[OnePlus 8T Guides, News, & Discussion] Mpolo87:
DO NOT FOLLOW THIS GUIDE IF YOU HAVE ANDROID 12

Visit this thread for more information

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CAVEAT

I've only tested this on my device running Android 11 (KB2005 / KB05AA), but it should be universally helpful as it's using your own boot.img so there's no need to find a matching package for your variant and os version.

CREDIT

The steps were buried across a few threads, I'm posting this so it'll be easier for others to find the information. All credit goes to xb360, FullOfHell, and TheUnkn0wn.

INFO​

The basic rundown is:

Use the semi-broken TWRP package to give yourself temporary su access through adb.

Extract the boot.img your phone is currently using to your pc.

Reboot to OxygenOS, copy over the boot.img you just extracted and then use Magisk to patch it.

Copy the boot.img back to your pc and use adb to temporarily boot your phone with it, giving you root access until reboot.

Use your temporary root access to allow Magisk to patch your internal as-yet unmodified boot.img to give you permanent root.

There seems to be some confusion in the thread, I'll try to clear up what's happening and why:

The primary issue at hand is that you can't root your device without already having root privileges, for security reasons. Without a custom recovery like TWRP, there are a few more steps than usual (but mostly simple stuff).​

Because we don't flash anything with this guide, it shouldn't cause any permanent bootloops if you use the wrong boot.img, if you get stuck in one just power cycle your phone. ​

Updating with OTAs should be the same process as the other guides here.​

Because of changes in Android, devices that launched with Android 10 and above will not allow you to modify the system partition, even with root. This is not a fault of this rooting method.​

Prerequisites:

ADB and Fastboot installed.​

An unlocked bootloader and USB debugging enabled.​

Android 11. (Android 12 introduced problems with this method, per other users. See link at top of page)​

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STEPS:​

1. Connect your phone to your pc and boot it into fastboot mode. You can leave it connected throughout this guide.

2. On your computer open a terminal/cmd prompt. Set the directory (on your pc) you want to work from, I'm using the desktop:

for Windows, type cd C:\Users\Yourname\Desktop​

for Mac, type cd desktop or cd /Users/yourname/Desktop​

Spoiler content hidden.

3. Next, use the terminal to check which A/B partition is active on your phone:

fastboot getvar all

a. You'll find it on this line: (bootloader) current-slot:a/b​

b. For simplicity I'll be referring to boot_a.img throughout the guide, make sure to use boot_b.img if that's the one marked as active on your device. ​

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4. Download the semi-broken TWRP package to your desktop. We'll be using it to extract a copy of your active boot_a.img. It will give you temporary su access via adb, but there won't be a gui. Only boot from it, DO NOT FLASH IT:

fastboot boot recovery.img
adb shell
dd if=/dev/block/by-name/boot_a of=/sdcard/boot_a.img
exit
adb pull /sdcard/boot_a.img boot_a.img
adb reboot

5. Copy the extracted boot_a.img file to a user accessible area of your phone, like your downloads folder.

6. Install the latest Magisk Canary apk on your phone. Open it and:

a. Select the Install option.​

b. Use Select and Patch a File on boot_a.img​

7. Copy the patched magisk_patched_a.img file back to your computer. In terminal, type adb reboot bootloader to get back to fastboot mode.

8. Temporarily boot with the patched image that corresponds to the active partition, DO NOT FLASH IT:

fastboot boot magisk_patched_a.img

Spoiler content hidden.

9. By booting with the patched image, you now have temporary root access. To make it permanent open Magisk:

a. Select the Install option.​

b. Use Direct Install (Recommended) to root your internal boot.img​

10. Reboot and verify it worked.