Quick fix: A 25H2 upgrade can leave a partial install if it failed mid-process. Boot from Windows 11 install USB → Repair your computer → Troubleshoot → Advanced options → Uninstall Updates → Uninstall latest feature update. The system rolls back to the previous version (24H2). After rollback, you can retry the upgrade.

You started a 25H2 enablement package install (or full feature upgrade). It rebooted partway through. Now Windows boots, shows the spinning dots, and reboots again. Endless loop. The upgrade is half-applied, neither old nor new version fully usable.

Symptom: Boot loop after a Windows 11 25H2 upgrade failed mid-process.
Affects: Windows 11 systems that attempted 25H2 upgrade and failed.
Fix time: 30–60 minutes.

What “partial upgrade” means

Windows feature upgrades replace system files atomically — either fully or not at all. If interrupted by a power loss, hardware error, or unrecoverable error during install, Windows leaves both versions on disk and tries to revert. The revert sometimes fails too, leaving partial state in either version.

Method 1: Uninstall latest feature update from WinRE

Boot from Windows 11 install USB.
Click Next → Repair your computer (bottom-left).
Choose Troubleshoot → Advanced options → Uninstall Updates.
Click Uninstall latest feature update. Confirm.
The system rolls back to the previous version (typically 24H2).
Boot to Windows. Verify with winver.

Method 2: Force boot to Safe Mode and uninstall via WUSA

If Windows partially boots, force three failed boots to trigger WinRE.
From WinRE → Troubleshoot → Advanced options → Startup Settings → Restart → F4 for Safe Mode.
If you reach Safe Mode, run wusa /uninstall /kb:KB#### for the 25H2 KB.
Reboot.

Method 3: In-place reinstall to the previous version

If rollback isn’t available (the 10-day window expired or Windows.old is gone), use a 24H2 install USB.
Boot the USB, run setup.exe, choose Keep my files and apps.
This reinstalls 24H2 over the broken state.

Verification

Windows boots to the sign-in screen.
winver shows your previous version (24H2 if rolled back).
Apps and files are intact.

If none of these work

If rollback fails and reinstall also fails, the disk may have damaged sectors from the interrupted write. Run chkdsk from WinRE Command Prompt. As a final option, clean install to a different drive and migrate data.

Bottom line: Partial 25H2 upgrades roll back via WinRE’s Uninstall latest feature update. If unavailable, in-place 24H2 reinstall preserves your data while restoring a clean state.