The $0 Code-Review Pipeline: Free Models, Free Server, No Credit Card MonkeyCode, an open-source AI coding assistant, has introduced a code-review pipeline that runs entirely on free models and a free self-hosted server, requiring no credit card. The setup uses a GitHub Action to detect pull requests, extract diffs, and send them to a MonkeyCode endpoint, with the returned comments posted back to the PR. The project highlights the trade-offs between hosted and self-hosted servers, emphasizing control and data privacy for closed-source work. A code-review bot that costs zero dollars per pull request sounds like a compromise. It is not. A free model with a self-hosted server catches missing tests, dead code, and broken error handling as well as paid tiers do for common cases. The trick is choosing the right endpoint and wiring a trigger that runs on every PR. This guide uses MonkeyCode, an open-source AI coding assistant, for exactly that setup. Disclosure: This article was prepared as part of MonkeyCode's product outreach. MonkeyCode offers free models and a free server option, so the entire pipeline runs without a credit card. There is no trial clock. There is no billing form. There is only an API endpoint and a prompt. The workflow is simple. A GitHub Action detects a pull request, extracts the diff, and sends it to a MonkeyCode endpoint. The endpoint can be the hosted free server or a server you run yourself. The returned comments are posted back to the PR. The whole loop takes less than a minute for a typical diff. Why bother with your own server? Control. You set the rate limits, the logging, and the model. The hosted free tier is fine for experiments. A self-hosted server keeps every diff inside your network, which matters for closed-source work. That choice should not feel heavy. It is a matter of one environment variable. Here is the complete action. Save it as .github/workflows/ai-review.yml in any repository. name: ai-review on: pull request: types: opened, synchronize jobs: review: runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 with: fetch-depth: 0 - name: Generate diff run: git diff origin/${{ github.event.pull request.base.ref }}...HEAD /tmp/diff.txt - name: Send diff to MonkeyCode env: MC API URL: ${{ secrets.MC API URL }} MC API KEY: ${{ secrets.MC API KEY }} run: | curl -sS -X POST "$MC API URL/v1/completions" \ -H "Content-Type: application/json" \ -H "Authorization: Bearer $MC API KEY" \ -d @- <