assistant-ui

assistant-ui is an open-source React component library that lets developers drop a fully-featured, ChatGPT-style chat surface into any web application in minutes rather than weeks. It handles the messy parts of AI UX that teams typically rebuild from scratch: streaming tokens, tool-call visualization, message branching and editing, file attachments, voice input/output, generative UI components rendered inline in the chat, and accessible keyboard navigation. The library is framework-agnostic on the backend — it ships adapters for the Vercel AI SDK, LangChain, Mastra, AWS Bedrock, OpenAI, Anthropic, and any custom backend that streams chunks. A hosted runtime tier called Cloud handles thread persistence, multi-user history, and team collaboration without forcing teams to design their own database schema. Styling is built on shadcn/ui and Tailwind, so the components match modern React apps out of the box and are fully customizable down to the primitive level. The project has grown rapidly on GitHub and is used by AI startups, internal enterprise tools, and developer tools that need a polished chat surface without becoming a UI shop. Pricing offers a generous free open-source core, plus paid Cloud plans for hosted persistence and team features.