Build 26300.7939 (KB5077243) for Windows 11 26H2 expands Shared audio and safer batch files (Dev)

Windows 11 build 26300.7939 (KB5077243) was released to the Dev Channel with a small set of improvements.
The update introduces more secure execution of batch files, a shared audio feature via Bluetooth, and more.
In addition, there are several fixes and improvements for Narrator, Windows Update, and more.
Windows 11 build 26300.7939 also rolls out in the Beta Channel with the same changes.

Microsoft has released Windows 11 build 26300.7939 as the update KB5077243 for version 25H2 through the Dev Channel of the Windows Insider Program. This preview introduces one new feature, fixes, and some improvements.

In addition, the company is rolling out Windows 11 Insider Preview Build 26220.7934 (KB5077242) in the Beta Channel, with most of the same features as those available in the Dev Channel.

According to the company, the “Windows 11 Insider Preview Quality Update (26300.7939)” introduces a more secure method for processing batch files and adds the ability to share audio with up to two people using Bluetooth LE Audio headphones, speakers, earbuds, or hearing aids.

This release also includes changes to Windows Narrator, Storage, and input. Also, the update KB5077243 temporarily halts the animation improvements for the Taskbar.

Although this article lists the changes for version 26H2, Windows 11 still shows 25H2 as the version number, but the version number will eventually change to 26H2.

What’s new on Windows 11 build 26300.7939

These are the new features and improvements rolling out in the Dev Channel:

Batch files security enhancement

Starting with builds 26300.7939 and 26220.7934, Microsoft is improving how the system handles batch files and Command Prompt scripts to enhance both security and performance.

As part of this change, you can now enable a protected execution mode that prevents batch files from being modified while they are running. This is done by creating the LockBatchFilesInUse (DWORD) value under: HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor.

Setting the value to 1 turns on the protection, while 0 leaves it disabled. In addition, you can activate the same behavior through the LockBatchFilesWhenInUse application manifest control.

When Code Integrity is enabled, this change also reduces overhead. Instead of validating a script’s signature for each individual command in the batch file, Windows 11 now performs signature verification only once at launch. The result is faster execution combined with stronger safeguards against tampering during runtime.

Shared audio feature

Updates KB5077243 and KB5077242 expand the Shared audio (preview) experience with more granular controls and broader device support.

The operating system now includes separate volume sliders for each person when two Bluetooth LE Audio devices are connected for audio sharing. The primary system volume controls in Quick Settings, as well as hardware and keyboard controls, still adjust audio for both listeners simultaneously.

There’s also a new Taskbar indicator that appears whenever audio sharing is active. This visual cue makes it clear that your sound is being shared and provides one-click access to the sharing settings.

On the hardware side, support for shared audio continues to expand, and now, it’s available on the Samsung Galaxy Buds 4, Samsung Galaxy Buds 4 Pro, Sony WF-1000XM6, and the Xbox Wireless Headset.

Windows Narrator improvement

This rollout adds a new shortcut for Windows Narrator users to quickly access status bar information without changing focus.

You only have to press “Narrator key + \” to have the bar read aloud in supported apps. In Word, this can announce the page or word count. In Microsoft Excel, selecting cells lets you see calculations such as sum or average directly on the status bar.

Other changes

As part of updates KB5077243 and KB5077242, you will also find smaller changes that improve. For example, this rollout addresses liability issues when deleting Windows Update files and the Windows.old folder, and it improves typing stability when using the ADLaM keyboard layout.

Microsoft also notes that the rollout of the updated animations for the auto-hide taskbar has been temporarily paused while refinements are made.

Download Windows 11 update KB5077243

To download and install these Windows 11 builds, enroll your Devices in the Dev or Beta Channels through the “Windows Insider Program” settings from the “Update & Security” section. Once you enroll the computer in the program, you can download the build from the “Windows Update” settings by turning on the “Get the latest updates as soon as they’re available” option and clicking the “Check for Updates” button.