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.

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