Optimize middleware for large datasets

**Problem**
When working with models, 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, test, or entry point is named. Start by locating the middleware and model error-handling paths, then reproduce the current errors for large datasets. Done means the relevant failures produce more descriptive messages and the behavior is covered by tests.

Written by the indexing model from the issue text.