While many people are enjoying — or lamenting — the upgrade to Android 10, there are some out there that are just as interested in the final source code. With each major release of Android, a huge code drop is made to the Android Open Source Project (AOSP) with everything a developer needs to build the latest version of the OS. As of this morning, the code is now fully available and ready for consumption.
A post to the Android Building group by Bill Yi confirms that the upload completed sometime around 1:20 AM PDT, including the base Android 10 code and the device-specific configuration and kernels for each Pixel phone from the original up through the 3a. It's also noted that the development team released a reference android10-dev branch and a reference for Android Mainline.
To those that will be downloading the full source code, may the download go quickly. And for those first timers out there, now is a good time to practice your binge watching skills.