[Google Pixel 6 Pro] gururoop:
Caution: I originally wrote this guide when it was necessary to disable verity and verification before flashing patched boot.img. Now Magisk has overcome this requirement and some users have reportedly flashed updates without disabling verification and verity and did not have to wipe their phones, but request everyone, who have verification and verity disabled and using this guide, make sure you backup all the data and post your results here (I suggest backing up data anyway for everyone).

Following is a guide to update Pixel 6 Pro (perhaps all Pixel devices) every month, without wiping and retaining root. I tested it on my Pixel 6 Pro from 12.0.0 (SD1A.210817.015.A4, Oct 2021) to 12.0.0 (SD1A.210817.036, Nov 2021). There is no reason that it should not work on subsequent monthly patches, but just take the backups to be sure.

1) Download the latest factory image for your device and platform-tools from the official Google site and extract them in one folder.

2) Extract the boot.img from image-raven-xxxxxxx.zip which was extracted from the image in the above step and patch it in Magisk Manager (latest canary build from https://github.com/topjohnwu/Magisk) on your phone and copy it back to the folder where you extracted the factory image and platform-tools. Rename the copied file to magisk_patched.img

3) Open flash-all.bat in notepad, add --skip-reboot and remove -w from the fastboot update line. Also add the following lines after the fastboot update line to flash the Magisk patched boot.img automatically:

fastboot reboot-bootloader

ping -n 5 127.0.0.1 >nul

fastboot flash boot magisk_patched.img

fastboot reboot

After editing, the edited part of your flash-all.bat should look something like this:

fastboot --skip-reboot update [****image_name****]
fastboot reboot-bootloader
ping -n 5 127.0.0.1 >nul
fastboot flash boot magisk_patched.img
fastboot reboot

echo Press any key to exit...

Note: [****image_name****] is just a placeholder and needs to be the name of zip file which was originally there in flash-all.bat, do not change that. Be careful to rename the Magisk patched boot.img to magisk_patched.img or in the alternative make appropriate modifications in the flash-all.bat

4) Open command prompt and go the folder where you extracted factory image and platform-tools. Type the following commands:

adb reboot bootloader

flash-all.bat

Your device should be upgraded to the latest factory image, while retaining root, without wiping data.

Update 1: I updated from 12.0.0 (SD1A.210817.036, Nov 2021) to 12.0.0 (SD1A.210817.037, Nov 2021) successfully using my method, without loosing data and root.

Update 2: I updated from 12.0.0 (SD1A.210817.037, Nov 2021) to 12.0.0 (SQ1D.211205.016.A1, Dec 2021) successfully using my method, without loosing data and root.

Update 3: I updated from 12.0.0 (SQ1D.211205.016.A1, Dec 2021) to 12.0.0 (SQ1D.220105.007, Jan 2022) successfully using my method, without loosing data and root.

Update 4: I updated from 12.0.0 (SQ1D.220105.007, Jan 2022) to 12.0.0 (SQ1D.220205.003, Feb 2022) successfully using my method, without loosing data and root.

Update 5: I updated from 12.0.0 (SQ1D.220205.003, Feb 2022) to Android 12L DP 3 successfully using my method, without loosing data and root.

Update 6: I updated from Android 12L DP 3 to Android 13 DP successfully using my method, without loosing data and root.