Game concept
Agent Discovery
The game also links it as Discovered.
From the game's encyclopedia
Discovered Secret Scheme Agents may be seen as Criminals by their Liege, and are likely to be Imprisoned if so.
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.
Agent Discovery is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Discovered Secret Scheme Agents may be seen as Criminals by their Liege, and are likely to be Imprisoned if so." It is part of Scheme. The game also links it as Discovered. 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.