Microsoft chairman and CEO Satya Nadella’s yearly letter to shareholders contains the sentence everyone quoted, about the company’s apps becoming “a new operating system for work.” The more revealing sentence comes right after it, and almost nobody repeated it: as those apps turn into agents that can be called and orchestrated, Nadella writes, “the system becomes more valuable and more deeply embedded.”

Read next to the rest of the letter, that line explains the strategy. Microsoft is making the AI model the part of its stack you can swap out, and making everything around the model, the memory, the company data and the controls, the part you can’t. The cost of switching does not go away. It moves to the layers Microsoft owns.

What Satya Nadella told Microsoft shareholders about AI agents

The letter opens Microsoft’s annual report and describes how Nadella wants work to change. “Computing has historically been interactive. A user moved from app to app or tool to tool to get something done,” he writes. “With agents, we can now macro delegate and micro steer. In other words, we define a goal and the system works on our behalf, returning for direction and judgment when needed.”

Then comes the line the coverage led with: “We increasingly think of all our apps together as a new operating system for work that transcends traditional software categories to understand user intent and act on it.” Nadella calls the rebuilt Copilot app, which puts chat, Cowork, code and autopilot agents in one place, “the first version of this.”

Times Now summed up the vision as agents handling complex tasks “without needing much human involvement.” The letter is more careful. A person sets the goal and gets called back for judgment, and Nadella insists the change should happen “with people, not to them.” What it leaves open is who decides when judgment is needed. In the design he describes, the system does.

Interchangeable models, embedded everything else

The mechanism sits a few paragraphs later. Microsoft is building “a new multimodel system where the harness—including context, memory, and action space—is separate from the model,” Nadella writes, so that “models become interchangeable.” Its cloud catalog lists more than 11,000 models from OpenAI, Anthropic, Mistral and others, next to Microsoft’s own MAI family.

For a company buying AI, that is a real protection: no single model vendor can hold its workflows hostage. Nadella sells it in exactly those terms. Customers, he writes, should be able to switch out a “generalist” model without losing the “company veteran” expertise built up in their own systems, and should demand that this value accrues “to them, not to an external provider.”

The question is where that company-veteran expertise lives. By the letter’s own account, it runs through Microsoft IQ, the context engine that connects a firm’s emails, documents, meetings and records to its agents. Work IQ alone spans more than 17 exabytes of data. Agent 365, introduced this year, is the “control plane” that lets companies “manage agents the same way they manage people,” with identity, security and a FinOps component to track what the agents spend. The model can be swapped. The memory, the permissions and the meter run on Microsoft’s software.

Why an operating system for work is also a billing model

The letter is frank about the money. Customers “will increasingly measure the cost of tokens against the outcomes they produce,” Nadella writes, calling this the “cost-to-outcome” frontier, and Microsoft is “evolving our business models to reflect the value and usage of our services” across subscriptions, consumption, advertising and hardware. A system that agents work inside is also a system where work gets metered.

The base is already large. Microsoft reported revenue of $331.8 billion for fiscal 2026, and Nadella says Microsoft 365 Copilot passed 30 million paid seats. The company now reports through two new segments, Agents and Infra and Devices and Consumer, which puts the word agents on the same line as Azure.

The first version of the OS for work is still a web app

The product is younger than the sentence. When Nadella repeated the “new OS for work” line in an October 1 post announcing that LinkedIn CEO Ryan Roslansky will leave Microsoft at the end of 2026, Windows Latest took the Copilot app apart. It found that the main program is a 4.99MB rebranded Microsoft Edge launcher backed by a full Chromium build, which loads Microsoft’s Copilot website. Home and Code were still rolling out through Microsoft’s Frontier early-access program, and Autopilot had only just entered private preview.

That does not undercut the plan, which was never about the desktop. Apps built with Code are meant to run on a Copilot Managed Runtime inside a company’s own Microsoft 365 environment, Windows Latest reports. The operating system Nadella describes in the letter, dated October 14, is the layer that holds the context, routes the work and keeps the ledger, and it lives in the cloud tenant, not in the executable.

Under that design, a company could change its AI model in an afternoon. Moving its agents, their permissions and the memory they have built up is another matter, and that is the part Nadella told shareholders becomes “more deeply embedded.”

Tags: microsoft, AI agents, Satya Nadella, Copilot, Agent 365