Windows 11 build 27686

10.0.27686.1000.rs_prerelease.240809-2254
	Build of Dilithium
OS family	Windows 11 (NT 10.0)
Version number	10.0
Build number	27686
Build revision	1000
Architecture	AMD64, ARM64
Build lab	rs_prerelease
Compiled on	2024-08-09
Expiration date
Timebomb	2024-09-15 (+37 days)
SKUs
	Home (N, Single Language, China); SE (N); Pro (N, Single Language, China); Pro Education (N); Pro for Workstations (N); Education (N); Enterprise (Evaluation, G, GN, N, N Evaluation); IoT Enterprise (Subscription)
About dialog

Windows 11 build 27686 is the only available build of Dilithium, the 25H1 development semester of Windows as a service. It was released to the Windows Insiders in the Canary Channel on 15 August 2024.

New features and changes[edit | edit source]

Windows Sandbox[edit | edit source]

A preview of the new Windows Sandbox app named "Windows Sandbox Client Preview" has been introduced alongside several new features, including runtime clipboard redirection, audio/video input control, the ability to share folders with the host at runtime, and the early implementation of command line support. Windows Sandbox Client Preview will be updated via Microsoft Store at launch, and will be reverted to the classic Windows Sandbox app when update fails.

Settings[edit | edit source]

A new "Detach VHD" button has been added to the VHD properties page under System > Storage > Disks & volumes for simply detaching VHD or VHDx images.
A new "Allowing HDR video streaming even when HDR is off" toggle switch has been added under System > Display > HDR. This change can be activated manually by enabling the 51228992 velocity staging key.
The ability to manually set separate power modes for plugged in and on battery via System > Power (or Power & battery), previously implemented in build 26252, has been gradually rolled out. It can be activated manually by enabling the 39007349 velocity staging key.
Changes to the Windows Update > Advanced options > Delivery Optimization page that shows all delivery optimization settings on a single page, initially implemented in build 25982, has been refined. It's disabled by default, but can be activated manually by enabling the 33235889 velocity staging key.
The Privacy & security > Generative AI page for managing generative AI access, initially implemented in build 26236, has been removed.

Shell[edit | edit source]

The additional quick status (sports, traffic and finance) beside weather on the lock screen, previously implemented in build 26252, has been disabled by default. It can still be activated manually by enabling the 47921515 and 47921574 velocity staging keys.

Miscellaneous[edit | edit source]

The reported version string has been changed back to "Dev", which was represented in Cobalt builds 21313 through 21390.
The 32 GB limit of FAT32 partition size for the format command-line utility, initially implemented since Windows 95 OEM Service Release 2, has been removed. The utility now supports formatting FAT32 partitions up to 2 TB, the maximum addressable storage space of MBR partition table. This change does not affect the built-in Windows shell disk format tool.
Starting from this build, the system will run certain network tests in the background periodically to collect diagnostic data for evaluating future improvements in network performance. These tests use a small amount of data (up to 10 MB/day) and only run on Ethernet and Wi-Fi connections that are not marked as metered.
The ReFS file system has been updated to version 3.15.
Several under-the-hood optimizations have been made to improve battery life for PCs.

Bugfixes[edit | edit source]

General[edit | edit source]

Fixed an issue in Registry Editor where pasting hexadecimal values when editing QWORD or DWORD values could corrupt the value, e.g. pasting 0x1 would become 0x411.
Fixed an issue in the Windows Security app where when browsing the networks under Firewall & Network protection, it would show a broken glyph (a rectangle) next to the network name rather than a network icon.

Shell[edit | edit source]

Addressed an issue where the battery icon displayed on the lock screen might be out of sync with the actual battery level.

Settings[edit | edit source]

Fixed an issue where there was no space between the "Create VHD" and "Attach VHD" buttons under System > Storage > Disks & volumes.
Fixed an issue where the power mode option under System > Power & battery was showing in cases where it couldn't be changed, leading to a blank dropdown.
Fixed an issue where when searching for "kiosk" and clicked the result for setting up kiosk mode, it wouldn't navigate to the correct page.

Dev Drive[edit | edit source]

Fixed an issue where Dev Drive VHD or VHDx images weren't automatically re-mounting when the underlying volume was dismounted and brought back online.

Bugs and quirks[edit | edit source]

Enrolling to the Windows Insider Program on a new Copilot+ PC may cause Windows Hello PIN and biometrics to lose with the 0xd0000225 ("Something went wrong, and your PIN isn't available") error.
Users may experience a hang at the boot screen and roll back with the 0xc1900101 error when upgrading to this build.
Text on highlighted items in Microsoft Management Console and some of its snap-ins may have a yellow color.
Switching to the kaomoji and symbols sections or selecting an emoji may cause the emoji panel to close unexpectedly.
Drive Optimizer may fail to launch due to missing SXSHARED_UCRT.dll file. To work around this issue, make a copy of sxshared.dll under %SystemRoot%\System32 and rename it to SXSHARED_UCRT.dll.