OnePlus One devices have started receiving OTA updates to CyanogenMod 12.1, based on Android Lollipop v5.1.1. The update is reportedly 645MB in size, and has the build number YOG4PAS1N0. As per reports, the OTA update of CM 12.1 is available for only 2% of OnePlus One users as of now, and will reach out to others in coming weeks.
In case you do not want to wait till the time the OTA update will reach your device, then you can download the update directly from CyanogenMod website and flash it. There is also a smaller version of the update, for users already running on Android Lollipop v5.0. The smaller update is of 304MB in size.
The OTA update notification shows the message, "This update provides critical security fixes for your device to address recently publicized vulnerabilities on Android devices. As this is a sizable update, please allocate 20 minutes for the installation process and ensure your device is fully charged before proceeding with the install."
The CyanogenMod 12.1 update will bring a lot of new features and visual elements to the OnePlus One. The update is also expected to have the Stagefright bug patch, as OnePlus has released the patch for its OxygenOS users recently. The patch was released for both OnePlus One and Two users.
One interesting change reported to be brought by the CM 12.1 update is the activation of the Home button in Chrome. Another thing worth noticing is that the start page of Chrome is set to Bing by default, which is presumably because of the tie-up between Microsoft and Cyanogen.
Earlier, OnePlus One users had received the CM 12 update based on Android Lollipop 5.0 earlier this year. It was also around 600MB in size, like the CM 12.1 one. However, OnePlus had to pause it for some time after encountering some issues, again resumed later.