/root-why

description: "Root cause analysis and debugging"
argument-hint: "[problem-description] - Optional: --depth=[3|5|7-whys] --output=[text|diagram|report]"

NW-ROOT-WHY: Toyota 5 Whys Root Cause Analysis

**Wave**: CROSS_WAVE **Agent**: Rex (nw-troubleshooter)

Overview

Systematic root cause analysis using Toyota's 5 Whys with multi-causal investigation and evidence-based validation. Investigates multiple cause branches at each level|validates solutions against all identified root causes.

Agent Invocation

@nw-troubleshooter

Execute \*investigate-root-cause for {problem-statement}.

**Configuration:**

• investigation_depth: 5
• multi_causal: true
• evidence_required: true

Usage: DELIVER Wave Retrospective (Phase 3.5)

When invoked as part of `/nw-deliver` Phase 3.5, analyze across 4 categories:

1. **What worked well** (and why — preserve these practices) 2. **What worked better than before** (and why — reinforce improvements) 3. **What worked badly** (5 Whys root cause, actionable fix) 4. **What worked worse than before** (5 Whys root cause, prevent regression)

**Inputs**: Evolution document|execution-log.json|mutation results|git log. **Output**: Retrospective section appended to evolution document. **Skip**: If clean execution (no skips|no failures|no tooling issues), generate brief summary only.

Tag items requiring nWave framework changes as **meta-improvements**.

Progress Tracking

The invoked agent MUST create a task list from its workflow phases at the start of execution using TaskCreate. Each phase becomes a task with the gate condition as completion criterion. Mark tasks in_progress when starting each phase and completed when the gate passes. This gives the user real-time visibility into progress.

Success Criteria

• [ ] All 5 WHY levels investigated with evidence
• [ ] Multi-causal branches explored at each level
• [ ] Root causes identified and validated
• [ ] Solutions address all identified root causes
• [ ] Backward chain validation performed

Next Wave

**Handoff To**: {invoking-agent-returns-to-workflow} **Deliverables**: Root cause analysis report with solutions

Examples

Example 1: Investigate test flakiness

/nw-root-why "Integration tests fail intermittently on CI but pass locally"

Rex investigates 5 WHY levels with multi-causal branches, discovers race condition in database cleanup, proposes transaction-isolated test fixtures.

Expected Outputs

docs/analysis/root-cause-analysis-{problem}.md