GitReview Prototype

A minimal GitHub App that listens for opened pull requests and posts an AI-generated PR description as a comment.

Why

This is the Week 1 deliverable of the CEO-led bootstrap sprint for GitReview. It validates whether engineering teams will pay for an AI-powered PR Assistant before committing to the full MVP build.

Stack

• Node.js 20 + TypeScript
• Express (local / Render)
• Serverless adapter for Vercel (src/vercel.ts)
• @octokit/webhooks + @octokit/rest + @octokit/auth-app
• Anthropic Claude API

What it does

1. Listens for pull_request.opened webhooks from GitHub.
2. Authenticates as the GitHub App installation that owns the event.
3. Fetches the PR diff.
4. Sends the diff + original title/body to Claude.
5. Posts the generated description as a PR comment.
6. Skips if a GitReview comment already exists (idempotent).

Prerequisites

• A GitHub App with:
  • App ID and private key (PEM)
  • Webhook secret
  • Permissions: Pull requests (read), Issues (write, to post comments), Contents (read, for diffs)
  • Subscribe to Pull request events
• An Anthropic API key

Run locally

1. Install dependencies:

   npm install

2. Copy .env.example to .env and fill in credentials:

   cp .env.example .env

   For local testing with a personal access token you can use GITHUB_TOKEN instead of GITHUB_APP_ID / GITHUB_PRIVATE_KEY. For the real webhook flow, use the GitHub App credentials.

3. Start the dev server:

   npm run dev

4. Expose locally (e.g., ngrok) and configure the GitHub App webhook URL to https://your-tunnel/webhooks.

5. Open a PR in a repo where the app is installed.

Deploy

Vercel (free tier)

1. Push this repo to GitHub.
2. Import the repo in Vercel.
3. Add environment variables in the Vercel dashboard:
   • GITHUB_APP_ID
   • GITHUB_PRIVATE_KEY
   • GITHUB_WEBHOOK_SECRET
   • ANTHROPIC_API_KEY
   • ANTHROPIC_MODEL (optional, defaults to claude-sonnet-4-6)
4. Set the GitHub App webhook URL to https://your-project.vercel.app/webhooks.

The included vercel.json routes /webhooks and /health to src/vercel.ts.

Render (free tier)

1. Push this repo to GitHub.
2. In Render, choose New > Blueprint and point it at render.yaml.
3. Fill in the secret environment variables when prompted.
4. Render builds with npm run build and starts with npm start.
5. Set the GitHub App webhook URL to https://your-service.onrender.com/webhooks.

Verify the deployment

1. GET /health should return {"status":"ok","version":"0.1.0"}.
2. Open a pull request in a repo with the app installed.
3. The PR should receive a comment starting with ## AI-generated PR description.

Project layout

src/
  index.ts    # Express entry point (local / Render)
  vercel.ts   # Serverless handler (Vercel)
  github.ts   # GitHub App auth, diff fetch, comment post
  claude.ts   # Claude API prompt and response handling

Next step

Week 2 validation: MIN-5