fix(rules): disarm drops the wielded weapon (weapon_dropped) instead of a synthetic -4 penalty

README.md

@@ -1317,7 +1317,10 @@ Règles modélisées :
     (tentative refusée,
     journalisée `rejected (target too large)`, aucun jet, pas d'AoO provoquée) ;
     les autres manœuvres (disarm, sunder, grapple…) n'ont pas de limite de taille.
-   trip → `prone` ; disarm → `disarmed` (−4 attaque) ; bull_rush → pousse la
+   trip → `prone` ; disarm → l'arme tenue est **au sol** (SRD « Disarm » :
+   « your target drops one item it is carrying » — `weapon_dropped`, exclue
+   de `usable_attacks()` jusqu'à un `retrieve_weapon` ; un échec de 10 ou
+   plus fait tomber **l'arme de l'attaquant**) ; bull_rush → pousse la
    cible (direction sélectionnable via `Action.direction`) ; conformance L6
    (SRD « Bull Rush ») : la poussée vaut 5 ft plus « For every 5 by which
    your attack exceeds your opponent's CMD you can push the target back an
@@ -1473,7 +1476,7 @@ Règles modélisées :
   state) -> tuple[Action, ...]`). Schéma enrichi (E1-E5) :
   - Par combattant : id, side, pos, occupied_cells, hp/hp_max, active/dead,
     dying/stabilized, conditions (noms + rounds_left), resources_left (+ `spell_slot_{level}`),
-    weapon_broken/weapon_stolen, grappled_with, moved_this_turn, power_attack,
+    weapon_broken/weapon_stolen/weapon_dropped, grappled_with, moved_this_turn, power_attack,
     name, level, size, natural_reach_ft (S4c : allonge naturelle du gabarit
     en pieds — 0 pour Tiny/Diminutive/Fine, 5 pour Small/Medium, 10 pour
     Large… ; l'allonge effective d'une attaque reste `max(allonge naturelle,

src/pf1e_simulator/combat.py

@@ -178,6 +178,7 @@ _CHARGE_AC_PENALTY = 2  # PF1e: -2 AC until start of next turn after charging
 _CHARGE_MIN_CELLS = 2  # PF1e: charge must move at least 10 ft (2 squares)
 _UP_CLOSE_RANGE_FT = 30  # PF1e: Up Close and Deadly works within 30 ft
 _GRAPPLED_CMB_PENALTY = 2  # PF1e: grappled/pinned -2 on non-grapple/escape CMB
+_DISARM_RETALIATION_MARGIN = 10  # PF1e SRD: disarm fails by 10 -> attacker drops
 # PF1e: Point-Blank Shot grants +1/+1 within 30 ft with ranged weapons
 _POINT_BLANK_RANGE_FT = 30
 _FIRING_MELEE_PENALTY = -4  # PF1e: ranged attack into melee
@@ -701,6 +702,11 @@ class CombatantState:
     # Runtime weapon theft (not in the frozen data model): weapon ids taken by
     # steal maneuvers.
     weapon_stolen: set[str] = field(default_factory=set)
+    # Runtime disarmed weapons (not in the frozen data model): weapon ids the
+    # combatant DROPPED on a failed disarm maneuver (SRD Disarm: "your
+    # opponent drops the weapon"). A retrieve_weapon move action picks the
+    # weapon back up.
+    weapon_dropped: set[str] = field(default_factory=set)
     # Dying & stabilization (not in the frozen data model): the hp at which
     # this combatant stabilized while dying; None = not stabilized.
     stabilized_hp: int | None = None
@@ -752,8 +758,11 @@ class CombatantState:
 
     def usable_attacks(self) -> list[AttackSpec]:
         return [
-            w for w in self.combatant.attacks
-            if w.id not in self.weapon_broken and w.id not in self.weapon_stolen
+            w
+            for w in self.combatant.attacks
+            if w.id not in self.weapon_broken
+            and w.id not in self.weapon_stolen
+            and w.id not in self.weapon_dropped
         ]
 
     def occupied_cells(self) -> frozenset[Pos]:
@@ -1422,6 +1431,7 @@ class CombatEngine:
             "resources_left": resources,
             "weapon_broken": tuple(sorted(state.weapon_broken)),
             "weapon_stolen": tuple(sorted(state.weapon_stolen)),
+            "weapon_dropped": tuple(sorted(state.weapon_dropped)),
             "grappled_with": state.grappled_with,
             "moved_this_turn": state.moved_this_turn,
             "power_attack": state.power_attack,
@@ -4674,10 +4684,14 @@ class CombatEngine:
         self._resolve_aoo(target, state)
 
     def _retrieve_weapon(self, state: CombatantState, weapon_id: str | None) -> None:
-        """Restore a stolen weapon to its owner (remove it from ``weapon_stolen``).
+        """Pick a stolen or dropped weapon back up.
 
-        No-op (with a log line) when ``weapon_id`` is None or the id was never
-        stolen. Once restored, the weapon is usable again via ``usable_attacks()``.
+        Removes ``weapon_id`` from ``weapon_stolen`` (steal maneuvers) or
+        ``weapon_dropped`` (disarm maneuvers — SRD Disarm: the disarmed
+        creature "drops one item it is carrying"; retrieving a dropped item
+        is a move action). No-op (with a log line) when ``weapon_id`` is
+        None or the id was never stolen or dropped. Once restored, the
+        weapon is usable again via ``usable_attacks()``.
         """
         if weapon_id is None:
             self._log(
@@ -4685,13 +4699,16 @@ class CombatEngine:
                 f"retrieve: nothing to retrieve"
             )
             return
-        if weapon_id not in state.weapon_stolen:
+        if weapon_id in state.weapon_stolen:
+            state.weapon_stolen.remove(weapon_id)
+        elif weapon_id in state.weapon_dropped:
+            state.weapon_dropped.remove(weapon_id)
+        else:
             self._log(
                 f"round {self._current_round} {state.combatant.id}: "
                 f"retrieve {weapon_id}: nothing to retrieve"
             )
             return
-        state.weapon_stolen.remove(weapon_id)
         self._log(
             f"round {self._current_round} {state.combatant.id}: "
             f"retrieve {weapon_id} (restored)"
@@ -4822,21 +4839,38 @@ class CombatEngine:
     ) -> None:
         if not m.success:
             self._maneuver_fail(state, target, "disarm", m)
+            # PF1e (SRD Disarm): "If your attack fails by 10 or more, you
+            # drop the weapon that you were using to attempt the disarm."
+            if m.total <= m.target_cmd - _DISARM_RETALIATION_MARGIN:
+                own = next(
+                    (w for w in state.usable_attacks() if w.kind == "melee"), None
+                )
+                if own is not None:
+                    state.weapon_dropped.add(own.id)
+                    self._log(
+                        f"round {self._current_round} {state.combatant.id}: "
+                        f"disarm backfire -> drops {own.name}"
+                    )
             return
-        target.active_conditions.append(
-            ActiveCondition(
-                condition=Condition(
-                    name="disarmed",
-                    modifiers=(StatModifier(target="attack", value=-4),),
-                ),
-                rounds_left=1,
-                source="maneuver: disarm",
-            )
-        )
+        # PF1e (SRD Disarm): "If your attack is successful, your target drops
+        # one item it is carrying of your choice" — the weapon lands on the
+        # ground (unusable until a retrieve_weapon move action picks it back
+        # up), NOT a synthetic -4 attack penalty. The engine chooses the
+        # target's first usable melee weapon (the wielded weapon, same choice
+        # as the AoO machinery).
+        weapon = next((w for w in target.usable_attacks() if w.kind == "melee"), None)
+        if weapon is None:
             self._log(
                 f"round {self._current_round} {state.combatant.id}: disarm vs "
                 f"{target.combatant.id} d20={m.roll}+{m.attacker_cmb}={m.total} "
-            f"CMD {m.target_cmd} -> SUCCESS (disarmed)"
+                f"CMD {m.target_cmd} -> SUCCESS (no weapon to drop)"
+            )
+            return
+        target.weapon_dropped.add(weapon.id)
+        self._log(
+            f"round {self._current_round} {state.combatant.id}: disarm vs "
+            f"{target.combatant.id} d20={m.roll}+{m.attacker_cmb}={m.total} "
+            f"CMD {m.target_cmd} -> SUCCESS ({weapon.name} dropped)"
         )
 
     def _maneuver_bull_rush(

tests/test_maneuvers.py

@@ -284,6 +284,62 @@ def test_unrestricted_maneuver_ignores_size_limit() -> None:
     assert not engine._rng._queue
 
 
+# --- SRD Disarm: the target DROPS the weapon (no synthetic -4 penalty) --------
+
+
+def test_disarm_success_drops_target_weapon() -> None:
+    # SRD Disarm: "If your attack is successful, your target drops one item
+    # it is carrying." The dropped weapon is unusable until retrieved; the
+    # old synthetic "disarmed" -4 attack condition is gone.
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 1))
+    b = make_state(make_combatant("b"), "monsters", (1, 2))
+    engine = make_engine([1, 12], [a, b])
+    engine._execute_maneuver(a, b, "disarm")
+    assert "b-w" in b.weapon_dropped
+    assert [w.id for w in b.usable_attacks()] == []
+    assert engine.weapon_for(b, a) is None
+    assert not any(c.condition.name == "disarmed" for c in b.active_conditions)
+    assert "SUCCESS (sword dropped)" in engine._transcript[-1]
+
+
+def test_retrieve_weapon_picks_dropped_weapon_back_up() -> None:
+    # Picking the dropped weapon back up is a move action (retrieve_weapon);
+    # once restored, the weapon is usable again.
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 1))
+    b = make_state(make_combatant("b"), "monsters", (1, 2))
+    engine = make_engine([1, 12], [a, b])
+    engine._execute_maneuver(a, b, "disarm")
+    assert "b-w" in b.weapon_dropped
+    engine._retrieve_weapon(b, "b-w")
+    assert "b-w" not in b.weapon_dropped
+    assert [w.id for w in b.usable_attacks()] == ["b-w"]
+    assert "retrieve b-w (restored)" in engine._transcript[-1]
+
+
+def test_retrieve_weapon_still_restores_stolen() -> None:
+    # The steal path keeps working: retrieve removes the weapon from
+    # weapon_stolen.
+    b = make_state(make_combatant("b"), "monsters", (1, 2))
+    b.weapon_stolen.add("b-w")
+    engine = make_engine([], [b])
+    engine._retrieve_weapon(b, "b-w")
+    assert not b.weapon_stolen
+    assert [w.id for w in b.usable_attacks()] == ["b-w"]
+
+
+def test_disarm_fail_by_10_drops_attacker_weapon() -> None:
+    # SRD Disarm: "If your attack fails by 10 or more, you drop the weapon
+    # that you were using to attempt the disarm." a total 2+2=4 vs CMD 14
+    # fails by 10 -> a drops its sword; b's weapon is untouched.
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 1))
+    b = make_state(make_combatant("b", attack_bonus=20), "monsters", (1, 2))
+    engine = make_engine([1, 2], [a, b])
+    engine._execute_maneuver(a, b, "disarm")
+    assert "a-w" in a.weapon_dropped
+    assert not b.weapon_dropped
+    assert any("disarm backfire -> drops sword" in line for line in engine._transcript)
+
+
 def test_overrun_knocks_prone_and_moves_through() -> None:
     # d20=15+2=17 vs CMD 12: margin 5 -> prone AND moved through (CRB
     # "Overrun": prone only when the attack exceeds CMD by 5 or more).