We were there last Sunday. There were a couple of men wearing shorts and a polo shirt, but they were very out of place. Shirt and the or a sports coat is highly recomended!
It's business casual. No jeans, shorts, or tennis shoes.
It is a very formal restaurant, I believe shorts are not allowed, for sure no hats so to be on the safe side just wear proper formal clothes.
I was there on Sunday and I definitely saw a male wearing long shorts. The only hats allowed seem to be cowboy hats as i also saw a gentleman at the bar wearing one. Though that was at the bar and NOT seated at a table (hats should always be removed when indoors!).
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