linkEventPairingByContainer

Link throw and catch events must pair within the same immediate container (process / subProcess / transaction / adHocSubProcess); N→1 valid, orphans and 1→N ambiguity errored.

Full reference documentation for linkEventPairingByContaineris in progress. In the meantime, the rule's summary above describes the check, and the source implementation in lib/bpmn/rules/* on GitHub is the canonical specification.