Microsoft starts replacing OpenAI and Anthropic with its own MAI models in Excel and Outlook

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Bloomberg reported July 7 that Microsoft has begun swapping OpenAI and Anthropic models for its internally built MAI models inside products like Excel and Outlook, with tens of thousands of prompts now completed weekly on MAI. This is a distinct, material step beyond the $2.5B Frontier deployment unit announced earlier: Microsoft is now dogfooding its own frontier models in flagship apps. For builders, it signals the largest AI distributor is de-risking away from its partners at the product layer.