debugginglisted

# Comprehensive Debugging Skill **Core Principle:** ALWAYS find root cause before attempting fixes. Symptom fixes are failure. ## The Iron Law of Debugging ``` NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST ``` ## When to Use / Not Use **Use when:** - Test failures (unit, integration, E2E) - Bugs in production or development - Unexpected behavior or performance problems - Build failures or CI/CD pipeline issues - Browser/UI issues - ESPECIALLY when under time pressure, "just one quick fix" seems obvious, or you've already tried multiple fixes **Do NOT use when:** - Writing new tests or setting up test frameworks -> use `testing-framework` - TDD methodology or writing tests before code -> use `test-driven-development` - Reviewing code quality or PRs -> use `code-review` - Designing CI/CD pipelines -> use `cicd-pipelines` ## Decision Tree ``` What type of issue are you debugging? ├── Test failure │ ├── Always fails (deterministic) -> Phase 1-4 systematic debugging │ ├── Intermittently fails (flaky) -> find-polluter.sh + timing analysis │ └── Only fails in CI, not locally -> Environment audit (OS, runtime, services) ├── Browser/UI bug │ ├── Visual/layout issue -> Chrome DevTools scripts + screenshot │ ├── Console errors -> console.js monitoring │ ├── Network/API issue -> network.js tracking │ └── Performance issue -> performance.js + Core Web Vitals ├── CI/CD pipeline failure │ ├── Build error (module not found, etc.) -> Root cause tracing + cache check