Jason had known already, of course. Diana had broken the news to him, gently, sympathetically, logically.
"I don't want there to be any lies between us, Jason. You know that. I didn't agree at first, but Nightwing made a compelling argument. And it seems…to be true so far."
Even if Diana had tried to keep it a secret, tried to pull a Bruce on him, it would have come out sooner or later, probably sooner considering Kon had already heard it through the weird, super-bat-whatever the fuck they wanted to call it (that is, the volatile but unrelenting partnership that seems to exist between Batman's clan and Superman's clan), grapevine and then Bart had found out just because, well, he's Bart. Diana, being Diana, probably hadn't even factored that in when being honest with him, though.
But knowing and seeing were two very different things.
The information had processed through his mind as a completely impersonal thing. Roy would probably call it denial, like Speedy could talk considering his own volatile relationship with his mentor, but Jason didn't think it was that. Whatever the reason, being told hadn't affected him.
Standing face to face with a boy wearing pixie boots, eyes blank behind a cowl, and a familiar cape hanging from his shoulders in spite of some obvious alterations to the suit… Well, it's a completely different story.
It makes something twist around in his gut. It brings up old wounds as if it was only yesterday and not two years ago since he'd traded one sidekick name for another. It trudges up a haunting memory, the very real fear he'd had that he was going to die and the very real ache that the person who was always supposed to be there for him wasn't. It brings back echoes of arguments and cruel laughter and bitter words and apologies.
"The last thing I wanted was for you to get hurt. I was a damned fool for letting you put on the costume. For thinking…"
"For thinking you could replace, Dick."
"It was never that, Jason. Despite what you think. But my reckless behavior toward you has been selfish and imprudent just the same. I won't let it continue. I won't let this ever happen again."
But it had been another empty vow from the Dark Knight. Sure, he'd gone longer than Jason had expected, but Jason had also expected Dickiebird would go running back to Bruce in the wake of Jason walking away and they'd live happily ever after or something like that. Maybe Bruce had even held out longer because he was expecting the same thing.
The Robin standing across from Jason now is not Dick. Maybe more lean and lithe like Dick than Jason had ever been, and more black hair, but that's about as similar as it gets. Even if it wouldn't be obvious right away that this Robin is still a kid, where Dick is not anymore, his physique and presence alone give away his pretense.
Maybe that's why this stings now, why it suddenly feels personal. Bruce had let someone else step into the suit, even after everything. Bruce had decided someone could replace Jason, or better said, replace Jason in replacing Dick. Bruce's apologies, his attempts here and there to convince Jason he still cared for him as the son he had wanted him to become, the feeble house of cards they had rebuilt comes crashing down again.
Maybe that's why his first words to the newest Teen Titan are, "What the fuck are you doing here, Replacement?"