[Feat]: Streaming mode append msg

[HLhuanglang]

Is your feature request related to a problem? Please describe.

When I use streaming mode, the agent's return value is split into N parts, which is not user-friendly in terms of interaction experience.

Describe the solution you'd like

Describe alternatives you've considered

No response

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[brycewcole]

I see this behaviour a lot when using AWS's Stands A2A implementation. Is it spec compliant to emit tokens as they stream via status-update? My understanding was that was for things like "Working on finding available tools..., Searching the web..." and that streaming should be done via the artifact update event for the final message.

[nikp1172]

Just to clarify here, if using stream mode for A2A agent. Can two events have same message ID?

I mean does each "event" represent a new message? Or can multiple events be emitted for a single message?