Bug Protection: Multi-Layered

Overview

A single validation point is easy to bypass — different code paths, refactoring, or mocks can circumvent it. Real protection requires checks at every layer data passes through.

Core principle: One fix removes the bug. Validation layers make the invalid state structurally impossible; instrumentation makes missed failures diagnosable.

For coding-related work, load engineering-principles before this skill. This skill turns its validation, boundary, and fail-fast defaults into layered bug protection.