# Root Cause Debugging

Finds the root cause of failing tests, broken builds and unexpected errors.

- Repository: https://github.com/addyosmani/agent-skills (112533 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add addyosmani/agent-skills --skill debugging-and-error-recovery -g -a claude-code -y`
Codex: `npx skills add addyosmani/agent-skills --skill debugging-and-error-recovery -g -a codex -y`
Cursor: `npx skills add addyosmani/agent-skills --skill debugging-and-error-recovery -g -a cursor -y`
Gemini CLI: `npx skills add addyosmani/agent-skills --skill debugging-and-error-recovery -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add addyosmani/agent-skills`

## Description

Guides systematic root-cause debugging. Use when tests fail, builds break, something that worked yesterday broke, behavior doesn't match expectations, or you encounter any unexpected error. Use when you need to figure out what broke and why, a systematic approach to finding and fixing the root cause rather than guessing.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Debugging and Error Recovery

## Overview

Systematic debugging with structured triage. When something breaks, stop adding features, preserve evidence, and follow a structured process to find and fix the root cause. Guessing wastes time. The triage checklist works for test failures, build errors, runtime bugs, and production incidents.

## When to Use

- Tests fail after a code change
- The build breaks
- Runtime behavior doesn't match expectations
- A bug report arrives
- An error appears in logs or console
- Something worked before and stopped working

## The Stop-the-Line Rule

When anything unexpected happens:

```
1. STOP adding features or making changes
2. PRESERVE evidence (error output, logs, repro steps)
3. DIAGNOSE using the triage checklist
4. FIX the root cause
5. GUARD against recurrence
6. RESUME only after verification passes
```

**Don't push past a failing test or broken build to work on the next feature.** Errors compound. A bug in Step 3 that goes unfixed makes Steps 4-6 wrong.

## The Triage Checklist

Work through these steps in order. Do not skip steps.

### Step 1: Reproduce

Make the failure happen reliably. If you can't reproduce it, you can't fix it with confidence.

```
Can you reproduce the failure?
├── YES → Proceed to Step 2
└── NO
    ├── Gather more context (logs, environment details)
    ├── Try reproducing in a minimal environment
    └── If truly non-reproducible, document conditions and monitor
```

**When a bug is non-reproducible:**

The rest: https://github.com/addyosmani/agent-skills/blob/HEAD/skills/debugging-and-error-recovery/SKILL.md