OpenAI rolls out GPT-5.5 Instant as ChatGPT’s new default model

OpenAI announced GPT-5.5 Instant as the new default model in ChatGPT and said the rollout starts today for all users, replacing GPT-5.3 Instant. The company said GPT-5.3 Instant will remain available to paid users for three months through model configuration settings before retirement.

OpenAI described the update as smarter, more accurate, clearer, and more personalized. The company said internal evaluations showed GPT-5.5 Instant produced 52.5% fewer hallucinated claims than GPT-5.3 Instant on high-stakes prompts in areas including medicine, law, and finance, and reduced inaccurate claims by 37.3% on especially challenging conversations users had flagged for factual errors.

OpenAI also said GPT-5.5 Instant improves image analysis, STEM question answering, and decisions about when to use web search. In a separate system card, OpenAI said this is the first Instant model it is treating as high capability in its cybersecurity and biological and chemical preparedness categories, with corresponding safeguards.

Source: https://openai.com/index/gpt-5-5-instant Source: https://openai.com/index/gpt-5-5-instant-system-card