This is the most important part of this write-up.
You cannot downgrade via a standard "Over-the-Air" (OTA) update. The downgrade process requires using a local installation package (MSM Tool or OxygenOS ZIP) that wipes your device completely.
Android 11 uses a classic partition layout; Android 12+ uses a super partition (logical volumes for system, product, vendor). Direct flashing of Android 11 images fails due to size mismatches. downgrade oneplus 9 to android 11 exclusive
Solution: The super partition must be erased and recreated using fastboot delete-logical-partition commands before flashing raw images.
Downgrading the OnePlus 9 to Android 11 is technically demanding, requires an unlocked bootloader, and permanently sacrifices SafetyNet and Widevine L1. However, for users prioritizing: This is the most important part of this write-up
This exclusive downgrade path remains the only solution. Not recommended for daily drivers unless you have a spare device and Qualcomm EDL cables.
Last tested: OnePlus 9 LE2115_11_C.15 (Android 11) downgraded from LE2115_13_F.75 (Android 13). This exclusive downgrade path remains the only solution
There are generally two ways to revert the OnePlus 9 (Codename: Lemonade) back to Android 11, depending on your technical comfort level.