Earlier this week, Bloomberg reported that Microsoft was replacing some of OpenAI’s software with its own in-house models in an effort to cut costs. Those in-house models, known as MAI, were increasingly being used to power apps like Word and Excel. The story raised an increasingly common question about the two companies, which were once seemingly inseparable and have recently sent mixed signals about the status of their relationship: Were Microsoft and OpenAI drifting apart? Now, OpenAI is attempting to put any insinuations of such a break to rest. During OpenAI’s launch of GPT 5.6 on Thursday, the company announced that it would become the “preferred model” powering Microsoft’s 365 Copilot.
OpenAI Confirms GPT 5.6 as the Preferred Model for Microsoft 365 Copilot
OpenAI noted in a blog post published Thursday that GPT 5.6 would support Microsoft users across the company’s suite of productivity apps, including Word, Excel, PowerPoint, and Cowork. “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,” OpenAI wrote.
What being a “preferred model” actually means isn’t entirely clear, other than that OpenAI’s software will continue to power Microsoft’s apps. That said, it was never reported that OpenAI’s software would stop powering Microsoft’s apps — merely that Microsoft was relying increasingly on its own software in an effort to reduce costs. The new “preferred model” disclosure doesn’t appear to negate that previous reporting.
What Does “Preferred Model” Mean for Microsoft 365 Users?
The designation of GPT 5.6 as the preferred model for Microsoft 365 Copilot signals that OpenAI’s latest large language model will be the primary AI engine driving productivity features in Word, Excel, PowerPoint, and the newer collaboration platform Cowork. For end users, this means the AI-assisted writing, data analysis, presentation generation, and document summarization features across these apps will be powered by GPT 5.6’s capabilities.
However, the term “preferred” rather than “exclusive” leaves room for Microsoft to continue integrating its own MAI models alongside GPT 5.6. This dual-model approach aligns with Microsoft’s broader cost optimization strategy while still leveraging OpenAI’s frontier model for marquee features where performance is paramount.
The Context Behind the OpenAI-Microsoft Partnership
The relationship between OpenAI and Microsoft has been under scrutiny in recent months. Microsoft’s reported push to rely more heavily on its own MAI models for some productivity tasks was widely interpreted as a sign of growing distance between the two companies. By securing the “preferred model” status for GPT 5.6 inside Microsoft 365 Copilot, OpenAI is making a public statement about the continued centrality of its technology to Microsoft’s AI roadmap.
Yet the two realities can coexist. Microsoft can reduce its cost base by routing simpler tasks through its own MAI models while still depending on GPT 5.6 for the most demanding or user-facing AI interactions in Copilot. The preferred model designation confirms that OpenAI will remain a key — even if no longer exclusive — provider for one of the world’s largest enterprise AI deployments.
What This Means for Professionals Using Microsoft 365 Copilot
For professionals in the US, UK, Australia, and Canada who rely on Microsoft 365 Copilot, the announcement means that the AI features they use daily will continue to draw from OpenAI’s most advanced publicly available model. GPT 5.6 brings improvements in reasoning, context handling, and instruction following that translate directly into more accurate document drafting, cleaner spreadsheet formulas, and more coherent presentation generation.
If you are a current Microsoft 365 Copilot user, no immediate action is required — the transition to GPT 5.6 as the preferred model is handled by Microsoft on the backend. The practical benefit is that you should experience improved response quality and reliability across Word, Excel, PowerPoint, and Cowork without any change to your workflow or subscription.
