Python: Fix Foundry hosted session SDK calls

[ekkoitac (ekkoitac)]

Motivation & Context

Hosted FoundryAgent sessions currently fail against azure-ai-projects==2.2.0 when allow_preview=True and an isolation_key is provided. The Foundry SDK no longer exposes the agent-name .get(...) lookup used by get_agent_version(), and create_session(...) expects user_isolation_key instead of isolation_key.

Description & Review Guide

• What are the major changes?
  • Stop looking up a hosted agent version through the missing project_client.beta.agents.get(...) API when no explicit agent_version is configured.
  • Pass user_isolation_key to project_client.beta.agents.create_session(...).
  • Add a regression test for SDK objects without the removed lookup method and update the session creation assertion.
• What is the impact of these changes?
  • Hosted session creation can proceed with the current Azure SDK shape while preserving explicit agent_version behavior when callers provide one.
  • Checked with:
    • uv run pytest tests/foundry/test_foundry_agent.py::test_raw_foundry_agent_chat_client_get_agent_version_skips_sdk_lookup tests/foundry/test_foundry_agent.py::test_raw_foundry_agent_prepare_run_context_creates_service_session_from_isolation_key -q
    • uv run pytest tests/foundry/test_foundry_agent.py -q
    • uv run poe test -P foundry -m "not integration"
    • uv run ruff check packages/foundry/agent_framework_foundry/_agent.py packages/foundry/tests/foundry/test_foundry_agent.py
    • uv run ruff format --check packages/foundry/agent_framework_foundry/_agent.py packages/foundry/tests/foundry/test_foundry_agent.py
    • uv run pyright packages/foundry/agent_framework_foundry/_agent.py
• What do you want reviewers to focus on?
  • Whether hosted sessions should continue omitting version_indicator when callers do not pass agent_version.

Related Issue

Fixes #6857

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change. If it is a breaking change, add the breaking change label (or add "[BREAKING]" to the title prefix, before or after any language prefix) — a workflow keeps the label and title prefix in sync automatically.

[Copilot]

Pull request overview

Fixes Python Foundry hosted-session creation against azure-ai-projects==2.2.0 by removing reliance on an SDK agent-name lookup API that no longer exists and by aligning the session creation kwargs with the SDK’s current parameter name.

Changes:

• Removed the preview-only SDK agent lookup from get_agent_version() when no explicit agent_version is configured (now returns None unless agent_version is set).
• Updated hosted session creation to pass user_isolation_key (instead of isolation_key) to project_client.beta.agents.create_session(...).
• Added/updated unit tests to validate the new behavior (no SDK lookup required; updated session creation kwargs assertion).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
python/packages/foundry/agent_framework_foundry/_agent.py	Stops SDK-based agent-name version resolution and updates hosted session creation to use user_isolation_key.
python/packages/foundry/tests/foundry/test_foundry_agent.py	Adds regression coverage for missing SDK lookup method and updates the hosted session kwargs assertion to user_isolation_key.

[Evan Mattson (moonbox3)]

Could we keep resolving a version through project_client.agents.get(...), or otherwise always supply a valid VersionIndicator here? With the pinned azure-ai-projects==2.2.0, beta.agents.create_session() treats version_indicator as required and raises TypeError("missing required argument: version_indicator") before sending a request, so the reported HostedAgent path with no explicit agent_version still crashes. The new test stops at get_agent_version(), while the session-creation test supplies agent_version="1.0", so neither exercises this failure path.

[Evan Mattson (moonbox3)]

Tao Chen (@TaoChenOSU) is this PR still required?

[Evan Mattson (moonbox3)]

There's been a lot of churn in the Foundry related projects these days. Tao Chen (@TaoChenOSU) will be checking if this is still needed.