After updating ComfyUI, many users encounter the "Legacy ComfyUI-Manager data backup exists" warning message. This alert appears because ComfyUI-Manager is now integrated as an official dependency, and old manager data was automatically backed up during the transition. The legacy backup is stored in the hidden folder ComfyUI/user/__manager/.legacy-manager-backup and can be safely removed if your installation works correctly. On Windows, you can delete it via File Explorer or PowerShell using the Remove-Item command. Linux users can use the rm -rf command or shred for secure deletion of sensitive data. The warning will disappear after removing the backup folder and restarting ComfyUI. If the backup keeps recreating, ensure ComfyUI-Manager is fully updated to the latest version. This guide provides step-by-step instructions, automation scripts, and troubleshooting tips for both Windows and Linux systems.