# Codex CLI

The second coding agent. Heavy implementation legs and adversarial review passes run here while the main session reviews and verifies.

## What it is
A second agentic coding CLI, wired into the same sessions as the primary one. It takes the heavy self-contained implementation legs, runs long autonomous build loops, and — just as important — runs the adversarial pass: before anything is called done, it gets the claim and the evidence and tries to falsify them.

## Why
A second, independent executor does two things one agent can't: it works in parallel on heavy legs, and it disagrees. Its adversarial pass on my done claims catches the plausible-but-wrong finish my own confidence lets through.

## How Andrew uses it
Two standing uses: delegate substantial coding legs so the main session stays free to review, and fire a report-only devil's-advocate pass before every completion claim. Diagnosis prompts carry an explicit 'report only, do not edit any files' fence, and the diff gets checked before reading its output.

## How to get it
Install the Codex CLI from npm (`npm i -g @openai/codex`), authenticate, and hand it self-contained tasks with a written spec. The division of labor matters more than the vendor.

_Distilled from: method/tools/codex.md_
