GPT-5.6: preferred model in Microsoft 365 Copilot for Word, Excel

GPT-5.6 will be the preferred model powering Microsoft 365 Copilot, covering core apps including Word, Excel, PowerPoint, Chat and Cowork. OpenAI announced the designation during the launch of GPT 5.6, saying the model will support Microsoft users across those products.

What did OpenAI announce?

GPT-5.6 is now the "preferred model" for Microsoft 365 Copilot, and it will power features across Word, Excel, PowerPoint, Chat and Cowork. The primary source describing the rollout says GPT-5.6 delivers "stronger AI capabilities" across those apps to enable faster, higher-quality work, and TechCrunch notes OpenAI made the preferred-model claim during GPT 5.6's launch.

How does this fit with Microsoft’s recent work on in-house models?

OpenAI’s preferred-model disclosure sits alongside reporting that Microsoft has been using its own MAI models more often in Office apps. Bloomberg reported Microsoft was replacing some of OpenAI’s software with in-house models called MAI to reduce costs, and TechCrunch says that reporting raised questions about whether the two companies were drifting apart. TechCrunch also points out that the new "preferred model" statement does not explicitly reverse the earlier reporting that Microsoft had been relying increasingly on its own models.

What does "preferred model" actually mean?

The phrase "preferred model" is not defined in the provided sources, and TechCrunch notes the term's practical implications are unclear beyond signaling that OpenAI's software will continue to power Microsoft’s apps. OpenAI framed the relationship positively in its announcement, writing, "Our partnership with Microsoft has always been about bringing the benefits of advanced AI to more individuals and organizations, and we’re excited to continue building on that shared commitment." Beyond that quote, the sources do not detail contractual terms, traffic shares, or cost arrangements.

Why it matters

The designation keeps OpenAI's model explicitly tied to Microsoft’s productivity suite at a time when Microsoft is also developing its own MAI models. That dual track—Microsoft building MAI while continuing to use OpenAI models—affects enterprise customers and product road maps. For Microsoft customers, the near-term effect is continuity: GPT-5.6 will power Copilot capabilities across Word, Excel, PowerPoint, Chat and Cowork. For both companies, the relationship mix will influence who controls model updates, where costs land, and which provider shapes long-term feature development.

What to watch

Watch for clarity from Microsoft on how it will split workload between MAI and OpenAI models and for any product-level notices showing which model powers specific Copilot features. OpenAI’s future announcements about GPT-5.6 deployments and Microsoft statements about MAI adoption will be the concrete signals that determine whether "preferred model" reflects a strategic lock-in or a branding choice alongside an evolving multi-model stack.