Python: [Bug]: Unreasonable extraction of context_id from request messages in A2AAgent

[lixiaoqiang]

Description

The current implementation of A2AAgent handles the context_id of messages sent to A2AServer in an unreasonable way.
At present, it extracts the context_id from additional_properties.
The proper approach should be to use AgentSession.service_session_id as the context_id.
This aligns with the intended purpose of service_session_id and ensures session consistency across the entire system.

Code Sample

Error Messages / Stack Traces

Package Versions

agent-framework: 1.0.1

Python Version

Python 3.13

Additional Context

No response

[izzymsft]

The semantics for how the context id should be managed is addressed here in the spec.

https://a2a-protocol.org/latest/specification/#341-context-identifier-semantics

I generally prefer if this is server generated so that it is handled consistently. Unless both the client and server are on the same page about how this identifier should be handled, it could lead to misunderstandings from experience, I generally prefer it to be server-generated.