ionix.iowriteupWe built an AI PR reviewer. The hard part was teaching it to say nothing.
Ionix's engineering team describes building an in-house AI PR reviewer using OpenAI's Codex CLI against a self-hosted Azure AI Foundry model deployment, wired into CircleCI and Bitbucket, after dropping Atlassian Rovo for cost and low signal-to-noise. The piece details prompt design to suppress low-value comments, agentic repo-wide review (vs. diff-only), sharding for large PRs, JSON output validation against git ls-files, storing review state inside PR comments via base64-in-markdown, and a dedicated prompt-injection defense section (scrubbed environment, secret redaction, sandboxed execution, egress restriction). It also covers two production failures: a silently-broken bubblewrap sandbox that kept "reviewing" without running any tools, and an unpinned Codex CLI npm dependency that broke Azure API calls across every repo.
AI Security, DevSecOps· 2026-08-13T14:32:05+00:00