OnePlus has now confirmed that Cyanogen OS 13, which is based on Android 6.0 Marshmallow, will begin rolling out to the OnePlus One via an over-the-air update imminently. Speaking on OnePlus' forums, a OnePlus representative announced the rollout, stating:
Our friends over at Cyanogen have informed us that CM 13.0 (ZNH0EAS26M) based on Marshmallow will drop starting tomorrow. The rollout will be staged so only some of you (random) will get it at first, and as always, patience is appreciated.
While CyanogenMod is referenced rather than Cyanogen OS, some users have already begun receiving the OTA update, confirming that it is indeed CyanogenOS 13.
Regardless, OnePlus One owners should begin seeing the update arrive over the coming days. Once updated, you'll have access to all of Android 6.0 Marshmallow's goodies, which include Doze mode, granular app permissions and more.
Once you've received your update, be sure to chime in with your thoughts in the comments and on our forums!
Thanks for the tip, Leo!