When OnePlus released the OxygenOS Open Betas 13 and 11 for the OnePlus 5 and 5T, respectively, The company snuck in a little surprise in the form of support for Project Treble. That's a pretty big perk since Treble makes updates (and ROMs) easier for developers by further separating hardware from software when it comes to updating Android. Now that feature appears to have silently made its way to the OnePlus 5 and 5T with the recent Oxygen OS 5.1.5 update.
It can be a bit tough to keep track of these version numbers across time, since OnePlus mixes and matches them across hardware lines, and the same version can have different features and monthly security patches between devices. 5.1.5 originally landed for the Oneplus 6 back in May, and this latest update — though it shares a version number — doesn't really have much to do with it.
In this case, OxygenOs 5.1.5 for the OnePlus 5/5T was a deceptively small update that we didn't originally cover, as the changelog only stated updating Android to the August security patches, and a minor tweak to PIN security on the lockscreen:
Updated Android security patch to 2018.8
Confirm PIN without tapping √ to unlock the phone (Settings -> Security & lock screen -> Screen lock -> PIN)
Bit of a snore, right? Turns out, the update also includes Treble support.
Update changelog/size for the 5T (left), positive Treble Check results on 5.1.5 (right).
We've only confirmed for ourselves the addition of Treble support is present in this update for the OnePlus 5T, but there are other accounts that OnePlus 5 also has the feature in this update. Notably, OnePlus previously stated that none of its older devices, including the OnePlus 5 and 5T, would be getting Treble. A/B partition support is still not present, though — not that it's really necessary, in my opinion.
We knew that Treble was eventually going to hit the stable branch for both handsets, as it was introduced in the Open Betas for each at the beginning of July. At that time, OnePlus was cognizant enough of the feature to make sure it was it in the changelog. For whatever reason, it appears to have escaped notice this time.
Whatever the motivation, the 5.1.5 update for the OnePlus 5 and 5T is definitely one you shouldn't miss, two-line changelog or not. The update is rolling out now, though OnePlus does typically stagger the deployment in case of unanticipated bugs. Downloads for this version haven't been posted just yet, but you can pull down the update manually a bit early via Oxygen Updater over on the Play Store.