SAMBUCKY ARE FINE
Chill people! Sambucky are gonna be fine.
Likely scenarios are probably various combinations of the following:
1. The Events of TFATWS meant Bucky might have unintentionally violated or broken whatever remains of his Parole rulings after John Walker got demoted. (Walker just magicked them away but i’m assuming it did not stay that way) Or they will just find a way to SAY Bucky broke his Parole rulings because they still deem him a danger. Val (or someone) probably uses this as an opportunity to sneak in and recruit him the same way she did with US AGENT (EVEN THOUGH HE SHOULD DEFFO BE IN PRISON/NO WHERE NEAR BEING USED IN THIS CAPACITY)
2. Less likely but also possible is that Bucky is there technically undercover/ gather intel/ keep an eye on Walker etc for someone (?) plus seeing the Thunderbolts/Val long term intentions. He is fine to do missions like this solo now as he no longer has trigger words, currently not working for anyone and seems on the road to being much more secure in himself after the events of TFATWS.
3. (If Thunderbolts takes place after CA:NWO) Maybe because of the events of Captain America: New World Order, working for a team like this becomes a thing he needs to do, not wants to? No Idea.
4. ITS HEALTHY TO WANT TO DO SOME THINGS SEPARATE FROM EACH OTHER. They clearly love each other deeply (I mean as family but with these two honestly take it however you see fit) but Sam has just accepted the mantle of Captain America. He needs to figure out how he is Captain America, get comfortable with all the responsibility & bullshit that will throw his way and Joaquin has his back.(Fuck those two are going to be so great together, I’m literally screaming) Bucky is still figuring out who he wants to be & maybe some time away from being Captain America’s sidekick yet again is nothing but a good thing.
JUST BECAUSE THEY ARE NOT ON EVERY MISSION TOGETHER DOES IN NO WAY MEAN THEY HATE EACH OTHER NOW. THEY ARE & WILL BE FINE. ....and breathe.