Python: Fixed use_agent_middleware calling private _normalize_messages

[dmytrostruk]

Motivation and Context

Resolves #1576

1. Moved _normalize_messages to a shared normalize_messages function in _types.py so the use_agent_middleware decorator no longer depends on BaseAgent internals. This allows the decorator to work with any agent implementing AgentProtocol.
2. Made normalize_messages public, so it can be reused in A2A and Copilot Studio agents, and should be useful for end-users as well (similarly to normalize_tools).

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.

[Copilot]

Pull request overview

This PR fixes issue #1576 where the use_agent_middleware decorator was calling a private method _normalize_messages that wasn't part of the AgentProtocol interface. The fix extracts the message normalization logic into a shared utility function.

Changes:

• Moved _normalize_messages from a private BaseAgent method to a shared normalize_messages function in _types.py
• Updated use_agent_middleware decorator to use the new shared function instead of calling a private method
• Added a test to verify the decorator works with agents implementing only AgentProtocol (not inheriting from BaseAgent)

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
python/packages/core/agent_framework/_types.py	Added new normalize_messages utility function to handle message normalization without requiring BaseAgent
python/packages/core/agent_framework/_middleware.py	Updated to import and use the new normalize_messages function instead of calling self._normalize_messages()
python/packages/core/agent_framework/_agents.py	Removed private _normalize_messages method and updated to use the new shared function from _types.py
python/packages/core/tests/core/test_middleware_with_agent.py	Added test case validating that use_agent_middleware works with minimal agents implementing only AgentProtocol

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/a2a/agent_framework_a2a
_agent.py	139	7	94%	355–356, 393–394, 423–425
packages/copilotstudio/agent_framework_copilotstudio
_agent.py	75	4	94%	154–155, 190, 198
packages/core/agent_framework
_agents.py	297	54	81%	51, 90, 96, 99, 102, 404–406, 452, 634, 803, 806–808, 925–928, 930, 933–935, 1036, 1077, 1079, 1088–1093, 1099, 1101, 1111–1112, 1119, 1121–1122, 1130–1134, 1142–1143, 1145, 1150, 1152, 1186, 1231–1232, 1234, 1236, 1247
_middleware.py	402	7	98%	805, 821, 868–869, 1074–1075, 1120
_types.py	1023	120	88%	99, 139, 141, 143, 145, 147, 149, 156–159, 177–178, 315, 317, 324, 343, 383, 429–430, 466, 616, 730–731, 733, 758, 765, 782–784, 869, 874–875, 877, 884–885, 887, 914, 923, 926–928, 933–934, 941, 945–947, 1103, 1192–1195, 1203–1204, 1295, 1476, 1482, 1877, 1893, 1895–1902, 1931, 1964–1966, 1972–1973, 2034, 2289, 2294, 2298, 2302, 2494, 2504, 2549, 2594–2599, 2621, 2626, 3085, 3171–3173, 3246, 3257–3258, 3482–3484, 3487–3489, 3493, 3498, 3502, 3614–3616, 3644, 3680, 3698, 3702–3704, 3706, 3717–3718, 3723, 3731
TOTAL	17429	2663	84%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3149	213 💤	0 ❌	0 🔥	1m 8s ⏱️