An innovative numerical approach that integrates parametric modeling with Finite Element Limit Analysis (FELA) to evaluate the seismic behavior of masonry cross vaults is proposed. The core of this methodology is represented by PoliBrick, a Rhinoceros plugin able to generate three-dimensional assemblages of bricks while explicitly considering stereotomy effects. Such parametric tool is linked to a computerized heterogeneous limit analysis code, which adopts the Upper Bound theorem with infinitely resistant blocks interconnected through rigid-plastic interfaces. The reliability of the approach proposed is first assessed with reference to some experimental results available in literature and obtained for an in-scale cross vault built on a tilting plane, the latter progressively rotated up to the collapse of the structure. The accuracy of the predicted failure tilt angle is verified using a reduced block count while maintaining computational accuracy. After such validation, four different brickwork patterns are systematically examined under the application of standard seismic loads: running bond pattern perpendicular to lateral arches, two angular running bond variations (45° converging and circular arrangements), and herringbone configuration. Key findings reveal how stereotomy selection critically influences both failure mechanisms and load-bearing capacity. The computational efficiency of the proposed approach is particularly noticeable, enabling rapid yet accurate assessments of vaulted masonry structures subjected to seismic loads.