Python: Fix CopilotStudioAgent to reuse conversation ID from existing session

[giles17]

Motivation and Context

CopilotStudioAgent._run_impl and _run_stream_impl unconditionally called _start_new_conversation() on every run() invocation, overwriting the session's service_session_id even when a persistent session was passed in. This made multi-turn conversations impossible because each call started a fresh server-side conversation with no memory of prior turns.

Fixes #5285

Description

The root cause was that both _run_impl and _run_stream_impl always replaced session.service_session_id with a new conversation ID, ignoring any existing value. The fix adds a guard (if not session.service_session_id) so that _start_new_conversation() is only called when the session does not already carry a conversation ID, allowing calers to reuse the same session across multiple run() calls for continuous dialog. Regression tests verify that both the non-streaming and streaming paths skip start_conversation and pass the existing conversation ID to ask_question when a session already has a service_session_id.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

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Note: PR autogenerated by giles17's agent

[giles17]

Automated Code Review

Reviewers: 4 | Confidence: 93%

✓ Correctness

The fix correctly guards _start_new_conversation() behind if not session.service_session_id: in both _run_impl and _run_stream_impl, matching the pattern used by other agents (GitHub Copilot, Claude). AgentSession.service_session_id defaults to None (confirmed in _sessions.py:179), so the falsy check works correctly. The two new tests properly verify that an existing service_session_id is preserved and start_conversation is not called. The orjson type-ignore comments in the sample files are harmless cosmetic changes. No correctness issues found.

✓ Security Reliability

The fix is correct and well-tested. It adds a simple guard (if not session.service_session_id) before calling _start_new_conversation() in both the streaming and non-streaming paths, preventing the agent from discarding an existing conversation ID. The service_session_id attribute on AgentSession defaults to None (confirmed at _sessions.py:739), so the truthiness check is appropriate. Two new tests properly verify that start_conversation is not called when a session already has a conversation ID. The orjson type-ignore comments in the sample files are harmless cosmetic changes. No security or reliability concerns.

✓ Test Coverage

The test coverage for the bug fix is solid. Two new tests (test_run_reuses_existing_conversation and test_run_streaming_reuses_existing_conversation) properly verify both the non-streaming and streaming paths. The assertions are meaningful: they check that start_conversation is not called, that ask_question receives the existing conversation ID, and that the session ID is preserved. The existing tests continue to cover the new-conversation path (where service_session_id starts as None). No blocking issues found.

✓ Design Approach

The core fix is correct and well-motivated: adding if not session.service_session_id: guards in both _run_impl and _run_stream_impl matches the pattern used by every other agent in the framework and is backed by solid tests. The new tests verify both non-streaming and streaming session reuse paths, check that start_conversation is not called, and confirm the existing ID is forwarded to ask_question. No design issues with the main change. A minor issue exists in the sample file changes: # type: ignore[reportMissingImports] is not valid syntax for either mypy (which uses error codes like import) or pyright (which uses # pyright: ignore[...]). The repo's own convention, as seen in other sample files, is # pyright: ignore[...], so the suppression comment as written is effectively a no-op.

Suggestions

• Consider adding a multi-turn integration-style test that calls run twice on the same session: first without a service_session_id (triggering _start_new_conversation), then a second time verifying the session reuses the ID from the first call. This would exercise the full lifecycle and catch any mutation issues between calls.
• The # type: ignore[reportMissingImports] comment added in both sample files uses invalid mixed syntax — reportMissingImports is a pyright code but # type: ignore is mypy syntax. Neither tool will recognize this. Change to # pyright: ignore[reportMissingImports] to match project convention and actually suppress the warning.

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Automated review by giles17's agents

[moonbox3]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/copilotstudio/agent_framework_copilotstudio
_agent.py	86	2	97%	174, 182
TOTAL	27692	3198	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
5613	20 💤	0 ❌	0 🔥	1m 33s ⏱️

[Copilot]

Pull request overview

Fixes Copilot Studio multi-turn behavior by preserving an existing AgentSession.service_session_id (conversation ID) across repeated run() calls, enabling server-side conversation continuity (Fixes #5285).

Changes:

• Guarded _start_new_conversation() in both non-streaming and streaming execution paths so it only runs when session.service_session_id is unset.
• Added regression tests verifying start_conversation is skipped and ask_question receives the existing conversation ID when a session already has one.
• Updated two conversation sample files to suppress optional orjson import typing errors.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
python/packages/copilotstudio/agent_framework_copilotstudio/_agent.py	Reuses existing service_session_id instead of always starting a new conversation.
python/packages/copilotstudio/tests/test_copilot_agent.py	Adds regression tests for conversation ID reuse in both streaming and non-streaming paths.
python/samples/02-agents/conversations/file_history_provider.py	Adds typing ignore for optional orjson import in sample.
python/samples/02-agents/conversations/file_history_provider_conversation_persistence.py	Adds typing ignore for optional orjson import in sample.