CLAUDE.md Supremacy

What is CLAUDE.md?

CLAUDE.md is Claude Code's core configuration file, located in the project root directory. It acts like a project handbook for Claude, defining the project's context, rules, conventions, and expectations.

This is not just a configuration file, but a bridge for human-AI collaboration.

Why is CLAUDE.md so important?

1. Context is Power

Claude Code's capabilities largely depend on its understanding of the project. A well-crafted CLAUDE.md can:

🧠 Build project cognition: Help Claude deeply understand project goals and structure
🎯 Set work standards: Define code quality and style requirements
⚡ Improve execution efficiency: Avoid repetitive explanations and wrong directions
🛡️ Ensure consistency: Team members share the same set of collaboration rules

2. From Chaos to Order

Project without CLAUDE.md:

> Help me refactor this function

Claude: What does this function do? What framework? Any conventions?
You: This is a React component, we use TypeScript...
Claude: Got it, any other rules?
You: We use functional components, no class components...
Claude: Understood, what's the testing framework?
You: Jest... (endless cycle)

Project with CLAUDE.md:

> Help me refactor this function

Claude: Got it, based on project configuration, I'll use functional components, TypeScript types, follow your naming conventions, and add corresponding Jest tests. Starting refactoring...

CLAUDE.md Structure

Basic Template

# Project Name

## Project Overview
[Brief description and main objectives of the project]

## Tech Stack
- Frontend: React 18 + TypeScript
- State Management: Redux Toolkit
- Styling: Styled Components
- Testing: Jest + React Testing Library
- Build: Vite

## Project Structure

src/ ├── components/ # Reusable components ├── pages/ # Page components ├── hooks/ # Custom Hooks ├── services/ # API services ├── store/ # Redux store ├── types/ # TypeScript types ├── utils/ # Utility functions └── styles/ # Style files

## Coding Standards
- Use functional components + Hooks
- All components must have TypeScript types
- Use ESLint + Prettier for formatting
- Component names use PascalCase
- File names use kebab-case
- Prefer named exports

## Testing Requirements
- All components must have unit tests
- Coverage requirement: >80%
- Test file naming: `*.test.tsx`

## Git Workflow
- Use feature branch
- Commit message format: `type(scope): description`
- PR must pass all checks

## Important Notes
- API calls must have error handling
- Sensitive information uses environment variables
- New features need documentation updates

Advanced Configuration Tips

1. Modular Configuration

For large projects, configuration can be split into multiple parts:

# My Large Application

## Core Information
[Basic project information]

## Architecture Decision Records (ADR)

### ADR-001: State Management Choice
We chose Redux Toolkit over Context API because:
- Complex state logic
- Need time-travel debugging
- Team familiar with Redux ecosystem

### ADR-002: API Layer Design
Using RTK Query for data fetching:
- Automatic caching and synchronization
- Built-in loading/error states
- TypeScript first

## Development Workflow

### New Feature Development Process
1. Create feature branch: `feature/feature-name`
2. Use TDD approach: write tests first, then implement
3. Ensure TypeScript has no errors
4. Run full test suite
5. Submit PR and request code review

### Code Review Checklist
- [ ] TypeScript types are correct
- [ ] Tests cover new functionality
- [ ] Error handling is complete
- [ ] Performance considerations (memo, callback, etc.)
- [ ] Accessibility support

2. Context Enrichment

## Business Context

### Target Users
- Primary: 25-40 year old professionals
- Devices: Mobile-first, desktop support
- Use cases: Commute time, office breaks

### Core Features
1. **User Authentication**: OAuth2 + JWT
2. **Data Sync**: Real-time sync, offline support
3. **Notification System**: Push + email alerts

### Performance Requirements
- First screen load: <2 seconds
- Interaction response: <100ms
- Support 1000+ concurrent users

3. Team Collaboration Standards

## Team Conventions

### Naming Standards
- **Components**: `UserProfile.tsx`
- **Hooks**: `useUserData.ts`
- **Services**: `userService.ts`
- **Types**: `UserType.ts`

### Error Handling Pattern
```typescript
// Unified error handling for API calls
try {
  const data = await userService.getProfile();
  return { data, error: null };
} catch (error) {
  logger.error('Failed to get user profile', error);
  return { data: null, error: error.message };
}

Code Review Standards

Functional correctness ✅
Code readability ✅
Performance impact ✅
Security considerations ✅

## Real-World Case Studies

### Case 1: Refactoring Failure

**Problem**: No clear CLAUDE.md configuration
```bash
> Refactor user authentication module

# Claude's confusion:
# - What authentication scheme to use?
# - What's the existing code style?
# - Need backward compatibility?
# - What are the testing requirements?

Result: Refactoring direction didn't match project requirements, needed multiple reworks.

Case 2: Refactoring Success

Configuration: Detailed CLAUDE.md

## Authentication System Configuration
- Use JWT + Refresh Token
- Support multiple login methods: email, third-party OAuth
- Session management: Redis storage
- Security requirements: 2FA support, password policy enforcement

## Existing Authentication Module
- `src/auth/` directory contains all authentication-related code
- `AuthContext` provides global authentication state
- `authService` handles API calls
- `authUtils` provides authentication utilities

Execution:

> Refactor user authentication module, improve security and add 2FA support

Result: Claude accurately understood requirements and completed high-quality refactoring in one go.

Dynamic Configuration Strategy

1. Progressive Improvement

Start simple, gradually enrich:

Week 1: Basic structure

# Project Name
- React + TypeScript
- Use functional components

Month 1: Detailed specifications

# Project Name
[Detailed tech stack, file structure, coding standards]

Month 3: Deep context

# Project Name
[Including business logic, architecture decisions, team conventions]

2. Team Collaboration

📝 Version Control: Include CLAUDE.md in Git management
🔄 Regular Updates: Update synchronously with project development
👥 Team Consensus: Ensure all members understand and follow
🔍 Regular Review: Check configuration effectiveness and accuracy

Best Practices Summary

✅ Things to Do Right

Be Specific and Clear: Avoid vague descriptions
Keep Updated: Update configuration as project evolves
Include Examples: Provide code examples and patterns
Document Decisions: Record important architectural and technical choices
Team Consistency: Ensure team members share configuration

❌ Traps to Avoid

Over-detailed: Don't write a novel, keep it concise and practical
Outdated Information: Regularly clean up useless or incorrect information
Personal Preferences: Avoid overly personalized configurations
Ignoring Business: Technical configuration should align with business needs
Static Thinking: Configuration should adapt to project changes

After mastering the essence of CLAUDE.md, you can continue learning Plan Mode to understand how to handle complex multi-step tasks.

What is CLAUDE.md?​

Why is CLAUDE.md so important?​

1. Context is Power​

2. From Chaos to Order​

CLAUDE.md Structure​

Basic Template​

Advanced Configuration Tips​

1. Modular Configuration​

2. Context Enrichment​

3. Team Collaboration Standards​

Code Review Standards​

Case 2: Refactoring Success​

Dynamic Configuration Strategy​

1. Progressive Improvement​

2. Team Collaboration​

Best Practices Summary​

✅ Things to Do Right​

❌ Traps to Avoid​