Handle edge cases in search

**Problem**
When working with config, 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, so first locate the config and search error-handling paths in the repository. Reproduce the relevant edge cases and document the expected result before changing anything; done means descriptive errors are produced for the identified cases and the related checks pass.

Written by the indexing model from the issue text.