defense-in-depth

Installation
SKILL.md

Defense-in-Depth Validation

Overview

When you fix a bug caused by invalid data, adding validation at one place feels sufficient. But that single check can be bypassed by different code paths, refactoring, or mocks.

Core principle: Validate at EVERY layer data passes through. Make the bug structurally impossible.

Why Multiple Layers

Single validation: "We fixed the bug" Multiple layers: "We made the bug impossible"

Different layers catch different cases:

  • Entry validation catches most bugs
  • Business logic catches edge cases
  • Environment guards prevent context-specific dangers
  • Debug logging helps when other layers fail
Related skills
Installs
40
GitHub Stars
15
First Seen
Jan 24, 2026