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by OpenAI · reviewed July 25, 2026
OpenAI's open-source terminal agent. Runs locally in a sandbox, with cloud delegation for longer tasks.
Codex CLI is an open-source coding agent that runs in your terminal and executes work in a sandbox on your machine. It reads instructions from an AGENTS.md file, supports approval modes ranging from ask-every-time to fully autonomous within the sandbox, and can hand longer jobs to Codex cloud. There are companion IDE extensions and a GitHub code-review integration.
OpenAI models (GPT-5 family / codex variants)
Teams already on ChatGPT plans who want a terminal agent with a clear sandbox story.
Reviewed July 25, 2026. Pricing changes often — check the official page before deciding.
Every tool here reads a project instruction file, and every one of them does better work when that file is accurate. The free Foundations track covers writing one; the Agent Operating Kit is the templates already written.