GPT-5.5 Instant

GPT-5.5 Instant is OpenAI's latest Instant model and the default ChatGPT model released on May 5, 2026. It improves factuality, everyday reasoning, image understanding, STEM answers, concision, conversational tone, and personalization over GPT-5.3 Instant. In the API, it is exposed through the chat-latest alias, which points to the latest Instant model used in ChatGPT.