JPMS modularized shade of org.mongodb:bson exposing the org.mongodb.bson module. Upstream ships only an Automatic-Module-Name, which jlink refuses: "automatic module cannot be used with jlink". The whole MongoDB driver chain (bson -> bson-record-codec -> mongodb-driver-core -> mongodb-driver-reactivestreams) arrives transitively through io.vertx:vertx-mongo-client, so each link needs a real module descriptor for a clean runtime image.