OpenAI Releases GPT-5.3-Codex

OpenAI announced the release of GPT-5.3-Codex, its most capable agentic AI coding model to date.

“GPT‑5.3-Codex 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 percent faster,” OpenAI explains. “This enables it to take on long-running tasks that involve research, tool use, and complex execution. Much like a colleague, you can steer and interact with GPT‑5.3-Codex while it’s working, without losing context.”

Notably, GPT-5.3-Codex is the first OpenAI model that was used to create itself: The team used early versions of the model to debug its training, manage its deployment, and diagnose test results and evaluations. And it says the team was “blown away” by how much Codex was able to accelerate its own development.

As with Anthropic Claude Opus 4.6, also released today, GPT-5.3-Codex can be used for more than software coding. OpenAI says it supports all the work in the software lifecycle, including debugging, deploying, monitoring, writing PRDs, editing copy, user research, tests, metrics, and more. It can be used to create and analyze slide decks and spreadsheets, for example.

GPT‑5.3-Codex is available to anyone with a paid ChatGPT plan and is everywhere you can use Codex, including the app, CLI, IDE extension, and on the web. OpenAI says it will enable API access soon as well.