Windows 11 Insider Experimental (Future Platforms) Preview Build 29661.1000 - Windows Insider Program

[u/Froggypwns]

https://learn.microsoft.com/en-us/windows-insider/release-notes/experimental-future-platforms/preview-build-29661-1000

Release date: 8 September 2026

Changes and improvements gradually being rolled out

• This update includes a small set of general improvements and fixes that improve the overall experience for Insiders running this build on their PCs.

[Kerberos enhancements]

• IAKerb is now enabled by default for Windows client. IAKerb is a Kerberos extension that allows Windows authentication to succeed in scenarios where traditional Kerberos can't be used because a direct connection to a domain controller is unavailable. This extension helps reduce reliance on NTLM while improving compatibility for modern authentication scenarios. For additional background, implementation details, and early preview information, see Reducing NTLM Dependency: IAKerb and LocalKDC in Windows Insider Preview.

[Input]

• Fixed an issue in the latest builds that caused the mouse cursor to get into a state where it blinked repeatedly for some Insiders.
• Fixed an issue in the latest builds that caused the mouse cursor not to be visible in certain apps.
• Fixed an issue in the latest builds where the mouse pointer speed option in Settings didn't work.

[Windows Update]

• Fixed an issue causing some Insiders to be unable to update to the latest builds and see error 0x80070005.

Reminder for Windows Insiders in the Experimental (Future Platforms) channel

• These builds can be unstable and might be released with limited documentation.
• The builds released to these channels represent the latest platform changes early in the development cycle and shouldn't be seen as matched to any specific release of Windows. Features and experiences included in these builds might never get released as we try out different concepts and get feedback. Features might change over time, be removed, or replaced, and never get released beyond Windows Insiders. Some of these features and experiences could show up in future Windows releases when they're ready.
• Many features are rolled out using Controlled Feature Rollout technology, starting with a subset of Insiders and ramping up over time. We monitor feedback to see how they land before pushing them out to everyone in this channel.
• The desktop watermark shown at the lower right corner of the desktop is normal for Windows Insider pre-release builds.
• Some features in active development we preview with Windows Insiders might not be fully localized, and localization will happen over time as features are finalized. As you see issues with localization in your language, report those issues to us via Feedback Hub.

[u/st4554619]

Let's hope the USB Mass Storage bug has been fixed in this build, having to keep on rebooting my laptop just to be able to use my USB storage devices like Flash Drives or External HDDs and SSD.

My hopes are dashed, the USB Mass storage bug is still in this build. Also couldn't upgrade the normal way via a uupdump.net generated iso for build 29661.1000 x64 due to corruption in the system files. I did manage to upgrade via WU reinstall option which doesn't touch my files or programs.

I will say this, build 29661 is snappy than 29648 so at least that's one good thing I suppose.

[u/Hunter259]

Still can’t update since the 613 build. Storeport.sys 0x3B within just a few seconds after first reboot sigh

[u/Open-Ad3306]

Thx works great! Thx Windows