PRLens 🔍

PRLens is a brutally honest, AI-powered code reviewer built as a GitHub App. It doesn't sugarcoat problems—it tears your code apart and points out security flaws, bugs, and sloppy engineering directly on your Pull Requests where it hurts.

Built with FastAPI, GitHub Apps API, and Claude Sonnet 4 via OpenRouter.

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What It Does

When someone opens a Pull Request or pushes code directly to a branch, PRLens:

1. Skips lock files, binaries, and generated code to save tokens.
2. Slices the code changes (the "diff") line by line.
3. Analyzes it aggressively for Security, Bugs, Performance, Architecture, Quality, and Error Handling.
4. Posts brutally honest, inline comments directly on the PR, or a massive commit comment for direct pushes.
5. If the issues are severe, it blocks the PR with a REQUEST_CHANGES review.

Tech Stack

• Python 3.10+ (FastAPI, Uvicorn, PyJWT)
• GitHub App Webhooks
• LLM: Anthropic Claude 3.5 Sonnet (via OpenRouter)

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Local Setup

1. Requirements

• Python 3.10+
• An OpenRouter API key for the LLM
• A registered GitHub App with the following permissions:
  • Pull requests: Read & write
  • Contents: Read-only
  • Events to subscribe to: Pull request, Push

2. Installation

Clone the repo and install the required dependencies:

git clone https://github.com/your-username/PRLens.git
cd PRLens
python -m venv venv

# Windows
.\venv\Scripts\activate
# Mac/Linux
source venv/bin/activate

pip install -r requirements.txt

3. Configuration

Copy the default environment variables and fill them in:

cp .env.example .env

Inside .env, you must supply:

• GITHUB_APP_ID: From your GitHub App's "General" settings.
• GITHUB_WEBHOOK_SECRET: A secret string you configure in your GitHub app settings to verify webhooks.
• PEM_FILE_PATH: The absolute path to the private key .pem file you downloaded from GitHub.
• OPENROUTER_API_KEY: Your OpenRouter API key.

(Optional) You can also tweak review behaviors in .env (like maximum files, maximum characters, and which LLM to use).

4. Running the Server

Start the local FastAPI server:

uvicorn app.main:app --port 8000 --reload

You can access the server at http://127.0.0.1:8000.

5. Exposing Localhost (for GitHub Webhooks)

GitHub needs a public URL to send webhooks to. Run ngrok in a new terminal window:

ngrok http 8000

Take the public URL ngrok gives you (e.g., https://xxxx.ngrok.app) and append /webhook to it. Put THAT URL in your GitHub App's Webhook URL settings.

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Deployment (Docker)

This app includes a Dockerfile for effortless deployment to cloud platforms like Render, Railway, or Fly.io.

1. Build the image:

docker build -t prlens .

2. Run it (passing in all required environment variables):

docker run -p 8000:8000 --env-file .env prlens

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Project Structure

PRLens/
├── app/
│   ├── config.py           # Environment variables configuration
│   ├── main.py             # FastAPI entrypoint
│   └── services/           
│       ├── diff_processor.py # Parses github diffs and filters lines
│       ├── github.py       # Interacts with the GitHub API
│       ├── llm.py          # Formats the brutal prompt and talks to OpenRouter
│       └── reviewer.py     # Orchestrates the review flow
├── tests/                  # Unit tests 
├── .env.example            # Sample config variables
├── Dockerfile              # Docker image definition
└── requirements.txt        # Python package dependencies

Disclaimer

PRLens was explicitly engineered to be mean, nitpicky, and ruthless. Do not use it on a junior developer's PR unless you want them to cry. Use responsibly.