GPT-5.3-Codex (Generative Pre-trained Transformer 5.3 Codex) is a Large language model (LLM) released by OpenAI on February 5, 2026.
It is made as a competitor to Claude's Opus 4.6, focusing on code generation, speed and the ability to search repositories, run terminal commands and at the same time, debug code. In technical benchmarks, it is reported that GPT-5.3 Codex is 25% faster than Opus 4.6.
GPT-5.3 Codex is available in the 'Codex' app.