Codex (OpenAI)
Japanese Codex（OpenAI）
Codex is OpenAI's coding agent: you describe a task in plain words, and it reads code, edits files and runs commands. Because it can change files on your computer, decide first how much it is allowed to do.
Codex is not just an AI you chat with; it is an AI that carries out the work you ask for. You open a work folder and write something like "make a program that tidies up this spreadsheet", and it writes code, runs commands and then shows you what it changed. It is like a repair worker you hand a key to: inside the rooms you allow, they work on their own, but you decide which rooms they may enter. You can pick it inside the ChatGPT desktop app, and there is also Codex CLI for the terminal and an editor extension.
Watch out Start in "Ask for approval" mode, which asks each time before editing files outside the work folder or using the internet. "Full access" can reach every file on your computer and the internet without limits. Keep customer lists and password files out of the work folder, and copy the folder before you start so you can go back easily.
Source: ChatGPT desktop app | ChatGPT Learn · Permissions | ChatGPT Learn · Pricing | ChatGPT Learn · Codex CLI | ChatGPT Learn · Custom instructions with AGENTS.md | ChatGPT Learn · GitHub - openai/codex: Lightweight coding agent that runs in your terminal (checked 2026-10-26)