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assistant-ui

Y Combinator LogoW25
Active
developer-tools
generative-ai
San Francisco
 
https://assistant-ui.com

Open Source Typescript/React 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.
assistant-ui
Founded:2024
Team Size:1
Status:
Active
Location:San Francisco
Group Partner:Jared Friedman
   
Active Founders

Simon Farshid, Founder

Simon is the Founder and CEO of assistant-ui. Before assistant-ui, he co-founded and exited READO, a book recommendation engine and community with over 140k monthly active users. Simon is a hacker at heart - he started coding at age 12 and has won 8 hackathons. Simon grew up in Iran and Germany and moved to the San Francisco early 2024.
Simon Farshid
Simon Farshid
assistant-ui
  
Company Launches
💬 assistant-ui - Open Source Typescript/React Library for AI Chat
See original launch post ›

Hi YC! I’m Simon, building assistant-ui, an open source Typescript/React library for AI chat.

Hundreds of projects use assistant-ui to build in-app AI assistants, including companies like:

With >50k+ monthly downloads, assistant-ui is the most popular UI library for AI chat.

Getting Started

You can get started by running `npx assistant-ui create` (new project) or `npx assistant-ui init` (existing project) in your terminal.

Features

  • Pre-built components, fully customizable
  • Connects to your backend
    • We have first class integration for AI SDK and LangGraph or build your own
  • Generative UI: Map LLM tool calls and JSONs to custom UI components
  • Frontend Tool Calls: Let LLMs take action in your frontend app
  • Human Tool Calls: Human approvals and input collection
  • Chat history and analytics via assistant-cloud (the hosted offering)

Customization

The API of assistant-ui is inspired by libraries like Radix UI and cmdk. Instead of a single monolithic chat component, we give you composable primitives and a great starter configuration. You have full control over the look and feel of every pixel while leaving auto-scrolling, LLM streaming and accessibility to us.

Sample customization to make a perplexity lookalike:

Demo Video

Demo Video

About

I’ve wanted to build my own dev tool company since high school. Last year, I built the first version of assistant-ui because I needed the UX of ChatGPT in my own app. The app I was building didn’t work out, but few friends asked me about the chat UI. Since then, AI chat has became increasingly popular as a means for delegating tasks to AI agents. My focus is on enabling human <> agent collaboration through better UX and AX (agent experience).

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