OpenAI Rolls Out GPT-5.5 Instant as Default ChatGPT Model, Cutting Hallucinations by Over 50%

OpenAI rolls out GPT-5.5 Instant as ChatGPT's new default model, slashing hallucinations by over 52% on high-stakes topics like medicine and law, while delivering smarter, more personalized responses using past conversations and connected files.

• OpenAI is rolling out GPT-5.5 Instant as the new default model for all ChatGPT users, replacing GPT-5.3 Instant, with significant improvements in accuracy including 52.5% fewer hallucinated claims on high-stakes topics like medicine, law, and finance.
• The updated model delivers more concise, personalized responses by intelligently leveraging context from past chats, connected files, and Gmail, while new 'memory sources' controls allow users to see, edit, or delete what context is being used to shape their answers.
• Enhanced personalization features are rolling out now to Plus and Pro users on the web, with mobile and broader plan support coming soon, and GPT-5.3 Instant will remain available for paid users for three months before being retired.