By skyforbes 
OpenAI today upgraded GPT-5 to GPT-5.1, the next-generation version of the AI model that powers ChatGPT. There are two versions of GPT-5.1, including Instant and Thinking.
Instant is warmer, more intelligent, and better at following instructions, according to OpenAI, while GPT-5.1 Thinking is easier to understand, faster on simple tasks, and more persistent on complex tasks.
OpenAI says that users can expect a more enjoyable communication experience, with options to more easily customize ChatGPT’s tone. There are new presets for tone, including Professional, Candid, and Quirky. The new presets join the existing Default, Nerdy, Cynical, Friendly (previously Listener), and Efficient (previously Robot) options. ChatGPT can also proactively offer to update preferences during conversations when you ask for a certain tone or style, and there are fine tuning options to adjust how concise, warm, or scannable responses are, along with how often it employs emojis.
By default, GPT-5.1 Instant is warmer and more playful, and more likely to adhere to parameters that you set. GPT-5.1 Thinking is able to adapt thinking time more precisely to the question, and responses are clearer with fewer undefined terms. It’s also warmer and more empathetic than before.