Use .claude/rules/ for Conditional Instructions

Instead of stuffing everything into one CLAUDE.md, use .claude/rules/ to load instructions conditionally based on which files Claude is working with.

Setup

.claude/rules/
  typescript.md    # Loaded when editing *.ts, *.tsx
  python.md        # Loaded when editing *.py
  testing.md       # Loaded when editing *test*, *spec*
  security.md      # Loaded when editing auth/*, crypto/*

Each rule file uses YAML frontmatter with a glob pattern:

---
globs: ["*.ts", "*.tsx"]
---

- Use `type` instead of `interface` for object types
- Prefer `z.infer<typeof schema>` over manual type definitions
- All API responses must use the `ApiResponse<T>` wrapper

Benefits

• Lean context: Only relevant rules load, saving tokens
• No conflicts: Python rules don’t pollute TypeScript sessions
• Easy maintenance: Each concern lives in its own file
• Team-friendly: Different team members can own different rule files

vs. Subdirectory CLAUDE.md

Feature	.claude/rules/	Subdirectory CLAUDE.md
Matches by	File glob pattern	Working directory
Best for	Language/file type rules	Module-specific context
Granularity	Fine (per file type)	Coarse (per directory)

Tip

Keep each rule file focused and short. The same 200-line attention limit applies. Splitting into many small files is better than a few large ones.

Set up .claude/rules/ with separate rule files for TypeScript, Python, and test files that only load when working on those file types.