What happened
OpenAI announced GPT-5.5 Instant on May 5, 2026. It is the new default model in ChatGPT, replacing GPT-5.3 Instant. The model is also available in the API as chat-latest. GPT-5.3 Instant remains available to paid users for three months through model settings before it is retired.
What changed
OpenAI lists three main upgrades. The model is more accurate, with 52.5 percent fewer hallucinated claims on high-stakes prompts in medicine, law, and finance. Replies are tighter and more conversational, with fewer extra emojis. And the model uses past chats, files, and connected Gmail data more carefully when personalization helps.
Enhanced personalization is rolling out first to Plus and Pro users on the web and is coming to mobile and other plans over the following weeks.
Why it matters
GPT-5.5 Instant is the everyday model for most ChatGPT users. Quality jumps in the default tier reach more people than improvements to flagship reasoning models. Less hallucination on legal, medical, and financial prompts also makes the default model safer for casual research.
MintedBrain take
Most ChatGPT users do not pick a model on purpose. They use whatever loads. With GPT-5.5 Instant as the default, day-to-day answers should feel sharper and more concise. API users on chat-latest will see the change automatically.
Discussion
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