Do enemies ever open doors?

Answer: its yes and no! It depends on;

• If aliens ARE activated, THEN they will 'run' through doors, and open them.

• If aliens are NOT activated (i.e. you have not 'seen' them and they have not 'seen' you) then they 'teleport' through the map, and will NOT open doors. This applies to both UFO doors, and normal 'human' doors on buildings.

So tactically you can safely approach a door if you have no activated groups of aliens running around. But remember they can 'teleport' on top of your units - so you still cant let you guard down.

I have also seen aliens who 'teleport' half on one side of a door, and half on the other side. This means when I activated the group, the door was closed, but there was an 'activated' alien on the other side.

Yes, aliens do open doors. Its easy to spot if you manage to expose some aliens near a door. Sometimes they'll run through the door for cover.

I've seen many aliens open doors, particularly as they move for cover upon being spotted.

However, if you don't have visibility on the door, aliens can move through without leaving the door open.

Anecdote: I once ran into a pack of Chrysalids that did not see me. This herd patrolled out of the enclosed area, through a door that I did not have visibility on. The door was still closed when I moved up to see it. I later encountered the patrolling pack deeper in the combat zone.