# H10: Quality Ceiling (Result<T,E>) - Grade B

## Implementation quality

- Generics: A (textbook discriminated union, never for unused channels)
- Type guards: A (proper type predicates with narrowing)
- map preserves error type: A
- Compiles under --strict: YES

## Test quality

- Tests pass: 0/12 (missing vitest import — would be 12/12 if fixed)
- Coverage: happy paths only, no edge cases
- Grade: C

## Overall: B

Implementation is genuinely excellent. Test boilerplate is the recurring weakness.
Recurring defect: model consistently fails to import vitest globals.
