using request a computer analysis after the game

I just requested a computer analysis after a game and i saw that my recent opponent was sitting in on what i was doing. Is there a policy that lichess has when that happens? If so, where is written on the website?

Do you mean that you noticed your opponent's presence in the spectator room? Nothing unusual about it, especially if the game has just been finished.

The requested computer analysis will be performed in any case, it is up to your opponent to hide it if they want to think about the game for themselves before looking what the engine says.