OpenAI says GPT 5.6 is the preferred model for Microsoft 365 Copilot

OpenAI says its GPT 5.6 model will power Microsoft 365 Copilot as the “preferred model,” following reports that Microsoft is increasing use of its own MAI models in Office apps to reduce costs. The disclosure signals the partnership is continuing, even if Microsoft is diversifying the stack behind Word, Excel, PowerPoint, and other productivity tools.

During the launch of GPT 5.6 on July 9, 2026, OpenAI announced that this new model will serve as the "preferred model" for Microsoft 365 Copilot. The software will be integrated across Microsoft's productivity suite, including PowerPoint, Word, Excel, and Cowork.

This announcement follows a Bloomberg report indicating that Microsoft has been integrating its own in-house MAI models into Office applications to reduce operational expenses. While the term "preferred model" remains loosely defined, OpenAI's statement aims to dispel rumors of a rift between the two companies.

Despite the move toward diversifying its AI stack with internal models, the partnership continues. OpenAI emphasized that the collaboration remains focused on expanding the reach of advanced AI to a broader range of organizations and individuals.