He’s very polite about it, of course, but I think he prefers outside with a run in or at least in/out access. Or just being left in the pasture with the trees to stand under. The problem is I can’t just put the other horses in and leave him out - he gets upset being left alone, naturally, and will stand out in the rain at the gate closest to the barn.
After Cooper rearranged his stall this morning due to boredom (and not for lack of food) I just tossed everyone back out to fend for themselves. No more mrs. nice lady trying to shelter the ingrates from the bad weather and sloppy mud.