OpenAI Launches GPT-5.1 Upgrade, Adds Deeper Customisation to ChatGPT

OpenAI has begun rolling out GPT-5.1, an upgrade to the GPT-5 model family that introduces new reasoning features, faster performance on simple tasks, and expanded personalisation tools across ChatGPT.

The update 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, which serves as the default chat model, and GPT-5.1 Thinking, which is the company’s advanced reasoning system. Both models now adjust their “thinking time” depending on task complexity.

According to OpenAI, GPT-5.1 Instant is warmer and more conversational, while GPT-5.1 Thinking provides clearer explanations and more persistent reasoning on difficult prompts.

OpenAI said users had made it clear that “great AI should not only be smart, but also enjoyable to talk to,” adding that GPT-5.1 responds more reliably to instructions and maintains tone more consistently across prompts.

The company also introduced expanded tone-setting tools, allowing users to adjust ChatGPT’s style in real time.

Updated preset styles—Default, Professional, Friendly, Candid, Quirky, Efficient, Nerdy, and Cynical—now apply across all chats immediately. 

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

GPT-5.1’s improvements include adaptive reasoning, which lets the model decide when to generate longer internal reasoning traces for complex tasks. OpenAI reported that GPT-5.1 Thinking is roughly twice as fast on the simplest tasks and twice as slow on the most complex ones compared with its predecessor.

The new models will also 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 be released under the GPT-5.1 endpoint with adaptive reasoning enabled. GPT-5 will remain under the legacy models tab for three months “to give people time to compare and adapt,” the company said.

OpenAI described GPT-5.1 as “a step forward in both capability and usability” and said future upgrades to GPT-5 will follow the same naming pattern.