Tried searching the forums and reading other users’ experiences but I’m even more confused.
This prevents the device from rolling back to previous vulnerable versions of the bootloader. After flashing the May 2025 update on these devices you won’t be able to flash and boot older Android 15 builds.
Just acquired this model device and it came from the retailer with BP3A.251105.015. Android 16.
From reading the forums (which I could be misunderstanding), some users report bricked devices. Some users report eOS won’t install if the newer bootloader is installed. One user appears to have had success even with a very new build of stock OS.
I have a bunch of questions. I’m used to older Samsung models. This is my first Pixel.
My desire is to (potentially) switch between eOS/Lineage/Stock to see what works best for me. Am I doomed to screw myself over at some point? * How do I tell the bootloader version I’m running?
Is the bootloader shared with all slots (like a UEFI firmware??) or is it per-slot? How do I reveal any per-slot difference?
Do OTA images also upgrade the bootloader, or just the factory image?
Is it possible to downgrade the bootloader from the A16 to A15 or A14 versions? After all, the wording from Google is it “prevents”, not “blocks”. In my experience “prevent” typically indicates “you can do it, but you need to take additional steps”. Is this the OEM unlocking?
Do I risk creating a paperweight at any point due to the unique nature of the Pixel 8 and this bootloader anti-rollbacking ““feature””?
fastboot getvar all reports version-bootloader:ripcurrent-16.3-13642541
I did a Pixel 8 last week from stock Android 16 to e/OS/ official A15 and in my experience the only thing that matters is the Security Patch date. No issues when locking the bootloader since the security patch level of /e/OS was more recent than Stock.
I have no shame in admitting I’m not as familiar with how android works.
When we say “bootloader” are we talking about something analogous to system firmware or something more like a GRUB2/systemd-boot/syslinux? Or the linux kernel?
I find it all pretty confusing when trying to take all the info in at once.
For the purposes of the OP, are future bootloaders backwards compatible with older ROMs? The compatibility matrix is hard to understand.
I’m happy to take “RTFM” (with links) as a response.
Well, you could compare the bootloader with Grub. So unlocking the bootloader is making it possible to change the OS that will be loaded.
As far as my level of understanding goes, you will be able to change this to other ROMS. It just points to where the process of booting needs to start.
It may be obliged to go back to stock Android before you install an other ROM.
Going to add a summary of my notes from the last couple weeks. I feel like a lot of the documentation is geared towards people who already know what they’re doing. These notes are mainly for myself, but hopefully they benefit others:
I ended up switching to GrapheneOS on the recommendation of a friend and found their CLI installation guide to be really high quality (helps that it’s all on one page). That guide plus my experiments below gave me the confidence I needed.
My device came from retailer with official build BP3A.251105.015 and bootloader ripcurrent-16.3-13642541
Before I could OEM unlock, I had to get it connected online and as soon as that happened, it started an auto-update which I allowed to complete.
After the update, it landed on CP1A.260305.018
4. I didn’t log what bootloader it had post-OTA. My understanding is OTA updates can update the bootloader too, but I didn’t do thorough testing of that.
For fun/practice I then used the official CP1A.260305.018 factory image to do a full flash of the device. That went as expected, no real version changes on that.
I then did a downgrade to the official factory image version BP1A.250505.005 (May 2025, can’t go back any further than this, to my understanding).
a. Before downgrade, bootloader was ripcurrent-16.4-14540574
b. During downgrade, bootloader went to ripcurrent-15.3-13272266 without error/issue
c. No errors with remaining downgrade, went as expected
After the above testing is when I felt comfortable switching to a third-party ROM, now knowing I could downgrade all the way back to May 2025 factory image and in theory any 3P ROM will work so long as the bootloader it flashes is greater than or equal to ripcurrent-15.3-13272266, which is easy to discover within its flash scripts/instructions.
In the middle of the above (I think between 5 and 6) I did some other experiments using recovery mode instead of bootloader mode to apply the factory images as well to better understand that.
One thing that drove me NUTS and took me FOREVER to figure out (had to take a round-about path to getting there) was that THESE are the steps to bring up a meaningful user interface in recovery mode to activate sideloading:
Once in recovery (accessible via bootloader interface or adb reboot recovery), USE KEYSTROKE to bring up menu for ADB/etc options:
Hold Power button
Press Volume Up once
Release both buttons
a. A UI for Recovery Mode appears, navigation instructions at the top.
Scroll and use ‘Apply update from ADB’ to then activate sideload function.
adb devices output sill show the device with sideload text next to it
It’s also worth noting that no unlocking needs to be done if you’re just using the recovery mode to apply OTA updates
Edit/forgot to include:
My understanding of the bootloader/boot process for Pixels has evolved a bit. This is almost certainly wrong, but my current impression based on observations and what little “plain English” documentation exists is:
There’s an untouchable ROM/boot process in the device that bootstraps the system.
Part of that ROM is ensuring the anti-rollback function works, tracking which slot (A/B) is preferred, and failing back to the other slot if the preferred slot is detected as damaged or if failure counters breach a threshold.
The bootloader is the second stage. How exactly it integrates with the ROM to blow those fuses and prevent rollback is unclear to me. What seems more clear (but I’m not brave enough to test it) is there is no way after those fuses are blown to flash an older bootloader than May2025. It’s not “anti-rollback” in the sense that it prevents rollback, it’s more “secure-rollback” in that it is impossible to rollback to an older bootloader.
It appears that Lineage, /e/ OS, and GrapheneOS all use Google’s official bootloader, so I’m assuming this is one of those things where for the secure boot/platform trust to work, there’s not much option and that the bootloaders are all backwards compatible. I’m definitely starting to see this as analogous to GRUB/systemd-boot/et al. Again, how the anti-rollback actually functions between these two systems is unclear to me. Presumably there’s some kind of trust system between the ROM and Google’s bootloaders because otherwise blowing those fuses seems like a way to accidentally (or maliciously) brick devices.
Warning: The May 2025 update for Pixel 6 (6, 6 Pro, 6a) and Pixel 8 (8, 8 Pro, 8a) devices contains a bootloader update that increments the anti-roll back version for the bootloader. This prevents the device from rolling back to previous vulnerable versions of the bootloader. After flashing the May 2025 update on these devices you won’t be able to flash and boot older Android 15 builds.
The following content there, no longer contains the full context, merely saying
the older bootloader, the device enters an unbootable state.
Loosely speaking, Google devs found a security weakness in their hardware. They really don’t want this weakness exploited so decided to allow the bootloader to “blow the fuse” on the device. This is said to make the device “non repairable” to original “weak hardware”.
How is it solved? Be extra careful follow the guidance exactly (loosely speaking, not to roll back into the hazard timeframe).
Hello,
I am not sure to really understand the situation about how to install /e/OS on a Google Pixel 8.
I just purchase one that has Android 16, build CP1A.260305.018
I understand from Install /e/OS on a Google Pixel 8 - “shiba” that I need to have Android 15 on the device before flashing /e/OS with Android 15.
I may have understood the “May 2025 bootloader anti-rollback” seems to prevent installing easily Android 15 on this device.
I have played with installing Android on devices for more than 10 years (from my beloved HTC HD2), so I am not new to this flashing process, but I am not an expert and I am not sure to understand what should I do (and not do) to make my device able to receive /e/OS.
Thanks in advance for your advices
This comment has been replaced by the original author due to the original being flagged as off-topic.
When navigating the May 2025 bootloader anti-rollback considerations for the Pixel 8 (shiba), I found it helpful to consult Android bootloader documentation from other custom ROMs alongside the official /e/ guide to clarify the bootloader flashing consequences. Reviewing broader Pixel-specific flashing guides provided essential context on handling anti-rollback triggers safely.
Thanks @aibd and @jamesaepp for your answers.
This phone is not for me and the owner already use /e/OS easily, so I am trying to keep him on the same system
If it was for me, I would have probably tried GrapheneOS
Just a last precision, if I install /e/OS community build A16, I will not risk to brick the phone due to the “May 2025 bootloader anti-rollback” feature Google added to this phone, won’t I ?
I understand as I stay on A16, I don’t have this risk (but there is always risk in changing the Android system, I know). Can you confirm me?
Thanks in advance
The community build is undocumented of course, but the downgrade to a15 was required to install a15. If one plans to install a16 one takes a leap of faith that one can install on top of a16 but don’t update such that Google a16 is actually ahead of /e/OS a16.
You won’t be bricking anything with the community build because you will not be locking the bootloader.
But, to make things easier: A15 over A16 will install just fine. I did that a few weeks ago on a Pixel 8 myself without issues after locking. The thing that matters is the security patch level. If your Pixel is on the latest version now, you’ll have to wait a few days for /e/OS 4.1 to release (because it will be behind at this moment). Write the security patch level down before you flash /e/OS and confirm that the date of Android security patch is higher than it was before you changed to /e/OS.
The only reason why in the install instructions is stated that your device needs to be on the latest A15 release is because they did not update the text which is a copy from the lineage site.
It just needs to have the latest firmware available.
Thanks again for your advices and information. I am not sure to really fully understand the issue becasue I understand that rolling back to previous version of bootloader can brick the device. But I don’t know where to find the version number of the bootloader and I am not sure to understand “previous to may 2025” or previsous to the one present currently on my device.
So I think I understand that this is not a question of A15 or A16 but rather of security patch date (linked to bootloader date?).
Could you tell me where I can find the security patch date on my stock Android (I know where this information is on /e/OS)? I have build CP1A.260305.018, does that mean that 2026-03-05 is the security patch date?
And the same where this security patch date is writen on the release page of /e/OS?
So if the patch date of the desired /e/OS ROM is later than the patch date of my stock A16, then I can flash the /e/OS ROM, is it correct?
Yes, you are correct. CP1A.260305.018 is the march update. In that case the current version /e/OS 4.0 will be fine.
You can find the Security patch level date in the settings app when you scroll down to ‘about phone’. This is quite similar to stock Android.
/e/OS builds will contain the latest security patches so you can deduce it from the build name. IMG-e-4.0-a15-20260610633983-official-shiba.zip is released on year 2026 month 06 day 10. So it will contain the security patches up to the first of june because that’s the latest patch release of Android. They are released on the first of every month.
Throwing out a few comments based on what I learned a month+ ago now. I’m not being too careful with how precisely I word these, so I could be wrong.
I don’t think this is true. Whether or not the bootloader is locked does not (to my understanding) influence the path to bricking a device. It’s whether the first-stage bootloader/ROM will even load the “real” bootloader we’re all talking about here. That logic works regardless of lock state (to my understanding).
Second, this is what I’d recommend to give yourself “safety” before playing with custom ROMs/operating systems:
Flash the latest Google Pixel 8 stock ROM twice. That means, follow the “Factory images for Nexus and Pixel Devices” (NOT the OTA image) to flash the pixel device to the factory image. After you’ve done that, do it again.
Why? The logic is like this. Let’s pretend your device is currently booting from slot “B”.
The device is restarted to fastboot. It’s using slot B for the bootloader.
You use the flash script. The newest bootloader is flashed to slot A.
The device reboots, and it now uses the new bootloader from slot A.
You restart the device to fastboot. It’s still using slot A.
You use the flash script 9again). The newest bootloader is flashed to slot B.
Done. Now even if you flash an older bootloader before May 2025 by accident, at least one bootloader is new enough to end up in a non-bricked state.
This is what Google means in their guidance below. They just word it incredibly poorly IMO:
To avoid hitting this state, if you are flashing an impacted Pixel device with the May 2025 update or newer for the first time, flash the bootloader partition to the inactive slot after successfully updating and booting into Android 15 May 2025 at least once .
Thanks for your explanation. I am not sure to understand the slot A / slot B issue but I get the point about flashing factory image twice.
You advise me to flash the latest Google Pixel 8 stock ROM twice that is 17.0.0 (CP2A.260705.006, juil. 2026).
I was thinking to stay to A16 in order not to downgrade from stock A17 to /e/OS A15 (or community A16). But the latest stock A16 is 16.0.0 (CP1A.260505.005.A1, mai 2026, Telia), so older ROM than the latest stock A17.
Which one you advise me to flash, latest A16 or latest A17?
And then, @ieder1 and @aibd adviced me not to flash an /e/OS ROM with a security patch older than the stock Android on my Pixel 8.
With the latest A17 for Google Pixel 8 (from 5 July 2026), this is not possible. Will I then risk to brick my device?
