AG-UI
Open protocol for agent-to-frontend event communication.
About
AG-UI (Agent-User Interaction Protocol) is an open, event-based protocol created by CopilotKit that standardizes how AI agent backends communicate with frontends. Agents stream typed JSON events over HTTP/SSE: lifecycle signals, text chunks, tool calls and results, shared-state snapshots and JSON Patch deltas, and human-in-the-loop interrupts. The key insight is decoupling: one agent can be served to a React app, a Slack bot, or a CLI through the same event stream.
The protocol is framework-agnostic, with first-party adoption from LangGraph, CrewAI, Mastra, Microsoft Agent Framework, Pydantic AI, Google ADK, and others, plus React and Angular clients and a growing list of community clients. The reference implementation is MIT-licensed, reached spec 1.0, and the protocol repository has gathered roughly 16,000 stars. CopilotKit itself is the reference client for building production AI copilots on top of AG-UI.
What it can do
- Standardized event stream for agent-to-UI communication\nShared state sync, streaming, tool calls, and HITL interrupts\nFramework-agnostic with first-party adapters for major agent frameworks\nReact/Angular clients plus community SDKs in other languages
Setup
Add @ag-ui/core (TypeScript) or the ag-ui package (Python); read the spec at docs.ag-ui.com
Prerequisites
An agent backend and a frontend client that speaks AG-UI
Use cases
Works with
Trust score — 8/10
Scored 8/10 (verified tier, metrics-v1). Evidence: Verified via vendor site/docs/GitHub and reputable coverage, wave 101; Trending score 84/100 from researcher assessment.
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.