The Vector API resides in an incubating module `jdk.incubator.vector`. It however requires access to functionality in the `java.base` module for the support of runtime compiler intrinsics.

The class `jdk.incubator.vector.Vector` extends from the class `jdk.internal.vm.vector.VectorSupport.Vector` that resides in the `java.base` module. The package `jdk.internal.vm.vector` is exported only to `jdk.incubator.vector` (a qualified export).

The class `jdk.internal.vm.vector.VectorSupport.Vector<E>` and its super class `jdk.internal.vm.vector.VectorSupport.VectorPayload` are visible in the JDK 17 JavaDoc:

https://docs.oracle.com/en/java/javase/17/docs/api/jdk.incubator.vector/jdk/incubator/vector/Vector.html

In addition the protected method `VectorPayload.getPayload` is also presented.

When/if the Vector API exits incubation the `jdk.incubator.vector` module will collapse into `java.base` and this will no longer be an issue. Although this kind of pattern would not be generally recommended perhaps others might be affected by it.

Separately i will experiment with sealing to see if it reduces the exposure of `VectorPayload.getPayload` method.