Path-scoped rules

.claude/rules/ splits project instructions into topic files that can load conditionally. A rule without paths: frontmatter loads at session start like CLAUDE.md; a rule with paths: loads only when Claude reads a matching file — saving context.

.claude/rules/testing.md

---
paths:
  - "**/*.test.ts"
  - "**/*.test.tsx"
---

# Testing Rules

- Use descriptive test names: "should [expected] when [condition]"
- Mock external dependencies, not internal modules
- Clean up side effects in afterEach

Subdirectories are discovered automatically (.claude/rules/frontend/react.md works). Like CLAUDE.md, rules are guidance — for guaranteed behavior use hooks or permissions.

When to split

When CLAUDE.md approaches 200 lines, start splitting into rules. Language- or directory-specific guidelines are the first candidates.

Check your understanding

Question 1When does a rule with paths: frontmatter load?

AAt session startBWhen Claude reads a file matching the globsCNever automaticallyDWhen you type /rules

Further reading

• Rules