Updating OnePlus One from 11S to 12S. Downloads Required Android 5.0.2 Cyanogen OS 12S for OnePlus One Before we start. Ensure the OnePlus One is fully charged atleast 80% Verify that the phone is running on stock recovery and stock ROM. Back up if required, I did not back-up as all the data on my phone is stored on cloud. But the data was not affected by the Upgrade. Initial Steps to update Android 5.0.2 based Cyanogen OS 12S ROM on OnePlus One using stock recovery. Download the official CM12S ROM for OnePlus One “cm-12.0-YNG1TAS0YL-bacon-signed.zip” Copy the downloaded file to the root folder of your phone’s internal storage. ( 0/ Drive) Flashing the OTA via Stock Cyanogen recovery Power off your device. Reboot into stock recovery – Press and hold Power and Volume Down and release them when the OnePlus logo appears on screen. Choose Apply Update. Select Choose from internal storage. Select 0/ which is the internal storage. Choose the file cm-12.0-YNG