How can I automate Windows.old cleanup after a Windows 25H2 upgrade?

You can configure Cleanmgr once with cleanmgr /sageset:777, select the option for previous Windows installations, and note the registry value it creates. Then deploy that value to other machines and run cleanmgr /sagerun:777. For example: reg add "HKLMSOFTWAREMicrosoftWindowsCurrentVersionExplorerVolumeCachesPrevious Installations" /v StateFlags777 /t REG_DWORD /d 2 /f, followed by cleanmgr /sagerun:777. This avoids trying to take ownership of the directory directly.

Avoid using takeown or icacls recursively on Windows.old. The junctions can redirect the operation into protected system locations, potentially changing ownership and permissions on unrelated files. Test any cleanup command on a disposable machine before deploying it broadly.

Storage Sense can handle this through policy and is safer than manually deleting Windows.old. Depending on the upgrade state, Windows may also remove the previous installation automatically after the rollback window expires—usually around 10 days, though the timing can vary.

cleanmgr /autoclean is sometimes suggested for this, but it isn't reliable in every deployment scenario. The configured /sageset and /sagerun approach gives you more control, especially when running the cleanup through a remote deployment tool.