Thanks to a discovery by Windows Central's Zac Bowden, we have learned that Microsoft once developed an operating system codenamed "Aion," entirely dedicated to web-based applications and agentic AI, with no local application installations or usage. In a video dating back to 2024, Microsoft claimed that "Aion is an example of a web-based agent OS that natively integrates Copilot into the core of the shell." Microsoft aimed to create a lightweight, Edge browser-based OS that runs nearly all of its components in the cloud, as web-based applications have become indistinguishable from many local installations. This means the OS would run Office for the web, including Word, Excel, PowerPoint, and many other applications, as well as third-party web applications.

The OS is centered around Microsoft's Win3 codename, which doesn't share many similarities with the current Windows OS stack, and the Win3 code wouldn't allow Win32 applications to run at all. Since the whole point of this OS would be cloud applications running through the browser, no local apps would be needed, hence no Win32 support. Realistically, this could work on smaller client PCs across offices worldwide as a way to provide most office work functionality with very little computing power, meaning minimal investment in local hardware. While some enterprises might see this as a benefit, storing important files and work, as well as running applications locally, remains very important for many businesses. As a result, the idea didn't make it into any current product that Microsoft offers. Although Microsoft may have foreseen the agentic AI era back in 2024, there wasn't enough demand at the time to launch an operating system like this.