OpenAI released GPT-5.3-Codex, a return to code-specialized fine-tuning after years of generalist flagships. The agentic coding model hit 56.8% on SWE-bench Pro and 77.3% on Terminal-Bench 2.0, running about 25% faster on tool-driven tasks.

The name was a deliberate callback to the original 2021 Codex, but the model was a different beast: agent-optimized rather than a simple code completion engine. It reached GA in Copilot on February 9 across Pro, Business, and Enterprise tiers.

OpenAI later designated GPT-5.3-Codex its first long-term-support model, guaranteeing it for Business and Enterprise Copilot users through February 2027.