I built a custom Codex-powered code review bot for GitLab

A merge-request review by GitLab Duo Code Review costs us about $0.20. We're a small team of developers, so $1 for ~5 MR reviews gets expensive quickly. We had a ChatGPT subscription on the team budget already. The obvious move was to point the subscription we paid for at the reviews we wanted to automate. But Duo wouldn't let me. It only accepts pay-per-token providers, runs a couple model generations behind, and is closed to the prompt and workflow tweaks I wanted. So I built our team a replac