Each of the six fates starts from a defined set of chart angles between two people — specific planet-to-planet aspects, house overlaps, and a handful of sign-based compatibility rules drawn from traditional synastry technique. Chemistry weighs Venus-Mars and Sun-Moon aspects most heavily; Soul leans on Moon-Moon and inner-planet connections; Team weighs Saturn and 10th-house overlap, since that's the traditional territory of structure and responsibility.
Each aspect gets a raw compatibility value based on angle type — trines and sextiles score well, squares and oppositions score poorly, conjunctions depend on which planets are involved. Those raw values are summed per fate, then normalized against the distribution of scores across the whole user base, which is why a "92%" means "top decile," not "92 out of 100 points" in any absolute sense.
Nothing in the pipeline is randomized or adjusted per user for engagement — the same two charts produce the same six scores every time, a deliberate constraint from day one, not an accident of how the first version happened to work.