AG-UI (Agent-User Interaction Protocol) is an open, event-based protocol that streams an AI agent's text, tool calls, state and lifecycle events to a frontend over HTTP and Server-Sent Events. Use when the user wants to build an AG-UI server, connect an agent or framework (LangGraph, Mastra, CrewAI, Pydantic AI) to a React or custom UI, stream agent progress and state, or use CopilotKit with AG-UI.
