The original Google Pixel lineup was a sharp turn from the existing philosophy of Nexus series. Besides the revamped marketing and premium features, the original Google Pixel and Pixel XL were the first phones to feature the A/B partitioning scheme.

Has Google used A/B OTAs on any devices? Yes. The marketing name for A/B updates is seamless updates. Pixel and Pixel XL phones from October 2016 shipped with A/B, and all Chromebooks use the same update_engine implementation of A/B. The necessary platform code implementation is public in Android 7.1 and higher. (Source)

As the updater part is now integrated with the system itself, the standalone /recovery and /cache partitions are no longer needed to be present inside the device. The slot based design is also an effective countermeasure against bootloops for buggy software updates.

With time, non-Pixel phones also adopted the new layout. For example, OnePlus 6 and newer OnePlus phones came with A/B partition scheme out of the box. The design also boosts the weightage of a particular feature of the bootloader of the Android devices.

As you may know, you can directly boot an external kernel or recovery image from fastboot/bootloader interface using the fastboot binary on PC. Technically known as ‘tethered booting’, the process is immensely useful for testing purpose or getting a temporary root shell. But there is catch!

Some manufacturers deliberately crippled this functionality, like OnePlus did with the initial bootloader of OnePlus 7 Pro. We were the first publication to highlight the issue and submit a formal bug report.

OnePlus eventually got back to us, and they shipped an updated bootloader in subsequent software updates so that one can use the ‘fastboot boot’ command without hitting a rock. Thing is, yet another OEM ‘accidentally’ forgot to include this feature in their recently released Android One phone. Any guess?

Although Xiaomi’s existing Android One phones, i.e Mi A1, Mi A2 and Mi A2 Lite do support tethered booting un unlocked bootloader, Mi A3 allegedly does not. We can’t verify the claim due to the absence of the phone in hand, but plenty of users reported about the anomaly.

Thanks to the Android One goodness, Mi A3 already got the August security update across various regions. We still don’t know the reason to exclude this useful feature though, as regular users will face truckload of issues to root the phone or install TWRP in future.

Perhaps they will introduce it after getting enough pressure from the community?

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