GPT 5.5: First Full Retrain Since GPT 4.5, Doubled API Pricing, and the Six Week Cadence Reshaping Frontier AI - April 25, 2026

GPT 5.5: First Full Retrain Since GPT 4.5, Doubled API Pricing, and the Six Week Cadence Reshaping Frontier AI - April 25, 2026 OpenAI's GPT 5.5 launched April 23 as the first ground up retrain since GPT 4.5, topping the Artificial Analysis Intelligence Index at 60 and more than doubling MRCR long context performance to 74 percent at one million tokens. The model arrives just six weeks after GPT 5.4, with API pricing doubled to five dollars and thirty dollars per million tokens. Chris and La...