https://wccftech.com/oneplus-5-5ts-android-pie-beta-rolling-out/

Considering that OnePlus was a part of the Android Pie beta program, it was inevitable that a stable Pie update would make its way to all of their supported devices. The OnePlus 6T launched with Pie out of the box while the OnePlus 6 received its update a while ago. The previous generation were promised pie and today, the OnePlus 5 and OnePlus 5T are getting OxygenOS Open Beta 22 and 22 respectively based on Android 9 Pie.

A few weeks ago, OnePlus had released Android Pie-based HydrogenOS as a public beta, but that was only applicable for Chinese users of the OnePlus 5 and OnePlus 5T. OxygenOS is OnePlus’ international software which is what all non-Chinese variants run.  Android Pie brings a large number of changes and new features to the OnePlus 5 and OnePlus 5T. You get the brand new UI design, updated gestures (for the OnePlus 5T only), Adaptive Battery, Adaptive Brightness, and the likes. The full changelog is below: