On Monday, OpenAI launched Codex, an agentic coding tool marketed to software developers. Today, OpenAI also launched a new model designed to turbo-charge Codex: GPT-5.3 Codex.
The company says that the model transforms Codex from an agent that can merely “write and review code” to one that can do “nearly anything developers and professionals do on a computer, expanding who can build software and how work gets done.” Having tested its new model against a number of performance benchmarks, OpenAI claims that it can create “highly functional complex games and apps from scratch over the course of days.”
OpenAI says that GPT-5.3 Codex is also 25 percent faster than its previous model (GPT-5.2) and that it was the company’s first model that “was instrumental in creating itself,” meaning that the company’s staff used early versions of the program to debug itself and evaluate how it was performing.
The new model release notably follows hot on the heels of a new agentic coding model released by its competitor, Anthropic. Indeed, OpenAI and Anthropic had originally planned to release their two agentic coding tools at the exact same time: 10 a.m. PST. However, not long before the original release time, Anthropic moved its release date up by 15 minutes, slightly besting OpenAI in the race to publicize the models.
