GPT-5.3 Codex is blowing minds in early 2026! In this video, we put OpenAI’s fastest, most interactive coding AI to the test and compare it against Claude Opus 4.6—one of the deepest reasoning, long-horizon planning models out there.
OpenAI on Wednesday released GPT-5.3-Codex, which the company calls its most capable coding agent to date, in an announcement timed to land at the exact same moment Anthropic unveiled its own flagship model upgrade, Claude Opus 4.6. The synchronized launches mark the opening salvo in what industry observers are calling the AI coding wars — a high-stakes battle to capture the enterprise software development market.