Windows 11 KB5077239: What’s New in the February 24, 2026 Preview Update

Microsoft is rolling out a fresh Windows 11 preview update today with KB5077239, bumping version 26H1 up to OS Build 28000.1643. This one is a non‑security preview release, but it still carries a long list of quality improvements, AI tweaks, and reliability fixes that early adopters and admins will want to know about.​

What kind of update is KB5077239?

KB5077239 is a non‑security cumulative preview update for Windows 11 version 26H1, released on February 24, 2026. Microsoft notes that it includes the latest security fixes and improvements plus non‑security changes that were first tested in an earlier optional preview. Just like other recent Windows 11 updates, it is bundled with the latest servicing stack update so you don’t have to install SSUs separately.​

Microsoft is continuing to use a mix of “gradual rollout” and “normal rollout” phases. Gradual rollout means some devices will see the update earlier than others, while normal rollout is the broad release to all eligible devices when the update reaches general availability.​

Copilot+ PCs and AI experiences

The release notes explicitly call out changes “unique to Copilot+ PCs,” highlighting Microsoft’s ongoing focus on AI‑powered Windows. This section is all about improving AI experiences, performance, and user experience on Windows 11 devices that support Copilot+ features. Microsoft points users to its Copilot+ PCs documentation for a deeper dive into the different AI experiences that now sit on top of Windows.​

Even if your device isn’t branded as a Copilot+ PC, it’s clear that the Windows 11 update cadence is now heavily oriented around AI readiness, responsiveness, and reliability.​

Start menu, taskbar, and UI polish

Like most preview updates, KB5077239 ships with a long tail of UI and shell tweaks that will quietly make Windows 11 feel less quirky.​

Highlights include:

• Improved reliability when logging into your PC so Explorer.exe is less likely to hang the first time you sign in, which previously could cause the taskbar to go missing.​

• Desktop icon behavior has been tuned so icons stay put when you open or rename files, instead of jumping around unexpectedly.​

• The “Automatically hide the taskbar” setting now behaves more reliably and no longer shuts itself off after the “A toolbar is already hidden on this side of your screen” message.​

• Voice access works more reliably when you interact with the taskbar, including when you call out numbers to pick a specific item.​

On the Start menu side, Microsoft says that for users with the “new” Start experience, the Windows Search panel now matches the Start menu in size to create a smoother transition when you start typing. This is the sort of subtle alignment change that you probably won’t notice consciously, but it does make the overall experience feel more polished.​

Settings, OneDrive, and Virtual Workspaces

KB5077239 also makes some nice changes in Settings, particularly around advanced features and OneDrive integration.​

Notable items:

• A new “Virtual Workspaces” toggle appears in Settings > System > Advanced, letting you enable or disable virtualization environments like Hyper‑V and Windows Sandbox in one place.​

• The “About” page in Settings gets an updated layout that brings device details and related options into a single, cleaner view, with quicker access to storage and other key settings.​

• A new OneDrive section is called out in the changelog, reflecting Microsoft’s ongoing push to blend cloud storage more deeply into core Windows experiences.​

• Navigating to Settings > Network & Internet is now more reliable and less likely to cause Settings to become unresponsive.​

• Keyboard character repeat delay labels in Bluetooth & Devices > Keyboard have been refined so they display more clearly.​

For power users and IT admins, having a centralized Virtual Workspaces entry point should make it easier to toggle virtualization features without digging through multiple legacy dialogs.​

File Explorer, sandbox, and reliability fixes

There are several quality improvements aimed at stability and consistent behavior across File Explorer and Windows Sandbox.​

A few standouts:

• File Explorer now avoids showing an unexpected toolbar in some scenarios and has a fix for right‑click menus where the “Open” option could show a generic app icon instead of the default app for that file type.​

• A bug that caused Windows Sandbox to stop responding during startup with error 0x800705b4 has been addressed.​

• User Account Control (UAC) reliability is improved when launching Windows Terminal as an administrator from a non‑admin account, helping prevent scenarios where the PC could become unresponsive.​

BitLocker recovery also receives an improvement: after entering a recovery key, devices should now start Windows more reliably instead of getting stuck. This is the kind of behind‑the‑scenes fix that can make a huge difference when you’re recovering an important machine.​

Gaming, brightness, and Game Pass branding

Gamers and all‑in‑one PC owners get a few targeted fixes as well.​

• Some games recently showed an “Unsupported graphics card detected” error even when running on supported hardware; this has now been fixed.​

• The brightness slider on all‑in‑one PCs has been tuned to better remember your chosen brightness and avoid unexpected level changes.​

• References to Game Pass in Settings have been updated to reflect new branding and benefits, aligning Windows with Microsoft’s evolving subscription strategy.​

These are small tweaks individually, but together they help reduce friction around gaming and day‑to‑day use.​

Activation and licensing improvements

Another subtle but important change lands in the activation pipeline. Microsoft notes that Windows license migration during upgrades is now more robust, reducing cases where a valid digital license fails to migrate correctly and forces users to run the Activation troubleshooter. That should cut down on post‑upgrade activation headaches, especially in environments where devices are upgraded in batches.​

Known issues and how to install

Microsoft says it is not currently aware of any known issues with KB5077239. As usual, if you’ve already installed earlier updates, Windows Update will only download and apply the new bits contained in this package.​

To install KB5077239 on a compatible Windows 11 device, head to Settings > Windows Update and check for updates, and the preview build should appear as an optional install during the rollout window. If you prefer to wait for a fully supported release, these fixes should roll into a future Patch Tuesday cumulative update once testing wraps up.

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