assistant-ui

React chat primitives and shadcn-installable UI for LLM apps, copilots, and agents

Tier S · Best in classComponent LibraryPrimitiveRegistryassistant-ui.com

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assistant-ui is an open-source React library for AI chat interfaces, split into headless Radix-style primitives (Thread, Composer, Message, BranchPicker, ChainOfThought, ThreadList) and ~33 styled components you install through the shadcn CLI. It ships runtime adapters for Vercel AI SDK, LangGraph, LangChain, Mastra, AG-UI, A2A, Google ADK and custom servers, so streaming, tool calls, attachments, branching and voice are wired for you. Beyond React on the web it targets React Native and React Ink terminals, and an optional hosted Cloud product adds thread persistence and history. Aimed at teams building a production chat surface rather than reinventing a message list.

Install

npx assistant-ui@latest create

For an agent

Reach for this the moment a project needs a real chat surface with streaming, branching, tool-call rendering and attachments — hand-rolling a message list plus auto-scroll plus a composer costs days and will still miss stop-generation and branch state. It composes with shadcn/ui because the registry serves both Radix and Base UI flavors: point components.json at https://r.assistant-ui.com/styles/{style}/{name}.json so the flavor matches your project style, otherwise Base UI projects get Radix-compiled files. Do not adopt it as a generic component library — it is chat-shaped, brings a runtime and context providers, and its non-chat pieces (accordion, tabs, select) exist to serve the thread, not to replace your design system.

Why it is here. It is the default answer for 'build an AI chat UI in React' — the only library that covers primitives, styled components, runtime adapters and persistence at once, and one of the very few design resources built for agent consumption (llms.txt, MCP endpoint, Claude Code skills, per-page markdown).

Install command, framework, licence and component list.

Facts

License: MIT
Pricing: Open source, Free, Freemium
Framework: React, Next.js, React Native, Terminal UI
Styling: Tailwind CSS, CSS custom properties
Distribution: shadcn registry, npm package, CLI installer, GitHub repository, MCP server
Platform: Web, Cross-platform, Terminal / CLI
Content type: Code
Agent readiness: llms.txt, MCP server, Agent skill or rules pack, Machine-readable registry item, CLI installable, Structured documentation, Readable open source
Accessibility: Built on accessible primitives, Keyboard navigable, RTL and i18n aware
Maturity: Actively maintained
Pricing detail: Library is MIT and free. assistant-ui Cloud (managed thread persistence, search, history) is a separate hosted product; no price list appeared on the pages fetched.
GitHub stars: 11,671
Package: @assistant-ui/react

Components it ships

46 total

Helps you build

AI Chat Panel Chat Web App Chat Mobile Agent Run History Agent Settings Uploading Media

Notable for

headless chat primitives plus shadcn registry
Radix and Base UI flavors of every component
runtime adapters for AI SDK and LangGraph
React Native and React Ink targets
llms.txt, MCP endpoint and agent-skills index

Provenance

Verified 2026-08-15. HTTP 200. https://www.assistant-ui.com/docs, https://www.assistant-ui.com/llms.txt, https://www.assistant-ui.com/docs/installation.md, https://api.github.com/repos/assistant-ui/assistant-ui

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