A mobile handset with a fault tolerant update agent employs an efficient interruption point detection technique to recover from interruptions during the update of firmware or software. In one embodiment, the update agent updates firmware and/or software employing a plurality of transforms, each transform employing one pass or a subset of one pass to execute, each pass associated with its own bank order and with its own decision maker bank (for recovery following a fault, such as power failure). The devices and method disclosed are applicable to other electronic devices such as, for example, personal digital assistants (PDAs), personal computers (PCs), pagers, and the like.