KB5089555

Microsoft has released cumulative update KB5089555 (Build 26220.8491) for Windows 11, version 25H2 for Insiders on the Beta Channel. This build includes a small number of minor bug fixes and improvements aimed at increasing stability, as well as a new voice isolation feature for voice access.

• Voice isolation in Voice Access. A new mode has been added that helps the feature focus on the user's voice even when other people are speaking nearby. In a busy office, an open-plan room, or at home surrounded by family, Voice Isolation filters out extraneous voices and background noise so Voice Access can better recognize speech. All processing happens locally on the device. Three speech recognition modes are now available in Voice Access under Voice Access Settings > Improve speech recognition: Voice Isolation (requires a one-time voice setup), Remove only background noise (filters out non-speech sounds like keystrokes or door slams without extra setup), and No filtering (default microphone input without additional processing). To set up Voice Isolation, select it from the menu and read a short paragraph aloud so Voice Access can learn your voice. This takes about a minute, and voice data never leaves the device.
• Fix for explorer.exe crash loop. A problem has been resolved where after installing the previous build, an explorer.exe crash loop occurred, manifesting as flickering and constant refreshing of the screen or taskbar. After updating, the issue should be fixed.
• Fix for duplicate Energy Saver button. An issue has been fixed where for some Insiders in recent builds, the Energy Saver button in Quick Settings appeared twice.
• Fix for sudden sound cutout. A problem has been resolved where on some devices in recent builds, audio would unexpectedly cut out.

Installation of the update is done through Windows Update: go to Settings > Windows Update and click Check for updates. A computer restart is required to complete the installation.

How the new features work:

Voice Isolation in Voice Access: A local neural network filter has been added to the audio capture subsystem, utilizing directional beamforming and Voice Activity Detection based on spectral analysis. After a one-time registration of the voice profile (Voice Isolation), the model learns to isolate the user's unique vocal features. The Remove only background noise mode suppresses non-stationary broadband noises (keyboard, slams) via an adaptive threshold in frequency bands, while No filtering disables processing, passing a raw PCM stream from the microphone.

Fix for explorer.exe crash loop: The issue was an unhandled exception in the shell component, likely in the taskbar's XAML parser while rendering legacy extensions, causing a critical failure and restart of the explorer.exe process. The exception handler was not correctly releasing COM object resources, creating an infinite initialization and crash loop. The fix implements interface pointer integrity checks and a safe fallback to a default visual tree predicate, preventing desktop flickering and reloading.

Fix for duplicate Energy Saver button: A resource identifier conflict occurred in the Quick Settings markup due to an erroneous merge of manifest branches during an incremental build. This caused a double registration of the EnergySaver_Toggle trigger in the ActionCenter. The patch normalizes the tile provider factory, removing the secondary UI element entry from the dictionary and leaving a single active binding to the power-saving state.

Fix for sudden sound cutout: The failure occurred at the audio stack driver level (AudioEndpointBuilder) when switching the default stream format after waking from sleep mode. A synchronization timeout between WASAPI and the HD Audio codec caused a false endpoint disconnection. The fix modifies the interrupt re-initialization logic upon PortCls restart by resetting DMA buffers before recalculating the sample rate, ensuring the audio session remains active without playback interruption.

The last 10 Windows updates: