Codex

Codex is OpenAI's coding agent for software engineering tasks such as writing features, fixing bugs, answering questions about a codebase, and proposing reviewable changes. Rather than a single app, Codex is a family of surfaces — a desktop app for macOS and Windows, a terminal CLI, IDE extensions, a cloud web agent, and a security agent — that all run the same underlying agent. It connects to OpenAI's models and works with a ChatGPT account (Plus, Pro, Business, Edu, or Enterprise) or an OpenAI API key. First released in April 2025 as the Codex CLI, it has since expanded into a broad agentic development platform.

What It Is

Codex is an AI coding agent that can read, write, and run code on a developer's behalf, either locally in a sandbox or in a managed cloud environment. The same agent capability is exposed through several products: the Codex app (a desktop command center), the open-source Codex CLI, IDE extensions, Codex Web (the cloud agent at chatgpt.com/codex), and Codex Security. Per OpenAI's docs, a unified "App Server" architecture powers the CLI, the VS Code extension, the web app, the macOS desktop app, and third-party IDE integrations including JetBrains and Xcode, keeping long-running sessions and approval requests consistent across clients. By March 2026 OpenAI reported Codex had grown to more than 2 million weekly active users.

The Codex App

The Codex app is the desktop experience and, per the docs, is positioned as a "command center" for working on multiple Codex threads in parallel. It is available on both macOS and Windows, with most features shared across the two platforms; OpenAI lists Linux as a "get notified" waitlist rather than a current release. The app centers on a project sidebar, active thread view, and review pane. Features the docs describe include multitasking across projects, built-in Git worktree support for isolating parallel changes, an integrated terminal, an in-app browser for rendered pages and browser flows, computer use to drive macOS GUI apps, image generation inside a thread, scheduled automations, and a sidebar that surfaces plans, sources, and generated artifacts. The app can be launched from the CLI via codex app or downloaded directly. A Windows version released in March 2026 added native PowerShell support and a Windows-native agent sandbox.

Codex CLI

The Codex CLI is the open-source, terminal-native surface, built in Rust and licensed under Apache 2.0. Developers install it with npm install -g @openai/codex, brew install --cask codex, or a pre-built binary, then run codex to start an interactive terminal session. Per the docs, it can inspect a repository, edit files, run commands, switch between models and reasoning levels, accept image inputs, run a separate local code-review agent, use subagents to parallelize work, search the web, and launch Codex Cloud tasks from the terminal. The CLI is available on macOS and Linux, with Windows support documented as experimental and best run through WSL.

IDE Extension and Web Surfaces

Beyond the app and CLI, Codex installs as an extension for VS Code, Cursor, and Windsurf, bringing the agent into the editor with shared threads and Auto Context that sync with the desktop app. Codex Web is the cloud-based agent accessible at chatgpt.com/codex, which runs tasks in managed environments rather than on the local machine. Codex also offers integrations for GitHub, Slack, and Linear, plus a Codex SDK, App Server, and GitHub Action for automation. The docs note that Apple deepened the Xcode integration in Xcode 26.3, letting the agent inspect project structure and consult current Apple developer documentation.

Open-Source Core

The Codex CLI repository is hosted at github.com/openai/codex under the Apache License 2.0, with the codebase written primarily in Rust (around 96%). As of the latest release, version 0.130.0 (published May 8, 2026), the project had accumulated roughly 82,500 GitHub stars and about 11,900 forks since its creation in April 2025, across more than 780 releases. The repository documents contributing, installing, and building from source, and OpenAI maintains an open-source fund for ecosystem contributors. Note that the open-source designation applies to the CLI; the desktop app, web agent, and IDE extensions are distributed separately and are not themselves open source.

Codex Security

In March 2026 OpenAI introduced Codex Security, an application-security agent designed to identify and fix software vulnerabilities. It extends the Codex agent toward security review workflows, with documentation covering setup, threat-model tuning, and common questions. OpenAI has described positioning Codex as a broader enterprise agent platform that could eventually handle tasks beyond software development.