GPT-5.6 Rumors: OpenAI Stealth Testing New Model in ChatGPT?

OpenAI might be quietly testing a new model, rumored to be GPT-5.6, within ChatGPT for some Pro account holders. Users are noticing differences when selecting GPT-5.5 Pro. Developers and AI testers on X have observed longer response times, with one 3D browser game test taking over 60 minutes, compared to the usual 10-minute window for GPT-5.5 Pro. Another tester noted response times stretching to 20 or 40 minutes for a robotic simulation. Some users claim this new model, labeled GPT-5.6 Pro, can beat Anthropic's Fable 5 on specific 3D generation tasks. Leaked, unverified specs suggest a knowledge cutoff pushed to December 2025 and improved SVG and 3D design generation. The suspected model is reportedly being stealth tested for some Pro accounts, with a possible public launch around June 25. This could significantly change how users interact with advanced AI models.