CausalStamp

A span's position in kuilt's happens-before relation.

Each stamped span carries its own event id (dot) plus the set of events it had already observed when it was created (predecessors — the causal frontier at that moment). Together these record, with no wall clock, which span could have led to which: if span e1's dot sits in span e2's predecessors, then e1 happened-before e2.

Happens-before is a superset of true causality — e1 being a predecessor of e2 means e1 could have caused e2, never that it did. That honesty is deliberate: links derived from these stamps are always tagged kuilt.causality=potential.