Remove legacy modifier field from WeaknessResistance

Migrate all usages to the proper mode/value fields:
- Weakness: mode=MULTIPLICATIVE, value=2
- Resistance: mode=ADDITIVE, value=-30

Remove backwards compatibility code and legacy test.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/core/models/card.py

@@ -122,20 +122,12 @@ class WeaknessResistance(BaseModel):
             mode=ModifierMode.ADDITIVE,
             value=40,  # +40 damage instead of x2
         )
-
-    Legacy Support:
-        The old 'modifier' field is deprecated but still works for backwards
-        compatibility. If 'modifier' is provided without 'value', it will be
-        used as the value. The mode will still default to CombatConfig.
     """
 
     energy_type: EnergyType
     mode: ModifierMode | None = None
     value: int | None = None
 
-    # Legacy field for backwards compatibility
-    modifier: int | None = None
-
     def get_value(self, default: int) -> int:
         """Get the modifier value, falling back to default if not specified.
 
@@ -147,8 +139,6 @@ class WeaknessResistance(BaseModel):
         """
         if self.value is not None:
             return self.value
-        if self.modifier is not None:
-            return self.modifier
         return default
 
     def get_mode(self, default: ModifierMode) -> ModifierMode:

backend/tests/core/conftest.py

@@ -19,6 +19,7 @@ from app.core.config import RulesConfig
 from app.core.enums import (
     CardType,
     EnergyType,
+    ModifierMode,
     PokemonStage,
     PokemonVariant,
     TrainerType,
@@ -94,7 +95,9 @@ def pikachu_def() -> CardDefinition:
                 effect_description="Flip a coin. If heads, the Defending Pokemon is now Paralyzed.",
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.FIGHTING, modifier=2),
+        weakness=WeaknessResistance(
+            energy_type=EnergyType.FIGHTING, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
         retreat_cost=1,
         rarity="common",
         set_id="base",
@@ -123,7 +126,9 @@ def raichu_def() -> CardDefinition:
                 damage=60,
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.FIGHTING, modifier=2),
+        weakness=WeaknessResistance(
+            energy_type=EnergyType.FIGHTING, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
         retreat_cost=1,
         rarity="rare",
         set_id="base",
@@ -154,8 +159,12 @@ def charizard_def() -> CardDefinition:
                 effect_params={"count": 2, "type": "fire"},
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.WATER, modifier=2),
+        weakness=WeaknessResistance(
-        resistance=WeaknessResistance(energy_type=EnergyType.FIGHTING, modifier=-30),
+            energy_type=EnergyType.WATER, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
+        resistance=WeaknessResistance(
+            energy_type=EnergyType.FIGHTING, mode=ModifierMode.ADDITIVE, value=-30
+        ),
         retreat_cost=3,
         rarity="rare_holo",
         set_id="base",
@@ -185,7 +194,9 @@ def mewtwo_ex_def() -> CardDefinition:
                 effect_params={"count": 1, "type": "any"},
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.PSYCHIC, modifier=2),
+        weakness=WeaknessResistance(
+            energy_type=EnergyType.PSYCHIC, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
         retreat_cost=2,
         rarity="ultra_rare",
         set_id="ex_series",
@@ -215,7 +226,9 @@ def pikachu_v_def() -> CardDefinition:
                 effect_params={"amount": 30},
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.FIGHTING, modifier=2),
+        weakness=WeaknessResistance(
+            energy_type=EnergyType.FIGHTING, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
         retreat_cost=2,
         rarity="ultra_rare",
         set_id="v_series",
@@ -244,7 +257,9 @@ def pikachu_vmax_def() -> CardDefinition:
                 damage=270,
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.FIGHTING, modifier=2),
+        weakness=WeaknessResistance(
+            energy_type=EnergyType.FIGHTING, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
         retreat_cost=3,
         rarity="secret_rare",
         set_id="vmax_series",
@@ -642,7 +657,9 @@ def charmander_def() -> CardDefinition:
                 damage=10,
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.WATER, modifier=2),
+        weakness=WeaknessResistance(
+            energy_type=EnergyType.WATER, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
         retreat_cost=1,
         rarity="common",
         set_id="base",
@@ -671,7 +688,9 @@ def charmeleon_def() -> CardDefinition:
                 damage=30,
             ),
         ],
-        weakness=WeaknessResistance(energy_type=EnergyType.WATER, modifier=2),
+        weakness=WeaknessResistance(
+            energy_type=EnergyType.WATER, mode=ModifierMode.MULTIPLICATIVE, value=2
+        ),
         retreat_cost=1,
         rarity="uncommon",
         set_id="base",

backend/tests/core/test_effects/test_handlers.py

@@ -699,41 +699,6 @@ class TestAttackDamage:
         assert result.details["weakness"]["mode"] == "multiplicative"
         assert result.details["weakness"]["value"] == 3
 
-    def test_legacy_modifier_field_still_works(
-        self, game_state: GameState, rng: SeededRandom
-    ) -> None:
-        """
-        Verify backwards compatibility: old 'modifier' field still works.
-        """
-        # Using legacy 'modifier' field instead of 'value'
-        game_state.card_registry["charmander-001"] = CardDefinition(
-            id="charmander-001",
-            name="Charmander",
-            card_type=CardType.POKEMON,
-            stage=PokemonStage.BASIC,
-            hp=70,
-            pokemon_type=EnergyType.FIRE,
-            weakness=WeaknessResistance(
-                energy_type=EnergyType.LIGHTNING,
-                modifier=2,  # Legacy field
-            ),
-        )
-
-        ctx = make_context(
-            game_state,
-            rng,
-            source_card_id="pikachu-inst",
-            params={"amount": 30},
-        )
-
-        result = resolve_effect("attack_damage", ctx)
-
-        assert result.success
-        target = game_state.players["player2"].get_active_pokemon()
-        assert target is not None
-        assert target.damage == 60  # 30 * 2 (legacy modifier used as value)
-        assert result.details["weakness"]["value"] == 2
-
     def test_fails_with_no_target(self, game_state: GameState, rng: SeededRandom) -> None:
         """
         Verify attack_damage fails when no valid target exists.

backend/tests/core/test_models/test_card.py

@@ -11,6 +11,7 @@ These tests verify:
 from app.core.enums import (
     CardType,
     EnergyType,
+    ModifierMode,
     PokemonStage,
     PokemonVariant,
     StatusCondition,
@@ -156,27 +157,31 @@ class TestWeaknessResistance:
 
     def test_weakness(self) -> None:
         """
-        Verify weakness can be defined.
+        Verify weakness can be defined with multiplicative mode.
         """
         weakness = WeaknessResistance(
             energy_type=EnergyType.FIGHTING,
-            modifier=2,
+            mode=ModifierMode.MULTIPLICATIVE,
+            value=2,
         )
 
         assert weakness.energy_type == EnergyType.FIGHTING
-        assert weakness.modifier == 2
+        assert weakness.mode == ModifierMode.MULTIPLICATIVE
+        assert weakness.value == 2
 
     def test_resistance(self) -> None:
         """
-        Verify resistance can be defined.
+        Verify resistance can be defined with additive mode.
         """
         resistance = WeaknessResistance(
             energy_type=EnergyType.METAL,
-            modifier=-30,
+            mode=ModifierMode.ADDITIVE,
+            value=-30,
         )
 
         assert resistance.energy_type == EnergyType.METAL
-        assert resistance.modifier == -30
+        assert resistance.mode == ModifierMode.ADDITIVE
+        assert resistance.value == -30
 
 
 class TestCardDefinitionPokemon:
@@ -205,7 +210,9 @@ class TestCardDefinitionPokemon:
                     effect_id="may_paralyze",
                 ),
             ],
-            weakness=WeaknessResistance(energy_type=EnergyType.FIGHTING, modifier=2),
+            weakness=WeaknessResistance(
+                energy_type=EnergyType.FIGHTING, mode=ModifierMode.MULTIPLICATIVE, value=2
+            ),
             retreat_cost=1,
         )
 
@@ -1112,8 +1119,12 @@ class TestCardDefinitionJsonRoundTrip:
             abilities=[
                 Ability(name="Static", effect_id="static_paralysis"),
             ],
-            weakness=WeaknessResistance(energy_type=EnergyType.FIGHTING, modifier=2),
+            weakness=WeaknessResistance(
-            resistance=WeaknessResistance(energy_type=EnergyType.METAL, modifier=-30),
+                energy_type=EnergyType.FIGHTING, mode=ModifierMode.MULTIPLICATIVE, value=2
+            ),
+            resistance=WeaknessResistance(
+                energy_type=EnergyType.METAL, mode=ModifierMode.ADDITIVE, value=-30
+            ),
             retreat_cost=1,
             rarity="common",
             set_id="base",