Improve lib 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.

No file, entry point, or test is named. Start by locating the middleware error-handling path and existing error-message tests, then determine which failures need more context. Done means the affected middleware errors provide descriptive messages and the behavior is covered by tests.

Written by the indexing model from the issue text.