For an upcoming trip to Germany, departing from Switzerland, I purchased the corresponding one-country Interrail pass. Sooner, I also booked a sleeper compartment surcharge in a Zurich-Hamburg Nightjet train for Interrail passholders.
Later, I had a doubt, as the Interrail surcharge price class on the OBB website reads "Globalpass". I asked a local Swiss station agent about how to handle the situation. His advice was to purchase a Swiss equivalent second-class train ticket to cover the missing portion. That person was confronted to the issue for the first time and did not seem to be sure.
The situation leaves me in doubt.
Are Nightjet sleeper compartments considered second-class regarding passes? Not the couchettes; I mean the full-blown sleepers with breakfast service. I went through the information somewhere but it is difficult to confirm. Other railways sometimes treat those as first-class.
Is buying a second-class regular ticket for the missing portion of the trip a correct strategy? I will have the Interrail pass for the German portion + the extra ticket for the Swiss portion + the sleeper Interrail add-on for the sleeper cabin.