OpenAI has rolled out a new coding-focused AI model, GPT-5.3-Codex. The company says this is its most capable agentic coding model so far, designed not just to write code, but to handle long, complex tasks that stretch across the entire software workflow. The launch also comes after OpenAI recently introduced a dedicated Codex app for macOS, hinting at a sharper focus on AI agents that work alongside developers rather than just answering prompts. OpenAI’s claim that GPT-5.3-Codex played a role in building itself.
The company further claims that it is a single model that is around 25 per cent faster than its predecessor. That speed boost matters because Codex is meant to run for long periods, handling tasks that involve research, tool usage, debugging, and execution without constantly needing restarts.
OpenAI describes GPT-5.3-Codex as a “frontier model,” a term commonly used in the AI industry for systems operating at the cutting edge of current capabilities. The faster runtime allows the model to take on longer-running jobs, including processes that can stretch beyond a full day.
In its blog post, OpenAI said the Codex team used early versions of the model to debug training runs, manage deployment, and analyse test results.
“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,” OpenAI wrote.
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