Codex

0:24 Codex is OpenAI's AI coding agent: it reads a repository, writes and runs code, and opens pull requests, from the ChatGPT desktop app, the open-source Codex CLI, an IDE extension, the web and the ChatGPT mobile app. As of Nov 6, 2026 it is included in ChatGPT Free, Go ($8), Plus ($20), Pro (from $100), Business, Edu and Enterprise, or usable with an API key, and its default model is GPT-6.1 Sol. Limits depend on the plan and model: Plus gets an estimated 15 to 160 local messages every five hours on GPT-6.1 Sol, and Pro has no five-hour limit.

Codex is the natural pick for ChatGPT subscribers and anyone who wants OpenAI's newest coding models. Pick Claude Code for Anthropic's models, GitHub Copilot if your team works in GitHub and wants several companies' models on one bill, or Cursor for a full editor built around agents. The Best AI Coding Agent guide compares them.

Learn more: Codex on chatgpt.vi.ki

Quick facts

Plans and limits

Source: Codex pricing, read Nov 6, 2026. Cloud tasks use more of the allowance than local messages, and weekly limits can apply on top. Past the allowance you can buy credits: GPT-6.1 Sol costs 50 credits per million input tokens and 250 per million output tokens, and fast and Ultrafast modes cost 2x and 6x on purchased credits.

Features

0:39 Codex CLI. An agent in your terminal, open source under Apache-2.0 with about 133,000 GitHub stars on Nov 6, 2026. Install it on macOS or Linux with curl -fsSL https://chatgpt.com/codex/install.sh | sh, on Windows with irm https://chatgpt.com/codex/install.ps1 | iex in PowerShell, or with npm install -g @openai/codex or brew install --cask codex, then sign in with ChatGPT. Version 0.167.0 on Nov 6, 2026 added an agent command center. In OpenAI's Oct 5, 2026 video the CLI showed a full-screen interface, a voice mode that started three tasks at once, and an agent list to filter, search and fork tasks into a new worktree.

The ChatGPT desktop app. Since Jul 2026 Codex lives in one ChatGPT app for macOS and Windows beside Chat and Work, with a built-in browser and computer use; this app replaced OpenAI's ChatGPT Atlas browser (TechCrunch, Jul 9, 2026).

3:42 Codex Cloud. Tasks run in a sandbox in the cloud, each preloaded with your repository, so several can run in parallel while you do something else.

IDE extension. Codex in your editor, sharing sessions with the CLI and cloud.

Models

GPT-6.1 Sol has been Codex's default since Sep 29, 2026, with a 500,000-token context window in Codex. GPT-6.1 Terra joined the CLI's catalog on Oct 29, 2026. Both are offered on Plus, Pro, Business, Enterprise and Edu, and neither is in ChatGPT's Chat. GPT-6 Luna is the small model Free and Go get. GPT-5.5 left Codex for ChatGPT sign-ins on Oct 14, 2026 (pricing page).

History

• Apr 16, 2025: Codex CLI released as open source.
• May 16, 2025: Codex launched in ChatGPT as a cloud agent in research preview, running codex-1, a version of o3 (InfoQ, May 2025).
• Feb 4, 2026: Codex became a coding agent on GitHub through Agent HQ.
• Jul 2026: Codex merged into the new ChatGPT desktop app.
• Aug 28, 2026: OpenAI said it would stop supplying models to Cursor after SpaceX bought it (CNBC, Aug 29, 2026).
• Sep 29, 2026: GPT-6.1 Sol became the default.

Codex vs the alternatives

• Claude Code: Anthropic's agent on the same surfaces (terminal, IDE, desktop, web). Claude Code needs a paid plan from $20, while Codex works on ChatGPT Free. Pick by which company's models suit your work.
• GitHub Copilot: one subscription for models from several companies inside GitHub; it can run Codex itself as an agent through Agent HQ.
• Cursor: a full editor; after Nov 12, 2026 OpenAI's models are due to leave it.
• Gemini CLI: Google's open-source terminal agent for Gemini models.

Frequently asked questions

Is Codex free? Yes. As of Nov 6, 2026 Codex is included in ChatGPT Free and Go, with GPT-6 Luna in the desktop app subject to rollout; the bigger GPT-6.1 models need Plus or above.

How do I install the Codex CLI? On macOS or Linux run curl -fsSL https://chatgpt.com/codex/install.sh | sh, or use npm install -g @openai/codex or Homebrew's brew install --cask codex, then run codex and sign in with ChatGPT.

What are the Codex usage limits? On Plus they are estimated at 15 to 160 local messages every five hours on GPT-6.1 Sol and 35 to 285 on GPT-6.1 Terra, with weekly limits possible. Pro has no five-hour limit.

Is Codex open source? The Codex CLI is, under the Apache-2.0 license on GitHub. The models and the cloud service are not.

Codex or Claude Code? Both are coding agents for the terminal, IDE, desktop and cloud. Codex runs OpenAI's GPT models and is included even in ChatGPT Free; Claude Code runs Anthropic's Claude models and starts with Claude Pro at $20 a month.

Sources

• Pricing, OpenAI Codex docs, read Nov 6, 2026
• Codex docs, OpenAI, read Nov 6, 2026
• Changelog, OpenAI Codex docs, read Nov 6, 2026
• Codex CLI, OpenAI Codex docs, read Nov 6, 2026
• openai/codex, GitHub, read Nov 6, 2026
• OpenAI Launches Codex, InfoQ, May 2025
• OpenAI is shutting down Atlas, but its AI browser ambitions are still growing, TechCrunch, Jul 9, 2026
• Introducing the Codex app, OpenAI, Feb 2, 2026 (video)
• Meet the New Codex CLI, OpenAI, Oct 5, 2026 (video)
• Claude and Codex are now available in public preview on GitHub, GitHub Changelog, Feb 4, 2026