United Kingdom, Nov. 14 -- OpenAI has unveiled GPT-5.1, a major upgrade to its flagship model lineup that boosts reasoning, clarity, and customisation.

The update refreshes both of ChatGPT's primary models: GPT-5.1 Instant, now the default option for most users, and GPT-5.1 Thinking, the system's advanced reasoning model.

Instant has been redesigned to be "warmer, more conversational," and far better at following instructions.

GPT-5.1 also introduces adaptive reasoning, allowing the model to momentarily "think" before answering harder questions - yielding sharper performance in coding and math benchmarks like AIME 2025 and Codeforces.

GPT-5.1 Thinking receives deeper changes, as the model now varies its chain-of-thought duration based...