Q132804879

GPT-4.5 (codenamed "Orion") is a large language model developed by OpenAI as part of the GPT series. Officially released on February 27, 2025, GPT-4.5 is available to users subscribed to the ChatGPT Plus and Pro plans across web, mobile, and desktop platforms. Access was also provided through the OpenAI API and Developer Playground until July 14, 2025. On August 7, 2025, with the release of GPT-5, GPT-4.5 was removed from both the API and ChatGPT users with the Plus and Teams tier, while Pro users are still able to access to GPT-4.5 model under the "Legacy Models" tab.

== Overview == GPT-4.5 was primarily trained using unsupervised learning, which improves its ability to recognize patterns, draw connections, and generate creative insights without reasoning. This method was combined with supervised fine-tuning and reinforcement learning from human feedback. The computational resources needed for training were provided by Microsoft Azure.