Improve auth performance

**Problem**
When working with middleware, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

The issue does not name files, tests, or an entry point. Start by locating the authentication middleware and its current error handling, then determine the expected performance and message improvements with the maintainers; done should include a focused implementation and tests covering the revised behavior.

Written by the indexing model from the issue text.