OpenAI has unveiled a research preview of Codex, its most advanced AI coding assistant integrated into ChatGPT. Powered by codex-1—a specialized version of OpenAI’s GPT-4 model fine-tuned for programming tasks—Codex writes cleaner code, follows instructions more accurately, and can run and debug its code until it works flawlessly.
Running securely in a cloud-based virtual environment, Codex can connect directly to your GitHub account to access your code. It handles a variety of tasks, from writing simple functions and fixing bugs to answering coding questions and running tests—all usually within 30 minutes. Designed to multitask, Codex works quietly in the background, letting you continue coding or browsing without interruption.
Who Can Use Codex?
Starting now, Codex is available to users on ChatGPT Pro, Team, and Enterprise plans. OpenAI plans to provide generous access during this preview phase but will introduce usage limits soon, potentially requiring payment for extra use. In the near future, Codex will also be accessible to ChatGPT Plus and Edu users.
AI coding assistants—often called “co-pilots”—are rapidly gaining traction. Tech giants like Google and Microsoft report that AI already helps generate about 30% of their code. Other players such as Anthropic and Google have launched or upgraded their own AI coding tools recently.
This space is booming. For example, Cursor, an AI coding assistant, is generating roughly $300 million annually and valued at $9 billion. OpenAI also recently acquired Windsurf, a key coding AI company, for $3 billion, signaling their strong ambition to lead this market.
How Does OpenAI Codex Work?
Codex lives in the ChatGPT sidebar. Users can type coding tasks and click “Code,” or ask questions about their code with the “Ask” button. You can also track ongoing tasks and monitor progress.
Josh Tobin, OpenAI’s Research Lead, describes Codex as a “digital coworker” designed to handle tasks that might take human developers hours or even days. OpenAI is already leveraging Codex internally to accelerate repetitive tasks, build new features, and write documentation.
Safety and Limitations
Built with security at its core, Codex refuses requests to create harmful software. It runs in a restricted environment without internet or external API access to minimize misuse, though this also limits some capabilities.
Like all AI coding tools, Codex isn’t flawless—mistakes and bugs can still happen. Microsoft’s research highlights that top AI models struggle with debugging. Nevertheless, this hasn’t dampened enthusiasm or investment in AI coding assistants.
Codex CLI and API Pricing
OpenAI has upgraded Codex CLI—a command-line coding assistant—with a faster, smaller model called o4-mini. This model is also available via the OpenAI API at the following rates:
- $1.50 per 1 million input tokens
- $6.00 per 1 million output tokens
(For context, 1 million tokens roughly equals 750,000 words.)
More Tools Coming to ChatGPT
Codex is just one of several new tools OpenAI is rolling out in ChatGPT, including:
- Sora: AI video generation platform
- Deep Research: AI research assistant
- Driver: AI-powered web browsing assistant
These additions aim to boost ChatGPT’s usefulness, attract more users, and encourage subscriptions—especially with powerful tools like Codex leading the charge.