OnePlus is rolling out new updates to OnePlus 5 and 5T that bring OxygenOS Open Beta 15 to the former and Open Beta 13 to the latter.
We know that OnePlus did promise that Android P beta will arrive on the OnePlus 5 and 5T at some point this year, but no, these latest updates have nothing to do with the new OS, rather, they install optimizations that reduce accidental touches when pocket mode is enabled as well as update the security patch level to July 2018.
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The two devices are receiving the updates over the air, meaning it may take a few days before every unit gets the download notification, so sit tight.