Linux gets a systemd user unit (WantedBy=default.target, restarted on failure), macOS a LaunchAgent (RunAtLoad, KeepAlive on failure), Windows a PowerShell script started hidden by a shortcut in the Startup folder (a .ps1 there itself would open in Notepad), which restarts the service if it fails. Each runs this node and this bundle by absolute path, carrying over DAVSYNC_CONFIG_DIR/DAVSYNC_STATE_DIR. 'install --print' shows what it writes; 'uninstall' removes it and stops the service; 'status' says whether it is installed.