# Principle Fix Root Causes

> Apply when debugging. Trace each symptom to its root cause and fix it there; reproduce first, ask why until you reach it, resist nil-check guards that silence crashes.

- Skill: `v1truv1us-ai-eng-system/principle-fix-root-causes` (Agent Skill)
- Install (CLI): `npx skillmds add v1truv1us-ai-eng-system/principle-fix-root-causes`
- Raw SKILL.md: https://api.skillmd.com/api/skills/v1truv1us-ai-eng-system/principle-fix-root-causes/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: v1truv1us (https://skillmd.com/u/v1truv1us-ai-eng-system)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/v1truv1us-ai-eng-system/principle-fix-root-causes

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# Fix Root Causes

When debugging, do not paper over symptoms. Trace every problem to its root cause and fix it there.

**Why:** Symptom fixes accumulate. Each workaround makes the system harder to reason about, and the real bug remains. Root-cause fixes are slower upfront but reduce total debugging time.

**Pattern:**
- Reproduce first (if you can't reproduce it, you can't verify your fix)
- Ask "why" until you hit the root cause
- Resist the urge to add guards (adding a nil check to silence a crash is a symptom fix)
- Check for the pattern, not just the instance (grep for the same pattern, fix all instances)
- When stuck, instrument. Don't guess (add logging, read the actual error)

**Restart bugs: suspect state before code**

Code doesn't change between runs. State does. When something "fails after restart," suspect stale persistent state first: config files, caches, lock files, serialized state. If clearing a state file restores behavior, prioritize state validation as the fix.