OpenAI has begun rolling out GPT 5.1, the newest upgrade to the GPT 5 model family, introducing improved reasoning, faster performance on simpler tasks, and deeper personalisation across ChatGPT. The update is reaching paid users first and will expand to free users over the coming days.
GPT 5.1 comes in two versions. GPT 5.1 Instant is now the default chat model and is designed to feel warmer, more conversational, and faster. GPT 5.1 Thinking is the advanced reasoning model built for complex instructions. Both adjust their thinking time depending on task difficulty.
OpenAI said ChatGPT now responds more reliably to instructions and stays consistent with tone and personality across conversations. The company added that users want AI systems that feel smarter and more enjoyable to talk to, and GPT 5.1 is designed to reflect that.
A major addition is the new tone-setting interface. ChatGPT now lets users switch between eight preset styles — Default, Professional, Friendly, Candid, Quirky, Efficient, Nerdy, and Cynical — with changes applied instantly across all chats. Users can also fine-tune sliders for warmth, conciseness, and emoji frequency. ChatGPT may even suggest tone adjustments based on user behaviour.
GPT 5.1 also brings adaptive reasoning. The model now decides automatically when to generate longer reasoning traces for sophisticated prompts. OpenAI says the Thinking version is twice as fast as before on simple tasks and slower only on highly complex ones where deeper reasoning is required.
Both GPT 5.1 models will be available in the API later this week. GPT 5.1 Instant will appear as gpt 5.1 chat latest, while GPT 5.1 Thinking will launch under the GPT 5.1 endpoint with adaptive reasoning turned on. GPT 5 will stay under legacy models for three months so developers can compare before switching.
OpenAI described GPT 5.1 as a meaningful step toward more capable and more natural AI experiences, with future updates following the same naming pattern across the GPT 5 family.
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