5-Whys Root Cause Analysis Skill

A Claude Code skill that provides systematic root cause analysis methodology, tracing problems back to their fundamental causes instead of just addressing symptoms.

What is This?

This is a skill for Claude Code that enhances Claude’s ability to perform rigorous 5-Whys analysis for debugging, incident investigation, and problem-solving.

Installation

Option 1: Copy to your skills directory

# Clone the repo
git clone https://github.com/tt-a1i/5-whys-skill.git

# Copy to Claude Code skills directory
cp -r 5-whys-skill ~/.claude/plugins/superclaude/skills/5-whys

Option 2: Symlink

git clone https://github.com/tt-a1i/5-whys-skill.git ~/skills/5-whys-skill
ln -s ~/skills/5-whys-skill ~/.claude/plugins/superclaude/skills/5-whys

Usage

The skill triggers automatically when you use phrases like:

Example

User: 用5-whys分析一下为什么部署后服务变慢了

Claude: [Applies 5-Whys methodology]

## 5-Whys Analysis: Service Performance Degradation

### Problem Statement
**What:** API latency increased from 100ms to 500ms after deployment
**When:** After v2.1.0 deployment
**Impact:** User complaints, increased timeout errors

### Why Chain
| Level | Question | Answer | Evidence |
|-------|----------|--------|----------|
| Why 1 | Why did latency increase? | DB queries slower | Query metrics |
| Why 2 | Why are queries slower? | Full table scan | EXPLAIN ANALYZE |
...

Structure

5-whys-skill/
├── SKILL.md                           # Main skill definition (~1170 words)
├── README.md                          # This file
├── LICENSE                            # MIT License
├── references/
│   ├── toyota-origins.md              # Toyota Production System history
│   └── software-patterns.md           # Common root cause patterns
└── examples/
    ├── production-incident.md         # Payment service outage analysis
    └── performance-regression.md      # Latency investigation example

Core Methodology

The skill follows a 5-phase process:

1. Define the Problem - State the problem as specific, observable fact
2. Ask “Why?” Iteratively - For each answer, ask why it happened
3. Identify Root Cause - Actionable, preventable, fundamental
4. Validate the Chain - Work backwards to verify causality
5. Define Countermeasures - Immediate fix + prevention + detection

Output Format

## 5-Whys Analysis: [Problem Title]

### Problem Statement
**What:** [Specific behavior]
**When:** [Time/conditions]
**Impact:** [Consequence]

### Why Chain
| Level | Question | Answer | Evidence |
|-------|----------|--------|----------|
| Why 1 | ... | ... | ... |
| Why 2 | ... | ... | ... |
...

### Root Cause
**Identified cause:** [Statement]
**Type:** [Process/Design/Knowledge/Resource]

### Countermeasures
| Type | Action | Owner | Timeline |
|------|--------|-------|----------|
| Immediate | ... | ... | ... |
| Preventive | ... | ... | ... |

Key Principles

From the Toyota Production System:

• Go and See (Genchi Genbutsu) - Base analysis on facts, not assumptions
• Respect for People - Blame processes, not individuals
• Continuous Improvement - Every problem is an improvement opportunity
• Build Quality In - Prevention over detection over reaction

Common Pitfalls

Complementary Skills

This skill works well with:

• First Principles - Question if the problem definition is right
• Trade-off Analysis - Choose between countermeasures
• Hypothesis Testing - When evidence is uncertain

Contributing

Contributions welcome! Please feel free to submit issues or pull requests.

License

MIT License - see LICENSE file.

Author

Created for use with Claude Code’s skill system.