Entanglement does not necessarily lead to Einstein-Podolsky-Rosen steering, but a newly discovered boundary-geometric mechanism bridges this gap in specific regions of two-qubit state space. This mechanism is effective on product-null boundary strata, where the conditional states of one party approach the boundary of the Bloch ball. The primary obstacle to steering is local, related to the way projective assemblages touch the Bloch-sphere boundary with a first-order tangential displacement1. By understanding this boundary-geometric mechanism, researchers can better grasp the relationship between entanglement and steering, which is crucial for quantum computing and cryptography. The implications of this discovery are significant, as quantum computing developments continue to challenge traditional assumptions about computation and cryptography. This breakthrough matters to practitioners because it sheds new light on the fundamental principles governing quantum systems, ultimately informing the development of more secure and efficient quantum computing protocols.