an engine core assembly including a core flowpath, a compressor section, a combustor section and a turbine section, the core flowpath extending through the compressor section, the combustor section and the turbine section from an inlet into the core flowpath to an exhaust from the core flowpath, the compressor section comprising a compressor rotor, and the combustor section comprising a plenum and a combustor adjacent the plenum;

a fuel system including a fuel flowpath, a fuel reservoir, a fuel-cooling air heat exchanger and a fuel injector, the fuel flowpath configured to direct hydrogen fuel, received from the fuel reservoir, through the fuel-cooling air heat exchanger to the fuel injector, and the fuel injector configured to introduce the hydrogen fuel into the combustor; and

a cooling circuit configured to direct cooling air, bled from the plenum, through the fuel-cooling air heat exchanger to the turbine section, the cooling circuit configured to bleed core air from the core flowpath within the plenum to provide the cooling air;

the fuel-cooling air heat exchanger configured to exchange heat energy between the hydrogen fuel flowing within the fuel flowpath and the cooling air flowing within the cooling circuit; and

the fuel system further including a fuel-core air heat exchanger upstream of the compressor rotor along the core flowpath, and the fuel-core air heat exchanger configured to exchange heat energy between the hydrogen fuel flowing within the fuel flowpath and the core air flowing within the core flowpath.