Microsoft Windows 11 26H1 Update Version OS Build 28000.3086

KB5124006 for Windows 11 version 26H1 (OS Build 28000.3086) delivers quality improvements, new taskbar, Start, Search, and File Explorer features, plus Administrator protection and other platform enhancements. It also includes a File History fix and notes known issues with domain trust and USB Audio Class 1.0 devices. Reference IDs: KB5124005, KB5124012.

• Administrator protection hardens against elevation-of-privilege attacks by using just-in-time privileges and profile separation; it is off by default.
• Machine Identity Isolation enforcement can affect domain trust on some domain-joined devices when used outside supported Windows Server 2025 DFL environments.

• Improves reliability of loading the system tray area on non-touch PCs.
• Improves reliability of navigating to and interacting with Display settings.
• Improves persistence of brightness settings after energy saver turns off.
• Improves reliability of displaying app history in Task Manager.
• Improves restart behavior so manually sleeping PCs return to sleep after updates.
• Improves resiliency against VPN-related background issues that can cause processes to stop responding.
• Improves Japanese IME typing reliability and voice typing setting persistence.
• Improves the output of netsh wlan show wlanreport for Japanese users.
• Fixes File History backup and restore failures to external drives or network locations.

• Taskbar can now be positioned at the top, bottom, left, or right, with a smaller taskbar option and expanded Taskbar behaviors by default.
• Start menu adds small or large size options, renames Recommended to Recent, allows hiding the user name and profile picture, and redesigns settings with section-level toggles.
• Windows Search adds simplified home, clearer result source labels, optional web and Microsoft Store suggestions, and automatic indexing of most-used folders.
• File Explorer Home launches faster and Recommended supports touch scrolling.
• Updated progress indicators appear across startup, sign-in, restart, shutdown, and update installation.
• Windows Share can suggest and install relevant apps for work or school accounts.
• Windows Autopilot device preparation device association is now generally available.
• Microsoft Execution Containers adds Process Isolation for responsive workloads.
• Agentic process tagging preview is added for authenticated agent-aware workflows.
• Post-Quantum Cryptography ML-KEM can now be used as a standalone TLS key exchange algorithm.
• App updates can coordinate with Windows Update through the Windows Update Orchestration Platform.
• Microsoft Store now supports in-app purchases in packaged WinUI 3 apps that require elevation.

• Domain-joined devices might lose their secure trust relationship with the domain after KB5124012 or later if Machine Identity Isolation is enabled outside supported environments.
• USB Audio Class 1.0 devices might fail to start or produce audio, including Code 10 errors and unresponsive sound settings.

• This update is available through gradual rollout and normal rollout; feature availability may vary by device.
• If earlier updates are installed, only the new updates in this package are downloaded and installed.
• WMIC is removed from Windows 11 version 26H1 starting in September 2026 and is no longer available as a Feature on Demand; WMI remains supported.
• For dynamic updates applied to installation media, include boot.stl or use the Update WinPE script to avoid startup failures.
• The update includes SSU KB5124005 (Build 28000.3081) to improve update installation reliability.
• Administrator protection can be enabled through Microsoft Intune OMA-URI or Group Policy.

Product Information

Vendor: Microsoft

Product: Windows 11

Product type: Software

Application category: Utilities

Platform: Windows

Variant: 26H1

Version: OS Build 28000.3086

Vendor information published: Sep 22, 2026

Original release notes: View on vendor site

Published on updatealert.io: Sep 24, 2026

Description: Client operating system for modern desktop and enterprise environments.