---

name: poka-yoke-patterns description: "Master Poka-Yoke error-proofing from Toyota Production System. Design systems that prevent mistakes through structure, not vigilance." allowed_tools: "Read, Write, Edit, Bash(cargo make:*)"

Poka-Yoke Patterns

What is Poka-Yoke?

Poka-Yoke (ポカ・ヨケ): Japanese for "mistake-proofing"

Design systems so mistakes become impossible or immediately obvious.

Three Types

1. Prevent (Make mistakes impossible)

• Type system constraints (NewType patterns)
• Compiler verification (Result<T,E>)
• Zero unwrap/expect in production code

2. Detect (Catch mistakes immediately)

• Andon signals (RED/YELLOW/GREEN)
• Quality gates (pre-commit hooks)
• SLO timeouts (prevent hanging)

3. Recover (Minimize damage)

• Graceful degradation
• Automatic rollback
• Clear error messages

In ggen

• Cargo Make Only: Prevents bypassing quality gates
• Result<T,E>: Compiler enforces error handling
• Clippy -D warnings: Zero tolerance for warnings
• SHACL Validation: Prevents invalid specifications

Reference

See CLAUDE.md sections:

• Constitutional Rules (Poka-Yoke)
• Holographic Factory Metaphor (Quality Gates)