GPT-5.6 is now the preferred model in Microsoft 365 Copilot

Microsoft has flipped the switch: GPT-5.6 is now the preferred model powering Copilot across the full 365 suite. Word, Excel, PowerPoint, Chat, and the newer Cowork feature all route through it by default, according to the announcement from OpenAI's blog.

This isn't a flashy standalone product launch. It's an infrastructure swap, the kind of change most users won't consciously notice but will feel in the output. OpenAI frames the upgrade around speed and quality — faster responses, sharper formatting, better handling of the messy, half-formed requests people actually type into a chat box at 4pm on a Friday.

The timing matters more than the spec sheet. Copilot lives inside the tools hundreds of millions of people already use for spreadsheets, slide decks, and email threads. Every model bump OpenAI ships to Microsoft reaches that install base almost instantly, without anyone downloading anything or reading a changelog. That's a very different distribution story than shipping a new ChatGPT tier and hoping people notice.

It also underlines how tightly OpenAI's roadmap and Microsoft's product calendar are now stitched together. Whatever generation of GPT ships next essentially becomes Copilot's next generation too, on a lag measured in weeks rather than years. For a lot of office workers, GPT-5.6 will be the most powerful model they interact with all year — and most of them won't know its name.