Many of us were initially expecting to hear Microsoft talk about Windows Core OS, or at least the rumored "Lite" operating system, earlier this year during Build 2019, but that unfortunately ended up not happening. However, manufacturers like Lenovo have hinted at some new version of Windows coming in the future.
For those who don't know, Windows Core OS is supposed to be a new version of Windows that can adapt more easily to any kind of screen, thanks in part to a new infrastructure for the Shell, which separates it from the system itself. This means that Microsoft can create different Windows experiences for different form factors such as Lenovo's foldable ThinkPad, while using the same core components as a base.
Yesterday, Microsoft released Windows 10 build 18917 to the Fast Ring, and while it included some welcome improvements, perhaps the most interesting change went unnoticed. Twitter user Albacore has discovered that with this build, the company has started implementing some work towards the separation of the Shell from the rest of Windows. There's now a Shell Update Agent, which is meant to be able to update the Shell on demand.
Other tidbits found by Albacore include the name "Undocked Shell", and the user notes that the word "undocked" was also used around the time Microsoft separated Search and Cortana. There are also hints that, theoretically, the whole Shell could be packaged in a .appx file, like any other Store app. However, Albacore notes that, for now, the publisher ID for the update agent is used for non-Store apps. The user also mentions that the Action Center seems to be one of the components that Windows tries to source from a Shell package, if available.
On a different note, Albacore's digging also apparently revealed that Microsoft could be working on a new syncing mechanism for settings, which is "more advanced" and supports syncing things such as your File Explorer configuration. Possibly related, pinned items in the File Explorer are now saved in a new format.
Of course, all of these changes are under the hood, and it's not something general users will notice during normal operation. With almost a full year to go until Windows 10 20H1 becomes public, we're bound to see more work being done in this regard over the coming months.