Microsoft used its Build 2026 developer conference to announce that Excel's Agent Mode can now call on Anthropic's Claude. A frontier AI model is being placed directly inside the spreadsheet used by an estimated 750 million people worldwide. Next to the headlines about new phones and frontier models it looks modest, but for the many people whose daily work is a workbook, it may be the change that lands closest to home.

What You Can Ask Claude to Do Inside Excel

The bigger story here is not the capability itself but where it lives. Until now, getting AI to help with a sheet meant copying the data into a browser chat window and pasting the result back into Excel. With Claude in Agent Mode, that round trip disappears.

Inside Excel, Claude can write formulas and explain what they do, clean up and transform messy data, turn what a sheet shows into written analysis, and assemble repeatable steps to automate routine work. For someone sitting in front of a table, the effort of looking up a function or putting numbers into words is handled on the spot. The distance from "I have data" to "I have an answer I can explain in the meeting" shrinks dramatically.

It is also approachable. Because everything happens inside Excel, a tool most people already open every day, there is almost no new app to learn.

The Microsoft Foundry Platform and Its 11,000-Plus Models

The Excel integration is the doorway into a much larger effort by Microsoft, centered on its enterprise AI platform, Microsoft Foundry. The Foundry model catalog already holds more than 11,000 models.

The lineup is broad: high-performance models from major players such as OpenAI's GPT-5.5, Anthropic's Claude, and Google's Gemini, alongside Microsoft's own MAI family and a large number of open-source and task-specific small models. All of them are reachable through a single Azure endpoint and one billing relationship. In effect, Microsoft takes on the burden of contracting with multiple AI providers separately and adapting to each one's plumbing.

For users, that means more freedom to pick the right model for the job — using a capable model where deep reasoning is needed and a leaner one for simple, high-volume tasks.

How Developers Access It, and the Spread Into Copilot

For developers, Foundry offers Claude Sonnet 4.5, Haiku 4.5, and the higher-end Opus models. All run on Azure's standard authentication and billing, and can be called from SDKs for Python, TypeScript, and C#. If you are already on Azure, there is no separate authentication layer to set up.

The reach goes beyond Excel. Anthropic's models extend to Microsoft 365 Copilot Researcher, which supports document work and research, and to Copilot Studio, where teams build their own custom agents. Behind the easy-to-grasp entry point of the spreadsheet, a much deeper job of wiring AI through all of Microsoft 365 is underway.

The Token-Billing Caveat Worth Noting

For all the convenience, the cost side deserves a clear-eyed look. Microsoft bills Copilot AI usage based on the number of tokens processed. A token is the smallest unit AI uses to handle text, and the more text goes in and out, the higher the bill climbs.

In other words, the more you lean on Claude inside Excel, the more the usage charges stack up. One analyst described the arrangement as "the new gateway drug" — drawing people in with convenience, then billing accordingly once it has become indispensable to their work. Before wiring it into a recurring task such as a regular report, it is worth estimating what the cost will look like.

Summary

Bringing Claude into Excel puts a cutting-edge AI directly inside the most widely used analytical tool on earth. The payoff — being able to question your data in plain language from a familiar place, with almost no learning curve — is significant. For Anthropic, it opens a new point of contact reaching hundreds of millions of workdays just as its IPO preparations advance. For Microsoft, it further strengthens a setup where neither the work nor the billing ever leaves Azure. It may lack flashiness as a headline, but it is a change that takes effect right where everyday office work happens.