Im still playing on 9162 because I don't want to associate this PC with my Steam account. (Im away from my normal PC)
I dunno for sure or not if this is intended but I recall hearing that it isn't. I had a Hive Infestation appear in a "Single Tile Room" as shown at the red box in the attached picture. I had thought the room size had to be at least 2x2?
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I think the /mined out undermountain/ area has to be 2x2; if that wall on the left is constructed it may no longer count.. but IDK
They are both doors, and the blueprints are replacing doors that were already there before the hive arrived.
The insects destroyed the doors to get out.
Hives can by design appear in very small spaces now.
Thanks for reporting either way.