Claude Code Architecture Patterns: Designing for AI-First Development

1. The AI-First Codebase Philosophy

Traditional code organization optimizes for human navigation. AI-first design optimizes for context efficiency: helping Claude understand your codebase with minimal token consumption and maximum accuracy.

The Three Pillars

1. Discoverability

• →Semantic naming
• →Predictable paths
• →Logical grouping

2. Self-Documentation

• →Inline explanations
• →Type signatures
• →Purpose comments

3. Modularity

• →Single responsibility
• →Clear boundaries
• →Minimal dependencies

2. File Organization for AI Navigation

Claude uses Read, Grep, and Glob to navigate your codebase. Optimize for these tools.

Semantic Directory Structure

Feature-based (Recommended for AI):

src/
├── features/
│   ├── auth/
│   │   ├── components/
│   │   ├── hooks/
│   │   ├── services/
│   │   ├── types.ts
│   │   └── index.ts
│   ├── payments/
│   │   ├── components/
│   │   ├── hooks/
│   │   ├── services/
│   │   ├── types.ts
│   │   └── index.ts
│   └── users/
│       └── ...
├── shared/
│   ├── components/
│   ├── hooks/
│   └── utils/
└── config/

Why feature-based works better for AI:

• →Claude can find related code with one Glob: src/features/auth/**
• →Changes to a feature are contained in one directory
• →Less cross-referencing needed to understand context

3. Naming Conventions for Discoverability

Names should be searchable and semantic. Claude uses pattern matching extensively.

File Naming Patterns

Why suffix patterns matter:

# Claude can find all services instantly
Glob: **/*.service.ts

# Or all hooks
Glob: **/use*.hook.ts

# Or all tests
Glob: **/*.test.ts

Function and Variable Naming

Searchability principle:

Bad:  const x = await fn(data)
Good: const authenticatedUser = await validateUserCredentials(loginRequest)

Claude can grep for validateUserCredentials or authenticatedUser and find exactly what it needs.

4. Self-Documenting Code Patterns

Write code that explains itself to AI agents.

Type-First Development

TypeScript types are free documentation for Claude:

// ❌ Claude must infer what this does
function process(data) {
  // ...
}

// ✅ Types explain everything
interface PaymentRequest {
  userId: string;
  amount: number;
  currency: 'USD' | 'EUR' | 'GBP';
  paymentMethod: 'card' | 'bank_transfer';
}

interface PaymentResult {
  transactionId: string;
  status: 'success' | 'pending' | 'failed';
  processedAt: Date;
}

function processPayment(request: PaymentRequest): Promise<PaymentResult> {
  // Claude knows exactly what goes in and comes out
}

JSDoc for Complex Logic

For complex business logic, add JSDoc:

/**
 * Calculates the discount based on user tier and cart value.
 * 
 * @param user - The authenticated user with tier information
 * @param cartTotal - The cart total in cents
 * @returns Discount percentage (0-100)
 * 
 * @example
 * // Premium user with $100 cart gets 15% off
 * calculateDiscount({ tier: 'premium' }, 10000) // Returns 15
 * 
 * @businessRule Discounts cap at 30% regardless of tier
 * @businessRule New users get first-purchase bonus of 5%
 */
function calculateDiscount(user: User, cartTotal: number): number {
  // Implementation
}

5. Module Boundaries for Context Isolation

Clear module boundaries help Claude understand scope and prevent unintended side effects.

The Index Pattern

Every feature module should have an explicit public API:

// src/features/auth/index.ts
// This is the PUBLIC API - only export what should be used externally

export { AuthProvider } from './components/AuthProvider';
export { useAuth } from './hooks/useAuth.hook';
export { loginUser, logoutUser } from './services/auth.service';
export type { User, AuthState, LoginCredentials } from './types';

// Internal implementations are NOT exported
// Claude knows not to use them from outside this module

Benefits for AI:

• →Claude knows exactly what's available from each module
• →Internal refactoring doesn't affect external code
• →Grep for imports shows usage patterns

Dependency Direction

Import Rules:

• →features/ (auth, payments, users) → can import from shared/ and config/
• →shared/ (components, hooks, utils) → can import from config/ only
• →config/ (env, const) → no dependencies

6. Context Engineering for Large Codebases

When codebases exceed what fits in context, use these strategies:

The Entry Point Pattern

Create explicit entry points that explain the system:

// src/ARCHITECTURE.md (or in CLAUDE.md)
# System Architecture

## Entry Points
- API: src/api/index.ts - Express server setup
- Auth: src/features/auth/index.ts - All authentication
- Payments: src/features/payments/index.ts - Stripe integration

## Key Patterns
- Repository pattern for data access
- Service layer for business logic
- Controller layer for HTTP handling

## Data Flow
Request → Controller → Service → Repository → Database
Response ← Controller ← Service ← Repository ← Database

Semantic Anchors

Add semantic anchors that Claude can grep for:

// AUTH_FLOW: This is the main authentication entry point
// All login attempts flow through this function
async function authenticateUser(credentials: LoginCredentials): Promise<AuthResult> {
  // AUTH_FLOW: Step 1 - Validate credentials
  const isValid = await validateCredentials(credentials);
  
  // AUTH_FLOW: Step 2 - Generate tokens
  const tokens = await generateTokenPair(credentials.userId);
  
  // AUTH_FLOW: Step 3 - Create session
  return createSession(tokens);
}

Claude can now grep AUTH_FLOW to trace the entire authentication flow:

Grep: AUTH_FLOW
# Returns all steps in order

7. Testing Architecture for AI

Well-structured tests help Claude understand expected behavior.

Test as Documentation

describe('PaymentService', () => {
  describe('processPayment', () => {
    // Test name explains the business rule
    it('should apply 15% discount for premium users', async () => {
      const premiumUser = { tier: 'premium', id: 'user-1' };
      const payment = { amount: 10000, currency: 'USD' };
      
      const result = await paymentService.processPayment(premiumUser, payment);
      
      expect(result.discountApplied).toBe(1500);
      expect(result.finalAmount).toBe(8500);
    });

    it('should reject payments over $10,000 without manager approval', async () => {
      // Business rule: High-value payments need approval
      const payment = { amount: 1000001, currency: 'USD' };
      
      await expect(
        paymentService.processPayment(user, payment)
      ).rejects.toThrow('Manager approval required');
    });
  });
});

Test Organization

8. Configuration Architecture

Configuration affects how Claude understands your project.

Environment-Based Config

// config/index.ts
import { z } from 'zod';

// CONFIG_SCHEMA: All environment variables validated here
const configSchema = z.object({
  // Database
  DATABASE_URL: z.string().url(),
  DATABASE_POOL_SIZE: z.number().default(10),
  
  // Auth
  JWT_SECRET: z.string().min(32),
  JWT_EXPIRES_IN: z.string().default('1h'),
  
  // External Services
  STRIPE_SECRET_KEY: z.string().startsWith('sk_'),
  SENDGRID_API_KEY: z.string(),
});

export type Config = z.infer<typeof configSchema>;

// CONFIG_LOAD: Validated config object
export const config: Config = configSchema.parse(process.env);

Benefits:

• →Claude sees all config options in one place
• →Zod schema documents types and constraints
• →Semantic anchors (CONFIG_SCHEMA, CONFIG_LOAD) enable quick navigation

Feature Flags

// config/features.ts
export const featureFlags = {
  // FEATURE_FLAG: New payment provider integration
  USE_NEW_PAYMENT_PROVIDER: process.env.USE_NEW_PAYMENT_PROVIDER === 'true',
  
  // FEATURE_FLAG: Beta dashboard UI
  ENABLE_BETA_DASHBOARD: process.env.ENABLE_BETA_DASHBOARD === 'true',
  
  // FEATURE_FLAG: AI-powered recommendations
  AI_RECOMMENDATIONS: process.env.AI_RECOMMENDATIONS === 'true',
} as const;

export type FeatureFlags = typeof featureFlags;

9. Monorepo Patterns

For monorepos, additional organization helps Claude navigate multiple packages.

Package Structure

monorepo/
├── packages/
│   ├── api/
│   │   ├── package.json
│   │   ├── CLAUDE.md          # API-specific instructions
│   │   └── src/
│   ├── web/
│   │   ├── package.json
│   │   ├── CLAUDE.md          # Frontend-specific instructions
│   │   └── src/
│   └── shared/
│       ├── package.json
│       └── src/
├── CLAUDE.md                   # Root: org-wide standards
├── package.json
└── turbo.json

Cross-Package Dependencies

// packages/shared/src/types/user.ts
// SHARED_TYPE: Used by both api and web packages
export interface User {
  id: string;
  email: string;
  tier: 'free' | 'premium' | 'enterprise';
}

// packages/api/src/services/user.service.ts
import { User } from '@monorepo/shared';  // Clear dependency

// packages/web/src/hooks/useUser.ts
import { User } from '@monorepo/shared';  // Same shared type

10. Anti-Patterns to Avoid

Summary: AI-First Architecture Checklist

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