Opinion: Windows 10 Mobile build 15204 is “Redstone 3,” but it’s not “OneCore”

Kip Kniskern

Today, Microsoft made some significant Windows 10 Mobile announcements, one of which is that only a short list of Windows Phones will be able to move forward with the latest builds, or to get the Creators Update, officially, at all.

But some more, perhaps even more significant news has emerged from Dona Sarkar’s latest blog post. Let’s take a look and then break it down:

As we release new builds from our Development Branch for PC, we will also be doing the same for Windows 10 Mobile just like we have been in the past. However, Windows Insiders will likely notice some minor differences. The biggest difference being that the build number and branch won’t match the builds we will be releasing for PC. This is a result of more work we’re doing to converge code into OneCore – the heart of Windows across PC, tablet, phone, IoT, HoloLens, Xbox and more as we continue to develop new improvements for Windows 10 Mobile and our enterprise customers.

The first bit is pretty obvious, that Windows 10 PC and Windows 10 Mobile have diverged in their build numbers, notably with the release of 16176 for PC and 15204 for Mobile today. And yes, Windows 10 Mobile is an “RS3” build, as evidenced by Dona calling it out as part of the “development branch,” and further clarified in a tweet by Microsoft’s Brandon LeBlanc:

But read carefully what Sarkar says in the last bit:

This is a result of more work we’re doing to converge code into OneCore – the heart of Windows across PC, tablet, phone, IoT, HoloLens, Xbox and more as we continue to develop new improvements for Windows 10 Mobile and our enterprise customers.

If Microsoft were developing Windows 10 Mobile as part of OneCore, or OneCore as part of Windows 10 Mobile, then the build numbers they worked so hard to converge wouldn’t be diverging, nor would Windows 10 Mobile hardware development be effectively shut down, except for those third party “enterprise” devices.

Development for Windows 10 OneCore, which will power “PC, tablet, phone….” from here on out, is, if you read this carefully, on a *different path* than Windows 10 Mobile. In other words, Windows 10 Mobile and the 15204 and beyond branch, are separate from “OneCore,” or 16176 branch for “PC, tablet, phone…” etc., although W10M will still continue to be improved (for now).

If you remember, there was a big push back in the Gabe Aul days to merge Windows 10 and Windows 10 Mobile development and share similar build numbers, but recent builds have moved away from that, and now the cat is fully out of the bag.

This handwriting has been on the wall for quite some time, but today’s blog post is the clearest indication yet that Windows 10 Mobile is *NOT* the path forward for Microsoft’s future mobile endeavors. That lies with OneCore, with Windows 10 on ARM, and whatever rabbits Microsoft plans to pull out of its hat for new devices supporting cell connections (maybe, in effect, all new devices at some point).

It stands to reason that whatever OneCore ends up being, it probably won’t run on current Windows 10 Mobile devices, even the ones that made the cut. Or at least, that’s not part of the goal. Windows 10 on ARM, and OneCore, seems the clear path forward for Microsoft’s mobile development efforts, whatever they turn out to be.

We should start to get a glimpse of what that future looks like with Microsoft’s early May “Windows Cloudbook” event, and for sure at Build. But the way I’m reading this, Microsoft is in the process of moving away from “Windows 10 Mobile,” and has been for quite some time.