codex-cli

Codex CLI

Codex is a second agent on the same machine, with its own model behind it. That is the entire reason to reach for it: a model that did not write the code has no memory of intending it to work. Everything below follows from that one asymmetry — who wrote it, who reads it, and how much thinking each step is worth paying for.

This skill is for the supervising agent, not for Codex. If you are Codex, this does not apply — calling yourself buys nothing but a second opinion from the same mind. Claude Code is the intended caller.

It also assumes the machine is already set up: codex on PATH, the user logged in, and whatever MCP servers and tools they want available configured in ~/.codex/config.toml. If the binary is missing, auth has expired, or a run dies on permissions, report that plainly and stop — quietly falling back to doing it yourself hides the fact that the review the user asked for never happened.

Concrete flags belong to codex --help, which is authoritative and moves faster than this file. What follows is the judgment.

When to reach for it

Every invocation is a second model spending the user's money and your wall-clock time. It earns that when the problem is hard enough that another model changes the outcome — not as a reflex after every edit. Doing the work yourself and checking it with the project's own tests remains the normal path.

• When the user asks for it. They have already made the call; don't re-litigate it. Match the model and effort to the task and go.
• After writing something complex or expensive to get wrong. Your own review of your own diff is the weakest review available, because you are checking the code against the intent you already have in your head rather than against what it says. That weakness only matters when the defect would be costly — concurrency, migrations, security-adjacent paths, platform assumptions, anything on a compatibility surface. A routine edit that the suite already covers is not worth a review pass. Counter-example: an agent changed one side of a path comparison to a normalized form and left the other side platform-native; every test it wrote passed, because it wrote them against the same wrong mental model.
• When a demanding change is bounded well enough to describe in a prompt. A hand-off is worth it when you can state the goal, the files, and the acceptance check in a paragraph. That paragraph is also the honest test of whether you understand the change — if you cannot write it, delegating it just moves the confusion downstream. What "bounded" means is scoped-change, and it binds Codex exactly as it binds you: pass the boundary along in the prompt, because Codex cannot infer where the user drew it.
• When the work is long, mechanical, and verifiable. Wide renames, repetitive migrations, and mass edits with a green suite proving them buy throughput rather than insight, and they are cheap to check.
• When you are stuck. After two failed attempts on the same defect, a third attempt from the same context tends to repeat the second. A fresh agent with the symptom and the reproduction, and none of your accumulated theory, is a better use of the next few minutes.