Microsoft starts pulling OpenAI and Anthropic out of its own apps

Bloomberg reported this morning that Microsoft has begun swapping OpenAI and Anthropic models for its own MAI models inside Excel and Outlook, with tens of thousands of prompts a week now running on MAI. Source.

Read that number carefully. Tens of thousands of prompts a week is not a demo. It's not a pilot in a locked-down internal tenant. It's flagship consumer and enterprise surfaces, the apps that print money, quietly rerouting the actual inference to models Microsoft built itself. This is a different animal from the $2.5B Frontier deployment unit they announced days ago (more on that below). Frontier is about selling change management. This is Microsoft eating its own dependency.

Why it matters: Microsoft is the largest distributor of frontier AI on the planet, and it just showed you that being the distributor beats being the model. When you own Excel, you don't need the best model. You need a good-enough model you control end to end, so you keep the margin, the telemetry, and the roadmap. OpenAI got paid billions and got dogfooded out of the product in the same fiscal year.

If you're building on OpenAI or Anthropic, the lesson isn't "panic." It's "audit your vendor risk like Microsoft just did." The distributors above you in the stack are all running this same math right now. Salesforce, Notion, GitHub, every SaaS company with enough volume to justify a fine-tune is asking whether they keep paying per-token to a lab or train a house model on their own workflow data. Your model choice should be a config value, not a load-bearing wall. If ripping out Anthropic for a cheaper open-weight model would take you two weeks of refactoring, you built it wrong. Abstract the provider now, while it's cheap to do.

And watch the second-order effect. As Microsoft, Meta, and Google all backfill with in-house models, the labs lose their easiest distribution and get pushed toward selling directly. Which is exactly why Anthropic shipped Claude Science and enterprise admin controls this week. They can feel the platform layer closing.