Overview
OpenAI’s cloud-based software engineering agent that runs tasks in parallel sandboxes, plus a CLI version, all powered by Codex/GPT models.
Details
Codex is OpenAI’s autonomous software engineering agent, relaunched in 2025 as a cloud-hosted system that takes tasks (often from ChatGPT, GitHub, or its own UI), spins up isolated containers per task, and produces code changes and pull requests. It also ships as Codex CLI (open source) and IDE extensions, all powered by GPT-5/Codex-tuned models with reasoning. Codex supports parallel task execution, environment configuration, secret management, and integration with GitHub for PR review and updates. Not to be confused with the original 2021 Codex model.