OnePlus smartphones generally have three streams of software - Closed Beta, Open Beta, and Stable. Closed Betas are available for a limited number of testers, while the Open Betas are published on OnePlus' forums for anyone to install. Both of these builds are used for testing to iron out bugs and other issues, along with introducing new features. Finally, Stable builds are a culmination of all of the features and bug fixes after the Closed and Open Betas have run their course. OnePlus is now rolling out OxygenOS Beta 8 for the OnePlus 7 and OnePlus 7 Pro, which features an early version of a much-anticipated One-Handed Mode. You can check out the full changelog below.

OxygenOS Open Beta 8 Changelog

System

  • Optimized the mistouches when the phone was in pocket
  • Fixed the display issue on the uninstalling page
  • Updated Android security patch to 2019.12
  • Improved system stability and fixed general bugs

Camera

  • Fixed the crash issue while opening the App
  • Fixed the black screen issue

I've already gotten the update via OTA, but if you don't have it yet, you should soon. We also have full OTA installation zips so that you can install the update manually. You can either flash it via TWRP or go to your Settings, then System Update, then tap the overflow menu and select "Local upgrade". The zip file must be in the root of your phone's storage. You can check out some screenshots from the latest OxygenOS Open Beta of one-handed mode below. As mentioned in the above changelog, there are a number of bug fixes, along with the December 2019 security patches too.

OnePlus 7

Download OxygenOS Open Beta 8: Full OTA zip

OnePlus 7 XDA Forums

OnePlus 7 Pro

Download OxygenOS Open Beta 8: Full OTA zip

OnePlus 7 Pro XDA Forums

Thanks to XDA Senior Member Some_Random_Username for the tip!