Dimitri thinks he knows how engagement works.
That is, he thinks he is right. He is pretty sure some of the things he got told were made-up (by Sylvain, because who gives flowers to the girl they like?), plain lies (sitting on your spouse-to-be seems like a dangerous hobby, Glenn- shut up already, I’m right, you’re wrong) or actually foreign (rings haven’t been exchanged in Faerghus since the early 800s, Lady Rhea, no matter what the church says).
However, he knows one tradition, and that tradition remains strong in his head. It is why he gave El a dagger (so she will protect herself from her unwanted suitors, as family does), why Ingrid left her betrothal lance at home (would not want to give a wrong impression to others, even if she is technically available), why Felix only ever uses his rapier for the strongest of linked spells (Sylvain keeps claiming it is not a betrothal weapon, but everyone knows by now). It is also why the Professor and himself use each other’s weapons without distinction, since they belong to the both of them-
(Or at least, he hopes that is why. He hasn’t actually proposed, but his intentions have been clear for a while, haven’t they? Is he making a mistake? Byleth would have told him if he did something stupid, right... Besides, he does have that bell.)
So he knows his customs, he knows traditions. He was raised in Faerghus, which is very different from the rest of Fódlan, but it is close enough that, surely, some things are the same. Especially with the Alliance, as they were part of Faerghus once, and it wasn’t that long ago.
Then, he cannot, for the love of all Fódlan, the Goddess and the Lord of War too, figure out what is Claude thinking by giving his bow to Byleth.
(Lorenz, behind Dimitri and next to Ingrid, raises a hand to rub his temples. Ingrid herself is ready to throw Lúin at Claude, nevermind Lúin is not made for throwing. Ashe has to hold her back. Sylvain whistles, because he thinks all this is very amusing.
Felix wants to hit them all, because we just got Dimitri to calm down.)
Dimitri does what he does best. Well, maybe not what he does best, but accidentally ruining Claude’s schemes is one of his skills (according to some), and so before the Professor can take the bow, he reaches from behind Byleth and grabs it first.
“Thank you, Claude,” he tries to smile, but he knows it is not working -he hears Hilda whisper holy shit from somewhere, so he assumes he looks rightfully angry-
But Claude does not. care. He just, smiles, bright and blinding how can someone look like gold itself- and says:
“Great! You two will use it more than me.”
(It is a moment of enlightenment to some, with Lorenz throwing his hands up -that’s it, I’m done here, I’m done with this-, Sylvain almost falls on his face from how hard he is laughing, Annette’s spell dissolves as she squeals against Mercedes shoulder. Dedue is almost taking out his planning notebook to add in a whole country to the invitation list-
Felix still wants to hit them all, because this will end badly, he just knows, he asks Ashe to nock an arrow but he is being ignored-)
And Byleth is smiling, some soft response in their lips, as Dimitri runs some old memories and history facts trying to remember if this is legal, he is pretty sure it happened once before the Church was a thing, but Byleth is the Archbishop and they cannot just bend the laws as they want, but-
And then Claude leaves.