Oh I will be in kosice the day before so maybe it can be done at the ticket office? But might sell out...

Have you looked at the information about SK/RO on this page?

https://trainline.interrail.eu/en/plan-your-trip/reservations/how-do-i-book-my-reservations

Scroll down to SK and RO

AFAIK this is not 1 train-have to change in HU somewhere (Not necessarily Bp).

From SK its only optional.

For HU-RO it is not-ask at Kosice (town nicely spruced up on the last yrs-if have some time take that long tram to the steelworks to see how it was 30 yrs ago……...if they can do it, if not have to wait till  HU if above link does not work-which would not surprise me at all

Thanks both. It’s EC189 from kosice to Miskolc, then IC582 within Hungary to szolnok, then IR75 to Sibiu. Connections are tight (12 and 13 minutes) so no time to book en route.

Thanks for the steelworks tip — I’ll check it out.

They can’t sell any except ec189, the first leg, in Kosice station, which is not required anyway. I’ve managed to book IC582 only on the MAV Hungarian site. I’m absolutely at my wits’ end as to what to do about the final (long) leg — MAV only offers “seat only” for domestic journeys, and Romanian rail doesn’t offer “seat only” at all. Both websites are happy to sell my a full-price ticket, so should I just do that? I won’t have time to buy tickets in Miskolc or Szolnok. Or, shall I just get on the final train without a reservation and hope for the best?