NOOBS recovery mode defaults to reinstall when OS partition corruption is detected

When a Raspberry Pi OS upgrade fails and the system becomes unbootable, users may invoke NOOBS recovery mode by holding the Shift key during power-on. The feature is designed to reinstall the operating system onto the SD card, but it does not provide an explicit repair or filesystem-check option for the existing installation.

This creates an unresolved decision point: the recovery interface defaults to full reinstallation without offering partition repair or filesystem-check routines, leaving users to determine how to address a corrupted OS.

What mechanisms does NOOBS use to assess partition integrity before presenting reinstall options? Can a repair pathway be triggered within the recovery interface? How should users manage a corrupted OS when only reinstall is offered?