A2A to LiteLLM Completion Bridge

Routes A2A protocol requests through litellm.acompletion, enabling any LiteLLM-supported provider to be invoked via A2A.

Flow

A2A Request → Transform → litellm.acompletion → Transform → A2A Response

SDK Usage

Use the existing asend_message and asend_message_streaming functions with litellm_params:

from litellm.a2a_protocol import asend_message, asend_message_streaming
from a2a.types import SendMessageRequest, SendStreamingMessageRequest, MessageSendParams
from uuid import uuid4

# Non-streaming
request = SendMessageRequest(
    id=str(uuid4()),
    params=MessageSendParams(
        message={"role": "user", "parts": [{"kind": "text", "text": "Hello!"}], "messageId": uuid4().hex}
    )
)
response = await asend_message(
    request=request,
    api_base="http://localhost:2024",
    litellm_params={"custom_llm_provider": "langgraph", "model": "agent"},
)

# Streaming
stream_request = SendStreamingMessageRequest(
    id=str(uuid4()),
    params=MessageSendParams(
        message={"role": "user", "parts": [{"kind": "text", "text": "Hello!"}], "messageId": uuid4().hex}
    )
)
async for chunk in asend_message_streaming(
    request=stream_request,
    api_base="http://localhost:2024",
    litellm_params={"custom_llm_provider": "langgraph", "model": "agent"},
):
    print(chunk)

Proxy Usage

Configure an agent with custom_llm_provider in litellm_params:

agents:
  - agent_name: my-langgraph-agent
    agent_card_params:
      name: "LangGraph Agent"
      url: "http://localhost:2024"  # Used as api_base
    litellm_params:
      custom_llm_provider: langgraph
      model: agent

When an A2A request hits /a2a/{agent_id}/message/send, the bridge:

Detects custom_llm_provider in agent's litellm_params
Transforms A2A message → OpenAI messages
Calls litellm.acompletion(model="langgraph/agent", api_base="http://localhost:2024")
Transforms response → A2A format

Classes

A2ACompletionBridgeTransformation - Static methods for message format conversion
A2ACompletionBridgeHandler - Static methods for handling requests (streaming/non-streaming)