OpenAI has launched GPT-5.1, the latest upgrade to its flagship model series, designed to make ChatGPT both smarter and more conversational.  The update introduces two distinct variants: “GPT-5.1 Instant,” tuned for everyday use with a warmer tone and improved instruction-following, and “GPT-5.1 Thinking,” built for deeper reasoning tasks with clearer explanations and faster performance on simple queries.

A key new feature is the expanded personality and tone customization. Users can now choose from presets like Professional, Candid and Quirky (in addition to Friendly, Efficient, Nerdy and Cynical) to tailor how ChatGPT responds. OpenAI emphasises that the aim is not only higher accuracy, but an interaction that feels more natural and human-centred. According to the company, “great AI should not only be smart, but also enjoyable to talk to.” 

The rollout begins with paid tiers and will expand soon to API users and free-tier users. By focusing on tone, clarity and usability rather than just raw capability, OpenAI signals a shift in priorities: from model size and benchmarks to user experience and conversational feel.