OpenAI releases GPT-5.5 Instant, the next-generation default model for ChatGPT.

OpenAI has officially launched GPT-5.5 Instant, replacing GPT-5.3 Instant as the default model for ChatGPT. The model focuses on being more accurate, concise, and intuitive: the illusion rate in the medical/legal/financial fields has decreased by 52.5%, and math competition scores have significantly improved; replies are shorter and more natural, reducing formatting. Plus/Pro users can access historical conversations and files for personalized answers, and all consumer versions will add a "Memory Source" feature for users to view and manage.