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3.3 Path-Specific Rules for Conditional Convention Loading

Path-Specific Rules คืออะไร

Path-Specific Rules คือการกำหนดกฎ/conventions ที่ apply เฉพาะเมื่อ Claude ทำงานกับไฟล์ในบาง path — เช่น code ใน src/ ใช้กฎแบบหนึ่ง แต่ code ใน tests/ ใช้กฎอีกแบบ ทำให้ Claude ปรับ behavior ตาม context โดยอัตโนมัติ

Subdirectory CLAUDE.md

วิธีหลักคือใส่ CLAUDE.md ในแต่ละ directory:

project/
├── CLAUDE.md                    # Global project rules
├── src/
│   ├── CLAUDE.md               # Source code conventions
│   ├── components/
│   │   └── CLAUDE.md           # Component-specific rules
│   └── api/
│       └── CLAUDE.md           # API-specific rules
└── tests/
    └── CLAUDE.md               # Testing conventions

src/CLAUDE.md

- Use TypeScript strict mode
- All functions must have JSDoc
- No `any` type — use `unknown` if needed
- Prefer composition over inheritance

tests/CLAUDE.md

- Use vitest for all tests
- Each test file matches source: src/foo.ts → tests/foo.test.ts
- Use `describe` + `it` pattern
- Mock external services, never hit real APIs
- `any` type is OK in tests for mocking

src/components/CLAUDE.md

- Use functional components only
- Props interface must be exported
- One component per file
- CSS modules for styling

Conditional Loading Behavior

Claude loads CLAUDE.md files based on which files it’s currently working with:

  1. Claude reads src/api/handler.ts → loads: Global + src/CLAUDE.md + src/api/CLAUDE.md
  2. Claude reads tests/handler.test.ts → loads: Global + tests/CLAUDE.md
  3. Claude reads both → loads all relevant CLAUDE.md files

Use Cases

  • Language-specific rules — rust/CLAUDE.md vs python/CLAUDE.md ใน polyglot repo
  • Environment rules — infra/CLAUDE.md (Terraform conventions) vs app/CLAUDE.md
  • Safety rules — migrations/CLAUDE.md (“always create backup before ALTER TABLE”)

Key Concepts

  • Automatic loading — Claude detects which directories it’s touching and loads matching CLAUDE.md
  • Additive — subdirectory rules ADD to parent rules, don’t replace
  • Scope — rules only apply when Claude is working with files in that directory
  • Performance — every CLAUDE.md file costs tokens, keep them concise

Exam Tips

  • Subdirectory CLAUDE.md loads ONLY when Claude works with files in that directory
  • Rules are additive/merge — ไม่ override parent CLAUDE.md
  • ข้อสอบอาจให้ scenario: “Claude is editing src/api/route.ts” แล้วถามว่า CLAUDE.md ไหนบ้าง apply
  • Keep CLAUDE.md concise — long files waste tokens every turn
  • ใช้สำหรับ rules ที่ genuinely differ per directory — อย่า repeat global rules