Consider deprecating old hooks API

**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, tests, or entry points are named. Start by locating the handlers and old hooks API, then clarify whether the goal is API deprecation, more descriptive errors, or both; done requires an agreed scope and documented behavior for the replacement or error messages.

Written by the indexing model from the issue text.