Question: copy class hierarchy in an environment without Java Agent about byte-buddy

[dogourd]

ByteBuddy does not directly provide an API for this operation. You need to leverage the visitors provided by ASM to achieve this. You can refer to the suggested approach here for specifics. How to copy method body of a particular method to another method in different class using ASM
Similarly, you may encounter the side effects mentioned therein.

If you're only dealing with the specific requirement described in the issue, you could consider achieving it through redefine + visit, for example:

new ByteBuddy()
   .redefine(Child.class)
   .name("child2")
   .visit(new AsmVisitorWrapper.AbstractBase() {
                    @Override
                    public ClassVisitor wrap(TypeDescription instrumentedType, ClassVisitor classVisitor, Implementation.Context implementationContext, TypePool typePool, FieldList<FieldDescription.InDefinedShape> fields, MethodList<?> methods, int writerFlags, int readerFlags) {
                        return new ClassVisitor(OpenedClassReader.ASM_API, classVisitor) {
                            @Override
                            public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
                                super.visit(version, access, name, signature, Type.getInternalName(parentClass), interfaces);
                            }
                        };
                    }
                });

However, it still cannot avoid the potential errors mentioned in the link above, so you must be clear about what you are doing and have the ability to handle those issues on your own.