Microsoft is reportedly using its own in-house artificial intelligence models to handle some workloads in Excel and Outlook. According to the report, Microsoft has begun replacing some OpenAI and Anthropic models in Microsoft 365 applications with its MAI models for selected tasks.
Tens of thousands of prompts each week are now being processed by the in-house models, although they still account for only a small portion of Microsoft’s overall AI usage.
A Microsoft spokesperson declined to comment.
Microsoft executives have increasingly emphasized that the next phase of enterprise AI competition will be defined as much by deployment, economics, and operational efficiency as by raw model capability. This message became clearer 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. Among them was 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 report suggests those efforts are beginning to move from strategy into production.
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The development also reinforces a broader theme Microsoft Chief Executive Officer Satya Nadella has articulated publicly in recent months: that long-term AI leadership will depend not only on building powerful models, but also on creating the infrastructure, deployment capabilities, and ecosystems needed to deliver them efficiently.
For Microsoft, every interaction with Copilot consumes computing resources, including inference tokens, GPU capacity, networking, memory, storage, and safety systems. As enterprise adoption grows, even small reductions in per-request costs can translate into substantial operational savings.
The reported changes illustrate an architectural shift that is becoming increasingly common across enterprise AI platforms. Rather than relying exclusively on one foundation model, vendors are assembling portfolios of models optimized for different kinds of work.
Complex reasoning tasks may still require the most capable frontier models from OpenAI or Anthropic. Routine activities, including e-mail assistance, spreadsheet analysis, transcription, summarization, or document generation, can often be handled by smaller, less expensive models without a noticeable difference for end users.
Microsoft continues to move forward with its AI strategy, and the company’s use of internally developed models will affect its overall business. With the company’s emphasis on deployment, economics, and operational efficiency, Microsoft is committed to making AI a key part of its operations, similar to how point in time restore is a key feature in Windows 11.
