fix(combat): correct spell DC formula

data/pcs/esha.json

@@ -24,6 +24,8 @@
     "ref": 10,
     "will": 5
   },
+  "casting_ability": "int",
+  "resources": {},
   "attacks": [
     {
       "name": "Lance",

data/pcs/harvie.json

@@ -24,6 +24,8 @@
     "ref": 5,
     "will": 2
   },
+  "casting_ability": "wis",
+  "resources": {},
   "attacks": [
     {
       "name": "Talons (attaque naturelle)",

data/pcs/ierlieth.json

@@ -24,6 +24,8 @@
     "ref": 6,
     "will": 3
   },
+  "casting_ability": "wis",
+  "resources": {},
   "attacks": [
     {
       "name": "Bite (attaque naturelle)",

data/pcs/jeanne.json

@@ -24,6 +24,8 @@
     "ref": 6,
     "will": 2
   },
+  "casting_ability": "wis",
+  "resources": {},
   "attacks": [
     {
       "name": "Hooves (attaque naturelle)",

data/pcs/misty.json

@@ -24,6 +24,10 @@
     "ref": 9,
     "will": 3
   },
+  "casting_ability": "cha",
+  "resources": {
+    "bardic_rounds": 12
+  },
   "attacks": [
     {
       "name": "MWK Rapier",

data/pcs/nairda.json

@@ -24,6 +24,10 @@
     "ref": 5,
     "will": 7
   },
+  "casting_ability": "int",
+  "resources": {
+    "hexes": 5
+  },
   "attacks": [
     {
       "name": "Coup à mains nues (aucune arme encodée)",

data/pcs/oni.json

@@ -24,6 +24,10 @@
     "ref": 7,
     "will": 9
   },
+  "casting_ability": "wis",
+  "resources": {
+    "channel_energy": 6
+  },
   "attacks": [
     {
       "name": "Longbow",

data/pcs/tammara.json

@@ -24,6 +24,10 @@
     "ref": 10,
     "will": 8
   },
+  "casting_ability": "wis",
+  "resources": {
+    "grit": 3
+  },
   "attacks": [
     {
       "name": "Rapier (masterwork)",

src/pf1e_simulator/combat.py

@@ -834,8 +834,11 @@ class CombatEngine:
                 f"round {self._current_round} {caster.combatant.id}: "
                 f"cast {spell_name} -> NO LINE OF EFFECT"
             )
-            return
-        dc = spell.base_dc + caster.combatant.level
+        # DC = 10 + spell level + caster's casting ability modifier
+        ability_name = caster.combatant.casting_ability.lower()
+        ability_score = getattr(caster.combatant.abilities, f"{ability_name}_score")
+        ability_mod = (ability_score - 10) // 2
+        dc = 10 + spell.level + ability_mod
         save_result = (
             self.resolve_save(target, spell.save, dc) if spell.save != "none" else None
         )

src/pf1e_simulator/models.py

@@ -113,3 +113,5 @@ class Combatant(_FrozenModel):
     notes: str = ""
     features: list[AbilitySpec] = []
     spells: list[str] = []
+    casting_ability: str = "wis"  # ability used for spell DCs: str/dex/con/int/wis/cha
+    resources: dict[str, int] = Field(default_factory=dict)  # resource pools per combat

tests/test_spells.py

@@ -56,6 +56,7 @@ def _make_caster(cid: str = "caster", *, level: int = 5) -> Combatant:
         speed_land_ft=30,
         saves=Saves(fort=3, ref=4, will=4),
         attacks=[attack],
+        casting_ability="int",
     )
 
 
@@ -366,18 +367,18 @@ class TestSpellDispatchViaExecute:
         )
         assert t.hp < hp_before
 
-
 class TestSpellDcScalesWithLevel:
-    """Given: a caster with level N
-    When: a spell with base_dc 10 is cast
-    Then: the DC is 10 + N."""
+    """Given: a caster with level N and casting ability mod M
+    When: a spell of level L is cast
+    Then: the DC is 10 + L + M."""
 
-    def test_dc_is_base_plus_level(self) -> None:
-        caster = _make_caster(level=5)
+    def test_dc_is_ten_plus_spell_level_plus_ability_mod(self) -> None:
+        caster = _make_caster(level=5)  # int 18 -> mod +4
         target = _make_target()
         engine, c, t = _make_engine(caster, target, [20, 1, 1, 1, 1, 1, 1])
-        engine._cast_spell(c, t, "Fireball")
-        assert any("DC15" in line for line in engine._transcript)
+        engine._cast_spell(c, t, "Fireball")  # fireball is level 3
+        # DC = 10 + spell_level(3) + int_mod(4) = 17
+        assert any("DC17" in line for line in engine._transcript)
 
 
 class TestSpellDamageWithDr: