On 27 February 2025 OpenAI released a research preview of GPT-4.5. It called it its largest and best GPT model for chat so far, and said it does not think before it responds. It contrasted that with reasoning models such as o1. Pro users could pick it that day.
The official name is GPT-4.5. It sits on the unsupervised-learning line (GPT-3.5, GPT-4, GPT-4.5).
Intelligence Age Gulf wrote this note on 30 September 2026.
Source. OpenAI, Introducing GPT-4.5, 27 February 2025.