Y-Phil

Just an observation, but I don’t think your code in setup_output:
         If exposed_output_name:
                n1, _ = compound_data.ExposedOutputs()[0]
                n1.SetName(exposed_output_name)

Is needed. I had issues with creating a second compound node with two outputs getting labeled properly when connecting to another compound node.

With your code:

With code commented out:

After experimentation, I believe that the "compound_data.ExposeOutput(node.OutputByInternalName(output_name))" statement resolves the output name based on the internal name of node being connected.

I may be wrong, but I got the desired results by commenting out that section of your code.