The discontinuous behavior of AI citation: entity confidence operates as a switch, not a dial. Above the threshold, the entity is cited confidently; below it, the system hedges or omits. Small confidence reductions can trigger large behavioral changes if they cross the threshold. This explains contested posture invisibility: schema entropy accumulates gradually, but citation behavior changes abruptly when the threshold is crossed. Confidence threshold dynamics make entity infrastructure similar to structural engineering: loads accumulate gradually, but failures occur suddenly. Monitoring schema entropy rate detects approaching threshold before behavioral change occurs.