CLAUDE.md Writer

Creates and refactors CLAUDE.md files following official Anthropic best practices (2025).

Golden Rules

| Rule | Why | |------|-----| | CLAUDE.md < 200 lines | Loads on EVERY request, costs tokens | | Rules files < 500 lines each | Official recommendation per file | | Critical rules FIRST | Top = highest priority | | Modular rules → .claude/rules/ | Conditional loading, organized | | Use paths: frontmatter | Load rules only for matching files | | No linting rules | Use ESLint/Prettier/Biome instead | | Pointers over copies | Files change, references stay valid |

Memory Hierarchy

Claude Code loads memory in this order (higher = higher priority):

| Priority | Type | Location | |----------|------|----------| | Highest | Enterprise | /Library/Application Support/ClaudeCode/CLAUDE.md | | ↓ | Project | ./CLAUDE.md or ./.claude/CLAUDE.md | | ↓ | Rules | ./.claude/rules/*.md (conditional) | | ↓ | User | ~/.claude/CLAUDE.md | | Lowest | Local | ./CLAUDE.local.md (gitignored) |

Use /memory command to see currently loaded files.

3-Tier Documentation System

Official recommendation for large projects:

| Tier | Location | Loads | Target | |------|----------|-------|--------| | 1. Foundation | CLAUDE.md | Always | < 200 lines | | 2. Component | .claude/rules/{component}/ | When working in component | < 500 lines | | 3. Feature | Co-located with code | When working on feature | As needed |

Example structure:

.claude/
├── CLAUDE.md                 # Tier 1: always loaded
└── rules/
    ├── database.md           # Tier 2: SQL, migrations
    ├── api.md                # Tier 2: API patterns
    └── frontend/             # Tier 2: subdirectory
        ├── components.md     # paths: src/**/*.tsx
        ├── layout.md         # paths: src/pages/**/*.tsx
        └── tokens.md         # paths: **/*.tsx

Structure Template

markdown
# Project Name

One-line description.

## Commands

- `npm run dev` - Development
- `npm run build` - Production
- `npm run test` - Tests

## Architecture

| Path | Purpose |
|------|---------|
| `lib/` | Core logic |
| `app/api/` | API routes |

## Key Patterns

**Pattern Name**: One-line explanation.

## Database (if applicable)

| Table | Key Fields |
|-------|------------|

## Modular Docs

See `.claude/rules/` for:
- `database.md` - queries, schema
- `deploy.md` - deployment

## Tech Stack

One line: Next.js 15, PostgreSQL, TypeScript

Conditional Rules (Path-Specific)

Use YAML frontmatter for file-type-specific rules:

markdown
---
paths: "src/api/**/*.ts"
---

# API Rules

- All endpoints must validate input
- Use standard error format

Glob Patterns

| Pattern | Matches | |---------|---------| | **/*.ts | All .ts files anywhere | | src/**/* | All files under src/ | | *.md | Markdown in project root | | src/components/*.tsx | Components in specific dir |

Combining Patterns

yaml
# Multiple extensions
paths: "src/**/*.{ts,tsx}"

# Multiple directories
paths: "{src,lib}/**/*.ts, tests/**/*.test.ts"

Note: Wrap patterns in quotes for YAML safety.

Rules with paths: only load when working with matching files → saves tokens.

Workflow: New Project

1. Run /init for base CLAUDE.md
2. Review and trim generated content
3. Identify critical rules — what breaks if ignored?
4. Create .claude/rules/ for domain-specific docs
5. Keep main file < 100 lines

Workflow: Refactor Existing

1. Count lines — if > 300, must split
2. Find task-specific content — SQL, debugging, deploy → extract
3. Create .claude/rules/:

• database.md - queries, schema, connection
• deploy.md - deployment process
• messaging.md - integrations (Telegram, etc.)

1. Use @file references — don't duplicate
2. Keep in CLAUDE.md — only what applies to EVERY task

What Goes Where

| Content | Location | |---------|----------| | Project description | CLAUDE.md | | Critical constraints | CLAUDE.md (top!) | | Quick start (3 commands) | CLAUDE.md | | Architecture overview | CLAUDE.md | | Key patterns (1-liners) | CLAUDE.md | | SQL queries/schema | .claude/rules/database.md | | Deployment steps | .claude/rules/deploy.md | | API documentation | .claude/rules/api.md | | Git workflow | .claude/rules/git.md | | Personal preferences | CLAUDE.local.md (gitignored) | | Code style rules | .eslintrc / biome.json (NOT docs) |

Import Syntax

Reference files instead of duplicating:

markdown
@README.md
@docs/architecture.md
@~/.claude/snippets/common.md

• Relative: @docs/file.md
• Absolute: @~/path/file.md
• Max depth: 5 hops

CLAUDE.local.md

Personal project settings (auto-gitignored):

markdown
# My Local Settings

- Prefer verbose output
- Run tests after every change
- My worktree location: .trees/

Common Mistakes

| Mistake | Fix | |---------|-----| | 500+ lines | Split into .claude/rules/ | | SQL examples inline | → rules/database.md | | "Run prettier" rules | Use tool config files | | Full API docs | → rules/api.md | | Deployment instructions | → rules/deploy.md | | Code in CLAUDE.md | Use @file:line references | | Negative rules only | Add alternatives: "Don't X; use Y instead" |

Quality Checklist

Before finishing:

• ] CLAUDE.md < 200 lines?
• ] Each rules file < 500 lines?
• ] Critical rules at top?
• ] No task-specific content in main file?
• ] No code style rules (use ESLint/Prettier)?
• ] .claude/rules/ for domain-specific docs?
• ] Subdirectories for components (frontend/, backend/)?
• ] paths: frontmatter for conditional loading?
• ] @ references instead of duplication?
• ] CLAUDE.local.md for personal prefs?

Useful Commands

| Command | Purpose | |---------|---------| | /init | Generate initial CLAUDE.md | | /memory | View loaded memory files |

Sources

Official:

• code.claude.com/docs/en/memory (Memory management, paths, globs)
• anthropic.com/engineering/claude-code-best-practices
• claude.com/blog/using-claude-md-files

Community:

• thedocumentation.org/claude-code-development-kit (3-Tier System)
• claudefa.st/blog/guide/mechanics/rules-directory
• humanlayer.dev/blog/writing-a-good-claude-md

Updated: Jan 2026