Windows 11 Insider Canary preview build 25905 adds Rust in the kernel and more

It's been a while, but finally, members of Microsoft's Windows Insider Program in the Canary preview channel have a new Windows 11 build to download. The build number is 25905.

Microsoft says that this build also restores the desktop watermark to RS_PRERELEASE. This also means that some features that were removed when it switched to the ZN_RELEASE label are now back.

Microsoft also releases a new version of the Microsoft Store for all Windows Insider Program channels, and you can check out the details in this post.

The changelog for the new Canary build is below:

What’s new in Build 25905

New features from the Dev Channel

This build includes new features from the Dev Channel, such as Dev Drive, Backup and Restore improvements (Windows Backup), Dynamic Lighting, the Windows App SDK version of File Explorer and Gallery, and more.

Rust in the Windows Kernel

Rust offers advantages in reliability and security over traditional programs written in C/C++. This preview shipped with an early implementation of critical kernel features in safe Rust. Specifically, win32kbase_rs.sys contains a new implementation of GDI region. While this is a small trial, we will continue to increase the usage of Rust in the kernel. Stay tuned!

[We are beginning to roll this out, so the experience isn’t available to all Insiders in the Canary Channel just yet as we plan to monitor feedback and see how it lands before pushing it out to everyone.]

Arm32 UWP App deprecation

Starting in this Insider Preview build in the Canary Channel, we have removed support for Arm32 UWP applications from Windows on Arm, as documented here: Windows 11 Specs and System Requirements. After the OS upgrade, any installed Arm32 applications will no longer launch on your device. Note that this does not affect Arm64 applications.

During setup, you will see a message with a list of applications that are currently Arm32 installed on the system.

In many cases, the list of impacted applications will be reduced by manually forcing the Microsoft Store to install any pending application updates prior to the OS upgrade. To do this, launch the Microsoft Store application, choose “library”, then click on the “Get Updates” button.

After the OS upgrade is complete, to fix any Arm32 applications, you will need to manually uninstall then reinstall those applications from the Microsoft Store. By doing so, you will install a compatible version that will run on your device.

New PostAuthenticationAction support for terminating individual processes in Windows LAPS

Thank you everyone who gave us feedback on the new Windows Local Administrator Password Solution feature which we shipped a few months ago. Several customers pointed out that the new Post Authentication Actions feature (PAA) only handled termination of interactive logon sessions. This meant that PAA was not able to terminate specific individual processes that were launched in an OTS (over-the-shoulder) elevation scenahttps://learn.microsoft.com/windows-server/identity/laps/laps-concepts#password-reset-after-authenticationrio, for example using runas.exe. We are announcing an improvement with this build that addresses this feedback on that limitation. A new option has been added to the PostAuthenticationActions Group Policy in this Insider Preview build:

Enable the new PostAuthenticationAction setting.

The new option is described as “Reset the password, logoff the managed account, and terminate any remaining processes”. This new option is basically a superset of the previous “Reset the password and logoff the managed account” option. When the new setting is configured, PAA will first notify and then terminate any interactive logon sessions, followed by enumerating and terminating any remaining processes that are still running under the Windows LAPS-managed local account identity. No notification precedes this termination.

In addition, we’ve greatly expanded the event logging messages that are emitted during post-authentication-action execution, to give you deeper insights into exactly what was done during the operation.

Note: “Reset the password and logoff the managed account” remains the default PAA action.

Please try out this new feature and let us know what you think here on the Windows LAPS feedback page.

Changes and Improvements

[Emoji]

With the update of our colour font format to COLRv1, Windows is now able to display richer emoji with a 3D like appearance with support coming soon to some apps and browsers. These emoji use gradients to bring the design style that our customers have been asking for. The new emoji will bring more expression to your communications.

Before and after of the updated colour format for emoji.

[Zune]

In celebration of Marvel Studio’s Guardians of the Galaxy Volume 3, we temporarily re-launched Zune.net last month. We also took the opportunity to fix an issue that was causing some challenges in getting the original Zune drivers to install in Windows 11 with this build in the Canary Channel. So now it should be easier to use your (totally unsupported and still discontinued) Zune on Windows 11. Over time, the fix will make its way through the Insider Channels and eventually to all Windows 11 customers. For fun, check out how Scott Hanselman brought a few Zunes back to life.

Known issues

[NEW] This build will not be offered to ASUS devices or PCs with ASUS motherboards.

[NEW] Ethernet-connected devices may lose network connectivity after updating to this build. Unplugging the ethernet cable and re-plugging the cable in should resolve the issue.

You can check out the full blog post here. You can also download the ISO file for this build as well.

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