Python: Preserve Responses replay metadata across AG-UI continuations

[eavanvalkenburg]

Description

AG-UI multi-turn replay exercises two distinct continuation modes:

• stateless snapshot replay, where the complete message history is provider input;
• service-session continuation, where only the incremental turn is provider input and the provider conversation/response ID is persisted privately.

The current implementation has two gaps found by a provider compatibility matrix:

1. Stateless AG-UI can persist a provider response ID from store=True and later combine full-history replay with previous_response_id.
2. OpenAI Responses parses real assistant output_text.logprobs into response metadata but does not retain them on the assistant content for direct replay.

Expected behavior:

• Provider continuation IDs are persisted only when use_service_session=True.
• use_service_session=True fails clearly when provider storage is explicitly disabled.
• Real assistant logprobs are preserved and mirrored during direct Responses replay; absent logprobs are not fabricated.
• OpenAI, FoundryChatClient, Prompt Agent, and Hosted Agent continuation modes have live two-turn AG-UI integration coverage.

Code Sample

AgentFrameworkAgent(
    agent=agent,
    use_service_session=True,
    snapshot_store=snapshot_store,
)

Error Messages / Stack Traces

Foundry Hosted Agent stateless replay currently rejects assistant output_text without logprobs:

400 invalid_request
request body failed schema validation
Expected one of: string, array; got array
param: $.input

Package Versions

agent-framework-core: development main; agent-framework-ag-ui: development main; agent-framework-openai: development main; agent-framework-foundry: development main

Python Version

Python 3.13

Additional Context

The Hosted Agent stateless replay case should remain a strict expected failure until the upstream service accepts standard assistant output_text replay without fabricated logprobs. The strict xfail should be removed when that service fix lands.