AG-UI Protocol
AG-UI is an agent-to-frontend protocol for streaming interaction state, tool activity, generated UI, and human control through an interface instead of hiding the run inside opaque chat text.
Current Source Snapshot
As of 2026-06-30, npm @ag-ui/core latest is 0.0.57 and describes itself as TypeScript definitions and runtime schemas for the Agent-User Interaction Protocol. CopilotKit presents itself as a maker of the AG-UI Protocol and uses it as the foundation for Open Tag's multi-frontend agent clients. Source: npm registry, 2026-06-30; GitHub CopilotKit/CopilotKit, 2026-06-30
What The Protocol Is For
AG-UI belongs where an agent needs to expose more than final text:
| Surface need | Protocol implication |
|---|---|
| Streaming replies | Events must represent partial output and completion |
| Tool calls | UI needs structured tool state, not log strings |
| Generative UI | The model can request/render constrained UI parts |
| Human approvals | The frontend must pause, approve, edit, reject, or resume |
| Cross-client frontends | Web, Slack, Teams, Discord, and mobile need the same run state vocabulary |
This is a protocol-level version of AI-Native Design Patterns: the UI needs a typed event/state contract so product surfaces can show progress, provenance, approvals, and generated components consistently.
Routing
- Use Copilotkit first when building with the CopilotKit stack.
- Use AG-UI as a protocol reference when integrating custom agent runtimes, AWS Bedrock AgentCore AGUI targets, or non-web clients.
- Pair with Photon Spectrum when the surface is a messaging provider; Spectrum can deliver the agent into the channel, while AG-UI-style contracts define the run-state and approval vocabulary.
- Do not confuse AG-UI with MCP. MCP connects models/agents to tools and context; AG-UI connects an agent run to user-facing UI state.
- For risky actions, pair AG-UI-style events with Human-in-the-Loop Control so approval state is persisted and auditable.
Concept Position
| Field | Value |
|---|---|
| Concept family | Agent harness and runtime primitives |
| Concept owned | AG-UI is an agent-to-frontend protocol for streaming interaction state, tool activity, generated UI, and human control through an interface... |
| Category map | Concept System Map |
Timeline
- 2026-07-01 | Concepts category refresh added this page to the Agent harness and runtime primitives family, linked it to Concept System Map, and kept it standalone because it owns this reusable mental model: AG-UI is an agent-to-frontend protocol for streaming interaction state, tool activity, generated UI, and human control through an interface... Source: User request, 2026-07-01
- 2026-06-25 | Open Tag replies identified CopilotKit and AG-UI as the foundation for Slack/Teams early access and future frontend clients. Source: X/@ataiiam reply, 2026-06-25
- 2026-06-30 | Added the boundary with Photon Spectrum after the Photon iMessage/Spectrum bookmark review. Source: X bookmark artifact audit, 2026-06-30
- 2026-06-30 | Created page from the bookmark audit and npm/GitHub version check. Source: X bookmark artifact audit, 2026-06-30