OpenAI's new coding model GPT-5.3-Codex helped build itself during training and deployment

OpenAI has released GPT-5.3-Codex, its latest coding model. The company says it combines GPT-5.2-Codex's coding capabilities with GPT-5.2's reasoning and knowledge, while running 25 percent faster. Most notably, on Terminal-Bench 2.0 it beats the just-released Opus 4.6 by 12 percentage points—a significant gap by current AI standards—while using fewer tokens than its predecessors. On OSWorld, an agentic computer-use benchmark, it scores 64.7 percent versus 38.2 percent for GPT-5.2-Codex. On GDPval, OpenAI's benchmark for knowledge-work tasks across 44 occupations, it matches GPT-5.2.

OpenAI also claims the model played a role in its own development, with the team using early versions to find bugs during training, manage deployment, and evaluate results. The company says the team was "blown away by how much Codex was able to accelerate its own development."

GPT-5.3-Codex is now available to paying ChatGPT users in the Codex app, CLI, IDE extension, and on the web. API access will follow. OpenAI has classified the model as its first with a "High" cybersecurity risk rating, though the company says this is precautionary, as there's no definitive proof such a classification is necessary.