When Microsoft releases new test builds of Windows, there are usually a handful of features that are announced but only actually enabled for a small subset of testers. Sometimes it’s because the company is A/B testing a couple of different versions of the same thing or because Microsoft wants to roll out major changes to a few users before rolling them out to everyone.

Users normally have little control over whether new features actually appear in their Windows beta installs, but Microsoft has internal software called StagingTool that its own developers can use to switch things on and off themselves. And now StagingTool has leaked to the public, thanks to a “bug bash” the company is running this week to find and fix problems before the next big batch of new Windows features releases this fall.