KB5077243

Microsoft has released cumulative update KB5077243 for Windows 11 version 25H2 for Insiders on the Dev Channel — Windows 11 Insider Preview Quality Update (26300.7939). This update includes several significant changes, including a new protected mode for batch files, improved shared audio management, new features for Narrator, and a number of system reliability and performance improvements.

• Protected mode for batch files (.bat and CMD). Microsoft added a file locking mechanism during execution, preventing modification while running and reducing the risk of code substitution. To activate the mode, create the LockBatchFilesInUse (DWORD) registry parameter at HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor and set its value to 1 (0 disables the mode). Additionally, Application Control policies can use the LockBatchFilesWhenInUse element in the application manifest.
• Code integrity check performance improvement. Previously, digital signature verification was performed for each line of a batch file, slowing down large scripts. Now verification occurs once for the entire file, significantly speeding up operation, especially in corporate environments with strict security requirements.
• Shared audio (preview) — separate volume sliders. The feature introduced in the fall allows two users to simultaneously use compatible Bluetooth LE Audio devices (headphones, speakers, hearing aids). Windows now provides separate volume sliders for each listener, allowing independent level adjustment without affecting the other user. The master volume (via quick settings, hardware buttons, or keyboard) still changes sound for both simultaneously.
• Shared audio — taskbar indicator. When sharing audio, an indicator appears on the taskbar to remind that the audio stream is active. Clicking the indicator quickly opens sharing settings, adjusts volume, or stops the stream.
• LE Audio ecosystem expansion. The shared audio feature is now supported on Samsung Galaxy Buds 4, Samsung Galaxy Buds 4 Pro, Sony WF-1000XM6, and Xbox Wireless Headset.
• Narrator — new command for status bar. Narrator users can use the keyboard shortcut “Narrator key + \” to read the contents of the status bar in applications such as Microsoft Word, Excel, and PowerPoint. For example, in Word you can hear the number of pages or words in the document, and in Excel the sum or average of selected cells without changing the current focus.
• Taskbar — auto-hide animation pause and reliability improvements. The deployment of enhanced animations when using automatic taskbar hiding has been temporarily paused. Also, the reliability of loading taskbar components in Safe Mode has been improved.
• Storage — update file deletion reliability. Reliability when deleting Windows update files and the windows.old folder through Settings > System > Storage has been improved.
• Input — ADLaM keyboard reliability. Text input reliability when using the ADLaM keyboard has been improved.

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

Insiders on the Dev Channel who previously used build 26220 will be automatically migrated to build 26300 via the enabling package KB5073032.

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