By definition, the open circuit potential is the potential difference of two different terminals when there is no external load or external current flow in between. The open-circuit potential is exist when the circuit is open, not closed. But when we use the potentiostat to measure the open circuit potential between the working electrode and reference electrode, the electrolyte is the medium that can connect these two electrodes together. So in this way can we still name it "open-circuit potential"?