diff --git a/README.md b/README.md
index 6787776..44b7177 100644
--- a/README.md
+++ b/README.md
@@ -426,6 +426,51 @@ Règles modélisées :
   si l'action elle-même soigne la créature au-dessus de 0 pv, ce coût n'est pas
   appliqué.
 - `hp < 0` = inactive (mourante ou morte) ; `hp = 0` = active mais invalide.
+- Dégâts non-létaux (SRD « Nonlethal Damage ») : piste séparée `nonlethal`
+  du runtime (`CombatantState.nonlethal`), **jamais** déduite des pv (« Do not
+  deduct the nonlethal damage number from your current hit points. It is not
+  "real" damage »). Les seuils sont **dérivés** de (nonlethal, pv courants),
+  sans objet de condition : `nonlethal == hp` (et > 0) = **staggered** (une
+  action de mouvement OU standard, via le filtre `_is_staggered_limited` déjà
+  en place) ; `nonlethal > hp` = **inconsciente et inerme** (inactif via
+  `CombatantState.active` — ne peut rien faire, ne menace aucune case, compte
+  comme tombé pour la victoire de camp — et `helpless` via `_is_helpless` :
+  Dex effective 0, +4 contre elle en mêlée). Un soin qui remonte les pv
+  au-dessus du total non-létal (ou qui réduit ce total) restaure la
+  conscience automatiquement, la règle étant une fonction pure des deux
+  nombres. **Règle du plafond de pv maximaux** (SRD) : « If a creature's
+  nonlethal damage is equal to his total maximum hit points (not his current
+  hit points), all further nonlethal damage is treated as lethal damage » —
+  au-delà de `hp_max` accumulé, les dégâts non-létaux suivants deviennent
+  réels et peuvent tuer (l'exception des créatures à régénération n'est pas
+  modélisée : aucune créature du moteur n'a la régénération). **Immunité** :
+  morts-vivants et constructeurs ne subissent **pas** de dégâts non-létaux
+  (traits SRD « Undead » / « Construct », KB `rules/advanced-race-guide/
+  undead-16-rp.md` et `construct-20-rp.md` : « not subject to ... nonlethal
+  damage ») — les dégâts sont annulés. **Soins** : « When a spell or ability
+  cures hit point damage, it also removes an equal amount of nonlethal
+  damage » — un sort de soin ou `channel energy` qui rend N pv retire aussi N
+  points de non-létal. **Sources de dégâts non-létaux** : (1) l'attaque sans
+  arme — les coups sans arme infligent des dégâts non-létaux par défaut (SRD
+  « Unarmed Attacks » : « An unarmed strike deals nonlethal damage ») ; le
+  moteur reconnaît une attaque dont le nom d'arme est exactement
+  « Unarmed Strike » (insensible à la casse, comme transcrit dans
+  `data/pcs/*.json`) et route la totalité de son dégât (après RD et
+  résistances) vers la piste non-létale ; heuristique documentée : le modèle
+  de données n'a pas de champ « mode de dégâts », le nom est le marqueur.
+  (2) La règle du **dégât minimal** (CRB « Damage — Minimum Damage ») : « If
+  penalties reduce the damage result to less than 1, a hit still deals 1
+  point of nonlethal damage » — une touche réduite sous 1 par la RD ou une
+  résistance énergétique inflige désormais 1 point **non-létal** (approximation
+  « 1 point normal » de ae037c9 corrigée). Hors périmètre (documenté) : la
+  conversion déclarée avant le jet — arme létale frappant en non-létal à −4,
+  attaque sans arme frappant en léthal à −4 (choix du moine sans pénalité non
+  modélisé faute de marqueur de classe) ; la récupération hors combat
+  (1 pv de non-létal par heure et par niveau) ; les dégâts non-létaux ne sont
+  **jamais** comptés dans l'attrition (`damage_dealt`/`damage_taken` restent
+  strictement létaux) ; le snapshot d'observation expose la clé additive
+  `nonlethal` (int) par combattant — la politique dérive staggered/inconscient
+  en la comparant à `hp`.
 - Initiative : triée sur (total, modificateur, ordre de liste), sans re-jet.
 - Round de surprise (SRD « Surprise ») : le champ booléen `aware` du JSON de
   combattant (défaut `true`) encode la conscience des adversaires au début du
diff --git a/src/pf1e_simulator/combat.py b/src/pf1e_simulator/combat.py
index e1d8b40..2b0dea0 100644
--- a/src/pf1e_simulator/combat.py
+++ b/src/pf1e_simulator/combat.py
@@ -919,6 +919,17 @@ class CombatantState:
     # Bleeding (V5b, not in the frozen data model): damage taken at the start
     # of each turn; any effect that restores hit points clears it.
     bleed_damage: int = 0
+    # PF1e nonlethal damage (SRD "Nonlethal Damage", not in the frozen data
+    # model): a running total that is NEVER deducted from hp ("Do not deduct
+    # the nonlethal damage number from your current hit points. It is not
+    # 'real' damage"). The staggered/unconscious thresholds are DERIVED from
+    # this total against current hp (``nonlethal_staggered`` /
+    # ``nonlethal_unconscious``) rather than stored as condition objects -
+    # the SRD state is a pure function of the two numbers ("You cease being
+    # staggered when your current hit points once again exceed your nonlethal
+    # damage"), so a derived flag can never desync, double up with an
+    # injected condition, or fight the duration-tick machinery.
+    nonlethal: int = 0
     # PF1e recurring spell damage (S2c, not in the frozen data model): each
     # entry is one damage-over-time source (Acid Arrow's lingering acid) that
     # deals its dice at the start of this combatant's turn for `rounds_left`
@@ -989,14 +1000,58 @@ class CombatantState:
         self.spell_slots_left[level] = current - 1
         return True
 
+    def take_nonlethal(self, amount: int) -> int:
+        """Accumulate nonlethal damage; return the portion treated as LETHAL.
+
+        PF1e (SRD "Nonlethal Damage"): nonlethal damage is a running total
+        never deducted from hp, so the track simply grows - EXCEPT the max-hp
+        overflow rule: "If a creature's nonlethal damage is equal to his total
+        maximum hit points (not his current hit points), all further nonlethal
+        damage is treated as lethal damage" (the regeneration exception is not
+        modeled: no combatant has regeneration). Undead and constructs are
+        NOT subject to nonlethal damage (SRD undead/construct traits, KB
+        rules/advanced-race-guide/undead-16-rp.md:15, construct-20-rp.md:16)
+        - the damage is discarded. Returns the amount the caller must apply
+        as real hp damage (0 in every other case).
+        """
+        if amount <= 0:
+            return 0
+        if self.combatant.creature_type in ("undead", "construct"):
+            return 0
+        if self.nonlethal >= self.combatant.hp_max:
+            return amount
+        self.nonlethal += amount
+        return 0
+
+    @property
+    def nonlethal_unconscious(self) -> bool:
+        """PF1e (SRD "Nonlethal Damage"): "when it [nonlethal damage] exceeds
+        your current hit points, you fall unconscious" - and "While
+        unconscious, you are helpless". Derived, so healing hp back above the
+        nonlethal total (or removing nonlethal) restores consciousness with no
+        bookkeeping; below 0 hp the dying rules already govern the creature."""
+        return self.hp >= 0 and self.nonlethal > self.hp and self.nonlethal > 0
+
+    @property
+    def nonlethal_staggered(self) -> bool:
+        """PF1e (SRD "Nonlethal Damage"): "when your nonlethal damage equals
+        your current hit points, you're staggered ... You cease being
+        staggered when your current hit points once again exceed your nonlethal
+        damage." Strictly equal: exceeding the total is the unconscious case
+        (``nonlethal_unconscious``), which subsumes the staggered restriction."""
+        return self.hp >= 0 and self.nonlethal > 0 and self.nonlethal == self.hp
+
     @property
     def active(self) -> bool:
         """PF1e: hp > 0 acts normally; hp == 0 is DISABLED (CRB, Effects of
         Death: a living creature at exactly 0 hp can still take a single move
         or standard action), so it remains active. hp < 0 is dying/dead.
         Under the simple monster-death rule (``dies_at_zero``) hp <= 0 is
-        dead, so the disabled band never applies."""
-        return self.hp >= 0 and not self.dead
+        dead, so the disabled band never applies. A creature knocked
+        unconscious by nonlethal damage (SRD "Nonlethal Damage") is inactive
+        exactly like a dying one: it cannot act, threatens no square, and
+        counts as downed for the winner check - but its hp is untouched."""
+        return self.hp >= 0 and not self.dead and not self.nonlethal_unconscious
 
     @property
     def dead(self) -> bool:
@@ -1652,6 +1707,10 @@ class CombatEngine:
             "occupied_cells": tuple(sorted(state.occupied_cells())),
             "hp": state.hp,
             "hp_max": state.combatant.hp_max,
+            # SRD "Nonlethal Damage": separate running total; staggered when
+            # it equals hp, unconscious (helpless) when it exceeds hp - the
+            # policy derives the thresholds from (nonlethal, hp) itself.
+            "nonlethal": state.nonlethal,
             "active": state.active,
             "dead": state.dead,
             "dying": state.hp < 0 and not state.dead,
@@ -2238,19 +2297,24 @@ class CombatEngine:
     def _is_staggered_limited(self, state: CombatantState) -> bool:
         """True when the creature is limited to one move OR one standard
         action per round (CRB "Conditions — Staggered"; a disabled creature
-        at 0 hp is staggered). Such a creature cannot take full-round actions
-        — except Restricted Withdraw (SRD "Full-Round Actions"), which it may
-        take as a standard action moving up to its speed."""
-        return self._is_disabled(state) or self._has_condition_named(
-            state, "staggered"
+        at 0 hp is staggered; nonlethal damage equal to current hp staggers,
+        SRD "Nonlethal Damage"). Such a creature cannot take full-round
+        actions — except Restricted Withdraw (SRD "Full-Round Actions"),
+        which it may take as a standard action moving up to its speed."""
+        return (
+            self._is_disabled(state)
+            or self._has_condition_named(state, "staggered")
+            or state.nonlethal_staggered
         )
 
     def _is_helpless(self, state: CombatantState) -> bool:
         """PF1e (CRB): helpless = paralyzed, held, bound, sleeping, unconscious.
 
         Stunned is NOT helpless. A helpless creature has effective Dexterity 0
-        and melee attackers gain +4 (resolve_attack)."""
-        return any(
+        and melee attackers gain +4 (resolve_attack). A creature whose
+        nonlethal damage EXCEEDS its current hp is unconscious, hence helpless
+        (SRD "Nonlethal Damage": "While unconscious, you are helpless")."""
+        return state.nonlethal_unconscious or any(
             self._has_condition_named(state, name)
             for name in _HELPLESS_CONDITION_NAMES
         )
@@ -2379,6 +2443,45 @@ class CombatEngine:
         state.temp_hp -= absorbed
         state.hp -= amount - absorbed
 
+    def _apply_nonlethal(self, state: CombatantState, amount: int) -> int:
+        """Route ``amount`` of nonlethal damage to the separate track (SRD
+        "Nonlethal Damage"); returns the portion the max-hp overflow rule
+        converted to lethal damage, already applied to hp and booked to the
+        victim's damage_taken (the nonlethal portion is NOT real damage and
+        never touches the hp/damage counters - the attrition stats stay
+        lethal-only). Logs threshold crossings (staggered / unconscious)."""
+        if amount <= 0:
+            return 0
+        was_staggered = state.nonlethal_staggered
+        was_unconscious = state.nonlethal_unconscious
+        lethal_part = state.take_nonlethal(amount)
+        if lethal_part:
+            old_hp = state.hp
+            self._lose_hp(state, lethal_part)
+            self._stats[state.combatant.id].damage_taken += lethal_part
+            self._log(
+                f"round {self._current_round} {state.combatant.id}: nonlethal "
+                f"overflow at max hp - {lethal_part} treated as lethal "
+                f"(hp {old_hp}->{state.hp})"
+            )
+        else:
+            self._log(
+                f"round {self._current_round} {state.combatant.id}: "
+                f"nonlethal {amount} (nl {state.nonlethal - amount}->{state.nonlethal}, "
+                f"hp {state.hp})"
+            )
+        if not was_unconscious and state.nonlethal_unconscious:
+            self._log(
+                f"round {self._current_round} {state.combatant.id}: "
+                f"unconscious (nonlethal {state.nonlethal} > hp {state.hp})"
+            )
+        elif not was_staggered and state.nonlethal_staggered:
+            self._log(
+                f"round {self._current_round} {state.combatant.id}: "
+                f"staggered (nonlethal {state.nonlethal} = hp {state.hp})"
+            )
+        return lethal_part
+
     def _apply_bleed_damage(self, state: CombatantState) -> None:
         """PF1e bleeding: take ``bleed_damage`` at the beginning of the turn (CRB)."""
         if state.bleed_damage <= 0:
@@ -6222,6 +6325,10 @@ class CombatEngine:
         if affected_state.hp < 0:
             affected_state.stabilized_hp = affected_state.hp
         actual = affected_state.hp - old_hp
+        # SRD "Nonlethal Damage": curing hit point damage removes an equal
+        # amount of nonlethal damage (see _apply_heal_effect).
+        if actual > 0:
+            affected_state.nonlethal = max(0, affected_state.nonlethal - actual)
         # Healing is NOT damage dealt: the damage counters stay damage-only
         # (README "degats infligés/subis"); restored hp are booked to the
         # healer's separate healing_done counter (mirrors spell HealEffect).
@@ -7876,6 +7983,12 @@ class CombatEngine:
         if target.hp < 0:
             target.stabilized_hp = target.hp
         actual = target.hp - old_hp
+        # PF1e (SRD "Nonlethal Damage" - Healing Nonlethal Damage): "When a
+        # spell or ability cures hit point damage, it also removes an equal
+        # amount of nonlethal damage." (The out-of-combat recovery of 1 hp per
+        # hour per level is out of combat scope - documented, not modeled.)
+        if actual > 0:
+            target.nonlethal = max(0, target.nonlethal - actual)
         if caster_live is not None:
             caster_live.healing_done += actual
         self._stop_bleeding(target)
diff --git a/tests/test_nonlethal.py b/tests/test_nonlethal.py
new file mode 100644
index 0000000..3fdb476
--- /dev/null
+++ b/tests/test_nonlethal.py
@@ -0,0 +1,305 @@
+"""Nonlethal damage track (SRD "Nonlethal Damage", KB
+rules/prpg-core-rulebook/nonlethal-damage.md): a separate running total never
+deducted from hp, derived staggered/unconscious thresholds, the max-hp
+overflow-to-lethal rule, undead/construct immunity, and healing that removes
+an equal amount of nonlethal damage.
+
+This file covers the TRACK; the damage SOURCES (unarmed strikes, the CRB
+Minimum Damage floor) are locked in the "sources" section at the bottom,
+which exercises the routing through resolve_attack.
+"""
+
+from __future__ import annotations
+
+from pf1e_simulator.combat import Action, CombatantState, CombatEngine
+from pf1e_simulator.dice import parse_dice
+from pf1e_simulator.grid import Grid
+from pf1e_simulator.map import MapSpec, TerrainType
+from pf1e_simulator.models import (
+    AbilityScores,
+    ACProfile,
+    AttackSpec,
+    Combatant,
+    DamageComponent,
+    DamageReduction,
+    Saves,
+)
+from pf1e_simulator.rng import ScriptedRng
+from pf1e_simulator.spells import HealEffect
+
+
+def _combatant(
+    cid: str,
+    *,
+    hp: int = 6,
+    attack_bonus: int = 2,
+    weapon_name: str = "short sword",
+    damage: str = "1d4",
+    dr: DamageReduction | None = None,
+    creature_type: str = "living",
+) -> Combatant:
+    attack = AttackSpec(
+        id=f"{cid}-w",
+        name=weapon_name,
+        kind="melee",
+        attack_bonus=attack_bonus,
+        damage=[DamageComponent(formula=parse_dice(damage), types=["bludgeoning"])],
+    )
+    return Combatant(
+        id=cid,
+        name=cid,
+        level=1,
+        size="Medium",
+        abilities=AbilityScores(
+            str_score=10, dex_score=10, con_score=10,
+            int_score=10, wis_score=10, cha_score=10,
+        ),
+        hp_max=hp,
+        ac=ACProfile(total=13, touch=13, flat_footed=13),
+        bab=attack_bonus,
+        initiative_mod=0,
+        speed_land_ft=30,
+        saves=Saves(fort=0, ref=0, will=0),
+        attacks=[attack],
+        dr=dr,
+        creature_type=creature_type,
+    )
+
+
+def _state(
+    combatant: Combatant, side: str, pos: tuple[int, int], hp: int | None = None
+) -> CombatantState:
+    return CombatantState(
+        combatant=combatant, side=side, pos=pos,
+        hp=combatant.hp_max if hp is None else hp,
+    )
+
+
+def _grid() -> Grid:
+    legend = {".": TerrainType(type="floor", move_cost=1)}
+    spec = MapSpec(name="test", terrain=tuple(["." * 8] * 8), legend=legend)
+    return Grid.from_spec(spec)
+
+
+def _engine(
+    states: list[CombatantState], rolls: list[int] | None = None
+) -> CombatEngine:
+    return CombatEngine(ScriptedRng(rolls or [20] * 200), _grid(), states)
+
+
+# ── Track accumulation and separation from hp ────────────────────────────────
+
+def test_take_nonlethal_accumulates_without_touching_hp() -> None:
+    # SRD: "keep a running total ... Do not deduct the nonlethal damage
+    # number from your current hit points."
+    foe = _state(_combatant("foe", hp=10), "monsters", (0, 1))
+    assert foe.take_nonlethal(4) == 0
+    assert foe.nonlethal == 4
+    assert foe.hp == 10
+    foe.take_nonlethal(3)
+    assert foe.nonlethal == 7
+    assert foe.hp == 10
+
+
+def test_nonlethal_below_hp_is_no_state() -> None:
+    foe = _state(_combatant("foe", hp=10), "monsters", (0, 1))
+    foe.take_nonlethal(9)
+    assert not foe.nonlethal_staggered
+    assert not foe.nonlethal_unconscious
+    assert foe.active is True
+
+
+# ── Derived thresholds: staggered at == hp, unconscious at > hp ──────────────
+
+def test_staggered_when_nonlethal_equals_hp() -> None:
+    # SRD: "when your nonlethal damage equals your current hit points,
+    # you're staggered."
+    foe = _state(_combatant("foe", hp=10), "monsters", (0, 1))
+    foe.take_nonlethal(10)
+    assert foe.nonlethal_staggered is True
+    assert foe.nonlethal_unconscious is False
+    assert foe.active is True  # staggered still acts (limited)
+
+
+def test_unconscious_when_nonlethal_exceeds_hp() -> None:
+    # SRD: "when it exceeds your current hit points, you fall unconscious.
+    # While unconscious, you are helpless."
+    foe = _state(_combatant("foe", hp=10), "monsters", (0, 1))
+    foe.take_nonlethal(11)
+    assert foe.nonlethal_unconscious is True
+    assert foe.nonlethal_staggered is False  # subsumed by unconscious
+    assert foe.active is False  # cannot act, threatens nothing, counts downed
+    assert foe.hp == 10  # unconsciousness never costs hp
+
+
+def test_engine_treats_nonlethal_unconscious_as_helpless_and_staggered_as_limited() -> (
+    None
+):
+    # _is_helpless drives the Dex-0 / +4-melee package; _is_staggered_limited
+    # drives the one-move-or-standard action filter.
+    engine = _engine(
+        [
+            _state(_combatant("a"), "players", (0, 0)),
+            _state(_combatant("b", hp=20), "monsters", (0, 1), hp=10),
+        ]
+    )
+    staggered = engine._states[1]
+    staggered.take_nonlethal(10)
+    assert engine._is_staggered_limited(staggered) is True
+    assert engine._is_helpless(staggered) is False
+    staggered.take_nonlethal(1)
+    # Unconscious is NOT staggered-limited: it is total inaction (active is
+    # False, so the turn never reaches the action filter) plus helpless.
+    assert engine._is_staggered_limited(staggered) is False
+    assert staggered.active is False
+    assert engine._is_helpless(staggered) is True
+
+
+def test_staggered_from_nonlethal_downgrades_full_attack() -> None:
+    # The derived staggered state feeds the existing action-economy filter:
+    # a full attack collapses to a single standard attack.
+    engine = _engine(
+        [
+            _state(_combatant("a"), "players", (0, 0)),
+            _state(_combatant("b", hp=10), "monsters", (0, 1)),
+        ]
+    )
+    b = engine._states[1]
+    b.nonlethal = 10  # == hp -> staggered
+    kept = engine._filter_turn_actions(
+        b, (Action(kind="full_attack", target_id="a"),), []
+    )
+    assert [a.kind for a in kept] == ["attack"]
+
+
+# ── Nonlethal never kills below the max-hp ceiling ───────────────────────────
+
+def test_further_nonlethal_just_keeps_the_target_unconscious() -> None:
+    # SRD: nonlethal below total-max-hp is never hp damage; a pummeled
+    # unconscious creature simply accrues more nonlethal.
+    foe = _state(_combatant("foe", hp=30), "monsters", (0, 1), hp=10)
+    for _ in range(5):
+        assert foe.take_nonlethal(4) == 0
+    assert foe.nonlethal == 20  # far above hp...
+    assert foe.hp == 10  # ...but no hp was ever lost
+    assert foe.dead is False
+
+
+def test_overflow_at_max_hp_converts_to_lethal() -> None:
+    # SRD: "If a creature's nonlethal damage is equal to his total maximum
+    # hit points (not his current hit points), all further nonlethal damage
+    # is treated as lethal damage."
+    foe = _state(_combatant("foe", hp=10), "monsters", (0, 1))
+    assert foe.take_nonlethal(10) == 0  # reaches hp_max exactly: still nonlethal
+    assert foe.nonlethal == 10
+    assert foe.take_nonlethal(3) == 3  # at the ceiling: this instance is lethal
+    assert foe.nonlethal == 10  # the track stops growing
+
+
+def test_engine_apply_nonlethal_logs_thresholds_and_books_overflow() -> None:
+    engine = _engine(
+        [
+            _state(_combatant("a"), "players", (0, 0)),
+            _state(_combatant("b", hp=4), "monsters", (0, 1)),
+        ]
+    )
+    b = engine._states[1]
+    assert engine._apply_nonlethal(b, 5) == 0
+    assert "b: unconscious (nonlethal 5 > hp 4)" in engine._transcript[-1]
+    # b.nonlethal (5) >= hp_max (4): further nonlethal is lethal damage.
+    assert engine._apply_nonlethal(b, 2) == 2
+    assert b.hp == 2
+    assert engine._stats["b"].damage_taken == 2  # only the lethal part is booked
+
+
+# ── Undead / construct immunity ──────────────────────────────────────────────
+
+def test_undead_are_not_subject_to_nonlethal() -> None:
+    # SRD undead traits (KB undead-16-rp.md:15): "not subject to ... nonlethal
+    # damage".
+    lich = _state(
+        _combatant("lich", hp=10, creature_type="undead"), "monsters", (0, 1)
+    )
+    assert lich.take_nonlethal(8) == 0
+    assert lich.nonlethal == 0
+    assert lich.hp == 10
+
+
+def test_construct_is_not_subject_to_nonlethal() -> None:
+    # SRD construct traits (KB construct-20-rp.md:16): "not subject to ...
+    # nonlethal damage".
+    robot = _state(
+        _combatant("robot", hp=10, creature_type="construct"), "monsters", (0, 1)
+    )
+    assert robot.take_nonlethal(8) == 0
+    assert robot.nonlethal == 0
+
+
+# ── Healing restores consciousness ───────────────────────────────────────────
+
+def test_healing_above_the_nonlethal_total_restores_consciousness() -> None:
+    # Derived thresholds: raising hp back above the nonlethal total ends the
+    # unconscious state with no bookkeeping ("You cease being staggered when
+    # your current hit points once again exceed your nonlethal damage" - the
+    # same pure function governs both thresholds).
+    foe = _state(_combatant("foe", hp=10), "monsters", (0, 1), hp=4)
+    foe.take_nonlethal(6)  # 6 > hp 4 -> unconscious
+    assert foe.nonlethal_unconscious is True
+    assert foe.active is False
+    foe.hp = 7  # healed above the nonlethal total
+    assert foe.nonlethal_unconscious is False
+    assert foe.nonlethal_staggered is False
+    assert foe.active is True
+
+
+def test_spell_healing_removes_equal_nonlethal() -> None:
+    # SRD: "When a spell or ability cures hit point damage, it also removes
+    # an equal amount of nonlethal damage."
+    engine = _engine(
+        [
+            _state(_combatant("a"), "players", (0, 0)),
+            _state(_combatant("b", hp=10), "monsters", (0, 1), hp=3),
+        ]
+    )
+    b = engine._states[1]
+    b.nonlethal = 8  # unconscious (8 > 3)
+    effect = HealEffect(formula=parse_dice("6"))
+    out = engine._apply_heal_effect(
+        effect, b, caster_level=1, empower=False, maximize=False, saved=False
+    )
+    assert out == "+6 HP"
+    assert b.hp == 9
+    assert b.nonlethal == 2  # 8 - 6 equal removal
+    assert b.active is True
+
+
+def test_channel_heal_removes_equal_nonlethal() -> None:
+    engine = _engine(
+        [
+            _state(_combatant("a"), "players", (0, 0)),
+            _state(_combatant("b", hp=10), "monsters", (0, 1), hp=2),
+        ]
+    )
+    healer, b = engine._states[0], engine._states[1]
+    b.nonlethal = 5  # unconscious (5 > 2)
+    engine._channel_heal(healer, b, 4)
+    assert b.hp == 6
+    assert b.nonlethal == 1  # 5 - 4
+    assert b.nonlethal_staggered is False
+    assert b.active is True
+
+
+# ── Observation snapshot exposure ────────────────────────────────────────────
+
+def test_snapshot_exposes_nonlethal() -> None:
+    engine = _engine(
+        [
+            _state(_combatant("a"), "players", (0, 0)),
+            _state(_combatant("b", hp=10), "monsters", (0, 1)),
+        ]
+    )
+    b = engine._states[1]
+    b.nonlethal = 7
+    snapshot = engine._combatant_snapshot(b)
+    assert snapshot["nonlethal"] == 7
+    assert snapshot["hp"] == 10