Python: Fix: AgentRunResponse.created_at returns local datetime labeled as UTC

[Copilot]

• Investigate the issue - identify root cause
• Fix _chat_client.py line 217 to use UTC datetime
• Fix _chat_client.py line 252 to use UTC datetime
• Fix _responses_client.py line 818 to use UTC datetime
• Fix _workflows/_agent.py line 272 to use UTC datetime
• Add unit test(s) to verify correct UTC behavior
  • Added test_chat_response_created_at_uses_utc to verify ChatResponse uses UTC
  • Added test_chat_response_update_created_at_uses_utc to verify ChatResponseUpdate uses UTC
  • Added test_agent_run_response_update_created_at to verify AgentRunResponseUpdate handles created_at correctly
  • Added test_agent_run_response_created_at to verify AgentRunResponse handles created_at correctly
  • Added test_responses_client_created_at_uses_utc to verify OpenAIResponsesClient uses UTC timestamp
• Run existing tests to ensure no regressions
• Run code review and address feedback
• Run CodeQL security check (no alerts)

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[Copilot]

Pull request overview

This PR fixes a bug where AgentRunResponse.created_at and related timestamp fields were returning local server time but labeling it as UTC (with 'Z' suffix). The fix ensures all timestamps are genuinely in UTC by adding tz=timezone.utc parameter to datetime conversion functions.

• Updated datetime.fromtimestamp() calls to include tz=timezone.utc in OpenAI chat and responses clients
• Updated datetime.now() call to include tz=timezone.utc in workflow agent
• Added comprehensive unit tests to verify UTC timestamp conversion

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
python/packages/core/agent_framework/openai/_chat_client.py	Fixed ChatResponse and ChatResponseUpdate to use UTC timestamps via datetime.fromtimestamp(..., tz=timezone.utc)
python/packages/core/agent_framework/openai/_responses_client.py	Fixed ChatResponse in responses client to use UTC timestamps via datetime.fromtimestamp(..., tz=timezone.utc)
python/packages/core/agent_framework/_workflows/_agent.py	Fixed AgentRunResponseUpdate to use UTC timestamps via datetime.now(tz=timezone.utc)
python/packages/core/tests/openai/test_openai_chat_client_base.py	Added unit tests test_chat_response_created_at_uses_utc and test_chat_response_update_created_at_uses_utc to verify UTC conversion
python/packages/core/tests/core/test_types.py	Added unit tests test_agent_run_response_created_at and test_agent_run_response_update_created_at to verify timestamp handling

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[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/_workflows
_agent.py	232	40	82%	55, 63–69, 97–98, 248, 288–291, 297, 303, 307–308, 311–317, 321–322, 361, 368, 374–375, 381, 393, 425, 432, 453, 460, 464, 475
packages/core/agent_framework/openai
_chat_client.py	234	43	81%	110–111, 115, 133, 143–144, 146, 157, 171, 173–176, 185, 197, 233, 264, 269–283, 290–292, 367, 374, 376, 378, 396–397, 403, 419
_responses_client.py	462	91	80%	98, 144, 151–152, 155–156, 161–162, 165, 172, 191, 198, 201–208, 210, 215, 221, 224, 239, 242–243, 245, 272, 302, 330–331, 358, 362, 379, 384, 398, 434, 496, 571, 576, 580–582, 602, 617–618, 622–624, 672, 692–693, 706–707, 723–724, 762, 764, 802, 804, 813–814, 832, 834, 907–913, 930–935, 954, 972, 982, 984, 1002–1003, 1005–1007, 1018–1019, 1022, 1024
TOTAL	15886	2416	84%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
2287	130 💤	0 ❌	0 🔥	55.967s ⏱️