AG-UI protocol

AG-UI (Agent-User Interaction Protocol) is an open, lightweight, event-based protocol standardizing how agent backends connect to user-facing applications (streaming, bidirectional, multimodal). Originated by copilotkit in partnership with LangChain and CrewAI. It is the agent-to-user layer beside model-context-protocol (agent-to-tool) and a2a-protocol (agent-to-agent).

• SDKs: TypeScript and Python SDKs; backends can be any HTTP endpoint. Community SDKs listed for Kotlin, Go, Dart, Java, Rust, Ruby, C++ and .NET.
• Integrations: first-party in microsoft-agent-framework, google-adk, AWS Strands, mastra, Pydantic AI; partnership with langgraph and crewai.
• Governance: open-source on GitHub, community-driven; I found no evidence it is hosted by a foundation such as agentic-ai-foundation.
• Earlier note text said it “has a Vibe Coding MCP”; unverified, removed.

Sources

• https://docs.ag-ui.com/introduction (2026-09-30)