[OnePlus 8T Guides, News, & Discussion] Nimiskiv:
To start off, This is my first post...

Windows only

Please make a backup of your Phones Storage now before you begin and please read through it all before doing anything.

This is a guide for the INTERNATIONAL version Kebab 2005 but can be replicated for 2003 and 2001 and maybe 2007. recommending to just convert TMO to EU with this Guide ( https://xdaforums.com/t/guide-conve...m-unlock-or-bootloader-unlock-needed.4188491/ ) Then Locally converting to International

To unlock bootloader for TMO here. ( https://xdaforums.com/t/t-mobile-get-unlock-code-to-submit-to-oneplus-for-unlock-token.4201257/ )

2 guides, one for OOS 12 and one for OOS 11.

OOS 11,

1. [Skippable] You will need msm tool to go back to OOS 11 using edl if you have OOS 12 already installed. If on OOS 11 then you can skip the msm tool. [ Still Recommend restoring to stock OOS 11 with msm tool because I don't know if the OOS 11 you might have is the same version used in this guid. If the versions are the same or lower, you can skip the msm tool]

( https://xdaforums.com/t/op8t-oos-kb...l-to-restore-your-device-to-oxygenos.4180837/ )

( TMO = https://xdaforums.com/t/op8t-oos-tmo-kb09cb-unbrick-tool-to-restore-your-device-to-oxygenos.4180981/ )

2. Now you will need to download the latest OOS 11 v.11.0.13.13 from the stable section of the repo, It doesnt matter which is the last version. it cant have C11 or higher, or it will be OOS 12. I will show you OOS 12 in the OOS 12 guide.

( https://xdaforums.com/t/oneplus-8t-rom-ota-oxygen-os-repo-of-oxygen-os-builds.4193183/ )

3. you will also need payload dumper to extract boot.img from payload.bin in the OOS 11 update file from the repo.

( https://www.mediafire.com/file/3ydo1qez61s2qb3/Payload.rar/file )

4. you will need platform tools to flash anything to the device.

( https://developer.android.com/studio/releases/platform-tools )

5. I'm assuming that you have qualcomm drivers already installed for the phone and a working msm tool. if not use the file below and make sure that windows update has the driver and up to date.

( https://www.mediafire.com/file/emfun9l7a9unld5/OnePlus_USB_Drivers_Setup.rar/file ) ]

6. now assuming that all the prerequisites are complete, start by using the msm tool to go back to android 11 also assuming you made the backup as told before.

7. extract payload dumper in a folder and payload.bin from OOS 11 v.11.0.13.13, then drag and drop payload.bin to payload dumper and let it extract. you can close after boot.img is 100% because thats all we need. you can delete the rest. now assuming you went through the setup by skipping it all, go to settings and enable developer mode and turn on OEM then reboot into fastboot. extract platform tools into a folder and open a cmd into that folder then type "fastboot oem unlock" unlock the bootloader [ TMO users need to apply for an unlock.bin, I'm sure you can find a guide on that on XDA ] after the wipe you can go through the setup normally and restore your backup, download the latest magisk from ( https://github.com/topjohnwu/Magisk ) and open the app. click install and select the boot.img assuming you transferred it to your phones downloads folder. transfer the patched magisk boot.img from your phone back to the extracted folder with the original boot.img on your pc ( please keep the original as a failsafe if something happens in this step ) then go ahead and install the latest OOS 11 update in setting and update with local update at the top right of the screen showing a cog. after updating and booting OOS 11, reboot to fastboot and fastboot flash the magisk patched boot.img by just dragging the magisk patched boot.img into cmd, something like below.

fastboot flash boot "c:/usr/???/desktop/onplus8t/payload_dumper/extracted/your_magisk_patched_boot.img"

Now just open the magisk app and follow instructions.

8. you now have root on OOS 11, enjoy

9. Installing Twrp for OOS 11 official is available at ( https://twrp.me/oneplus/oneplus8t.html )

OOS 11 to OOS 12 with or without root. All prerequisites are in the guide above.

1. [Skippable] You will need msm tool to go back to stock OOS 11 using edl if you have latest OOS 12 already installed. If on OOS 11 then you can skip the msm tool.

( https://xdaforums.com/t/op8t-oos-kb...l-to-restore-your-device-to-oxygenos.4180837/ )

( TMO = https://xdaforums.com/t/op8t-oos-tmo-kb09cb-unbrick-tool-to-restore-your-device-to-oxygenos.4180981/ )

2. Now you will need to download the latest OOS 12 so assuming you have a running phone, go to settings and enable developer mode and turn on OEM unlocking, then reboot into fastboot. Extract platform tools into a folder and open a cmd into that folder then type "fastboot oem unlock" unlock the bootloader [ TMO users need to apply for an unlock.bin, I'm sure you can find a guide on that on XDA ] after the wipe you can go through the setup normally and restore your backup, Then download Oxygen Updater and set it up as oneplus 8T then select stable full update not increments. let it download and copy it from you /sdcard/ over to your pc. extract payload dumper in a folder and payload.bin from the full rom, then drag and drop payload.bin to payload dumper and let it extract. you can close after boot.img is 100% because thats all we need. you can delete the rest. download the latest magisk from ( https://github.com/topjohnwu/Magisk ) and open the app. click install and select the boot.img assuming you transferred it to your phones downloads folder. transfer the patched magisk boot.img from your phone back to the extracted folder with the original boot.img on your pc ( please keep the original as a failsafe if something happens in this step ) then go ahead and install the OOS 12 update in setting and about phone and update with local update at the top right of the screen showing a cog. after updating and booting OOS 12, reboot to fastboot and fastboot flash the magisk patched boot.img by just dragging the magisk patched boot.img into the cmd, something like below.

fastboot flash boot "c:/usr/???/desktop/onplus8t/payload_dumper/extracted/your_magisk_patched_boot.img"

Now just open the magisk app and follow instructions.

3. you now have root on OOS 12, enjoy

4. For incremental updates and keep your root just open magisk, uninstall, restore images, DO NOT REBOOT!!!!!. Go update the increment and wait till you get prompted to reboot, DO NOT REBOOT!!!!!. go back into magisk, select install and then OTA updates. run it and reboot using magisk. now you'll keep root and update to the latest. If It shows you an error that you don't have a back up then you need to follow these steps, assuming you already have platform tools. open up an adb and transfer extracted boot.img that I told you to keep safe into /sdcard/ basically where you got the OOS update.rar load these commands ( https://gist.github.com/pexcn/71d7d242c5e805d9346d2dc9db17fb90 ) modified to work with boot.img

1. "adb shell"

2. "su"

3. "SHA1=$(cat $(magisk --path)/.magisk/config | grep SHA1 | cut -d '=' -f 2)"

4. "gzip -9f /sdcard/boot.img"

5. "mkdir /data/magisk_backup_${SHA1}"

6. "mv /sdcard/boot.img.gz /data/magisk_backup_${SHA1}/boot.img.gz"

7. "chmod -R 755 /data/magisk_backup_${SHA1}"

8. "chown -R root.root /data/magisk_backup_${SHA1}"

Then go back and restore again BUT DO NOT REBOOT!!!!!!. Go update the increment and wait till you get prompted to reboot BUT DO NOT REBOOT!!!!! whether its from Oxygen Updaters local Increment update using System Updater apk or systems original updater. go back into magisk, select install and then OTA updates. run it and hit reboot from magisk.

If I made any errors please correct me!

Also there is another way using msm tool to extract the boot.img but I haven't tried and I think I would make a lot or errors trying to. That guide makes this one a lot more easier since all you have to do is extract the boot.img and run it through magisk to get the patched version and just flashing it back in.