Business model
A free open-source library plus a paid cloud backend as a service.
Go-to-market
Frontend developers and B2B software teams adopt the library self-serve from the open-source package, then convert to the hosted cloud product for backend infrastructure.
From the Y Combinator listing
Open Source React.js Library for AI Chat
assistant-ui helps frontend developers add AI chat to their apps. Our product is used by several dozen companies, like LangChain, Stack AI, Browser Use, and Athena Intelligence. We're building an open source Typescript/React library and a backend as a service, with first class integrations into popular agent frameworks like LangGraph and Vercel AI SDK.
Facts
- B2B / B2B -> Infrastructure
- San Francisco, CA, USA
- 3
- Active
- Early
Founders (1)
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