概要
The Defense-in-Depth skill provides a systematic framework for hardening software by implementing redundant, multi-layer validation. Rather than relying on a single check that could be bypassed by refactoring or mocks, this pattern guides you to validate data at the entry point, within business logic, through environment guards, and via debug instrumentation. This approach is essential for complex systems where data integrity is paramount, ensuring that invalid states are caught regardless of the code path taken or the execution context.