Microsoft has been moving more of Copilot’s agent mode back onto OpenAI models in recent months, because it can run them at no extra cost and OpenAI has caught up with Anthropic on quality, according to Aaron Holmes at The Information. Charles Lamanna, who now runs Office and Copilot, persuaded CEO Satya Nadella to add Anthropic’s models in 2025 after demos showed they were better at Excel math and PowerPoint design. Lamanna’s team also built a router that sends each task to the cheapest model that can handle it, and most Office users leave Copilot on that automatic setting, which has slowed the growth of a bill to Anthropic that is still on pace to top $2 billion a year.
