[OnePlus 6T  Guides, News, & Discussion] Dark Nightmare:
Note: Firmware flashing procedure is exactly the same for all firmware versions for conversions.

Local Updating using: 9.0.11 is safe

This is a basic write up to convert your bootloader unlocked T-Moilbe OnePlus 6T to the International Version firmware via fastboot flashable firmware files.

Contents:

-Disclaimer

-Full Device Backup - Precautionary - Optional, but Recommended.

-Firmware Conversion Process

-Update after conversion

-Rom Sources

-MSMDownloadTool

-FAQ's

-Additional/Optional Tools

-Credits

Disclaimer:

Like any other form of modding, there are risk involved, we have a near flawless option to recovery by use of the MSMDownload linked at the end of this post, but like with any form of modification, you are solely responsible for what is done to your device and you accept all risk involved, should something go wrong, for the most part, recovery is fairly simply, no matter how bad we screw up, thanks to OP.

Instructions to a full device backup:

1. Download the zip below and extract it to it's own folder

2. Run the backup.bat script

3. It will backup all partitions on your device, including your efs.

4. zip all of the image files and store it somewhere safe.

Backup: https://androidfilehost.com/?fid=11410963190603855581

Steps to convert from stock T-Mobile firmware to Global firmware:

FLASHING STEPS

Requirements:

1. Bootloader Unlocked T-Mobile OP 6T

Unlock Processs Can Be Found Here: https://support.oneplus.com/app/ans...-bootloader-for-oneplus-6t-(t-mobile-version)

2. OOS Stock ROM of your choice: all necessary zip files are included in the rom file, Not the TMOUS branded ROM. (Get the fastboot flashable full rom here: https://xdaforums.com/oneplus-6t/how-to/rom-stock-fastboot-roms-oneplus-6t-t3862516)

3. PC/MAC/LINUX

Flashing Process

1.. Whichever full rom zip you choose, extract its contents. (In my case I used the 9.0.5 full zip)

[IMG="Full Rom"]https://xdaforums.com/attachment.php?attachmentid=4641203&stc=1&d=1542066690[/IMG]

2. In each zip file you'll find images.zip as well as others_flashall.zip, extract both of them into the same folder/directory as the rest of the original zip file.

(Optional, download the modded flash-all-partitions-fastboot.bat file at the end of the thread, it includes the reboot command to auto reboot when done flashing)

Attached Below is also a flash-all-partitions-fastboot.sh script for Mac OS users (Note this script will not wipe your device, so if you need to wipe, run the ./fastboot -w command in fastboot manually)

All bat files, images and adb files should all be in the exact same folder, no subfolder(s)

[IMG="Additional Zips"]https://xdaforums.com/attachment.php?attachmentid=4640301&stc=1&d=1541972819[/IMG]

3. Now boot into fastboot using either the vol+/vol- and power key combo or via adb using the following adb command

adb reboot bootloader

.

4. Once in fastboot run the bat file called flash-all-partitions-fastboot.bat

[IMG="flash all"]https://xdaforums.com/attachment.php?attachmentid=4641272&stc=1&d=1542074248[/IMG]9

5. When asked, I would advise typing 'Y' for yes to format the device. (wipe only if you're converting for the first time)

The sparse header error is completely normal.

6. Upon completion, the script should pause and say press enter to continue, it will not reboot your device...

WAIT UNTIL NOTHING ELSE IS HAPPENING AND ITS NO LONGER FLASHING ANY FILES

At this point, hit power and reboot.

Note: Modded fastboot flashing script attached at the end with the reboot command included, also attached is a script for MAC users, mac script will not wipe your device, wipe manually if you need to using

./fastboot -w

B]

All done!

Update After Conversion (You can also update using the conversion process with the new fastboot files)

Use this if you'd like to convert and relock your bootloader or you've locked your bootloader or simply prefer this method.

1. Download the Full Official Rom from here, not the incremental update, the Full ROM only and copy it to the root of your device: HERE

2. Go to settings > system > system updates > tap settings in top right and choose local upgrade or you can use twrp

3. a) if using local upgrade, choose the ROM zip from the list and install, it will install and give you the option to reboot when complete.

b) if using twrp, boot into recovery, choose install zip and select the full rom file and flash, then follow the steps below

The following steps are for users who have/want root or a modified device or used twrp to install the ROM, device will not boot without the following steps if you installed using twrp:

4. Flash twrp installer HERE

5. Reboot back to TWRP

6. Flash Magisk (if you don't won't boot, you only need this step if your system was rooted/modified in any way) Magisk Here

Or you can skip the additional steps and simply do a factory reset.

NOTE: After using the local upgrade option, you can relock your bootloader if you choose to remain stock, enabling widevine L1 for HD videos, as well as a certified play store device.

You can continue with a locked bootloader using the local upgrade option, but be wary that you should confirm we can local upgrade prior to attempting an update. OTA updates will not show, but future local full ROM updates are working as of: current 9.0.11.

relock using fastboot oem lock command, this will wipe your device.

ROM Sources

Mauronofrio's Thread

T-Mobile 9.0 FULL Fastboot ROM

Saythis' International Firmware 9.0.6​

Full ROMs directly from OnePlus for Updating Purposes ONLY

Recovery - MSMDownloadTool

If for some WEIRD reason you brick, have a HW mismatch, etc, or you just can't boot go to this thread -> MSMDownloadTool - T-Mobile 9.0

OPTIONAL Steps

Root is available via two Options below:

- OnePlus Rooter

- Manual Root Using a Patched Boot Image

Automated Process

Luckily There are devs looking to make things simpler:

For [MENTION=1314742]Dameon87[/MENTION]'s automated tool to carry out this process, go to the thread below:

https://xdaforums.com/oneplus-6t/how-to/rom-oxygen-os-9-0-6-fastboot-windows-t3870170

WARNINGS!

-Advisable you disable automatic updates in developer options upon boot if it is enabled.

-Do not attempt to update using the OTA files, so far we've had one softbrick due to it and said user was unable to boot into fastboot to attempt any kind of recovery.

-ALSO DO NOT FLASH WITHOUT THE FILES IN THE FOLDER, IF YOU DO YOU WILL END UP WITH A SOFTBRICK

-If you get either dump mode or fastboot bootloop check your downloaded rom file to make sure its complete, unzip again and flash again

FAQ

Q. Will this enable dual sim functionality?

A. Dual sim functionality works, volte, Wifi calling and vvm.

Q. Can I take OTA's like a regular device?

A. No, sadly.

Q. What about when a new update comes out?

A. Update procedure is written above.

Q. What if I brick or have a HW/SW mismatch?

A. Use the MSMDownloadTool to recover.

Q. Do all the features work?

A. For the most part, there are minor bugs, but they aren't consistent, so can't really say.

Q. Is this a full conversion?

A. Somewhat.

Q. Do I have to wipe everytime I update?

A. No, wiping may only be necessary for conversions, no wipe needed to update.

Q. Do I have to root everytime I update?

A. Yup, sadly.

Q. Do I have to convert to a specific version?

A. Nope, you can convert to any version.

if any edits are suggested, I'll include them.

Credits:

[MENTION=2704440]mackentosh[/MENTION] for testing and unfortunately bricking using the OTA File

[MENTION=5833319]Velrix[/MENTION] for being the second successful tester, among others.

All the other users who've been testing/contributing to testing

I'll add names when I get to comb through the threads.

[MENTION=1314742]Dameon87[/MENTION] for the correct ROM source link of the unpacked ROM with batch files.

[MENTION=2022562]Krunk_Kracker[/MENTION] for the disable auto updates image

Thanks to [MENTION=4718504]Addiso[/MENTION] for the Stock T-Mobile Backup images

[MENTION=4712355]mauronofrio[/MENTION] for the scripts and for hosting the Rom zip [MENTION=1459374]hartleyshc[/MENTION] for testing and confirming full dual sim functionality.

[MENTION=4468902]Saythis[/MENTION] - for the 9.0.6 FULL ROM Zip

[MENTION=2836732]Taebom[/MENTION] for first testing/confirming 9.0.7 local upgrade