KB5101589

Microsoft has released cumulative update KB5101589 (Build 26300.8935) for Windows 11 version 26H2, aimed at insiders in the Experimental channel. The main focus of the build is on improving File Explorer performance, enhancing desktop background stability, and expanding interactive capabilities of widgets. Additionally, developers have fixed a critical error that prevented the installation of previous insider builds and made a number of refinements to the search interface and taskbar.

• File deletion in File Explorer has become faster. File deletion in File Explorer is now performed faster in certain scenarios — when deleting large fragmented files.
• Faster launch of the Home page in File Explorer. The launch of the Home page in File Explorer has become faster and more responsive.
• Touch scrolling in the Recommended section. The Recommended section on the File Explorer home page now supports touch scrolling, making it easier to browse files in the carousel.
• Improved desktop background preservation. Desktop background preservation has been improved in various scenarios, including when using multiple desktops. Minor cosmetic improvements have been made in Settings > Personalization > Background.
• Extended support for animated icons for widgets. Support for animated icons at the widgets entry point on the taskbar is being expanded. In addition to the animations already available to insiders with taskbar notifications enabled in widget settings, users may begin to see a broader set of dynamically updated animated content from supported widget providers — so that content updates are more noticeable at a glance.
• Fix for installation error 0xc0000409 in Windows Update. Fixed an issue where recent insider builds might fail to install with error 0xc0000409.
• Command autocompletion in the Run dialog. Pressing F4 now expands the list of suggestions for command autocompletion when using the new design of the Run dialog.
• Fixes for visual issues on the taskbar. Fixed several minor visual issues when using the taskbar in an alternative position. Fixed an issue where the Notification Center appeared in the wrong place when the taskbar was docked to the top.
• Increase in search box height. The height of the search box has been increased by 4 pixels.
• Fix for mouse pointer flickering and input settings preservation. Fixed an issue where the mouse pointer constantly flickered for some insiders after installing recent builds. Improved preservation of the selected mouse pointer size. Improved preservation of voice input settings — automatic punctuation and the launch panel.

To install the update, go to Settings > Windows Update and click Check for updates. A restart of the computer is required to complete the installation.

How the new features work:

Faster file deletion in File Explorer. Deletion of large fragmented files is now faster due to optimized NtSetInformationFile calls with the FileDispositionInformationEx flag, allowing the NTFS driver to process extent deallocation without redundant cache synchronization loops for each individual fragment.

Faster Home page launch in File Explorer. The responsiveness of Explorer.exe root element initialization has been improved: lazy loading of IShellFolder for non-visible items and asynchronous namespace provider initialization reduce UI thread blocking during tree construction.

Touch scrolling in the Recommended section. The recommended files carousel on the Home page now handles panning gestures via DirectManipulation, using the Windows.UI.Composition composition engine for smooth inertial scrolling without intercepting events at the Win32 window level.

Improved desktop background preservation. The wallpaper setting mechanism has been refined across various scenarios, including multiple virtual desktops: a race condition in the HKCU\Control Panel\Desktop registry key during monitor configuration changes has been fixed, along with cosmetic tweaks in Settings > Personalization > Background.

Extended animated icon support for widgets. The taskbar entry point expands dynamic content rendering: beyond notifications, animation within the widgets' WebView2 container is now triggered by a provider data update signal, employing Adaptive Cards with visual states to draw attention without opening the board.

Fix for installation error 0xc0000409 in Windows Update. The build installation interruption with code 0xc0000409 (STATUS_STACK_BUFFER_OVERRUN) has been resolved, caused by stack corruption during package manifest processing in the Component Based Servicing (CBS) phase when cryptographic catalog verification misinterpreted buffer boundaries.

Command autocompletion in the Run dialog. In the updated dialog design, pressing F4 invokes the IAutoComplete2::SetOptions method with the ACO_AUTOSUGGEST flag, forcibly expanding the suggestion dropdown from the built-in path handler's MRU (Most Recently Used) cache.

Taskbar visual fixes. The calculation of screen coordinates for the Notification Center flyout when the taskbar is docked to the top has been corrected: positioning relative to the MONITORINFO.rcWork work area is now fixed. Graphical artifacts with rounded corner anti-aliasing in the XAML layer at alternative taskbar positions have been eliminated.

Increased search box height. The visual container height of the taskbar search box in XAML markup has been incrementally increased by 4 pixels by adjusting the MinHeight property in the SearchBoxTextBoxStyle style resources to improve touch metrics and overall interface density harmony.

Fix for mouse pointer flickering and input settings preservation. Cyclic cursor redrawing caused by a SetCursor scheme conflict with IDXGISwapChain::Present in full-screen applications has been eliminated. Stability of selected pointer size preservation in the registry has been increased, and correct persistence of automatic punctuation and the voice input launch panel settings has been restored.

The last 10 Windows updates: