Microsoft MAI Models Take Over Everyday Copilot Work in Excel and Outlook

Microsoft MAI models are now doing the everyday AI work inside Excel and Outlook. The company began routing a meaningful share of Copilot prompts to its in-house models this week, Bloomberg reported. The shift steps back from years of heavy reliance on OpenAI and Anthropic.

The workloads are the unglamorous majority of AI use. Summarising an email thread. Drafting a reply. Formatting a spreadsheet. Microsoft says its own models now handle tens of thousands of such prompts each week.

Why Microsoft MAI models change the economics

Money explains most of it. Every prompt sent to an external frontier model costs Microsoft real margin. AI chief Mustafa Suleyman has said the goal is to eventually eliminate spending on Anthropic entirely. In-house models give the company control over cost, performance and integration.

This is not a full divorce. OpenAI’s frontier models will keep powering the hardest tasks, where raw capability still matters. But the routine traffic, which is most traffic, is moving home.

From Build demo to default engine

The MAI family only debuted at the Build conference in June. MAI-Thinking-1 and MAI-Code-1-Flash were the headline releases. Weeks later, they are serving real prompts in the world’s most widely used office suite. GitHub Copilot and Teams are next in line.

The strategic backdrop makes this sharper. Washington is tightening its grip on frontier AI, as FTD covered in our report on the proposed US government stake in OpenAI. A Microsoft that owns its own models is less exposed to both partner pricing and political weather.

The AI platform war has entered its vertical-integration phase. Renting intelligence was always a bridge. Microsoft is now building the other side.

For the wider industry, the signal is blunt. Routine intelligence is becoming a commodity, and commodity work migrates to the cheapest reliable supplier. Frontier labs will keep the premium tier. But the volume business that funds them is exactly what big platform owners can now claw back in-house.

Fact basis: Bloomberg (July 7, 2026), Crypto Briefing, and Windows News coverage of Microsoft 365 Copilot model routing. Product details from Microsoft Build June 2026 announcements.