Windows 11 KB5124010 preview update brings 46 changes

Microsoft has pushed out KB5124010, the September 2026 optional preview update for Windows 11 24H2 and 25H2. It contains 46 changes, including Bluetooth fixes, a way to remap the Copilot key, and support for Emoji 17.0.

The release is a non-security update. Monthly preview updates like this one give administrators and users an early look at fixes and features that will reach all devices with next month's Patch Tuesday, the regular monthly release of Windows security and quality updates. Unlike the cumulative updates shipped on Patch Tuesday, previews such as KB5124010 contain only quality improvements. They do not patch security vulnerabilities.

On 25H2 systems the update raises the build number to 26200.9550. On 24H2 systems it becomes 26100.9550.

Bluetooth problems addressed

A large part of the update deals with Bluetooth. Microsoft fixed a bug where the Bluetooth radio could be switched off while the toggle in Settings still reported it as on. It also resolved crashes with error code 0x139 that could happen while streaming audio over Bluetooth.

Microphones on some Bluetooth Classic audio accessories should now work better. Microsoft also says it has improved reliability and performance for LE Audio accessories.

Copilot key and accessibility changes

Users who never touch the Copilot key can now give it another job. A new setting in Windows 11 lets the key act as the Right Ctrl key or as the Context Menu key.

The preview also adds an accessibility option called "Open apps maximized". When turned on, app windows open maximized automatically.

For administrators, Microsoft added a recovery remote management plug-in. It extends the management capabilities of Windows Recovery Environment (WinRE), the built-in toolset Windows uses to repair a system that fails to start.

Other additions and fixes

Some of the other notable changes in KB5124010:

• Slideshow wallpapers now work with multiple desktops, so Windows no longer switches the background back to a single picture.
• More gesture controls for precision touchpads are available under Settings > Bluetooth & devices > Touchpad.
• A new Camera roll backup feature in Settings lets eligible users back up their photos to OneDrive. It can be switched on from the Settings Home or Accounts page, and setup is finished on a mobile phone by scanning a QR code.
• A known issue that caused the built-in File History backup to fail on some systems after the September 2026 security updates has been fixed.

PC-to-PC Migration removed

The update also takes something away. PC-to-PC Migration, a tool for moving files, settings and preferences to a new Windows device, has been removed. Microsoft now points users to Windows Backup, which uses OneDrive to move data to a new PC.

How to install it

KB5124010 is available through Settings > Windows Update > Check for updates. Because it is optional, users have to click "Download and install". The exception is devices with the "Get the latest updates as soon as they're available" option turned on, which install it automatically.

The update can also be downloaded manually from the Microsoft Update Catalog.

Last preview for 24H2

Microsoft reminded users that KB5124010 is the final preview update for Windows 11 24H2. That version reaches end of support in October 2026.

Why It Matters

For most readers this is not an urgent patch. KB5124010 contains no security fixes, and anyone who waits will get these changes with the October Patch Tuesday release anyway. Still, a few details are worth attention.

The File History fix is the most practical one. A backup feature that quietly fails after a security update is exactly the kind of problem that stays hidden until a restore is needed. Organisations that rely on File History may want to check that their backups actually worked after the September updates. This is also another example of monthly updates causing side effects, as seen recently when Windows 11 updates caused black screens on Azure Virtual Desktop hosts. Testing previews on a small group of machines first remains sensible.

The removal of PC-to-PC Migration and the new Camera roll backup both push more user data toward OneDrive. This suggests Microsoft wants cloud storage to be the default path for backup and device migration. Companies with rules on where data can be stored should review whether these features fit their policies.

The most important date is October 2026. Once 24H2 is out of support, those devices will stop receiving security updates. Admins still running 24H2 should plan the move to 25H2 now. It is worth watching how quickly organisations complete that upgrade.