Went GA on February 25, 2026, powered by GPT-5.5 with sub-agents that auto-delegate (Explore, Task, Code Review, Plan), background cloud delegation, and an autopilot mode for autonomous execution.
From Wikipedia
Codex is an AI coding agent developed by OpenAI for software engineering tasks such as writing code and fixing bugs, released in April 2025 as Codex CLI. Codex is available through ChatGPT's web app, the Codex CLI, a desktop app for Windows and macOS, and several IDE integrations. In March 2026, OpenAI introduced Codex Security, an application-security agent designed to identify and fix software vulnerabilities.