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.
