fix(rules): Lonely and Bitter drawbacks replace bogus +1 Will bonuses (SRD: Lonely -2 Sense Motive and -2 saves vs charm with mind_affecting standing in; Bitter reduces ally-sourced healing by 1 via engine hook)

src/pf1e_simulator/abilities.py

@@ -385,11 +385,16 @@ EXALTED_SOCIETY = AbilitySpec(
     resource_grants=(("channel_energy", 1),),
 )
 
-# Bitter: +1 trait bonus on saves vs fear
+# Bitter (Drawback): "When you receive healing from an ally's class feature,
+# spell, or spell-like ability, reduce the amount of that healing by 1 hit
+# point." It is a healing-application behavior, not a stat modifier: the
+# engine checks for this feature by name in _channel_heal/_apply_heal_effect
+# (like Power Attack is a behavior marker). The previous "+1 Will vs fear"
+# was the wrong effect (and a positive bonus for a drawback).
 BITTER = AbilitySpec(
     name="Bitter",
     category="trait",
-    effects=(StatModifier(target="will", value=1, condition="fear"),),
+    source_detail="drawback: ally healing received reduced by 1 (engine behavior)",
 )
 
 # Ambitious: +1 trait bonus on one Craft or Profession skill
@@ -427,11 +432,21 @@ FORTIFIED_DRINKER = AbilitySpec(
 # Fate's Favored: +1 luck bonus on all luck bonuses
 FATES_FAVORED = AbilitySpec(name="Fate's Favored", category="trait")
 
-# Lonely: +1 trait bonus on Will saves vs fear
+# Lonely (Drawback): "-2 penalty on Sense Motive checks and on Perception
+# checks to see through disguises, and on saving throws against charm spells
+# and spell-like abilities." The engine has no "charm" save descriptor, so
+# mind_affecting stands in for it (same documented convention as Inspire
+# Courage). The Perception-to-see-through-disguises check is a context the
+# engine never resolves, so only its Sense Motive half is modeled. The
+# previous "+1 Will vs fear" was a positive bonus for a drawback - wrong.
 LONELY = AbilitySpec(
     name="Lonely",
     category="trait",
-    effects=(StatModifier(target="will", value=1, condition="fear"),),
+    source_detail="drawback: -2 Sense Motive, -2 saves vs charm (mind_affecting stands in)",
+    effects=(
+        StatModifier(target="sense_motive", value=-2),
+        StatModifier(target="will", value=-2, condition="mind_affecting"),
+    ),
 )
 
 # Larger Than Life: +1 trait bonus on Intimidate

src/pf1e_simulator/combat.py

@@ -5459,6 +5459,7 @@ class CombatEngine:
     def _channel_heal(
         self, state: CombatantState, affected_state: CombatantState, dmg: int
     ) -> None:
+        dmg = self._bitter_reduced(state, affected_state, dmg)
         old_hp = affected_state.hp
         affected_state.hp = min(affected_state.hp + dmg, affected_state.combatant.hp_max)
         # PF1e (CRB, Stable Characters and Recovery): "If any sort of healing
@@ -6526,6 +6527,7 @@ class CombatEngine:
             return self._apply_heal_effect(
                 effect, target, caster_level=caster.combatant.level,
                 empower=empower, maximize=maximize, saved=saved,
+                healer=caster,
             )
         if isinstance(effect, PenaltyEffect):
             return self._apply_penalty_effect(
@@ -6719,6 +6721,23 @@ class CombatEngine:
             target.bleed_damage = max(target.bleed_damage, 1)
         return f"{condition_name} ({duration_rounds}r)"
 
+    def _bitter_reduced(
+        self, healer: CombatantState, target: CombatantState, amount: int
+    ) -> int:
+        """PF1e (Drawback "Bitter"): "When you receive healing from an ally's
+        class feature, spell, or spell-like ability, reduce the amount of that
+        healing by 1 hit point." Applies only to ally-sourced healing (an
+        ally is another creature on the same side); self-healing is untouched.
+        """
+        if (
+            amount > 0
+            and healer is not target
+            and healer.side == target.side
+            and self._has_feat(target, "Bitter")
+        ):
+            return amount - 1
+        return amount
+
     def _apply_heal_effect(
         self,
         effect: HealEffect,
@@ -6728,6 +6747,7 @@ class CombatEngine:
         empower: bool,
         maximize: bool,
         saved: bool,
+        healer: CombatantState | None = None,
     ) -> str:
         formula = effect.effective_formula(caster_level)
         heal = formula.roll(self._rng)
@@ -6742,10 +6762,13 @@ class CombatEngine:
             # resistance, and can attempt a Will save to take half damage."
             # SR is resolved upstream (_spell_delivery_blocked); the rolled
             # save halves here. Cure damage is spell energy: never reduced by
-            # DR, and it does not stop bleeding or stabilize.
+            # DR, and it does not stop bleeding or stabilize. Bitter reduces
+            # healing, not this damage.
             dmg = heal // 2 if saved else heal
             target.hp -= dmg
             return f"{dmg} damage (undead)"
+        if healer is not None:
+            heal = self._bitter_reduced(healer, target, heal)
         old_hp = target.hp
         target.hp = min(target.hp + heal, target.combatant.hp_max)
         # PF1e (CRB, Stable Characters and Recovery): "If any sort of healing