Python: [BREAKING] Removed default "store" value

[dmytrostruk]

Motivation and Context

Removed default value of store parameter to rely on server's default value in OpenAI Responses client.

Important

This is a breaking change. Currently, the default value of store parameter in OpenAI Responses client implementation is False. With this PR, the default value is removed from the codebase to rely on server's default value, which is True. To revert the logic back to False, set store=False explicitly in run/run_stream methods for ChatAgent and get_response/get_streaming_response for BaseChatClient.

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.

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/azure-ai/agent_framework_azure_ai
_client.py	141	22	84%	165–168, 172–173, 175, 323–324, 328, 330–331, 333–341, 343
packages/core/agent_framework
_clients.py	100	11	89%	268, 384, 430–433, 477, 666–667, 798, 800
packages/core/agent_framework/openai
_responses_client.py	411	70	82%	144–145, 148–149, 155–156, 159, 166, 201, 231, 259–260, 287, 291, 308, 313, 355, 417, 492, 497, 501–503, 523, 538–539, 543–545, 593, 613–614, 627–628, 644–645, 683, 685, 723, 725, 734–735, 751, 753, 826–832, 849–854, 873, 891, 901, 903, 921–922, 924–926, 937–938, 941, 943
TOTAL	15466	2351	84%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
2226	130 💤	0 ❌	0 🔥	54.520s ⏱️

[Copilot]

Pull request overview

This PR implements a breaking change that removes the default store=False value from the OpenAI Responses client implementation, allowing the code to rely on the server's default value of True instead.

Key Changes

• Removed automatic setting of store=False when the parameter is not specified
• Updated logic in get_conversation_id methods to properly handle None as "use server default"
• Removed validation that automatically set store=True when conversation_id was provided
• Updated sample code to explicitly set store=False where needed to maintain previous behavior
• Updated tests to verify that store is omitted from options when set to None

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
python/packages/core/agent_framework/openai/_responses_client.py	Updated get_conversation_id to return conversation ID when store is None; removed default store=False from prepare_options; refactored conversation ID assignment logic
python/packages/core/agent_framework/_clients.py	Removed validation logic that forced store=True when conversation_id was set
python/packages/azure-ai/agent_framework_azure_ai/_client.py	Removed default store value setting in prepare_options; updated get_conversation_id to handle None as server default
python/packages/core/tests/openai/test_openai_responses_client.py	Updated test assertions to verify store is not included in options when set to None
python/samples/getting_started/agents/openai/openai_responses_client_with_thread.py	Added explicit store=False to in-memory example; removed explicit store=True and related comment from server-side storage example