The new functionality in ChatGPT 5.1 includes:
1️⃣ GPT-5.1 Instant: The most used model, now warmer by default and more conversational, often surprising people with its playfulness while remaining clear and useful.
2️⃣ GPT-5.1 Thinking: An advanced reasoning model that is easier to understand and faster on simple tasks, more persistent on complex ones.
3️⃣ Tone Control: More intuitive and effective controls to better match the tone you want in responses.
Let me know your thoughts, and if this was helpful.