https://openai.com/index/gpt-5-1/
I didn’t see any difference yet but apparently is a new model tested for a while with refined multi-step reasoning and variant models amid competitive pressures before Gemini 3 Pro.
https://x.com/zaidmukaddam/status/1988702113053176258?s=20
https://www.testingcatalog.com/openai-readies-gpt-5-1-thinking-model-ahead-of-gemini-3-pro/