Codex Review 2026: OpenAI's Autonomous Coding Agent

What Is Codex?

Codex is OpenAI’s dedicated AI coding agent, available as a macOS app, open-source CLI, and VS Code extension. It operates as an autonomous agent that can read your codebase, plan changes, and execute them across multiple files. Codex is bundled with ChatGPT subscriptions, so existing Plus, Pro, or Team subscribers have access at no extra cost.

What Sets It Apart

Codex stands out by combining a large context window with true agentic capabilities across multiple surfaces. The CLI is open source, so terminal-first developers can inspect the code, contribute to it, and integrate it into automation pipelines, SSH sessions, or CI/CD workflows without adopting a new IDE.

Being bundled with ChatGPT subscriptions removes the “yet another subscription” barrier. Millions of developers already pay for ChatGPT, and getting a full coding agent included lowers the friction of trying agentic AI coding for the first time. The trade-off is that you are tied to OpenAI’s models and pricing tiers rather than choosing your own provider.

As a newer product still maturing, Codex is evolving quickly. Early adopters should expect the feature set and capabilities to shift as OpenAI iterates. The macOS-only desktop app also means Windows and Linux developers are limited to the CLI and VS Code extension for now.

Who It’s For

• Developers already subscribed to ChatGPT Plus, Pro, or Team who want a coding agent at no extra cost
• macOS developers who want a native agentic coding app
• Terminal-first developers who value an open-source CLI
• Teams working on large codebases that benefit from a generous context window
• Developers who prefer a standalone coding agent over editor-embedded AI

Sources

• OpenAI Codex
• Codex CLI on GitHub
• OpenAI Pricing