OpenAI's Codex GitHub Action is openai/codex-action@v1 : it installs the Codex CLI, starts a Responses API proxy that holds your OPENAI_API_KEY , drops sudo , and runs codex exec with your prompt. It never comments, commits or pushes on its own, so the safe shape is two jobs: Codex with read-only repository access, then a separate job that posts its final-message .

The review workflow as two jobs. The job that holds the OpenAI key has no write token; the job that writes has no key.

Codex reaches GitHub in two ways that are easy to confuse. Codex cloud has a code review tool of its own; openai/codex-action is a building block you put in a workflow you own, and its README presents it as the way to build your own review bot when you want more control.

The version covered is v1.13, the latest tag as of 2026-11-12: what it does on the runner, the two separate controls over what Codex can touch, the permissions each job needs, and a review workflow pinned to commits.

What the action does on the runner

The…