https://www.theverge.com/2017/10/25/16546686/android-oreo-developer-preview-8-1-release

Google has released the latest developer preview of Android Oreo. Version 8.1 will be released in December, but Android Beta Program users can test it now. Anyone can also download and install the system images with an unlocked bootloader. The Beta Program issues these updates over the air, although the developer preview is only compatible with the Nexus 5X, Nexus 6P, Pixel C, Pixel, Pixel XL, Pixel 2, and Pixel 2 XL.

Obviously, you're well aware of Android Oreo's new features. The new version builds on some of those iterations. It tests another change to notifications in which apps can only make a notification sound alert once per second. But more importantly, it contains an Easter egg: the Android Oreo logo now looks like an actual cookie.