Before i report this as a bug i wanted to check if it is not a bug.
On the turn i concede my tess greymane started to work for opponent i suspect it has something to do with reska
You can see in the replay i think the effect of tess greymane shifts from me to him if im right,
Seems intended. Yogg also worked like this when it switched sides mid Battlecry if it destroyed a Classsic Sylvanas for example and they never changed that interaction so it seemed like they intend this interaction. Won’t be surprised if Shudderwok also works that way.
But since it is a battlecry it should only affect me am i right i activated the battlecry effect of Tess Greymane shouldnt the effect only work for me ?
Don’t know what to tell you it always worked that way and they never bothered to fix that somewhat rare interaction of a big multiple action battlecry that gets mind control and switches sides in the middle of it’s battlecry.
I think they said somewhere that it is not exactly intended but they found it hilarious so won’t change it. Maybe I am misremembering, but it is not a bug, that much I am sure. If Reska steals your Tess at any point during the effect, your Tess will resume playing for your opponent instead. I also don’t like it and I think this should changed but I guess it’s a niche scenario anyway, so whatever.
It’s actually listed in the Hearthstone Rules Wiki under Tess’s Card.
Ok thank you it is rather funny 
Thank you Dalleen i was not aware this helps alot haha
Thanks now i know too 
I’m honestly surprised you’ve never seen this for as much as you play Rogue, but I guess I’ve seen it more often in Wild. In wild, if you play Psychic Scream as Rogue then play Tess, Tess will shuffle herself into the opponent’s deck when she replays Psychic Scream and then keep going for your opponent. I’ve done it once or twice on purpose because I think it’s hilarious
I have never seen my Rogue battlecry switch to another player but theres a first for everythiing