OpenAI releases GPT-5.5 Instant, a new default model for ChatGPT

OpenAI is making GPT-5.5 Instant ChatGPT’s new default, replacing GPT-5.3 Instant.

The model is designed to reduce hallucinations in sensitive topics and perform better on math and multimodal benchmarks.

It can also use context from past chats, files, and Gmail to deliver more personalized responses.

The rollout starts with Plus and Pro web users, with broader availability planned; developers can use it via the API as chat-latest.