I have only seen them with gifted mediums from minor races.

I've seen this problem a couple of times as well. Cravers tend to always be the ones to upgrade to the next hull first, but in my Serious Unfallen playthrough recently it was only Cravers with medium hull design while everyone else had small ships. This was even at the last turn before I won, and I had researched every tech there is 15 turns before this.

That's only one example recently, seen it plenty of times, although I had better luck at Impossible/Endless difficulty, but the AI barely ever gets the carrier hulls. Only once did I fight against Cravers who managed to at hard difficulty.

I feel as if the AI needs bigger prioritization for better hull designs during a certain amount of turns has passed or following whether the player has researched those hulls. They should also prioritize them as militarist factions (Cravers, Vodyani, United Empire) and if the enemy is at war, it should immediately focus on getting better hulls, not just military techs. Especially if it's fighting an enemy with greater hulls/stronger fleets and tends to lose battles.

Not just that, but I've also noticed the AI seems to sometimes just be able to merge their fleets properly, especially if you give them the tech. I gave my allies tech to get 24 command points instead of 10, and throughout the rest of the game the one of them refused to go beyond 10 even if they had 3x fleets of 10 on the same system. Not that it has anything to do with this, but it's just another issue I noticed in my Unfallen game recently.

A save. multipepper end.sav

Endless difficulty. Moultiplayer. Easy pirats.

The human players was Lumeriis, Sophons, cravers.

If you load the game as Riftborn, you can see they have only little ships, and they are just making research about new hulls. Also they search ofr advanced hunter hull without having already the hunter hull. The sophon playe fought the UE and faced also a ton of little ships.

Very weird. They had the best hull/ship management they ever had during closed beta of this build. What could have chanegd their behavior so much ? oO