Windows 11 24H2 and 25H2: August cumulative experience changes

KB5121003 is the August cumulative security update for Windows 11 24H2 and 25H2. It carries the prior preview improvements forward and sets the new targets to build 26100.9168 and 26200.9168.

What changed

The Windows Client What’s New feed now exposes the actual cumulative changes behind KB5121003, rather than only the KB number, build and Secure Boot note. The release includes File Explorer, Widgets, Windows Hello, touchpad, Voice Access, Search, Start, networking, printing, Remote Desktop and reliability changes.

Technical details

File Explorer: clearer size units in Details view, hover quick actions, and reliability fixes for OneDrive, paths, rename and address-bar scenarios
Widgets: accent-colour taskbar badges, less intrusive hover behaviour, configurable dashboard and performance improvements
Windows Hello ESS: support for compatible external fingerprint readers
Touchpad: configurable scroll and zoom speed plus accelerated scrolling controls
Voice Access: Voice Isolation and improved dictation support for French, German and Spanish
Search and Start: improved typo and partial-name app search, more relevant Settings results, reliable view preferences and apps-list keyboard navigation
Input and account control: mouse-cursor persistence, revised fluid-dictation default and updated Start account control for Microsoft-account users
Management and storage: MDM enrollment-compliance correction plus File History backup reliability for SMB network shares
Power and Windows Update: more reliable power-plan setting application, restored Energy Saver threshold and improved update progress and cleanup behaviour
Networking and remote work: more reliable DHCP renewal, Wi-Fi, cellular and VPN compatibility, plus improved IPPS printing and RDP or AVD clipboard reliability
Accessibility, Bluetooth and audio: screen tint and Magnifier refinements, more reliable Bluetooth and LE Audio behaviour, and HD Audio driver reliability
Platform reliability: WSL mirrored networking for VPNs, multi-monitor rendering and colour-profile persistence, BITS shutdown and Explorer reliability improvements
Security and servicing: additional high-confidence Secure Boot certificate targeting, AI components version 1.2605.856.0 and SSU KB5123304 build 26100.9156

Why it matters

Endpoint teams need to separate universally installed security and servicing content from experience changes that can be hardware-, policy- or phased-rollout dependent before defining pilot validation.

Known limitations

Microsoft added a known issue on 20 August 2026: systems with RGB-lighting components or drivers such as inpoutx64 can experience game hangs, application exits, EXCEPTION_ACCESS_VIOLATION or unexpected restarts
Microsoft is investigating and has not published a mitigation yet
The card is cumulative: some user-facing capabilities originate in prior preview releases and can be policy-, device- or rollout-dependent
AI component updates apply only to compatible Copilot+ PCs
Dynamic Update media must contain the matching boot.stl file or startup can fail with 0xc0430001

Now check

Deploy KB5121003 to separate 24H2 and 25H2 pilot rings and verify builds 26100.9168 and 26200.9168
Test File Explorer, Windows Hello ESS, touchpad, Voice Access, Search and Start only on applicable devices
Validate MDM compliance, SMB File History, VPN, IPPS printing and RDP or AVD scenarios
Validate Secure Boot certificate readiness and boot.stl in any updated installation media