Game concept
House Arrest
From the game's encyclopedia
House Arrest is a lenient form of Prison where Characters suffer from no ill effects except boredom. However, Rulers may throw them into the Dungeon, though it lowers the Opinions of the Prisoner's Close Family.
Captured Nobles are automatically put in House Arrest.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
House Arrest is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "House Arrest is a lenient form of Prison where Characters suffer from no ill effects except boredom." It is part of Prison. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.