Microsoft adds mobile APIs back into Windows 10, possibly for Surface Phone

We have seen many rumors, Microsoft patents, and other tidbits of information over the last year and a bit that points towards the potential release of a foldable mobile device from Microsoft, which is unofficially dubbed the ‘Surface Phone.’ Some of the more recent examples include a rear mounted display for “Back Touch” navigation, a determinative hinge that could allow for a mini laptop-style form factor with a virtual keyboard, and rumors of insider sources claiming that prototypes have been made with a possible announcement soon.

But one thing that helped to dampen hopes was the lack of mobile call related APIs in Windows 10 that Microsoft removed with the Fall Creators Update. Yesterday, Reddit user Firefly74 posted a Pastebin link showing that Microsoft has added the phone call related APIs back into Windows 10 Redstone 5 Build 17650, which rolled out to Windows Insiders in the 'Skip Ahead Insiders' group.

While this adds weight to the possibility of a Surface Phone running a build of Windows 10, this isn’t necessarily the only possibility here. Late last year Microsoft started shipping Surface Pro LTE models to businesses and then expanded availability to consumers in March, so as a commenter pointed out, this might be to enable additional functionality in these LTE enabled devices.