Claude Code Prompts:
The Complete Guide

Add a user notification system to this app. Requirements: - Users can receive in-app notifications (new message, comment, mention) - Notifications show as a badge count on the bell icon in the navbar - Clicking the bell opens a dropdown showing the last 10 notifications - Each notification is marked as read when clicked - Add a "Mark all as read" button - Persist notifications in the database with created_at, read, type, and message fields Look at the existing codebase first to understand the database schema and component patterns, then implement this feature end-to-end. Write tests for the notification service. Make sure existing tests still pass.

Analyze this codebase for performance issues and fix the top 3 most impactful ones. For each fix: 1. Explain what the problem is and why it hurts performance 2. Show the before and after code 3. Estimate the performance improvement 4. Add a comment in the code explaining why this pattern is used Focus on: database query optimization, unnecessary re-renders in React components, and any N+1 query patterns. Run the test suite after each change to make sure nothing breaks.

Add comprehensive tests to this codebase. First, run the existing tests to see what passes and what the current coverage is. Then: 1. Add unit tests for all utility functions in /lib and /utils that have no tests 2. Add component tests for the 5 most critical UI components 3. Add API route tests for all endpoints 4. Aim for 80% coverage on /lib, /utils, and /api directories 5. Use the existing testing patterns and imports already in the codebase Run the full test suite at the end and report the final coverage.

There's a bug where [describe the bug — e.g. "users get logged out randomly after about 20 minutes"]. I don't know where it's coming from. Please: 1. Search the codebase for all code related to authentication and session management 2. Identify the most likely causes of this bug 3. Add logging to help confirm which cause is the actual problem 4. Fix the root cause 5. Add a test that would catch this bug in the future Run the tests at the end to confirm nothing is broken.

I need to understand exactly how data flows through this app for [specific user action, e.g. "when a user submits a payment"]. Trace the complete flow from the frontend event handler through all middleware, API routes, service layers, and database operations. Create a clear summary showing: - Every file involved in order - What data is passed between each layer - Any validations or transformations that happen - Where errors are handled (or should be handled but aren't) Don't make any changes — just trace and document.

Perform a security audit of this codebase. Check for: 1. SQL injection vulnerabilities (raw queries, string interpolation) 2. XSS attack vectors (unsanitized user input rendered as HTML) 3. Authentication bypasses (routes that should require auth but don't) 4. Exposed sensitive data in API responses (passwords, tokens, PII) 5. Missing rate limiting on sensitive endpoints (login, signup, password reset) 6. Insecure dependencies (run npm audit and report critical/high issues) For each issue found: severity (Critical/High/Medium/Low), file and line number, explanation, and the fix. Implement fixes for all Critical and High severity issues.