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A2UI

A2UI is an open protocol for agents to generate rich, interactive user interfaces. Instead of returning plain text, agents produce structured JSON that client-side renderers transform into UI components — cards, forms, buttons, images, and more. A2UI is transport-agnostic and works over both A2A and AG-UI. See the A2UI documentation for the full protocol specification.

A2UIAgent#

AG2 supports A2UI through A2UIAgent, a specialized agent that handles prompt engineering with A2UI schema instructions, response parsing, optional schema validation with automatic retry, and integration with A2A and AG-UI serving.

A2A Integration#

A2UIAgent integrates with the A2A protocol through A2aAgentServer. When wrapped in A2aAgentServer, the agent is auto-detected and the server automatically:

  • Uses A2UIAgentExecutor to split responses into text + A2UI DataParts
  • Declares the A2UI version support in the agent card
  • Handles extension negotiation — clients that don't request A2UI get text-only responses
a2ui_server.py
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from autogen import LLMConfig
from autogen.agents.experimental import A2UIAgent
from autogen.a2a import A2aAgentServer, CardSettings

llm_config = LLMConfig({"api_type": "google", "model": "gemini-3.1-flash-lite-preview"})

agent = A2UIAgent(
    name="ui_agent",
    llm_config=llm_config,
    validate_responses=True,
)

server = A2aAgentServer(
    agent=agent,
    url="http://localhost:9000",
    agent_card=CardSettings(
        name="My UI Agent",
        description="An agent that generates rich UI.",
    ),
)

app = server.build()

# Run with: uvicorn a2ui_server:app --host 0.0.0.0 --port 9000

Clients connect via A2A JSON-RPC and request the A2UI extension through the A2A protocol's extension negotiation. The response contains standard A2A parts: - TextPart: The conversational text - DataPart: A2UI operations with MIME type application/json+a2ui

On the client side, Flutter's genui_a2a package provides a native A2UI renderer that connects to the A2A server and renders surfaces automatically.

Further Reading#

See the full A2UIAgent reference for details on configuration, validation, actions, custom catalogs, and AG-UI integration.