GPT-5 ☆

GPT-5 (August 2025) unified the GPT and o-series lines behind a real-time router that picks between fast and deep-reasoning paths per query, with state-of-the-art results in coding (SWE-bench Verified ~74.9% at launch), math and health evaluations. The launch's rockier notes — a briefly mourned GPT-4o personality, router glitches — led to the warmer GPT-5.1 update in November 2025. Parameters and training details: not disclosed.