PRobot — Local AI PR Reviewer

An automated pull request reviewer that runs entirely on your local machine. When a PR is opened on GitHub, PRobot fetches the diff, sends it to a local LLM via Ollama, and posts the AI-generated review back as a PR comment.

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How It Works

GitHub PR opened
      │
      ▼
GitHub Webhook (HTTP POST)
      │
      ▼
ngrok (tunnels to localhost)
      │
      ▼
FastAPI server (/webhook)
      │
      ├── Fetch PR diff via GitHub API
      │
      ├── Send diff to Ollama (local LLM)
      │
      └── Post AI review as PR comment

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Tech Stack

Component	Tool
Web server	FastAPI + Uvicorn
GitHub integration	PyGitHub
Local LLM	Ollama (qwen2.5-coder:7b)
Tunnel (dev)	ngrok
Config	python-dotenv

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Project Structure

probot/
├── app/
│   ├── main.py              # FastAPI app & webhook handler
│   ├── github_handler.py    # Fetch PR diff, post PR comment
│   ├── ollama_reviewer.py   # Send diff to Ollama, return review
│   └── prompts.py           # LLM prompt template
├── .env                     # Secrets (not committed)
├── requirements.txt
└── README.md

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Setup

1. Clone & install dependencies

git clone https://github.com/Kush05Bhardwaj/PRobot.git
cd PRobot/probot
python -m venv venv
venv\Scripts\activate        # Windows
pip install -r requirements.txt

2. Configure environment variables

Create a .env file in the probot/ directory:

GITHUB_TOKEN=your_github_pat_here
WEBHOOK_SECRET=your_webhook_secret
OLLAMA_MODEL=qwen2.5-coder:7b

• GITHUB_TOKEN — A GitHub Personal Access Token with repo scope.
• WEBHOOK_SECRET — A secret string; set the same value in your GitHub webhook config.
• OLLAMA_MODEL — Any code-capable model pulled in Ollama.

3. Pull the Ollama model

ollama pull qwen2.5-coder:7b

4. Start the server

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

5. Expose localhost with ngrok

ngrok http 8000

Copy the HTTPS URL (e.g. https://xxxx.ngrok-free.app).

6. Configure GitHub Webhook

In your GitHub repo → Settings → Webhooks → Add webhook:

Field	Value
Payload URL	https://xxxx.ngrok-free.app/webhook
Content type	application/json
Secret	value from WEBHOOK_SECRET in .env
Events	Pull requests

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Usage

Open a pull request in your GitHub repo. PRobot will automatically:

1. Receive the pull_request opened event
2. Fetch the changed files and diffs
3. Run the diff through the local LLM
4. Post a structured review comment on the PR

Example review output

🤖 PRobot Review

📋 Summary:
Adds basic Express authentication middleware and a login endpoint.

🐛 Bugs:
- Hardcoded credentials ('admin'/'secret') should never be used in production.

⚡ Performance:
- No issues for this scope.

🔒 Security:
- Plaintext password comparison is a critical vulnerability; use bcrypt or similar.
- JWT token is hardcoded ('fake-jwt-token'); replace with a real signing library.

📝 PR Description Feedback:
Consider documenting the expected request/response schema for the login route.

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Requirements

• Python 3.10+
• Ollama running locally
• ngrok (for local development tunneling)