An edge may not target a hidden input port
The rule
Normative: this is the rule
An edge whose target port is declared by the target node's node type but is not exposed on that node is refused with R7_EDGE_TARGET_NOT_EXPOSED at edge.{index}, where {index} is the edge's position in the workflow's edge list.
Rule identifiers are permanent and are never renumbered. Each implementation publishes its own standing against these rules; this specification does not.spec 1.0-draft · R7.a · changed in spec 1.0