We’ve seen a number of OEMs such as OnePlus, Nokia, Sony, and others say they’re currently working on the Android 8.0 update, so it’s somewhat of a race to see which one is able to push out an OTA first. It was recently leaked that OnePlus has started a closed beta test of Android Oreo for the OnePlus 3/3T with an alleged goal of rolling out an open beta by the end of this month. But today, OnePlus 3T users who want to get their hands on Android Oreo can do so through a leaked internal build of HydrogenOS that has been shared on our forums.
OnePlus manages two different versions of their software depending on your location. The company installs OxygenOS on most of their devices, but if your phone originated in China (or maybe you just manually flashed it yourself) then it will have HydrogenOS installed on it. For the most part, these two look and function mostly the same but there are some subtle differences (such as no Google apps and some pre-installed Chinese apps on HydrogenOS).
Apparently, a leaked version of a closed beta test for HydrogenOS based on Android 8.0 Oreo has been posted online and can try it out right now. XDA Junior Member JacobCeng has uploaded a version to our OnePlus 3T forum and this was mirrored by XDA Member standbyme91 so there are multiple sources you can download it from.
Remember though, this is the Chinese version of the ROM so while you can set the language to English, it will not be the same OxygenOS that you are used to. Plus, there are no Google apps pre-installed. However, you can install the Google Play Store from the pre-installed Market App.