Consider deprecating old core API

**Problem**
When working with components, 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 in the issue. First clarify which old core API and component errors are in scope, then locate their implementation and existing error tests; done should be defined by an agreed deprecation plan and specific, testable error-message changes.

Written by the indexing model from the issue text.