I Built an AI Code Reviewer Bot for GitHub - Using Only GitHub Actions (No External APIs!)

Vincenzo — Mon, 27 Apr 2026 18:10:25 +0000

I created a free, open-source GitHub Action that automatically reviews every pull request using GitHub's native capabilities. Zero external APIs, zero costs, 2-minute setup.

GitHub: https://github.com/basilevincenzo/ai-code-reviewer
Stars: ⭐ (please!)

The Problem

Code reviews are slow, expensive, and inconsistent:

Junior devs miss security issues
Teams can't afford dedicated reviewers
Manual reviews take hours
Knowledge isn't shared

I wanted a bot that:
✅ Works with ONLY GitHub (no external services)
✅ Catches real bugs automatically
✅ Costs absolutely nothing
✅ Requires zero configuration

The Solution: AI Code Reviewer Bot

A pure GitHub Action that:

🔍 Finds Security Issues

SQL Injection vulnerabilities
Hardcoded secrets (passwords, API keys)
Missing input validation
Debug code left in production

⚡ Instant Feedback

Reviews your PR in seconds
Comments on specific lines
Provides fix suggestions

💰 Completely Free

Uses GitHub's native capabilities
No external APIs
No credit card
Open source

How It Works

1   You open a PR on GitHub
2   GitHub Action is triggered (built-in)
3   Bot downloads changed files from your repo
4   Bot analyzes the code using GitHub's native tools
5   Bot posts comments on your PR
6   You get instant feedback

Everything stays within GitHub. No external dependencies.

Example

When you open a PR with this code:

function getUserById(id) {
  const query = "SELECT * FROM users WHERE id = " + id;
  return database.query(query);
}

const API_KEY = "sk-1234567890";
console.log("Debug");

The bot will comment:
🔴 CRITICAL SQL Injection vulnerability detected. User input is concatenated directly into SQL query.
Suggestion: Use parameterized queries db.query('SELECT * FROM users WHERE id = ?', [id])
Why? Concatenating user input allows attackers to execute arbitrary SQL.

Why This Is Different

❌ Other Solutions:

Require external APIs
Need credit cards
Add complexity
Cost money

✅ This Solution:

Pure GitHub Actions
Zero external dependencies
Zero cost
Dead simple

Real World Example

I tested this on actual projects and it:

Caught a SQL injection in a user query
Found hardcoded database passwords
Spotted debug console.log() before production
Suggested parameterized queries
Improved team code quality

All without leaving GitHub.

Who Should Use This?

Solo developers - Free security scanning
Small teams - No budget for expensive tools
Startups - Keep costs at zero
Learning - Understand code quality patterns
Portfolio - Show security awareness

Installation

Go to your GitHub repo
Create .github/workflows/review.yml
Copy the workflow from: https://github.com/basilevincenzo/ai-code-reviewer/blob/main/.github/workflows/review.yml
Save and commit
Open a PR - bot reviews automatically

Next Steps

Star the repo ⭐
Try it on your project
Open an issue if you find bugs
Contribute improvements!

No external dependencies, no APIs, no costs.

DEV Community: Vincenzo