Microsoft releases Windows 10 build 19559 to the Fast Ring with ARM64 support for Hyper-V

It's Wednesday, which means it's time for a new Windows 10 build to be released for Insiders in the Fast ring. As usual for the past few weeks, build 19559 doesn't come with any new features, and focuses mostly on fixing some issues and making smaller improvements.

One of the more notable improvements is that Hyper-V features can now be installed on ARM64 devices such as the Surface Pro X, as long as you have Windows 10 Pro or Enterprise:

• We fixed an issue with the IME candidate window for East Asian IMEs (Simplified Chinese, Traditional Chinese, and the Japanese IME) not opening sometimes on recent builds.
• We fixed an issue that could result in explorer.exe crashing when backing out of folders containing .heic or RAW files.
• We fixed an issue that could result in explorer.exe hanging when attempting to delete certain large .tif files.
• We fixed an issue resulting in the top few pixels of a window getting clipped when using WIN+Up and then snapping the window to the side using WIN+Left/Right).
• We fixed an issue resulting in Event Viewer crashing when selecting certain events recently.
• For any of our Insiders using an arm64 device, such as the Surface Pro X, running Enterprise or Pro edition, you’ll now be able to see and install Hyper-V features.
• We fixed an issue resulting in some Insiders experiencing a green screen in recent builds with error KMODE EXCEPTION NOT HANDLED.

This week's build still comes with a significant list of known issues:

• BattlEye and Microsoft have found incompatibility issues due to changes in the operating system between some Insider Preview builds and certain versions of BattlEye anti-cheat software. To safeguard Insiders who might have these versions installed on their PC, we have applied a compatibility hold on these devices from being offered affected builds of Windows Insider Preview. See this article for details.
• We are aware Narrator and NVDA users that seek the latest release of Microsoft Edge based on Chromium may experience some difficulty when navigating and reading certain web content. Narrator, NVDA, and the Edge teams are aware of these issues. Users of legacy Microsoft Edge will not be affected.
• We’re looking into reports of the update process hanging for extended periods of time when attempting to install a new build.
• We’re investigating reports that some Insiders are unable to update to newer builds with error 0x8007042b.
• We’re looking into reports that some Insiders are unable to update to newer builds with error 0xc1900101.
• East Asian IMEs (Simplified Chinese, Traditional Chinese, Korean and the Japanese IME) may be missing from the language/keyboard switcher (e.g. opened by Windows key + Space key) after upgrading from 20H1 Build 19041 or lower builds to Windows 10 Insider Preview build (19536 or later) if you have multiple languages/keyboards added. We are investigating the issue. In the meantime, please remove and re-add any keyboards that are missing from the keyboard switcher by going to Settings > Time & Language > Language > Preferred languages. It doesn’t happen if you updated from build19536 or later.
• The Documents section under Privacy has a broken icon (just a rectangle).
• We’re investigating reports that certain devices are no longer sleeping on idle. We have identified the root cause and are working on a fix for an upcoming flight. If your device is impacted, manually triggering sleep should work (Start > Power button > Sleep).
• WSL Issue 4860: Some Insiders are experiencing this error message when using WSL2: A connection attempt failed on Windows. Thank you if you were one of those who reported it on the previous flight—we have a fix ready which will be including in an upcoming flight.
• There’s an issue in this build where if you bring up clipboard history (WIN+V) and dismiss it without pasting anything, input in many places will stop working until you reboot your PC. We appreciate your patience.

Windows 10 development in the Fast ring has been pretty slow over the past few weeks, which tends to happen before a public release of a Windows 10 feature update. As we get closer to the general availability of Windows 10 20H1, new features will start showing up in vNext builds in the Fast ring. For now, the known issues will probably outweigh the improvements for most people.