Context Engineering Just Made Our Typescript Vibe Coding Workflow Actually Predictable

### 🔄 Project Awareness & Context
- **Always read `PLANNING.md`** at the start of a new conversation to understand the project's architecture, goals, style, and constraints.
- **Check `TASK.md`** before starting a new task. If the task isn't listed, add it with a brief description and today's date.
- **Use consistent naming conventions, file structure, and architecture patterns** as described in `PLANNING.md`.
- **Use the project's package manager** (npm/yarn/pnpm) as specified in `package.json` for all operations.

### 🧱 Code Structure & Modularity
- **Never create a file longer than 300 lines of code.** If a file approaches this limit, refactor by splitting it into modules or helper files.
- **Organize code into clearly separated modules**, grouped by feature or responsibility.
  For applications this looks like:
    - `src/` - Main source code
    - `src/types/` - Type definitions and interfaces
    - `src/utils/` - Utility functions and helpers
    - `src/services/` - Business logic and external API integrations
    - `src/controllers/` - Route handlers (for Express/Fastify apps)
    - `src/middleware/` - Express/Fastify middleware
- **Use barrel exports** (`index.ts` files) to create clean import paths.
- **Use absolute imports** when configured in `tsconfig.json` paths.
- **Use environment variables** with proper validation (zod, joi, or similar).

### 🧪 Testing & Reliability
- **Always create tests for new features** using the project's testing framework (Jest, Vitest, etc.).
- **After updating any logic**, check whether existing tests need to be updated. If so, do it.
- **Tests should live in a `__tests__` folder** next to the code they test, or in a separate `tests/` directory.
  - Include at least:
    - 1 test for expected behavior
    - 1 edge case test
    - 1 error handling test
- **Use proper mocking** for external dependencies and APIs.

### ✅ Task Completion
- **Mark completed tasks in `TASK.md`** immediately after finishing them.
- Add new sub-tasks or TODOs discovered during development to `TASK.md` under a "Discovered During Work" section.

### 📎 Style & Conventions
- **Use TypeScript** with strict mode enabled.
- **Follow the project's ESLint and Prettier configurations**.
- **Use modern TypeScript features**: utility types, branded types, const assertions, etc.
- **Prefer `const` over `let`**, and avoid `var` entirely.
- **Use `async/await` over Promises** for better readability.
- **Write JSDoc comments for all public functions and classes**:
  ```typescript
  /**
   * Brief description of what the function does.
   * 
   * @param param1 - Description of the parameter
   * @param param2 - Description of the parameter
   * @returns Description of what is returned
   * @throws {ErrorType} Description of when this error is thrown
   */
  function example(param1: string, param2: number): Promise<Result> {
    // implementation
  }
  ```
- **Use proper error handling** with custom error classes when appropriate.
- **Prefer composition over inheritance** and favor functional programming patterns.

### 🔧 TypeScript Specific Rules
- **Always use strict type checking** - no `any` types unless absolutely necessary.
- **Use `unknown` instead of `any`** when the type is truly unknown.
- **Define proper interfaces and types** for all data structures.
- **Use generic types** to create reusable, type-safe components.
- **Leverage discriminated unions** for complex state management.
- **Use `readonly` for immutable data** and `const assertions` where appropriate.
- **Prefer type guards and assertion functions** over type assertions.

### 📚 Documentation & Explainability
- **Update `README.md`** when new features are added, dependencies change, or setup steps are modified.
- **Comment complex logic** and ensure everything is understandable to a mid-level developer.
- **When writing complex logic, add a `// Reason:` comment** explaining the why, not just the what.
- **Keep `package.json` scripts up to date** with proper descriptions.

### 🧠 AI Behavior Rules
- **Never assume missing context. Ask questions if uncertain.**
- **Never hallucinate libraries or packages** – only use known, verified npm packages.
- **Always confirm file paths and module names** exist before referencing them in code or tests.
- **Never delete or overwrite existing code** unless explicitly instructed to or if part of a task from `TASK.md`.
- **Always run linting and type checking** before marking tasks complete.
- **Use the correct package manager** as specified in the project (check `package-lock.json`, `yarn.lock`, or `pnpm-lock.yaml`).

### 🔍 Validation Commands
- **Type checking**: `npx tsc --noEmit` or `npm run type-check`
- **Linting**: `npx eslint src/` or `npm run lint`
- **Testing**: `npm test` or `npm run test`
- **Building**: `npm run build`
- **Always run these commands** before considering a task complete.

import { Request, Response, NextFunction } from 'express';
import jwt from 'jsonwebtoken';
import { config } from '../config/environment';
import { UnauthorizedError } from '../utils/errors';

/**
 * JWT authentication middleware for protecting routes.
 * 
 * This example demonstrates:
 * - JWT token validation
 * - Request augmentation with user data
 * - Proper error handling
 * - TypeScript typing for Express middleware
 */

export interface JWTPayload {
  userId: string;
  email: string;
  iat: number;
  exp: number;
}

export interface AuthenticatedRequest extends Request {
  user: {
    id: string;
    email: string;
  };
}

/**
 * Middleware to authenticate JWT tokens.
 * Adds user information to request object if token is valid.
 */
export const authenticateToken = async (
  req: Request,
  res: Response,
  next: NextFunction
): Promise<void> => {
  try {
    // Extract token from Authorization header
    const authHeader = req.headers.authorization;
    const token = authHeader?.split(' ')[1]; // Bearer TOKEN

    if (!token) {
      throw new UnauthorizedError('No token provided');
    }

    // Verify token
    const payload = jwt.verify(token, config.JWT_SECRET) as JWTPayload;

    // Attach user information to request
    (req as AuthenticatedRequest).user = {
      id: payload.userId,
      email: payload.email,
    };

    next();
  } catch (error) {
    if (error instanceof jwt.JsonWebTokenError) {
      next(new UnauthorizedError('Invalid token'));
    } else if (error instanceof jwt.TokenExpiredError) {
      next(new UnauthorizedError('Token expired'));
    } else {
      next(error);
    }
  }
};

/**
 * Optional authentication middleware.
 * Adds user information if token is present and valid, but doesn't require it.
 */
export const optionalAuth = async (
  req: Request,
  res: Response,
  next: NextFunction
): Promise<void> => {
  try {
    const authHeader = req.headers.authorization;
    const token = authHeader?.split(' ')[1];

    if (token) {
      const payload = jwt.verify(token, config.JWT_SECRET) as JWTPayload;
      (req as AuthenticatedRequest).user = {
        id: payload.userId,
        email: payload.email,
      };
    }

    next();
  } catch (error) {
    // For optional auth, we ignore token errors and continue
    next();
  }
};

/**
 * Generate JWT access token.
 */
export const generateAccessToken = (userId: string, email: string): string => {
  return jwt.sign(
    { userId, email },
    config.JWT_SECRET,
    { expiresIn: config.JWT_EXPIRES_IN }
  );
};

/**
 * Generate JWT refresh token.
 */
export const generateRefreshToken = (userId: string): string => {
  return jwt.sign(
    { userId, type: 'refresh' },
    config.JWT_REFRESH_SECRET,
    { expiresIn: config.JWT_REFRESH_EXPIRES_IN }
  );
};

# Create PRP

## Feature file: $ARGUMENTS

Generate a complete PRP for TypeScript/Node.js feature implementation with thorough research. Ensure context is passed to the AI agent to enable self-validation and iterative refinement. Read the feature file first to understand what needs to be created, how the examples provided help, and any other considerations.

The AI agent only gets the context you are appending to the PRP and training data. Assume the AI agent has access to the codebase and the same knowledge cutoff as you, so it's important that your research findings are included or referenced in the PRP. The Agent has WebSearch capabilities, so pass URLs to documentation and examples.

## Research Process

1. **Codebase Analysis**
   - Search for similar features/patterns in the codebase
   - Identify files to reference in PRP
   - Note existing conventions to follow
   - Check test patterns for validation approach

2. **External Research**
   - Search for similar features/patterns online
   - Library documentation (include specific URLs)
   - Implementation examples (GitHub/StackOverflow/blogs)
   - Best practices and common pitfalls

3. **User Clarification** (if needed)
   - Specific patterns to mirror and where to find them?
   - Integration requirements and where to find them?

## PRP Generation

Using PRPs/templates/prp_base.md as template:

### Critical Context to Include and pass to the AI agent as part of the PRP
- **Documentation**: URLs with specific sections
- **Code Examples**: Real snippets from codebase
- **Gotchas**: Library quirks, version issues, TypeScript-specific issues
- **Patterns**: Existing approaches to follow

### Implementation Blueprint
- Start with pseudocode showing approach
- Reference real files for patterns
- Include error handling strategy
- List tasks to be completed to fulfill the PRP in the order they should be completed

### Validation Gates (Must be Executable) for TypeScript/Node.js
```bash
# Type checking
npx tsc --noEmit

# Linting
npm run lint

# Testing
npm test

# Building
npm run build
```

*** CRITICAL AFTER YOU ARE DONE RESEARCHING AND EXPLORING THE CODEBASE BEFORE YOU START WRITING THE PRP ***

*** ULTRATHINK ABOUT THE PRP AND PLAN YOUR APPROACH THEN START WRITING THE PRP ***

## Output
Save as: `PRPs/{feature-name}.md`

## Quality Checklist
- [ ] All necessary context included
- [ ] Validation gates are executable by AI
- [ ] References existing patterns
- [ ] Clear implementation path
- [ ] Error handling documented
- [ ] TypeScript-specific considerations included
- [ ] Modern Node.js patterns used

Score the PRP on a scale of 1-10 (confidence level to succeed in one-pass implementation using Claude Code)

Remember: The goal is one-pass implementation success through comprehensive context.

# Execute TypeScript PRP

Implement a TypeScript/Node.js feature using the PRP file.

## PRP File: $ARGUMENTS

## Execution Process

1. **Load PRP**
   - Read the specified PRP file
   - Understand all context and requirements
   - Follow all instructions in the PRP and extend the research if needed
   - Ensure you have all needed context to implement the PRP fully
   - Do more web searches and codebase exploration as needed

2. **ULTRATHINK**
   - Think hard before you execute the plan. Create a comprehensive plan addressing all requirements.
   - Break down complex tasks into smaller, manageable steps using your todos tools.
   - Use the TodoWrite tool to create and track your implementation plan.
   - Identify implementation patterns from existing code to follow.

3. **Execute the plan**
   - Execute the PRP
   - Implement all the code
   - Follow TypeScript best practices
   - Use proper error handling
   - Ensure type safety throughout

4. **Validate**
   - Run each validation command:
     - `npx tsc --noEmit` (type checking)
     - `npm run lint` (linting)
     - `npm test` (testing)
     - `npm run build` (building)
   - Fix any failures
   - Re-run until all pass

5. **Complete**
   - Ensure all checklist items done
   - Run final validation suite
   - Report completion status
   - Read the PRP again to ensure you have implemented everything

6. **Reference the PRP**
   - You can always reference the PRP again if needed

Note: If validation fails, use error patterns in PRP to fix and retry. Pay special attention to TypeScript compilation errors and ensure all types are properly defined.

git clone https://github.com/DwayneSamuels/typescript-context-engineering-template.git
cd typescript-context-engineering-template
cursor .