OpenAI launches GPT-5.3 Codex to transform software development

OpenAI has officially launched a Codex desktop application, named GPT-5.3 Codex, which will strengthen company's position in the fast-growing market for AI-powered coding tools. 

The company, in a blog post, said the model advances both the frontier coding performance of GPT‑5.2-Codex and the reasoning and professional knowledge capabilities of GPT‑5.2, together in one model, which is also 25% faster. This enables it to take on long-running tasks that involve research, tool use, and complex execution. 

"GPT‑5.3 Codex is our first model that was instrumental in creating itself. The Codex team used early versions to debug its own training, manage its own deployment, and diagnose test results and evaluations—our team was blown away by how much Codex was able to accelerate its own development.

"With GPT‑5.3 Codex, Codex goes from an agent that can write and review code to an agent that can do nearly anything developers and professionals can do on a computer. To test the model’s web development and long-running agentic capabilities, we asked GPT‑5.3‑Codex to build us two games: version two of the racing game from the Codex app launch⁠, and a diving game," said OpenAI.

The company further added that using the develop web game skill and preselected, generic follow-up prompts like "fix the bug" or "improve the game", GPT‑5.3-Codex iterated on the games autonomously over millions of tokens. 

How to use GPT-5.3 Codex?

Here's a guide in which Gadinsider has shared steps to use GPT-5.3 Codex:

1. Download the official Codex desktop app from OpenAI's website and install it on your laptop.
2. Once you have installed the desktop app, log in your OpenAI account on the platform.
3. After you're logged in, you can either start a new coding project or bring in an old one.
4. You can ask more than one AI agent to do different things. 
5. The dashboard shows what each agent is doing at the moment.
6. You can look at, change, and test the code that was written before you use it.
7. You can save finished projects on your computer or send them to someone else to work on.

GPT-5.3 Codex availability 

OpenAI said GPT-5.3 Codex is available with paid ChatGPT plans, everywhere you can use Codex: the app, CLI, IDE extension and web. "We are working to safely enable API access soon," said the company, adding that GPT‑5.3 Codex was co-designed for, trained with, and served on NVIDIA GB200 NVL72 systems.