fix(rules): stabilize is a StabilizeEffect that auto-stabilizes a dying creature

src/pf1e_simulator/combat.py

@@ -150,6 +150,7 @@ from pf1e_simulator.spells import (
     RecurringDamageSpec,
     SaveType,
     SpellEffect,
+    StabilizeEffect,
     SummonEffect,
     TempHpEffect,
     close_range_ft,
@@ -469,10 +470,22 @@ def _damage_effect_summary(effect: DamageEffect | PenaltyEffect, tags: list[str]
     return " ".join(parts)
 
 
+def _simple_effect_summary(
+    effect: OneShotEffect | TempHpEffect | StabilizeEffect,
+) -> str:
+    if isinstance(effect, OneShotEffect):
+        return (
+            f"one-shot +{effect.value} {effect.bonus_type} on {effect.track}"
+        )
+    if isinstance(effect, TempHpEffect):
+        return f"temp hp +{effect.amount} ({effect.duration_rounds}r)"
+    return "stabilize"
+
+
 def _non_damage_effect_summary(
     effect: (
         ConditionEffect | HealEffect | BuffEffect | AreaEffect | SummonEffect
-        | OneShotEffect | TempHpEffect
+        | OneShotEffect | TempHpEffect | StabilizeEffect
     )
 ) -> str:
     if isinstance(effect, ConditionEffect):
@@ -483,12 +496,8 @@ def _non_damage_effect_summary(
         return f"area {effect.radius_ft}ft"
     if isinstance(effect, SummonEffect):
         return f"summon {effect.creature}"
-    if isinstance(effect, (OneShotEffect, TempHpEffect)):
-        return (
-            f"one-shot +{effect.value} {effect.bonus_type} on {effect.track}"
-            if isinstance(effect, OneShotEffect)
-            else f"temp hp +{effect.amount} ({effect.duration_rounds}r)"
-        )
+    if isinstance(effect, (OneShotEffect, TempHpEffect, StabilizeEffect)):
+        return _simple_effect_summary(effect)
     return f"buff {effect.duration_rounds}r"
 
 
@@ -6904,7 +6913,12 @@ class CombatEngine:
                 caster, spell, spell_name, center_pos, has_area=has_area
             )
             return not point_ok
-        if not target.active:
+        if not target.active and not any(
+            isinstance(e, StabilizeEffect) for e in spell.effects
+        ):
+            # Stabilize (SRD spells/stabilize.md) targets a living creature
+            # at -1 or fewer hit points — an inactive state every other spell
+            # cannot reach, so it alone bypasses the active-target gate.
             return True
         dist_ft = self.creature_distance(caster, target) * _SQUARE_FT
         if dist_ft > spell_range_ft(spell, caster.combatant.level):
@@ -7155,7 +7169,7 @@ class CombatEngine:
         self,
         effect: (
             DamageEffect | ConditionEffect | HealEffect | BuffEffect
-            | PenaltyEffect | OneShotEffect | TempHpEffect
+            | PenaltyEffect | OneShotEffect | TempHpEffect | StabilizeEffect
         ),
         target: CombatantState,
         caster_live: _LiveStats,
@@ -7193,8 +7207,8 @@ class CombatEngine:
                 effect, target, caster=caster, saved=saved,
                 empower=empower, maximize=maximize, spell_name=spell_name,
             )
-        if isinstance(effect, (OneShotEffect, TempHpEffect)):
-            return self._apply_grant_effect(
+        if isinstance(effect, (OneShotEffect, TempHpEffect, StabilizeEffect)):
+            return self._apply_simple_effect(
                 effect, target, saved=saved, spell_name=spell_name,
             )
         return self._apply_buff_effect(
@@ -7202,9 +7216,9 @@ class CombatEngine:
             caster_level=caster.combatant.level,
         )
 
-    def _apply_grant_effect(
+    def _apply_simple_effect(
         self,
-        effect: OneShotEffect | TempHpEffect,
+        effect: OneShotEffect | TempHpEffect | StabilizeEffect,
         target: CombatantState,
         *,
         saved: bool,
@@ -7214,7 +7228,28 @@ class CombatEngine:
             return self._apply_one_shot_effect(
                 effect, target, saved=saved, spell_name=spell_name,
             )
-        return self._apply_temp_hp_effect(effect, target, saved=saved)
+        if isinstance(effect, TempHpEffect):
+            return self._apply_temp_hp_effect(effect, target, saved=saved)
+        return self._apply_stabilize_effect(target, saved=saved)
+
+    def _apply_stabilize_effect(
+        self, target: CombatantState, *, saved: bool
+    ) -> str:
+        """Stabilize a dying creature (SRD spells/stabilize.md).
+
+        The spell targets a living creature at -1 or fewer hit points and
+        automatically stabilizes it: stabilized_hp is set to the target's
+        current hp, the same marker a successful Constitution check writes in
+        _process_dying, so the per-round hp loss stops. New damage below that
+        hp clears the marker and the creature resumes dying normally; a
+        creature at hp >= 0 or dead is unaffected.
+        """
+        if saved:
+            return "stabilize negated"
+        if target.dead or target.hp >= 0:
+            return "stabilize no effect"
+        target.stabilized_hp = target.hp
+        return f"stabilized (hp {target.hp})"
 
     def _apply_one_shot_effect(
         self, effect: OneShotEffect, target: CombatantState, *, saved: bool, spell_name: str

src/pf1e_simulator/spells.py

@@ -303,6 +303,22 @@ class TempHpEffect:
     duration_rounds: int
 
 
+@dataclass(frozen=True)
+class StabilizeEffect:
+    """PF1e stabilize (SRD spells/stabilize.md: "you target a living creature
+    that has -1 or fewer hit points. That creature is automatically stabilized
+    and does not lose any further hit points").
+
+    The engine's dying track already carries the stabilization marker
+    (``CombatantState.stabilized_hp``, written by a successful Constitution
+    check in ``_process_dying``); the spell writes the same marker at the
+    target's current hp. The marker stops the per-round hp loss while
+    ``hp >= stabilized_hp`` and is cleared by new damage below it, so the
+    creature "continues dying normally" (SRD) after being hurt again. A
+    creature at hp >= 0 or dead is unaffected.
+    """
+
+
 @dataclass(frozen=True)
 class PenaltyEffect:
     """PF1e rolled ability penalty (SRD Ray of Enfeeblement).
@@ -385,6 +401,7 @@ class SummonEffect:
 SpellEffect = (
     DamageEffect | ConditionEffect | HealEffect | BuffEffect
     | PenaltyEffect | AreaEffect | SummonEffect | OneShotEffect | TempHpEffect
+    | StabilizeEffect
 )
 
 
@@ -801,6 +818,13 @@ def _parse_temp_hp_effect(effect: dict[str, Json]) -> TempHpEffect:
     return TempHpEffect(amount=amount, duration_rounds=duration)
 
 
+def _parse_stabilize_effect(effect: dict[str, Json]) -> StabilizeEffect:
+    if effect.keys() - {"type"}:
+        msg = f"stabilize effect takes no fields, got {sorted(effect.keys() - {'type'})}"
+        raise ValueError(msg)
+    return StabilizeEffect()
+
+
 def _parse_penalty_effect(effect: dict[str, Json]) -> PenaltyEffect:
     flat_raw = effect.get("scaling_flat")
     scaling_flat = None if flat_raw is None else _parse_flat_scaling(flat_raw)
@@ -855,6 +879,7 @@ _EFFECT_PARSERS: dict[str, Callable[[dict[str, Json]], SpellEffect]] = {
     "buff": _parse_buff_effect,
     "one_shot": _parse_one_shot_effect,
     "temp_hp": _parse_temp_hp_effect,
+    "stabilize": _parse_stabilize_effect,
     "penalty": _parse_penalty_effect,
     "area": _parse_area_effect,
     "summon": _parse_summon_effect,