In all probability, OnePlus will soon release the Android 7.0 Nougat based OxygenOS 4.0 for its newest device OnePlus 3T. Though not yet confirmed the update officially, a leaked version of OxygenOS 4.0.0 confirms this. As there is no official announcement about the update yet, full changelogs are not available now, but it comes with December Android security patches.
Based on the various reports, we are assuming that OnePlus will release the OxygenOS 4.0.0 (Android 7.0 Nougat) update for OnePlus 3T in the next week. If your device is running on the latest OxygenOS 3.5.4, you can install the OxygenOS 4.0.0 OTA update. Other users need to update their handset to OxygenOS 3.5.4 before applying the OxygenOS 4.0.0 OTA update.
Tech-savvy owners, who want to early access Android 7.0 Nougat on their OnePlus 3T, download the OxygenOS 4.0.0 (leaked version) and sideload/install it manually. However, we recommend all users to wait for the official update.
Before start installing OxygenOS 4.0 update, your OnePlus 3T should running on OxygenOS 3.5.4. Also, ensure that your device is fully charged.
2. Boot your phone into recovery (Power off, press Power + Volume Down buttons).
3. In recovery, select ‘Apply Update’ and navigate to OTA zip file (you have saved earlier).
4. It will start flashing the firmware. Once the process completed, reboot your phone and enjoy!
You can also apply the update via ADB sideload. If you have ADB and Fastboot setup on your computer, then check out the guide below.
1. Enable ‘USB debugging’ on your phone.
2. Save the downloaded OxygenOS 4.0.0 OTA update zip file to the folder where the ADB is installed.
3. Turn Off the phone and boot into recovery mode.
4. Choose Install from ADB Sideload, then connect your phone to your computer.
5. Inside the ADB folder, open a command window and issue the below command:
6. You device should be listed. If not, install proper fastboot driver for your device and follow.
7. Now, issue the below command to sideload the OxygenOS 4.0.0 OTA update:
adb sideload file name.zip
Once done reboot your phone and enjoy Android 7.0 Nougat (Source – XDA)