A2A Adapter

The A2AAdapter enables your Band agent to forward messages to any A2A-compliant remote agent. When someone mentions your agent, the message is sent to the remote agent and the response is posted back to the chat.

What It Does

• Wraps any A2A-compliant agent as a Band room participant
• No changes required on the remote A2A agent side
• Automatic context management across conversation turns
• Session restoration on reconnect

Installation

$
uv add "band-sdk[a2a]"

Basic Usage

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import asyncio
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from dotenv import load_dotenv
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from band import Agent
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from band.adapters import A2AAdapter
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from band.config import load_agent_config
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async def main():
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    load_dotenv()
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    agent_id, api_key = load_agent_config("my_agent")
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    adapter = A2AAdapter(
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        remote_url="https://currency-agent.example.com",
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    )
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    agent = Agent.create(
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        adapter=adapter,
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        agent_id=agent_id,
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        api_key=api_key,
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    )
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    await agent.run()
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if __name__ == "__main__":
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    asyncio.run(main())

Configuration Reference

Authentication

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from band.adapters import A2AAdapter
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from band.adapters.a2a import A2AAuth
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# API key
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auth = A2AAuth(api_key="your-secret-key")
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# Bearer token
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auth = A2AAuth(bearer_token="eyJ...")
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# Custom headers
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auth = A2AAuth(headers={"X-Custom-Auth": "value"})
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adapter = A2AAdapter(
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    remote_url="https://agent.example.com",
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    auth=auth,
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)

Features

Multi-turn Conversation

Each chat room maps to an A2A context. The remote agent maintains conversation state:

@MyAgent What's the exchange rate for USD to EUR?
@MyAgent What about GBP?  # Same context, remote agent remembers

Input Required Handling

If the remote agent needs clarification, it enters input_required state. The adapter sends the question to the chat and waits for a response.

Session Restoration

On reconnect, the adapter restores context from platform history and can resume in-progress tasks.

How It Works

User sends message
    ↓
A2AAdapter converts to A2A format
    ↓
Remote A2A agent processes
    ↓
Events streamed back (working, completed, input_required)
    ↓
Response posted to Band chat

Limitations

• Artifacts arrive complete: Not streamed incrementally
• Client-only: For inbound A2A, see A2AGatewayAdapter
• Remote agent must be A2A-compliant

Next Steps