Systems, devices, and methods for detaching an implantable device from a delivery system are disclosed herein. One aspect of the present technology, for example, is directed toward an elongated shaft having an inner polymer structure and an outer polymer structure disposed around the inner polymer structure, a braid positioned around at least a portion of the inner polymer structure and extending along at least a portion of the shaft, and a coil wound around at least a portion of the inner polymer structure. In some embodiments, at least a portion of one of the braid or the coil overlaps at least a portion of the other of the braid or coil, the outer polymer structure can be disposed in and around the braid and the coil, and the outer polymer structure can have a stiffness that decreases in a distal direction.
