Developer builds custom Codex bot

Short summary

A developer built a custom code review bot for GitLab using OpenAI's Codex SDK to avoid GitLab Duo's $0.20/review cost. The solution runs as a self-hosted service on OpenShift with threaded conversation support, using Fastify for webhooks, BullMQ for queuing, and careful security isolation. Key challenges included implementing concurrency control and working around Kubernetes security constraints.

• •Custom Codex bot reduces per-review cost by switching from GitLab Duo pay-per-token to ChatGPT subscription
• •Self-hosted architecture on OpenShift enables threaded conversations, deterministic job IDs, and conversation resumption
• •Security isolation: database stores only IDs, Codex sessions persist on PVC, full diffs never land in storage

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