Larian's games use a custom-built rule-based combat system that controls how enemies think and act during turn-based battles. The system is not machine learning: it works by running mathematical simulations of every possible action an enemy could take, scoring each one, and picking the highest-scoring option based on the enemy's assigned fighting style.

The system evaluates every available skill against every valid target in a combat encounter, calculating expected damage, healing value, buff effectiveness, and positional advantage. Each enemy type is assigned an archetype (such as Healer, Ranger, or Berserker) that applies score multipliers to favor actions matching that role: a Healer archetype will score healing spells higher and offensive spells lower. The system uses a separate AI Grid to track hazardous surfaces like fire and poison pools. Level designers can place special AiHint trigger zones to guide enemy positioning preferences. The game's difficulty is partly managed by intelligence-gating: less intelligent creatures are deliberately prevented from using advanced tactics. The system was updated during Baldur's Gate 3's Early Access period, including Early Access Patch 5 (July 2021), which improved enemy AI resource management and logical decision-making.