Handle edge cases in filtering

**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 names no files, tests, or entry points. Start by locating the middleware filtering logic and its current error handling, then trace the filtering failure paths. Done means the relevant failures produce more descriptive error messages and the behavior is covered by appropriate checks.

Written by the indexing model from the issue text.