conditionalFlowIntoEventBasedGateway

Sequence flow into an eventBasedGateway carries a conditionExpression — event-based gateways race on events, not predicates.

Full reference documentation for conditionalFlowIntoEventBasedGateway is 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.