AG-UI + A2UI Integration Skill

Overview

Use this skill to add A2UI rendering to an AG-UI application. Treat AG-UI as the transport and agent integration layer, @ag-ui/a2ui-middleware as the server-side bridge that detects and paints A2UI operations, and A2UI as the UI payload format that the client renderer displays.

This is a developer-facing skill artifact. It is meant to be loaded by coding agents and used against a real app or repo, not published as a docs page.

When to Use

• Adding A2UI rendering to an existing AG-UI app.
• Creating an AG-UI quickstart that should display A2UI surfaces.
• Connecting any AG-UI-supported framework or custom AG-UI agent to an A2UI-capable frontend.
• Adding or extending an A2UI component catalog.
• Debugging why an A2UI surface does not render or why a user action does not flow back to the agent.

When NOT to Use

• For AG-UI protocol event semantics only, use the AG-UI protocol skill or protocol docs.
• For A2UI renderer internals outside an AG-UI app, use the A2UI renderer docs or renderer-specific skills.
• For generic CopilotKit frontend work without A2UI, use CopilotKit-specific setup and React skills.

Workflow

1. Inspect the app shape: framework adapter, AG-UI agent endpoint, runtime host, frontend shell, and any existing A2UI renderer/catalog.
2. Decide the A2UI mode before editing code:
   • Fixed schema: backend tools return an a2ui_operations envelope with createSurface, updateComponents, and updateDataModel.
   • Dynamic schema: a framework A2UI tool (generate_a2ui) delegates to a sub-agent that streams render_a2ui args through A2UIMiddleware.
3. Select framework-specific wiring from references/framework-adapters.md, or use that reference to find the closest AG-UI integration pattern. Preserve the app's existing agent architecture.
4. Wire server middleware/runtime and client renderer using references/a2ui-runtime-and-renderer.md. Avoid double-applying A2UIMiddleware; use either runtime-level A2UI config or per-agent agent.use(new A2UIMiddleware(...)) for a given agent.
5. Register a catalog on the client. With CopilotKit >= 1.61.2, forwarding it to the provider (a2ui={{ catalog }}) auto-enables A2UI and auto-derives defaultCatalogId from the catalog's id. Only when you are not forwarding a catalog, ensure the middleware or adapter sets a defaultCatalogId matching the renderer-registered catalog.
6. Verify the streaming path with references/verification.md: AG-UI stream, a2ui-surface activity snapshots or a2ui_operations, rendered A2UI surface, and a user interaction flowing back through AG-UI.

AG-UI Framework Support

This skill is not limited to the framework examples below. For any target framework, first check the AG-UI repository's integrations/ directory, the AG-UI docs, the framework adapter's A2UI files, and the current CLI source. If AG-UI supports the framework, use that integration's documented package, endpoint helper, A2UI tool factory, or scaffold path. If there is no framework A2UI adapter, implement the custom AG-UI agent path, return a2ui_operations from backend tools for fixed layouts, and keep the middleware/client wiring the same.

Common AG-UI CLI Flags

Use the CLI flags that exist in sdks/typescript/packages/cli/src/index.ts. The table is a quick reference for known scaffold paths, not the full AG-UI support matrix. Do not invent flags.

Framework	CLI flag
ADK	--adk
LangGraph Python	--langgraph-py
LangGraph JavaScript	--langgraph-js
CrewAI Flows	--crewai-flows
Mastra	--mastra
Pydantic AI	--pydantic-ai
LlamaIndex	--llamaindex
Agno	--agno
AG2	--ag2

Strands has AG-UI integration packages and examples, but no Strands CLI flag is present in the current AG-UI CLI source. Use the Strands integration docs instead of guessing a scaffold command.

Key Rules

• Keep the integration AG-UI-first for every supported framework. CopilotKit is a common runtime/renderer path for web apps, but AG-UI owns the middleware, framework adapters, and wire events.
• Enable A2UI on both sides: A2UIMiddleware or runtime A2UI config on the server, and an A2UI-capable renderer/catalog on the client.
• For dynamic schema, prefer the framework adapter's A2UI tool factory or auto-injection path. The model should call generate_a2ui; the sub-agent should stream render_a2ui args so the middleware can progressively paint.
• For fixed schema, return an a2ui_operations envelope from backend tools rather than asking the model to invent component trees.
• Emit createSurface once per surfaceId; use update operations for later changes.
• Do not let the model invent catalog ids. When the client forwards a catalog to the provider (CopilotKit >= 1.61.2), its catalogId is derived automatically; otherwise the host/middleware/adapter should stamp a defaultCatalogId that matches the client-registered catalog.
• Preserve AG-UI run boundaries and error events. Do not swallow server or stream errors.
• Verify with a real browser or client run when possible. A static typecheck is not enough for streaming UI work.

References

• references/framework-adapters.md - framework-specific AG-UI adapter patterns.
• references/a2ui-runtime-and-renderer.md - server/client A2UI wiring and catalog patterns.
• references/verification.md - checks to confirm the integration works.
• sources.md - source files and docs used by this skill.