Microsoft Starts Swapping External AI for Its Own MAI Models in Excel

Microsoft has begun gradually replacing OpenAI and Anthropic models with its in-house MAI (Microsoft AI) models in select Microsoft 365 features such as Excel and Outlook. Bloomberg reported on July 7, 2026, citing people familiar with the matter, that tens of thousands of AI prompts per week are already being handled by MAI models in Excel and Outlook (Bloomberg). This is not a full migration but a partial switch limited to certain tasks, and OpenAI and Anthropic models reportedly remain dominant across overall Copilot traffic.