OpenAI Launches GPT-5.1 with Smarter Reasoning and Real-Time Personalisation Tools

OpenAI has begun rolling out GPT-5.1, the latest update to its GPT-5 model family, introducing faster performance, adaptive reasoning, and expanded personalisation features across ChatGPT.

The upgrade is being released gradually to paid users before reaching free and logged-out users in the coming days.

The release includes two models — GPT-5.1 Instant, the new default chat model, and GPT-5.1 Thinking, a more advanced reasoning system. Both models now dynamically adjust their “thinking time” based on task complexity.

According to OpenAI, GPT-5.1 Instant is “warmer and more conversational,” while GPT-5.1 Thinking offers “clearer explanations and persistent reasoning” for difficult problems.

The company said users have made it clear that “great AI should not only be smart, but also enjoyable to talk to.” GPT-5.1 is designed to maintain tone consistency and respond more reliably to instructions.

It also adds new tone-setting tools, letting users customise ChatGPT’s personality in real time with updated preset styles — including Default, Professional, Friendly, Candid, Quirky, Efficient, Nerdy, and Cynical.

Users can further fine-tune traits such as warmth, brevity, and emoji usage, and ChatGPT may even “proactively offer to update” tone settings based on user behaviour.

OpenAI said GPT-5.1 Thinking is twice as fast on simple tasks and twice as slow on complex ones, reflecting its adaptive reasoning engine.

Both models will be available in the API this week under new endpoints, with GPT-5 remaining accessible for three months to help developers transition.