GPT-5.5 is an AI model released by OpenAI on Apr 23 2026, 49 days after GPT-5.4-Pro. It is the 32th tracked release from OpenAI out of 33 total.
On published benchmarks, it scores 93.6% on GPQA Diamond (graduate-level science reasoning).
About OpenAI: Creators of ChatGPT and the GPT series of models. Pioneered large-scale language model research.