Microsoft Corp., looking to reduce AI costs, is starting to replace OpenAI and Anthropic with its own models in software products like Excel and Outlook.

Tens of thousands of AI prompts in the widely used spreadsheet and email applications are now being completed each week with Microsoft’s internally built MAI models, according to a person familiar with the work. Previously Excel and Outlook relied more heavily on models from OpenAI and Anthropic, said the person, who was granted anonymity to discuss an internal matter.

The scale of MAI model usage in Microsoft’s workplace products hasn’t been previously reported. A Microsoft spokesperson declined to comment.

While still accounting for a small share of overall AI usage, the move shows Microsoft is making progress in its efforts to build competitive artificial intelligence models at a lower cost. In June, AI model chief Mustafa Suleyman said the company was trying to reduce spending on Anthropic by using more MAI models.

Microsoft uses massive quantities of AI tokens — the unit of consumption for AI computing — in products like its workplace assistant Copilot. For now, the company gets a lot of that technology at a discount owing to its long-standing partnership with OpenAI. But the clock is ticking on that arrangement, and Suleyman’s team is working to make sure Microsoft isn’t left paying whatever the leading AI labs decide to charge.

The company announced seven new AI models at its annual Build conference for developers in June, including one it says can match the coding abilities of a prior-generation Anthropic model that remains very popular — Opus 4.6 — at a reduced cost. “We pay a lot of money to Anthropic — so our goal is to reduce and ultimately eliminate that cost,” Suleyman said at the time.

Microsoft’s MAI models are also available for use within GitHub Copilot, the company’s service for AI-assisted software development. Suleyman has said that a Microsoft-built model for transcription will start being used with the Teams videoconference apps and other products in the coming months.

(With assistance from Matt Day.)

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