OpenAI has named GPT 5.6 the “preferred model” for Microsoft 365 Copilot, days after a report suggested Microsoft was shifting some of its AI workloads to its own in-house software. OpenAI made the announcement during a launch event on Thursday.
The timing addresses a question that had been building around the two companies for weeks. Bloomberg reported earlier this week that Microsoft was replacing some OpenAI-powered features in Word and Excel with its in-house MAI models to cut costs. That report reignited speculation about whether the partnership, once described as inseparable, was starting to loosen. Microsoft has invested billions of dollars in OpenAI since 2019 and built its Copilot products on top of OpenAI’s models. Any sign of distance between the two companies draws close attention as a result.
How GPT 5.6 fits into Copilot’s model lineup
In a blog post tied to the launch, OpenAI said the new model would support Microsoft users across its productivity suite, 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,” the company wrote. “We’re excited to continue building on that shared commitment.”
OpenAI did not spell out exactly what “preferred model” status entails. The label confirms that its software will keep powering Microsoft’s apps. It also leaves room for Microsoft to run other models, including its own, alongside it rather than instead of it. Neither company has said how Copilot decides which model handles a given task. It also remains unclear whether users will eventually be able to choose between models directly, or whether that choice will stay hidden inside Microsoft’s infrastructure.
The cost-cutting report still stands
Nothing about the announcement contradicts the earlier Bloomberg reporting. That story never claimed ChatGPT’s software would stop powering Microsoft’s products. It only said Microsoft was leaning more on its own models to reduce costs. The “preferred model” framing does not undo that shift. It confirms that OpenAI’s software remains part of the mix, not that it is the only option running under the hood.
Microsoft and OpenAI have built one of the most closely watched partnerships in the AI industry. Microsoft has folded OpenAI’s models into Windows, Office, and Azure over the past several years. In turn, OpenAI has relied heavily on Microsoft’s cloud infrastructure to train and run its systems. As Microsoft develops MAI further, the two companies appear to be settling into an arrangement where GPT 5.6 supplies a leading model for Copilot rather than the only one available. Neither side has described the relationship as ending, but both are now visibly hedging their bets on a single AI supplier. For Copilot users, the practical impact of Thursday’s announcement is limited for now: the apps keep working the same way, just with a newer model doing more of the work behind the scenes.