The plugin allows the automatic saving of the project and layers in edit mode at a user-defined interval.

For PyQGIS plugin developers, the plugin will change the QgsProject filename in the background temporary. So QGIS will trigger the signal fileNameChanged.

If your plugin or script is listening to this signal, it's somehow a false positive because the user didn't change the filename on purpose and the plugin will set back the normal filename after the backup is made.

For this reason, when the fileNameChanged is emitted, you can check if the environment variable QGIS_PLUGIN_AUTO_SAVING is present. If yes, it means it has been the plugin doing the backup file.