OpenAI Frontier Models: From GPT-4 to GPT-6 Astra
OpenAI began this frontier-model line with GPT-4 in March 2023, then expanded it through cheaper, longer-context, multimodal, and reasoning-focused models. GPT-5 later combined fast and reasoning modes behind a router, while GPT-5.6 moved from a U.S.
53 dated entries · 55 sources · updated Sep 9, 2026
