OpenAI names GPT 5.6 as preferred model for Microsoft Copilot

OpenAI launched GPT 5.6 on Thursday and announced that the model would become the preferred model powering Microsoft’s 365 Copilot. OpenAI said GPT 5.6 will support Microsoft users across the company’s productivity suite, including Word, Excel, PowerPoint, and Cowork — the same set of apps at the center of recent reporting on Microsoft’s AI sourcing decisions.

The announcement follows Bloomberg’s report earlier this week that Microsoft was replacing some of OpenAI’s software with its own in-house models, known as MAI, in an effort to cut costs. Those in-house models were being used to power apps like Word and Excel, according to Bloomberg. The report reignited a question that has followed the two companies — once seemingly inseparable — as they’ve sent mixed signals about the state of their partnership: whether they were drifting apart. That framing has persisted even as both companies have continued to publicly describe the relationship as intact, leaving outside observers to parse each new product announcement for signs of distance.

OpenAI used the GPT 5.6 launch to push back on that narrative, writing in a blog post: “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.”

What being a preferred model actually means isn’t entirely clear, beyond the fact that OpenAI’s software will continue to power Microsoft’s apps. It was never reported that ChatGPT would stop powering those apps — only that Microsoft was relying increasingly on its own software to reduce costs. The new preferred model disclosure does not appear to negate that earlier reporting from Bloomberg, since a “preferred” designation for one product line doesn’t preclude Microsoft from continuing to route other workloads to its own MAI models where it makes financial sense.

Why it matters

OpenAI’s announcement of GPT 5.6 as the preferred model for Microsoft Copilot 365 is an attempt to counter reports that the two companies are drifting apart as Microsoft increasingly relies on its own in-house models to cut costs.