Optimize models for large datasets

**Problem**
When working with handlers, 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 files or tests are named. Start by locating the handlers and their current error paths, then identify which failures need more descriptive messages. Done means the relevant handler errors provide clearer debugging context and the existing behavior remains covered by the project’s available checks.

Written by the indexing model from the issue text.