# Thinking Five Whys Plus

When a fault is localized and the proximate cause is known but the systemic root is...

- Repository: https://github.com/tjboudreaux/cc-thinking-skills (1690 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-08-07
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -g -a claude-code -y`
Codex: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -g -a codex -y`
Cursor: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -g -a cursor -y`
Gemini CLI: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add tjboudreaux/cc-thinking-skills`

## Description

When a fault is localized and the proximate cause is known but the systemic root is not, chain evidence-linked whys with a counterfactual stop and a countermeasure.

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

# Five Whys Plus

Build an evidence-linked causal chain from a known proximate fault to an actionable systemic root, then prescribe a countermeasure that would have blocked it.

## When to Use

- A fault is already localized to a component, path, or subsystem.
- The proximate cause is known, but recurrence or systemic root is not.
- Prior symptom-only fixes failed and the failure returned.
- You need prevention that addresses why the proximate cause was possible.

## When NOT to Use

- Fault is not localized or multiple candidate causes remain, discriminate first.
- Root is evidenced and actionable, fix it.
- No evidence can answer the next "why", gather evidence.
- One-off error without a process, tooling, or design enabler.
- Selective defect needing IS/IS-NOT analysis.
- Forward failure forecasting before commitment.

## Procedure

The rest: https://github.com/tjboudreaux/cc-thinking-skills/blob/HEAD/skills/thinking-five-whys-plus/SKILL.md