AI-Powered PR Reviewer

A GitHub App that uses a multi-agent architecture to review Pull Requests with cross-file reasoning and codebase memory.

🌟 What Makes This Different

Unlike other AI reviewers that only see the diff, this bot understands your entire codebase:

• Indexes your repo on installation
• Finds related code across files you didn't change
• Learns patterns from your codebase
• Self-hosted = your code never leaves your infrastructure

Features

• 🚫 Block Bad PRs: High-risk PRs get a failing status check (can't merge!)
• 🔧 Auto-Fix Suggestions: AI generates code fixes for issues found
• 🌐 Multi-Language: Python, JavaScript/TypeScript, Java, C/C++, Go, Rust
• 🧠 RAG Context: Indexes your codebase for smarter reviews
• 📊 Map-Reduce: Handles large PRs by summarizing files individually
• 🌳 Tree-sitter: Parses code structure (functions, classes, imports)
• 🔗 Cross-File Impact: Identifies files affected by your changes
• 🔑 Multi-Key Manager: Rotates Gemini API keys with rate-limit handling
• ⚠️ Risk Scoring: Assigns risk based on size, tests, and impact

Setup

1. Install Dependencies:

   pip install -r requirements.txt

2. Configure Environment: Copy .env.example to .env and fill in:

   • APP_ID: Your GitHub App ID
   • PRIVATE_KEY_PATH: Path to your GitHub App private key
   • WEBHOOK_SECRET: Your webhook secret
   • GEMINI_API_KEYS: Comma-separated list of Gemini API keys

3. Run the Server:

   uvicorn app.main:app --reload

How It Works

On GitHub App Installation

1. Receives installation webhook
2. Indexes entire repository in background
3. Stores embeddings in local vector store

On Pull Request

1. Status: Pending → Shows "AI review in progress"
2. Diff Analysis → Fetch changed files
3. Tree-sitter → Parse code structure (7 languages)
4. Map → Summarize each file
5. RAG → Find related code in codebase
6. Risk → Calculate risk score (0-100)
7. Reduce → Generate final review
8. Auto-Fix → Generate code suggestions if issues found
9. Status: Pass/Fail → Block merge if risk ≥ 70

Architecture

app/
├── main.py                  # FastAPI + webhooks
├── core/
│   ├── config.py            # Settings
│   ├── security.py          # GitHub App JWT auth
│   ├── llm.py               # Gemini client
│   ├── key_manager.py       # Multi-key rotation
│   ├── embeddings.py        # Gemini embeddings
│   ├── vector_store.py      # ChromaDB wrapper
│   ├── indexer.py           # Codebase indexer
│   └── code_parser.py       # Tree-sitter parser
└── agents/
    ├── master.py            # Orchestrator
    ├── diff.py              # PR diff analysis
    ├── dependency.py        # Cross-file dependencies
    ├── file_summary.py      # File summarizer (MAP)
    ├── context.py           # RAG context retrieval
    ├── test.py              # Test impact
    ├── risk.py              # Risk scoring
    └── writer.py            # Review composer (REDUCE)

API Endpoints

Endpoint	Description
POST /webhook	GitHub webhook handler
GET /	Health check
GET /stats/{owner}/{repo}	Index statistics

Configuration

Variable	Description
APP_ID	GitHub App ID
PRIVATE_KEY_PATH	Path to private key file
WEBHOOK_SECRET	Webhook signature secret
GEMINI_API_KEYS	Comma-separated API keys

License

MIT