A gas turbine heat exchanger (20; 500; 600) for providing thermal energy transfer between a first flow along a first flowpath and a second flow along a second flowpath, the heat exchanger (20; 500; 600) comprising: at least one plate bank (40A, 40B) comprising a plurality of plates (50; 300; 350; 360), wherein the plates (50; 300; 350; 360) are optionally parallel to each other, each plate (50; 300; 350; 360) having: a first face and a second face opposite the first face; a leading edge along the second flowpath and a trailing edge along the second flowpath; a proximal edge having at least one inlet port along the first flowpath and at least one outlet port along the first flowpath; and at least one passageway along the first flowpath; an inlet manifold (82; 504) having at least one inlet port and at least one outlet port; and an outlet manifold (84; 506) having at least one outlet port (24A, 24B; 24) and at least one inlet port, the first flowpath passing from the at least one inlet port of the inlet manifold (82; 504), through the at least one passageway of each of the plurality of plates (50; 300; 350; 360), and through the at least one outlet port (24A, 24B; 24) of the outlet manifold (84; 506), characterized in that: the inlet manifold (82; 504) and outlet manifold (84; 506) are portions of a single unit (80; 502); a buffer cavity (115; 550; 650) is located between the inlet manifold (82; 504) and the outlet manifold (84; 502); and the buffer cavity (115; 550; 650) has at least one inlet (410A, 410B) and at least one outlet (412A, 412B). at least one plate bank (40A, 40B) comprising a plurality of plates (50; 300; 350; 360), wherein the plates (50; 300; 350; 360) are optionally parallel to each other, each plate (50; 300; 350; 360) having: a first face and a second face opposite the first face; a leading edge along the second flowpath and a trailing edge along the second flowpath; a proximal edge having at least one inlet port along the first flowpath and at least one outlet port along the first flowpath; and at least one passageway along the first flowpath; a first face and a second face opposite the first face; a leading edge along the second flowpath and a trailing edge along the second flowpath; a proximal edge having at least one inlet port along the first flowpath and at least one outlet port along the first flowpath; and at least one passageway along the first flowpath; an inlet manifold (82; 504) having at least one inlet port and at least one outlet port; and an outlet manifold (84; 506) having at least one outlet port (24A, 24B; 24) and at least one inlet port, the first flowpath passing from the at least one inlet port of the inlet manifold (82; 504), through the at least one passageway of each of the plurality of plates (50; 300; 350; 360), and through the at least one outlet port (24A, 24B; 24) of the outlet manifold (84; 506), the inlet manifold (82; 504) and outlet manifold (84; 506) are portions of a single unit (80; 502); a buffer cavity (115; 550; 650) is located between the inlet manifold (82; 504) and the outlet manifold (84; 502); and the buffer cavity (115; 550; 650) has at least one inlet (410A, 410B) and at least one outlet (412A, 412B).