Python: A2AExecutor: accept forwarded run kwargs from request metadata #9191

Description

A2AExecutor receives the inbound A2A RequestContext, including context.metadata (SendMessageRequest.metadata), but ignores it. run_kwargs is fixed when the executor is constructed, so runtime context a caller passes as function_invocation_kwargs and client_kwargs cannot reach the hosted agent. Middleware and tools on a hosted agent therefore see different context.kwargs than they would if the agent ran locally in the same workflow.

function_invocation_kwargs and client_kwargs are the only run-time inputs in the SupportsAgentRun.run contract besides messages, session and stream, so they are the natural thing to rehydrate on the server.

Proposal

Let A2AExecutor opt in to accepting selected keys of the kwargs a client forwards in SendMessageRequest.metadata["agent_framework"] (client side: #7973), and pass them to agent.run(function_invocation_kwargs=..., client_kwargs=...):

• Opt-in via a key allowlist (A2AExecutor(agent, accepted_kwargs=[...])). Nothing is accepted by default, because the values are chosen by a remote caller and client_kwargs can reach a provider client.
• run_kwargs configured on the executor win on conflict.
• Framework-owned names (stream, messages, options, session, middleware and similar, plus underscore-prefixed names) are rejected with ValueError at construction, so a remote caller cannot cause duplicate keyword errors.
• Missing or malformed metadata is ignored.

Code Sample

executor = A2AExecutor(agent, accepted_kwargs=["tenant"])

A caller that forwards function_invocation_kwargs={"tenant": "acme"} then gets context.kwargs["tenant"] == "acme" in function middleware and tools on the hosted agent.

Language/SDK

Python