Automated Code Review with Claude

Learn how to use Claude Code for comprehensive code reviews, catching bugs, security vulnerabilities, and style issues

title: Automated Code Review with Claude description: Learn how to use Claude Code for comprehensive code reviews, catching bugs, security vulnerabilities, and style issues

Code review is one of the most powerful use cases for Claude Code. This tutorial shows you how to leverage AI-powered code review to catch issues before they reach production.

Why Use Claude for Code Review?

Traditional code review has limitations:

• Time-consuming - Reviewers may rush through large PRs
• Inconsistent - Different reviewers catch different issues
• Limited expertise - Reviewers may miss security or performance issues outside their domain

Claude Code addresses these by providing:

• Comprehensive analysis - Every line gets attention
• Consistent standards - Same criteria applied every time
• Broad expertise - Security, performance, and best practices

Quick Start: Review a File

The simplest way to review code:

Review this file for bugs, security issues, and improvements:
[paste your code or reference a file]

Claude will analyze and provide:

• Critical bugs
• Security vulnerabilities
• Performance issues
• Style improvements
• Best practice suggestions

Review Strategies

Strategy 1: Full PR Review

Review all changes in a pull request:

Review all the changes in this PR. Look for:
1. Bugs and logic errors
2. Security vulnerabilities
3. Performance issues
4. Code style consistency
5. Missing error handling

Claude will:

1. Read all changed files
2. Understand the context of changes
3. Provide categorized feedback

Strategy 2: Security-Focused Review

For security-critical code:

Perform a security audit on the authentication module.
Focus on:
- SQL injection vulnerabilities
- XSS attack vectors
- Authentication bypass risks
- Sensitive data exposure
- CSRF protection

Strategy 3: Performance Review

For performance-critical sections:

Review this code for performance issues:
- N+1 query problems
- Memory leaks
- Unnecessary re-renders (React)
- Inefficient algorithms
- Missing caching opportunities

Strategy 4: Incremental Review

Review specific changes:

I just added error handling to the payment processor.
Review only the new error handling code for:
- Edge cases I might have missed
- Error message clarity
- Logging completeness

Review Checklist Template

Use this template for comprehensive reviews:

Review this code against the following checklist:

## Correctness
- [ ] Logic errors
- [ ] Off-by-one errors
- [ ] Null/undefined handling
- [ ] Edge cases

## Security
- [ ] Input validation
- [ ] SQL injection
- [ ] XSS vulnerabilities
- [ ] Authentication/authorization
- [ ] Sensitive data handling

## Performance
- [ ] Algorithm efficiency
- [ ] Database queries
- [ ] Memory usage
- [ ] Caching

## Maintainability
- [ ] Code clarity
- [ ] Naming conventions
- [ ] Documentation
- [ ] Test coverage

## Error Handling
- [ ] Try/catch blocks
- [ ] Error messages
- [ ] Logging
- [ ] User feedback

Real-World Examples

Example 1: API Endpoint Review

// Code to review
app.post('/api/users', async (req, res) => {
  const { email, password, role } = req.body;
  const user = await db.users.create({
    email,
    password,
    role: role || 'user'
  });
  res.json(user);
});

Claude's Review:

Critical Issues:

1. Password stored in plain text - Use bcrypt or argon2 to hash passwords
2. Role injection vulnerability - Attacker can set role: 'admin' in request body
3. No input validation - Email format and password strength not validated
4. Sensitive data exposure - Response includes password field

Recommended Fix:

TypeScript

app.post('/api/users', async (req, res) => {
  const { email, password } = req.body;

  // Validate input
  if (!isValidEmail(email)) {
    return res.status(400).json({ error: 'Invalid email' });
  }

  // Hash password
  const hashedPassword = await bcrypt.hash(password, 12);

  // Never accept role from client
  const user = await db.users.create({
    email,
    password: hashedPassword,
    role: 'user'  // Always default, admin set separately
  });

  // Exclude sensitive fields
  const { password: _, ...safeUser } = user;
  res.json(safeUser);
});

Example 2: React Component Review

// Code to review
function UserList() {
  const [users, setUsers] = useState([]);

  useEffect(() => {
    fetch('/api/users')
      .then(res => res.json())
      .then(data => setUsers(data));
  });

  return (
    <ul>
      {users.map(user => (
        <li>{user.name}</li>
      ))}
    </ul>
  );
}

Claude's Review:

Issues Found:

1. Infinite loop - useEffect missing dependency array, causing infinite API calls
2. Missing key prop - List items need unique keys for React reconciliation
3. No error handling - API failures will silently fail
4. No loading state - Users see empty list while loading

Recommended Fix:

TSX

function UserList() {
  const [users, setUsers] = useState([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  useEffect(() => {
    fetch('/api/users')
      .then(res => {
        if (!res.ok) throw new Error('Failed to fetch');
        return res.json();
      })
      .then(data => setUsers(data))
      .catch(err => setError(err.message))
      .finally(() => setLoading(false));
  }, []); // Empty array = run once

  if (loading) return <p>Loading...</p>;
  if (error) return <p>Error: {error}</p>;

  return (
    <ul>
      {users.map(user => (
        <li key={user.id}>{user.name}</li>
      ))}
    </ul>
  );
}

Integrating with Git Workflows

Pre-Commit Review

Review staged changes before committing:

Review my staged changes (git diff --staged).
Are there any issues I should fix before committing?

PR Description Generation

Generate PR descriptions from code changes:

Generate a PR description for these changes.
Include:
- Summary of what changed
- Why these changes were made
- Testing performed
- Any breaking changes

Automated Review with Hooks

Create a pre-push hook that asks Claude to review:

# .claude/commands/review-changes.md
Review the changes between HEAD and origin/main.
Provide a summary of:
1. Critical issues that must be fixed
2. Warnings that should be addressed
3. Minor suggestions for improvement

Best Practices

1. Provide Context

This is a payment processing module for an e-commerce site.
Users can pay with credit cards or PayPal.
Review for PCI compliance and security issues.

2. Specify Standards

Review against our team standards:
- Use TypeScript strict mode
- All functions must have JSDoc comments
- No console.log in production code
- Error messages must be user-friendly

3. Prioritize Feedback

Categorize issues by severity:
- CRITICAL: Must fix before merge
- WARNING: Should fix soon
- SUGGESTION: Nice to have

4. Request Actionable Feedback

For each issue found, provide:
1. The problem
2. Why it matters
3. How to fix it
4. Example code if applicable

Common Issues Claude Catches

| Category | Examples | |----------|----------| | Security | SQL injection, XSS, CSRF, auth bypass | | Performance | N+1 queries, memory leaks, blocking I/O | | Reliability | Missing error handling, race conditions | | Maintainability | Complex functions, poor naming, missing docs | | Best Practices | Anti-patterns, deprecated APIs, type safety |

Limitations

Be aware of Claude Code review limitations:

• Runtime behavior - Cannot catch issues that only appear at runtime
• Integration issues - May miss problems with external systems
• Business logic - Cannot verify correctness of business rules
• Performance benchmarks - Cannot measure actual performance

Always combine AI review with:

• Human review for business logic
• Automated tests for runtime behavior
• Integration tests for system interactions
• Performance testing for optimization

Next Steps

• Test Generation - Write tests for reviewed code
• Documentation Generation - Document your code
• Debugging Guide - Fix issues found in review