Motivation & Context

Passing a callable class instance (a class implementing __call__ with fewer than 2 parameters or an unresolvable middleware type) as middleware caused _determine_middleware_type() to raise an unhandled AttributeError: 'BadMiddleware' object has no attribute '__name__' during exception string formatting, masking the intended MiddlewareException.

Description & Review Guide

• What are the major changes?

  • Updated _determine_middleware_type() in python/packages/core/agent_framework/_middleware.py to safely resolve the middleware display name using getattr(middleware, "__name__", type(middleware).__name__) instead of accessing middleware.__name__ directly.
  • Added unit test suite TestCallableClassMiddlewareErrorHandling in python/packages/core/tests/core/test_middleware_with_agent.py covering parameter count mismatch, decorator/annotation mismatch, and undetermined type errors on callable class instances.

• What is the impact of these changes?

  • Callable class instances passed as middleware now properly raise clear, informative MiddlewareException errors with the class name rather than crashing with an AttributeError.

• What do you want reviewers to focus on?

  • Exception handling in _determine_middleware_type and regression test assertions.

Related Issue

Fixes #6697

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.