Microsoft is reportedly using its own in-house artificial intelligence models to handle some workloads in Excel and Outlook, according to Bloomberg. The company has begun replacing some OpenAI and Anthropic models in Microsoft 365 applications with its MAI models for selected tasks, with tens of thousands of prompts each week now processed by the in-house models, though they still account for only a small portion of Microsoft's overall AI usage. A Microsoft spokesperson declined to comment. At Microsoft's annual Build developer conference in June, Microsoft AI Chief Executive Officer Mustafa Suleyman introduced seven new MAI models spanning reasoning, coding, transcription, image generation, and other workloads, including MAI-Code-1, which Microsoft said delivers coding performance comparable to Anthropic's earlier Opus 4.6 model at lower operating cost. Suleyman said Microsoft wanted to reduce, and ultimately eliminate, spending on Anthropic models. The development reinforces a broader theme articulated by Microsoft Chief Executive Officer Satya Nadella: that long-term AI leadership will depend on creating infrastructure, deployment capabilities, and ecosystems to deliver models efficiently.