An airfoil includes an airfoil section that has an airfoil wall that define leading and trailing ends and first and second sides that join the leading and trailing ends. The first and second sides span in a longitudinal direction between first and second ends. The airfoil wall circumscribes an internal core cavity. The airfoil section extends form a platform. The platform defines a shelf that extends forward from the first end at the leading end of the airfoil section to a platform leading edge, aft from the first end at the trailing end of the airfoil section to a platform trailing edge, laterally from the first end at the first side of the airfoil section to a first platform side edge, and laterally from the first end at the second side of the airfoil section to a second platform side edge. The internal core cavity extends from the airfoil section into the shelf.