Game concept
Scheme Breach
The game also links it as Scheme Breaches, Breach, Breaches.
From the game's encyclopedia
A Breach represents a complication in a Secret Scheme. When a Scheme is breached, its Success Chance is reduced. The penalty to Success Chance increases for each cumulative Breach. Once a Scheme reaches 5 Breaches, it will automatically fail.
Schemes also check their Secrecy when they are finally executed — breaches have no effect on this one way or another.
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.
Scheme Breach is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Breach represents a complication in a Secret Scheme." It is part of Scheme. The game also links it as Scheme Breaches, Breach and Breaches. 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.