OpenAI launches GPT-5.5 Instant as new ChatGPT default

OpenAI has made GPT-5.5 Instant the new default ChatGPT model, replacing GPT-5.3 Instant for all users.

The upgrade is aimed at reducing hallucinations, improving reasoning, and delivering shorter, more concise answers.

GPT-5.5 Instant also adds stronger personalization using past chats, files, and Gmail where available.

OpenAI says the model is available in ChatGPT and via the API as chat-latest.