conditionalFlowIntoEventBasedGateway

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

Full reference documentation for conditionalFlowIntoEventBasedGatewayis 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.