# Systematic Debugging

> Use when encountering any bug, test failure, or unexpected behavior — before proposing fixes.

- Skill: `thedixitjain/systematic-debugging-5` (Agent Skill)
- Install (CLI): `npx skillmds add thedixitjain/systematic-debugging-5`
- Raw SKILL.md: https://api.skillmd.com/api/skills/thedixitjain/systematic-debugging-5/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: thedixitjain (https://skillmd.com/u/thedixitjain)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/thedixitjain/systematic-debugging-5

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# Systematic Debugging

## Four Phases

### Phase 1: Reproduce
- Get a minimal, reliable reproduction
- Never fix what you can't reproduce

### Phase 2: Understand
- Read the error message fully — the answer is often there
- Trace the call path from symptom to root cause
- Check: recent changes, environment differences, assumptions about inputs

### Phase 3: Hypothesize
- Form 1-3 specific hypotheses about root cause
- Test each hypothesis with the smallest possible change
- Never change multiple things at once

### Phase 4: Fix and Verify
- Fix the root cause, not the symptom
- Run the reproduction case — confirm fixed
- Run full test suite — confirm no regressions
- Invoke `hotl:verification-before-completion`

## Red Flags

- "Let me try X and see what happens" without a hypothesis
- Changing multiple things before verifying
- Marking done without running full tests

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**Source:** [`hashgraph-online/awesome-codex-plugins`](https://github.com/hashgraph-online/awesome-codex-plugins) → `plugins/yimwoo/hotl-plugin/skills/systematic-debugging/SKILL.md`