Optimize auth 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 files, tests, or entry points are identified. Start by locating the model authentication and error-handling paths, then clarify which large-dataset behavior and messages are expected. Done should include agreed descriptive errors and focused coverage for the specified cases.

Written by the indexing model from the issue text.