Hey!

1. yeah, just buy it at the station. Usually it is not a problem. If you wanna catch the 15.10 service from Budapest, it is usually not so full (especially the seating is quite empty)
2. this train is mostly empty (if there are no refugees from Ukraine traveling, but don’t know how that situation is right now in RO/BG) and no reservation is required (although CFR staff sometimes asks for one and at the station in Bucharest they always sell you a reservation together with the ticket, but if you have interrail you can just board it)
3. in November it shouldn’t be a problem to book it there. This year in May I booked it direct at the station and it was no problem… also on the way back in Istanbul I just booked it on the day of departure. But there were some reports that it was fully booked often this summer and even in autumn. But November is usually low season. If it is fully-booked, then you can still catch one of the many buses (check Metro, Arda Tur, ...) traveling between Sofia and Istanbul. 
   But if I understand right you will so or so stay first a bit in Sofia and then take the train from there, so you can go in the morning before your evening departure to the station and buy the reservation.
   I’d only be worried a bit on Fridays and Sundays.

Thanks a lot for your answers !

1. It would be to take the 19:10 but if full, I will take the 15:10.

2. So I don't need to book anything even though, the app says something else (6€) or should I ask at the station ?

3. Yes exactly I will stay 2 days in Sofia so I will have time to figure it out and I plan on taking the train on Saturday evening. 

Last question, which is a bit more general, the cost of seat reservations are fixed (depending on the train but not depending on the time of the reservation) right ? And the rail app planner prices should be quite accurate no ?

Many thanks again ! 

1. 19.10 should be also no problem and there would be still the late night one coming from Vienna… but don’t worry, there are 3 connections which are possible (if you stay in Bucharest). 
   19.10 is definitely a good idea - you will have the more beautiful scenery ;-)
2. I have used the train several times with Interrail and never showed a reservation and conductors didn’t care about it… The app often provides wrong information.
   I wouldn’t ask at the station - they will sell you one (in RO). Just show the conductor the ticket when boarding. I asked in Ruse (BG) about this and they said no reservation needed. But Romania handles it different, I would just board it!
3. Then wouldn’t worry at all. Just buy on your arrival or the morning after (ticket office might be closed on arrival) the reservation.

In Eastern Europe the prices are fixed. Depending on the kind of comfort you want (seat, couchette, sleeper, they have different price levels, but fix ones). The app is showing it with a fee, bought at the station it will be cheaper (3 instead of 6 euro for a seat).

Perfect

I cannot thank you enough ! I was starting to get worried 

Have a good day :)

Side note you can buy your reservation at many stations in Austria and Hungary; you don't have to wait until you get to Budapest.

The app is often wrong and is therefore not a reliable source. If you ask at the station in Bucharest, they will sell you a reservation.

The price is fixed indeed for most trains. Only for domestic trains in France, there's a limited 10€ quota and wenn it sells out, it’s 20€. The rail planner app prices are the prices for which Interrail/Eurail sell the reservations, so often 2€ too high (and sometimes more).

Are you sure that you can book the 19.10 from Austria? Since ÖBB changed its reservation software a few years ago many things aren’t possible anymore… and online it is not possible, so I doubt that you could get this reservation at the station.

And one more side note: at smaller stations in Hungary theoretically they can sell reservations but they are mostly unfriendly and tell you to buy it in Budapest… if you don’t buy an international ticket for a train departing from their station. (experienced in Mosonmagyarovar). Maybe since they have electronic tickets and not handwritten anymore this got a bit better.

And one last side note: AFAIK there is no reservation needed anymore for seats on the trains between Budapest and Romania… at least I read it in several reports (DSO) and there was also some news posted 2-3 years ago about this. But I still made one the last few times.

@Maë : there’s no 100% guarantee that you can use the Bucharest-Sofia train without reservation but in my cases it worked this year two times and also heard it from other travelers. So I wouldn’t buy it and maybe have some RON with you in case the conductor makes problem (but would pay only in the last case).

About reservations: the seats cost as said 3 euro (in local currency), the couchette from Sofia to Istanbul is 10 Euro (around 20 Leva, also payable by card in Sofia). There are no seats available on the Sofia-Istanbul nighttrain.

Have a good trip! :)

I'm not 100% if they can book it but I'd be surprised if they couldn't. I also doubt the ÖBB website is a good measure for the possibilities at their ticket offices.

Well, they use the same system nowadays at the ticket office like online. For a while they were still having the old system in some stations (e.g. Wien Hbf) together with the new one but that isn’t the case anymore since 2-3 years already.
With the old system you could buy Interrail reservations for almost all trains - France, Spain, Italy, …
Nowadays beside Italy and standard stuff like Germany, Switzerland etc. you can only get mostly reservations for trains departing from/to Austria.
They are not even able to sell you a reservation for e.g. Berlin-Warszawa… 
The reservation for the Budapest-Bucharest nighttrain is not available on ÖBB website but for the Dacia coming from Vienna you can book it from Budapest (because it starts in Austria), so you can give it a try next time you are in Austria, but I’d bet with you, you won’t get this reservation at an ÖBB ticket office :-p

I manged to get the reservations from Austrian Ticket offices Sometimes you have to go to the “ÖBB Reisebüro” instead of the Ticketoffice for such reservation as these have still access to the Old or the German system and can reserve more trains as the “Standard ticket offices with the Webtool”  

Do you have any idea what ÖBB's plan for the future is?

• Will they extend their web tool functionality so it includes everything the old system could do?
• Will they limit what they sell after phasing out the old system?
• Will they keep an extended access for the ÖBB Reisebüro?

What kind of access does the ÖBB phone service have? I surely hope it's the extended access...

Final note. There are no seats between Sofia and Istanbul. Only couchettes and sleepers cross the border. Book in advance for a Saturday!

Thanks everybody ! 

1. The ÖBB Reisebüro are only open on the morning so I will try tomorrow. I can confirm though that the regular ticket office/counters at the station display the same results as the website in Vienna.

3. Yes I meant couchette and not seats ;) 

In which year was it?

I’ve been trying to get some more “special” reservations which worked previously in Dornbirn, Bregenz and Wien Hbf and it didn’t work (2020). The guy at the counter, who did me a lot of reservations in former years, said I should go to SBB because they can do it, but ÖBB not anymore. He also didn’t forward me to the Reisebüro in Bregenz but directly said I should do it in Switzerland. 
In the end I went without reservation until Milano and bought there a reservation for the IC to La Spezia (the nighttrain which I wanted to use was fully booked! so had to replan whole trip)

In Bulgaria, almost no train requires a mandatory reservation. There are no trains between Ruse and Sofia with a mandatory reservation.

https://razpisanie.bdz.bg/en/ruse/sofia/12-11-2022

To close the subject, I did all the reservations at the train stations as it was the only way and it worked out well. 

For the Bucharest-Sofia trip, I should have asked only a seat reservation for the Bucharest-Ruse train to avoid paying for the Ruse-Sofia part but I forgot in the moment. But anyway, it was cheap so it was okay. 

@Maë Thanks for letting the Community know how it worked out. That is valuable information. 

Thanks for the feedback. Did the Romanian conductor ask for the reservation or you showed it by yourself? 

I think I showed it by myself, so can't tell if it's required or not