It's not unusual to see slightly customized builds of Android rolling out to Nexus devices shortly after the release of a new version. It certainly happened a few times with KitKat, and it looks like Lollipop is on track to do the same. As the rush of factory images and OTAs roll out, AOSP is also receiving commits for the new device-specific builds; and Al Sutton was quick to put out changelogs for each version. These begin with the version currently residing on the Nexus Player, 5.0.0_r2 (LRX21M), and run through LRX21Q, which just appeared on the Nexus 9.

Since each build only appears on select devices, they're organized below to show where they've been distributed. The list of build numbers as they relate to devices and versions can also be found here.

The changelogs don't contain any particularly special changes. These are mostly small bug fixes that were probably slipped in at the last moment. Eventually, all of these changes will be wrapped up into a single build that appears across all (or most) of the Nexus family.

Since the Nexus 4 is expected to roll out very soon with LRX21T, we might see an explanation for its short delay. We'll update this post when it arrives. Update [Nov 15]: The Nexus 4 changelog is up. It looks like the rumors about a Wi-Fi issue for the N4 may have been accurate, after all, which may explain the brief delay in its release. There are also a few additions to the CTS platform tests and dEQP support package for benchmarking and testing OpenGL ES and OpenCL GPUs.

Update [Nov 19]: It's not a major Android release without a bunch of little update builds, and here are a couple more. Of course, anybody who got their hands on a Nexus 9 early enough (before the Q update rolled out) has already faced the partially failed OTA processes and had to make the decision to unlock the bootloader to flash a factory image or waiting for another OTA to repair the error. It's clear from the changelog that the R build for the Nexus 9 doesn't bring anything new besides a fix for the bad flash, as the only changes are related to CTS and dEQP, nearly matching those for the T build on the Nexus 4. The Nexus Player also started receiving its first update to LRX21V, but the changes are incredibly minimal. The only changes to code include a bug fix for security certificates and added support for SmartClip. While nothing here is particularly exciting, it helps to know where each device stands. It looks like most of the critical launch issues have been resolved, so the OTAs might spread out a bit more as Google's developers work to fine-tune the experience. We can hope, right?