Improve error messages in middleware

**Problem**
When working with store, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Start by locating the middleware and store error-handling paths mentioned in the issue, then trace how their current errors are produced. Define which diagnostic context the messages should expose and verify that the resulting errors are more useful for debugging without changing unrelated behavior.

Written by the indexing model from the issue text.