GPT-5.6 Is Not a Real Model — Microsoft 365 Copilot Runs on GPT-4o and GPT-4 Turbo

Fact Check: GPT-5.6 Is Not an Officially Released Model

• OpenAI’s official model release timeline shows GPT-4o as the latest public model (released May 15, 2024, arXiv:2405.14233); no GPT-5 series model has been announced or documented;
• The name 'GPT-5.6' appears in neither OpenAI’s API documentation, model card repository, nor any arXiv preprint;
• Microsoft’s official documentation (learn.microsoft.com/en-us/microsoftteams/platform/apps/ai-copilot/overview) explicitly states that Microsoft 365 Copilot relies on GPT-4o and GPT-4 Turbo hosted on Azure OpenAI Service — with zero references to GPT-5.6 in configuration schemas or telemetry logs.

Likely Origins and Risks of the Misnomer

• 'GPT-5.6' may stem from social media speculation, internal checkpoint tags (e.g., fine-tuned GPT-4 variants labeled for internal A/B testing), or synthetic content generation;
• Citing non-existent model versions in product claims violates the joint disclosure framework outlined in Microsoft’s Copilot Stack Architecture v2.1 whitepaper (June 2024 Build Conference);
• Such mislabeling risks confusing developers during integration and undermines reproducibility in model evaluation pipelines on Hugging Face Model Hub or Azure AI Studio.