Microsoftは5月26日(現地時間)、Windows 11 Version 25H2/24H2用のプレビューアップデートKB5089573を公開しました。オプション扱いの更新プログラム(プレビュー版)で、多数の不具合が修正されています。Windows Updateの「更新プログラムのチェック」を利用するか、Microsoft Update Catalogからファイルをダウンロードすることで、手動でインストールすることができます。May 26, 2026—KB5089573 (OS Builds 26200.8524 and 26100.8524) PreviewWindows 11 Version 25H2/24H2用の更新プログラムKB5089573には、アプリの起動や、スタートメニュー・検索・アクションセンターといったWindowsの中核的なシェル機能の動作を高速化する改良が含まれています。[General Performance] This update accelerates app launch and core shell experiences such as Start menu, Search, and Action Center.これは、CPUを一時的にブーストして処理速度を改善する「Low Latency Profile」を指していると見込まれています。その他、Shared Audio(音声共有)やNPU(AI処理)可視化の強化、マルチアプリカメラなど、日常の使い勝手に直結する改善も多く含まれています。リリースノートは以下の通りです。ハイライトGradual rolloutThe following summary outlines features from AI-powered Windows 11 PC experiences, along with improvements and fixes. The bold text within the brackets indicates the item or area of the change.Windows 11 PC experiencesThis section highlights some new features and enhancements for Windows 11 PCs, including AI-powered capabilities, continuous innovation, and performance improvements.[Shared Audio] New! Shared Audio enables two people to listen to the same audio from a single Windows 11 PC at the same time. It uses Bluetooth® LE Audio broadcast technology to make sharing easy. For example, you can watch a movie while traveling or listen to music while studying together. To start sharing audio, open Quick settings from the taskbar, select Shared Audio, choose two supported, paired, and connected devices, and then select Start sharing. To learn more about Shared Audio, see Extending Bluetooth® LE Audio on Windows 11 with Shared Audio.[Magnifier in Windows] New! Magnifier now provides clearer and more consistent announcements when working with a screen reader. You’ll hear helpful announcements when you zoom in or out, switch views, turn color inversion on or off, or turn Magnifier on or off. This makes it easy to stay oriented while you work. New! Magnifier now supports magnification of permitted protected content.This update improves smoothness when moving Magnifier in lens mode.[Task Manager] New! Task Manager now offers improved visibility into NPU usage on PCs with an NPU. New optional NPU and NPU Engine columns are available on the Processes, Users, and Details pages, along with NPU Dedicated Memory and NPU Shared Memory optional columns on the Details page. Neural engines that are part of a GPU now appear on the Performance page, providing a more complete view of AI‑related activity. A new optional Isolation column on the Processes and Details pages shows which apps are running in an AppContainer. You can add any of the new columns by right‑clicking a column header in Task Manager and selecting them from the menu.This update improves CPU speed display on the Performance page of Task Manager for VMs, so it doesn’t show higher than unexpected numbers after resuming from hibernate.[Camera] New! Windows 11’s Multi-App Camera feature allows multiple applications to access your camera stream at the same time. Basic Camera mode in Windows 11 enables simplified camera functionality, useful for troubleshooting or improving stability when your camera is not working correctly. Enterprise admin can now set Multi-App Camera mode or Basic Camera mode through Group Policy, under Computer Configuration > Administrative Templates > Windows Components > Camera > Configure Camera Options.[Windows Setup] New! You can now choose a custom name for your user folder on the Device Name page during Windows setup. The updated experience makes it easier to select a custom name during setup only. If this step is skipped, Windows uses the default folder name and continues setup as usual. User folder names must follow standard Windows naming requirements.[General Performance] This update accelerates app launch and core shell experiences such as Start menu, Search, and Action Center.[Windows Hello]This update optimizes the Windows Biometric service (WinBio) to help improve performance when your device resumes from Modern Standby.This update reduces unexpected authentication blocks in Windows Hello Enhanced Sign‑in Security by resolving missing secure enrollment metadata.This update improves sign‑in behavior on the lock screen and sign‑in screen. When Windows Hello face or fingerprint is set up and available, it is now the default sign-in method every time you sign in, even if you used a different method previously. If you need to use your Windows PIN instead and use it three times in a row, Windows will stay with PIN until you switch to another sign-in method.[Windows Search Box] Windows Search will now find and prioritize files with as few as two characters.[Storage]The dialog box for creating a Dev Drive now supports specifying the size in gigabytes (GB) instead of only megabytes (MB). This option is also available when resizing volumes in Settings > System > Storage.In Settings > System > Storage, you now see a User Account Control (UAC) prompt only when you choose to view temporary files, instead of immediately when opening the page.[USB] This update improves reliability for displays attached to USB4 docks and hubs. These displays now light up more consistently, particularly when coming out of standby.The USB3 stack is updated to have additional resiliency and recovery measures in place against certain unexpected hardware faults and conditions. Users will experience higher reliability with USB devices.[Sensors] This update improves resiliency against apps that could keep the sensor hub powered on and drain power, impacting battery life.[Human Interface Device (HID)] This update improves battery life related to the HID and Input stack for failed HID devices. Power hygiene is also improved against applications that might initiate HID transfers during standby.[Input] The update improves:Reliability of the touch keyboard on the sign‑in screen, including when entering or changing a password.Reliability of explorer.exe when closing the input switcher.Performance when opening or navigating to clipboard history.[Fonts] The Times New Roman font family is updated to improve the rendering of combining diacritical marks across Greek and Cyrillic scripts. This update provides more accurate and visually consistent text by addressing mark positioning issues. These changes improve readability, reduce rendering inconsistencies, and better support for global language users working with Greek and Cyrillic content.[Task Scheduler] Task Scheduler now saves column width adjustments in task list view across sessions.[Desktop icons] This update improves reliability of loading desktop app shortcuts.[Microsoft Store] This update includes underlying changes that improve download performance and bandwidth usage.This update improves error reporting when downloads fail due to Windows Update group policy settings being enabled.[Reliability] This update improves Windows reliability on the sign-in and lock screens, in File Explorer, when using touch gestures on touchscreen devices, and when changing themes in Settings.Normal rolloutThis non-security update includes quality improvements. The following summary outlines key issues addressed by the KB update after you install it. Also, included are available new features. The bold text within the brackets indicates the item or area of the change.[Secure Boot] With this update, Windows quality updates include additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Devices receive the new certificates only after demonstrating sufficient successful update signals, maintaining a controlled and phased rollout.This update adds the LimitSecureBootRequiredServiceData Group Policy and mobile device management (MDM) setting under Computer Configuration > Administrative Templates > Windows Components > Secure Boot. When enabled, Windows limits the Secure Boot service data it sends by suppressing the event normally sent to Microsoft. This policy is included in the Windows Restricted Traffic Limited Functionality Baseline. For information about the policy, see Manage connections from Windows 10 and Windows 11 operating system components to Microsoft services.If you installed earlier updates, your device downloads and installs only the new updates contained in this package.既知の不具合更新プログラムには以下の1件の既知の不具合が存在します。May 2026 security update fails to install with error 0x800f0922SymptomsAfter you install this update (KB5089549), some devices might fail to complete installation with error code 0x800f0922. This issue occurs on devices that have limited free space on the EFI System Partition (ESP), especially if it has 10 MB or less available.What you might experience on affected devices:The update installs successfully during the initial phases.The installation fails during the restart phase at approximately 35–36% completion.Windows then rolls back the update.You may see the message:“Something didn’t go as planned. Undoing changes.”The installation fails with error code 0x800f0922.As a result of this issue, you might see log entries similar to the following in C:\Windows\Logs\CBS\CBS.log, indicating insufficient free space on the EFI System Partition:SpaceCheck: Insufficient free spaceServicingBootFiles failed. Error = 0x70SpaceCheck: used by third-party/OEM files outside of Microsoft boot directoriesWorkaroundAffected customers can use one of the following workarounds to mitigate this issue.Option 1: Allow the update to install by modifying an ESP registry settingImportant: Editing the registry incorrectly can cause serious system problems. Always back up the registry before making any changes.Open Command Prompt as an administrator.Run the following command: reg add “HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc /v EspPaddingPercent /t REG_DWORD /d 0 /f”Restart the affected device.Retry installing the update.Option 2: Mitigate the issue by using Known Issue Rollback (KIR)This issue is mitigated using Known Issue Rollback (KIR). The resolution has already propagated automatically to consumer devices and non‑managed business devices. Restarting your Windows device might help the resolution apply more quickly.Enterprise-managed devicesFor devices where Windows updates are managed by IT departments, administrators can apply the mitigation by installing and configuring a special Group Policy. You can find the policy at Computer Configuration > Administrative Templates > .Group Policy download Windows 11, version 25H2 and Windows 11, version 24H2: KB5089549 260514_06221 Known Issue RollbackImportant: You must install and configure the Group Policy that matches your version of Windows to resolve this issue. You must also restart affected devices to apply the policy. This Group Policy temporarily disables the change that causes the issue.For more information, seeHow to use Group Policy to deploy a Known Issue Rollback.A resolution is in progress and will be included in a future Windows update. This documentation will be updated once the resolution is available.更新プログラムはWindows Updateの他、Microsoft Update Catalogを利用してインストールすることができます。