System for fuel and diluent control

According to various embodiments, a system includes a fuel controller (182) configured to control a fuel transition between a first flow of a first fuel (168) and a second flow of a second fuel (172) into a fuel nozzle (252) of a combustion system (166). The fuel controller (182) is configured to adjust a third flow of a diluent (176) in combination with the second flow of the second fuel (172) to maintain a pressure ratio across the fuel nozzle (252) above a predetermined operating pressure ratio.