This names the previous FSM workflow that ran against this slot before the current one started. For this chassis slot's endpoint for whatever blade currently occupies it, fsmPrev gives an admin the history needed to tell whether the current in-progress workflow was triggered by a normal operation (like association) or is a retry following a prior failed workflow, which changes how urgently a stuck stage should be treated. If fsmPrev reads 'Decommission' and the slot is now running a fresh 'Discover' workflow, that tells an admin this slot's blade was just removed and reseated, not merely rebooted.