Of course, the biggest change with this beta is the fact that you're getting updated to Android 8.1 Oreo, but there are also some other changes afoot here.
A new Open Beta build for the OnePlus 5 and 5T has started rolling out.
You will receive the update over the air only if you have already flashed another OxygenOS beta build. After the installation of the update, you will be able to work with the refreshed auto pickup gesture, which helps you to attend to incoming calls just by raising the smartphone. If you are already running the beta software from OnePlus, this update will come through as an OTA, so there's no need to sideload this update. The update also adds support to migrate application data as well as brings optimized full-screen gesture support (OP5T only).
According to the OnePlus blogpost, the Android 8.1 Oreo update on OnePlus 5T will include some new features, including improved gestures for using the phone. It also comes packed with general bug fixes and improvements. Now when it comes to OnePlus' older devices like the OnePlus 3 and OnePlus 3T, there's no official word on when those will be updated, but they will likely be getting Android Oreo at some point. It adds new optimisations in gaming mode as well for a more immersive gaming experience, along with power-saving and pausing adaptive brightness when a user is in this mode. In case you are facing major bugs, you can give the feedback on the OnePlus feedback forums.
Users can download the open beta ROM for their OnePlus 5T by downloading it from the official website. OnePlus says users should wait for sometime while the selected build is updated to their phone.
In addition to this, the Open Beta 4 update rolls out the gaming mode to the OnePlus 5T. Note: Connect to a working Wi-Fi before installing the update, and also back up your data.