Microsoft has published a new preview release of Windows 10, build 18836, to participants of the "Skip Ahead" group. But it's not quite the preview that they were expecting to get.

Microsoft's preview program has a number of different channels to let people use and test Windows feature updates, Microsoft's twice-yearly Windows 10 upgrades. The two main channels are Fast and Slow; Fast receives builds more regularly, while Slow generally receives only those builds that are felt to be stable. Both channels look ahead to the next feature update. For example, right now, the stable Windows 10 version is 1809. The Fast and Slow channels are receiving previews of version 1903, codenamed 19H1, which is due for release in April.

Skip Ahead is a third channel. Most of the time, Skip Ahead is identical to the Fast channel, but in the last few weeks of each update's development, the two diverged. The Fast ring continues to receive builds of the next feature update; Skip Ahead, well, skips ahead to the update after the next one. As such, one would expect today's Skip Ahead release to be a preview of 19H2, version 1909, due in October. But it isn't; it's skipping ahead not one but two releases, all the way to 20H1, due in April 2020.

(There's also a fourth channel, Release Preview, which is used for builds that Microsoft thinks might make the grade as stable releases.)

Microsoft says that 19H2 builds will start shipping in spring. Some of the features planned for 20H1 will take longer to develop, though the blog post gives no indication of what these features might be, and it lists no new features relative to the 19H1 previews at all. So Microsoft wants to get previews out and tested already. One hopes that we'll get an inkling of what 20H1 will bring sooner rather than later, but for now we just have a new build that looks like the old build but is from a different development branch.