AI code review on every pull request. Any model. Zero infrastructure.

carl is a GitHub Action that reads your PR diff, looks up the linked issue to understand the task, and posts a review comment. One .yml file. No servers. No subscriptions.

- uses: deyna256/carl@v1
  with:
    openrouter-api-key: ${{ secrets.OPENROUTER_API_KEY }}

What carl does

On every PR open or push:

1. Fetches the diff and the linked issue from GitHub
2. Loads your review guidelines from .github/carl.md
3. Asks the model: did this PR solve the task, and is the code correct?
4. Posts the answer as a PR review comment

If the diff exceeds max_diff_chars or max_files, carl fails fast with a clear error. If OpenRouter is unavailable, it posts a notice instead of silently failing.

Quick start

1. Add your OpenRouter key to repository secrets

Settings → Secrets and variables → Actions → New repository secret
Name: OPENROUTER_API_KEY

2. Create .github/carl.yml

model: google/gemma-4-26b-a4b-it
guidelines: .github/carl.md
max_diff_chars: 20000
max_files: 10
ignore:
  - '*.lock'
  - 'dist/**'

3. Create .github/carl.md — tell carl what to look for

Check whether the PR solves the linked issue.
Then review the code for logic errors, security issues, and missing test coverage.
Skip stylistic comments.

4. Add .github/workflows/carl.yml

on:
  pull_request:
    types: [opened, synchronize]

jobs:
  review:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
    steps:
      - uses: actions/checkout@v4
      - uses: deyna256/carl@v1
        with:
          openrouter-api-key: ${{ secrets.OPENROUTER_API_KEY }}

Private repository? The default token won't work. See configuration → private repositories.

Why carl

• Any model. Switch from Claude to Gemini to Llama by changing one line in carl.yml — no code changes.
• Your guidelines. The review prompt lives in your repository. Tailor it to your stack, your standards, your team.
• Linked issue awareness. carl fetches the GitHub issue linked to the PR and tells the model what problem was supposed to be solved — so it can judge whether it actually was.
• No infrastructure. Runs entirely inside GitHub Actions. Nothing to host, nothing to maintain.

Inputs

Input	Required	Default	Description
openrouter-api-key	yes	—	Your OpenRouter API key
github-token	no	${{ github.token }}	GitHub token with pull-requests: write permission
config-path	no	.github/carl.yml	Path to carl config file

Docs

• Configuration reference — all carl.yml options, writing carl.md, private repo setup
• Project structure — architecture, source modules, CI/CD

Requirements

• GitHub repository (public or private)
• OpenRouter account with API key
• Any model available on OpenRouter