Failed GrapheneOS install: failed to flash partition (bootloader_b): -7

Eddie_DS

Hi,
I’m trying to reinstall GrapheneOS on a Pixel 10 Pro after temporarily flashing stock Android in order to migrate WhatsApp data from iOS.

The device is currently in fastboot mode and the bootloader is unlocked.
Current fastboot info:
product: blazer
current-slot: a
unlocked: yes
version-bootloader: deepspace-17.1-15016913

I first tried the Web Installer, but it failed with:
Error: Bootloader replied with FAIL: failed to flash partition (bootloader_b): -7

Then I tried the CLI installation method using the official guide. I tested both:
blazer-install-2026042100.zip
blazer-install-2026050400.zip

Both signatures verified correctly with ssh-keygen.
However, flash-all.bat fails at the same point:

Available devices:
xxxxADB IDxxxx fastboot
Warning: skip copying bootloader_b image avb footer (bootloader_b partition size: 0, bootloader_b image size: 21915024).
Sending 'bootloader_b' (21401 KB) OKAY [ 0.543s]
Writing 'bootloader_b' (bootloader) Flashing pack version deepspace-16.4-14791471
(bootloader) flashing platform lga
(bootloader) Validating partition ufs
(bootloader) Validating partition ufs
(bootloader) Validating partition partition:0
(bootloader) Validating partition partition:1
(bootloader) Validating partition partition:2
(bootloader) Validating partition partition:3
(bootloader) Validating partition dbl_b
(bootloader) failed: generic error
(bootloader) image(dbl_b): rejected, fails validation
(bootloader) failed to validate partition (dbl_b)
FAILED (remote: 'failed to flash partition (bootloader_b): -7')
fastboot: error: Command failed

It looks like my current stock bootloader is deepspace-17.1-15016913, while the GrapheneOS install images appear to be trying to flash deepspace-16.4-14791471.

Is this a rollback protection / firmware version mismatch issue? Was this caused when getting back to stock Android?

Any workaround would be appreciated, right now I don't have a backup phone.
Thanks in advance.

GrapheneOS

Eddie_DS Our new release is out with the new Pixel firmware and you should be able to use the current Alpha channel release to install it. If you want to use the web installer, you can use https://staging.grapheneos.org/install/web since it uses the Alpha channel instead of the Stable channel as the production site does.

Setech

Eddie_DS 1 use chrome browser 2) webinstall works u do something wrong. Chrome settings enable USB setting . use dev mode to unlock BL . if u have bad USB cable change.
Use fastest USB port on computer .

yutan6

same error code on web install, pixel 10.
probably the results of yesterday android update...

yutan6

falled back to previous android version, install succesfull

de0u

yutan6 Thanks for reporting back!

Eddie_DS

yutan6 Could you elaborate on that? Is there a way to chose another version on the installer?

Eddie_DS

yutan6
I've tried to install Stock Android CP1A.260405.005 to see if that solved the issue, however during the process (using Google's web installer) I receive the next message:

Flash Failed
The build you are flashing is no longer compatible with your device due to anti-rollback protection. Your device is running a bootloader with an incremented anti-rollback version to prevent previous vulnerable versions of the bootloader from being flashed on the device.

How did you manage to fall back to the previous version?
Thanks!

GrapheneOS

You'll brick your device if you did successfully downgrade it. Don't do that. Wait until after today's GrapheneOS release.

Eddie_DS

GrapheneOS
Thought he could be referring to some actual method I might be overlooking. I’ll wait for the release then, good to hear it’ll come with the new firmware.

Thanks!

GrapheneOS

The web installer on the production site has been switched to using the Alpha channel for the Pixel 10, Pixel 10 Pro, Pixel 10 XL and Pixel 10 Pro Fold to avoid issues due to the anti-rollback counter update blocking installing a release with older firmware. This will avoid this issue for people using the web installer but not CLI install unless they download the Stable channel release.

Unfortunately, there are Wi-Fi issues with the Pixel 8a and Pixel 9a with the new release which draws into question whether it should be moved forward to Beta and Stable despite no issues noticed on other devices yet. We'll need to decide if it makes sense to move the release all the way to Stable for other devices without those 2. The main blocker is that it indicates there may be issues elsewhere even though there are no reports of it and no symptoms on our test devices.

Eddie_DS

Setech As the officail GrapheneOS account pointed out, it was an issue with rollback protection.
Once the update with the new firmware was released I could reintall it without issue.

Thanks for answering anyway.