The Agent–User Interaction (AG-UI) Protocol
AG-UI is an open, lightweight, event-based protocol that standardizes how AI agents connect to user-facing applications. AG-UI is designed to be the general-purpose, bi-directional connection between a user-facing application and any agentic backend. Built for simplicity and flexibility, it standardizes how agent state, UI intents, and user interactions flow between your model/agent runtime and user-facing frontend applications—to allow application developers to ship reliable, debuggable, user‑friendly agentic features fast while focusing on application needs and avoiding complex ad-hoc wiring.
Agentic Protocols
AG-UI is one of three prominent open agentic protocols.| Layer | Protocol / Example | Purpose |
|---|---|---|
| Agent ↔ User Interaction | AG-UI (Agent–User Interaction Protocol) | The open, event-based standard that connects agents to user-facing applications — enabling real-time, multimodal, interactive experiences. |
| Agent ↔ Tools & Data | MCP (Model Context Protocol) | Open standard (originated by Anthropic) that lets agents securely connect to external systems — tools, workflows, and data sources. |
| Agent ↔ Agent | A2A (Agent to Agent) | Open standard (originated by Google) which defines how agents coordinate and share work across distributed agentic systems. |
Confused about “A2UI” and “AG-UI”? That’s understandable! Despite the naming similarities, they are quite different and work well together. A2UI is a generative UI specification - allowing agents to deliver UI widgets, where AG-UI provides the complete bi-directional runtime connection between the agent and the application.
Building blocks (today & upcoming)
Streaming chat
Live token and event streaming for responsive multi turn sessions, with cancel and resume.
Multimodality
Typed attachments and real time media (files, images, audio, transcripts); supports voice, previews, annotations, provenance.
Generative UI, static
Render model output as stable, typed components under app control.
Generative UI, declarative
Small declarative language for constrained yet open-ended agent UIs; agents propose trees and constraints, the app validates and mounts.
Shared state
(Read-only & read-write). Typed store shared between agent and app, with streamed event-sourced diffs and conflict resolution for snappy collaboration.
Thinking steps
Visualize intermediate reasoning from traces and tool events; no raw chain of thought.
Frontend tool calls
Typed handoffs from agent to frontend-executed actions, and back.
Backend tool rendering
Visualize backend tool outputs in app and chat, emit side effects as first-class events.
Interrupts (human in the loop)
Pause, approve, edit, retry, or escalate mid flow without losing state.
Sub-agents and composition
Nested delegation with scoped state, tracing, and cancellation.
Agent steering
Dynamically redirect agent execution with real-time user input to guide behavior and outcomes.
Tool output streaming
Stream tool results and logs so UIs can render long-running effects in real time.
Custom events
Open-ended data exchange for needs not covered by the protocol.
Why Agentic Apps need AG-UI
Agentic applications break the simple request/response model that dominated frontend-backend development in the pre-agentic era: a client makes a request, the server returns data, the client renders it, and the interaction ends.The requirements of user‑facing agents
While agents are just software, they exhibit characteristics that make them challenging to serve behind traditional REST/GraphQL APIs:- Agents are long‑running and stream intermediate work—often across multi‑turn sessions.
- Agents are nondeterministic and can control application UI nondeterministically.
- Agents simultanously mix structured + unstructured IO (e.g. text & voice, alongside tool calls and state updates).
- Agents need user-interactive composition: e.g. they may call sub‑agents, often recursively.
- And more…
AG-UI in Action
You can see demo apps of the AG-UI features with the framework of your choice, with preview, code, and walkthrough docs in the AG-UI Dojo
Supported Integrations
AG-UI was born from CopilotKit’s initial partnership with LangGraph and CrewAI - and brings the incredibly popular agent-user-interactivity infrastructure to the wider agentic ecosystem.Direct to LLM
| Framework | Status | AG-UI Resources |
|---|---|---|
| Direct to LLM | Supported | Docs |
Agent Framework - Partnerships
Agent Framework - 1st Party
| Framework | Status | AG-UI Resources |
|---|---|---|
| Microsoft Agent Framework | Supported | Docs, Demos |
| Mastra | Supported | Docs, Demos |
| Pydantic AI | Supported | Docs, Demos |
| Agno | Supported | Docs, Demos |
| LlamaIndex | Supported | Docs, Demos |
| AG2 | Supported | Docs |
| AWS Bedrock Agents | In Progress | – |
| AWS Strands Agents | In Progress | – |
| Microsoft Agent Framework | In Progress | – |
Agent Framework - Community
| Framework | Status | AG-UI Resources |
|---|---|---|
| Vercel AI SDK | Supported | Docs |
| OpenAI Agent SDK | In Progress | – |
| Cloudflare Agents | In Progress | – |
Agent Interaction Protocols
| Protocol | Status | AG-UI Resources | Integrations |
|---|---|---|---|
| A2A Middleware | Supported | Docs | Partnership |
SDKs
| SDK | Status | AG-UI Resources | Integrations |
|---|---|---|---|
| Kotlin | Supported | Getting Started | Community |
| Golang | Supported | Getting Started | Community |
| Dart | Supported | Getting Started | Community |
| Java | Supported | Getting Started | Community |
| Rust | Supported | Getting Started | Community |
| .NET | In Progress | PR | Community |
| Nim | In Progress | PR | Community |
| Flowise | In Progress | GitHub Source | Community |
| Langflow | In Progress | GitHub Source | Community |
Clients
| Client | Status | AG-UI Resources | Integrations |
|---|---|---|---|
| CopilotKit | Supported | Getting Started | 1st Party |
| Terminal + Agent | Supported | Getting Started | Community |
| React Native | Help Wanted | GitHub Source | Community |
Quick Start
Choose the path that fits your needs:Build agentic applications
Build agentic applications powered by AG-UI compatible agents.
Build new AG-UI integrations
Build integrations for new agent frameworks, custom in-house solutions, or use AG-UI without any agent framework.
Build AG-UI compatible clients
Build new clients for AG-UI-compatible agents (web, mobile, slack, messaging, etc.)
Explore AG-UI
Dive deeper into AG-UI’s core concepts and capabilities:Core architecture
Understand how AG-UI connects agents, protocols, and front-ends
Events
Learn about AG-UI’s event-driven protocol
Resources
Explore guides, tools, and integrations to help you build, optimize, and extend your AG-UI implementation. These resources cover everything from practical development workflows to debugging techniques.Developing with Cursor
Use Cursor to build AG-UI implementations faster
Troubleshooting AG-UI
Fix common issues when working with AG-UI servers and clients
Contributing
Want to contribute? Check out our Contributing Guide to learn how you can help improve AG-UI.Support and Feedback
Here’s how to get help or provide feedback:- For bug reports and feature requests related to the AG-UI specification, SDKs, or documentation (open source), please create a GitHub issue
- For discussions or Q&A about the AG-UI specification, use the specification discussions
- For discussions or Q&A about other AG-UI open source components, use the organization discussions