feat(combat): grant soft cover (+4 AC) to ranged attacks through creatures

README.md

@@ -72,10 +72,10 @@ players : 3 combatants
 monsters : 2 combatants
 1000 combats simulés (seed 1, plafond 100 rounds)
 
-Victoires players : 98.1% (981) — bande 3σ : [96.8%, 99.4%]
-Victoires monsters : 1.9% (19) — bande 3σ : [0.6%, 3.2%]
+Victoires players : 97.8% (978) — bande 3σ : [96.4%, 99.2%]
+Victoires monsters : 2.2% (22) — bande 3σ : [0.8%, 3.6%]
 Nuls : 0.0% (0)
-Rounds moyens : 6.6
+Rounds moyens : 6.9
 ```
 
 ## Utilisation de la CLI
@@ -276,8 +276,9 @@ Règles modélisées :
   peut pas être attaquée — la politique se déplace jusqu'à gagner une ligne de
   visée.
 - Couvert (règle des coins) : la cible gagne +4 CA sur la touche et la
-  confirmation de critique ; le couvert octroyé par les créatures n'est pas
-  modélisé.
+  confirmation de critique ; couvert mou : une créature active entre
+  l'attaquant et la cible octroie aussi +4 CA aux attaques à distance (les
+  attaques de mêlée ignorent les créatures).
 - Distance : pénalité cumulative de −2 par incrément de portée complet au-delà
   du premier, appliquée au jet d'attaque et à la confirmation de critique ;
   l'arme ranged reste utilisable jusqu'à 10 incréments. Les armes de jet
@@ -288,7 +289,6 @@ appliquées dans la résolution) :
 
 - Sorts, jets de sauvegarde, conditions et états.
 - Attaques d'opportunité, flanquement, manœuvres de combat.
-- Couvert mou des créatures.
 - Effets mécaniques de hauteur/élévation.
 - Tailles Large+ (2×2), allonge > 5 ft, itératifs de BAB, économie d'action
   complète (charge, pas de placement…).
@@ -305,7 +305,8 @@ appliquées dans la résolution) :
 - `grid.py` — grille 5-10-5 : `distance`, `step_cost`, règle des coins
   (`diagonal_allowed`), Dijkstra `reachable` avec ou sans budget.
 - `los.py` — ligne d'effet et couvert par la règle des coins : gate de ligne
-  d'effet dans `weapon_for`, bonus de couvert +4 CA dans `resolve_attack`.
+  d'effet dans `weapon_for`, bonus de couvert +4 CA (terrain et couvert mou
+  des créatures) dans `resolve_attack`.
 - `combat.py` — `CombatEngine` déterministe : initiative, actions, résolution
   des attaques (couvert, ligne d'effet, pénalités de portée), états de vie,
   transcripts, politique par défaut.
@@ -324,7 +325,7 @@ appliquées dans la résolution) :
 La gate de validation complète (tests + lint + types) :
 
 ```bash
-uv run pytest -q          # 189 tests
+uv run pytest -q          # 196 tests
 uv run ruff check src tests
 uv run basedpyright src   # mode strict
 ```

src/pf1e_simulator/combat.py

@@ -15,11 +15,12 @@ Phase 0 documented deviations from PF1e (conventions):
 - Line of effect gates all attacks: a target fully behind blocking terrain
   cannot be attacked, and the policy moves to gain sight instead.
 - Cover (corner rule) grants +4 AC on hit and crit-confirm rolls; melee and
-  ranged reuse the same corner rule.
+  ranged reuse the same corner rule. Soft cover: active creatures between
+  attacker and target also grant +4 AC on ranged attacks (CRB soft cover);
+  melee attacks ignore creatures.
 - Ranged: cumulative -2 per full range increment beyond the first, up to 10
   range increments; the penalty applies to attack and crit-confirm rolls.
-  Thrown weapons (5 increments max) are not distinguished; soft cover from
-  creatures is not modeled.
+  Thrown weapons (5 increments max) are not distinguished.
 """
 
 from __future__ import annotations
@@ -221,7 +222,16 @@ class CombatEngine:
         penalty = self.range_penalty(weapon, dist_ft)
         total = roll + weapon.attack_bonus + penalty
         ac = target.combatant.ac.total
-        if has_cover(self._grid, attacker.pos, target.pos, ranged=weapon.kind == "ranged"):
+        occupied = frozenset(
+            s.pos for s in self._states if s.active and s is not attacker and s is not target
+        )
+        if has_cover(
+            self._grid,
+            attacker.pos,
+            target.pos,
+            ranged=weapon.kind == "ranged",
+            occupied=occupied,
+        ):
             ac += _COVER_AC_BONUS
         hit = roll == _NATURAL_TWENTY or (roll != _NATURAL_ONE and total >= ac)
         crit = False

src/pf1e_simulator/los.py

@@ -75,10 +75,12 @@ class _LineGrid:
         a: Pos,
         b: Pos,
         blocking: Callable[[TerrainType], bool],
+        occupied: frozenset[Pos] = frozenset(),
     ) -> None:
         self._grid = grid
         self._exclude = frozenset({a, b})
         self._blocking = blocking
+        self._occupied = occupied
 
     def blocked(self, p1: Pt, p2: Pt) -> bool:
         min_x = min(p1[0], p2[0])
@@ -90,9 +92,9 @@ class _LineGrid:
                 pos = (row, col)
                 if pos in self._exclude or not self._grid.in_bounds(pos):
                     continue
-                if self._blocking(self._grid.terrain_at(pos)) and _segment_hits_cell(
-                    p1, p2, row, col
-                ):
+                if (
+                    pos in self._occupied or self._blocking(self._grid.terrain_at(pos))
+                ) and _segment_hits_cell(p1, p2, row, col):
                     return True
         return False
 
@@ -113,16 +115,30 @@ def has_line_of_effect(grid: Grid, a: Pos, b: Pos) -> bool:
     )
 
 
-def has_cover(grid: Grid, attacker: Pos, target: Pos, *, ranged: bool) -> bool:
+def has_cover(
+    grid: Grid,
+    attacker: Pos,
+    target: Pos,
+    *,
+    ranged: bool,
+    occupied: frozenset[Pos] = frozenset(),
+) -> bool:
     """Cover iff every attacker corner has at least one blocked target corner.
 
     The attacker picks their single best corner (PF1e ranged cover rule);
-    Phase 0 documented deviation: melee reuses the same corner rule.
+    Phase 0 documented deviation: melee reuses the same corner rule. For
+    ranged attacks, squares occupied by other creatures also block the
+    lines (soft cover, CRB); melee ignores creatures.
     """
     if attacker == target:
         return False
-    _ = ranged
-    lines = _LineGrid(grid, attacker, target, _grants_cover)
+    lines = _LineGrid(
+        grid,
+        attacker,
+        target,
+        _grants_cover,
+        occupied if ranged else frozenset(),
+    )
     return not any(
         all(not lines.blocked(corner_a, corner_t) for corner_t in _corners(target))
         for corner_a in _corners(attacker)

tests/test_combat.py

@@ -664,3 +664,58 @@ def test_ranged_weapon_unusable_beyond_maximum_range() -> None:
     assert engine.weapon_for(states[0], states[1]) is None
     result = engine.run()
     assert result.transcript[2] == "round 1 archer: move (0,0)->(0,1)"
+
+
+def test_ranged_soft_cover_from_creature_between() -> None:
+    """A creature between shooter and target grants soft cover (+4 AC)."""
+    archer = make_combatant("archer", attack_bonus=4, kind="ranged", range_increment_ft=60)
+    blocker = make_combatant("blocker", speed=0)
+    target = make_combatant("target", ac=13)
+    states = [
+        make_state(archer, "players", (1, 1)),
+        make_state(blocker, "players", (1, 2)),
+        make_state(target, "monsters", (1, 4)),
+    ]
+    engine = CombatEngine(ScriptedRng([12, 3]), make_grid(), states)
+    result = engine.resolve_attack(states[0], states[2], archer.attacks[0])
+    assert result.ac == 17  # 13 + 4 soft cover
+    assert result.hit is False  # 12 + 4 = 16 < 17
+
+
+def test_melee_soft_cover_ignored_in_resolution() -> None:
+    """Melee attacks ignore creatures for soft cover (CRB: ranged only)."""
+    attacker = make_combatant("attacker", attack_bonus=2)
+    blocker = make_combatant("blocker", speed=0)
+    target = make_combatant("target", ac=13)
+    states = [
+        make_state(attacker, "players", (1, 1)),
+        make_state(blocker, "players", (1, 2)),
+        make_state(target, "monsters", (1, 4)),
+    ]
+    engine = CombatEngine(ScriptedRng([12, 3]), make_grid(), states)
+    result = engine.resolve_attack(states[0], states[2], attacker.attacks[0])
+    assert result.ac == 13  # melee ignores soft cover
+    assert result.hit is True  # 12 + 2 = 14 >= 13
+
+
+def test_ranged_soft_cover_shown_in_transcript() -> None:
+    """Soft cover raises the AC displayed in the attack log line."""
+    archer = make_combatant("archer", attack_bonus=4, kind="ranged", range_increment_ft=60)
+    blocker = make_combatant("blocker", speed=0)
+    target = make_combatant("target", speed=0)
+    states = [
+        make_state(archer, "players", (0, 0)),
+        make_state(blocker, "players", (0, 2)),
+        make_state(target, "monsters", (0, 4)),
+    ]
+    engine = CombatEngine(ScriptedRng([10, 9, 8, 12]), make_grid(), states, round_cap=1)
+    result = engine.run()
+    assert result.transcript == (
+        "initiative: archer d20=10+0=10",
+        "initiative: blocker d20=9+0=9",
+        "initiative: target d20=8+0=8",
+        "round 1 archer: short bow vs target d20=12+4=16 AC 17 -> MISS",
+        "round 1 blocker: wait",
+        "round 1 target: wait",
+        "battle over: draw after 1 rounds",
+    )

tests/test_los.py

@@ -88,3 +88,31 @@ def test_cover_melee_uses_same_corner_rule_in_phase0() -> None:
 def test_cover_same_square_is_false() -> None:
     grid = make_grid(["."])
     assert has_cover(grid, (0, 0), (0, 0), ranged=True) is False
+
+
+def test_soft_cover_creature_between_grants_cover() -> None:
+    """A creature between shooter and target grants cover on ranged attacks."""
+    grid = make_grid([".....", ".....", "....."])
+    occupied = frozenset({(1, 2)})
+    assert has_cover(grid, (1, 0), (1, 4), ranged=True, occupied=occupied) is True
+
+
+def test_soft_cover_melee_ignores_creatures() -> None:
+    """Melee attacks ignore creatures for soft cover (CRB: ranged only)."""
+    grid = make_grid([".....", ".....", "....."])
+    occupied = frozenset({(1, 2)})
+    assert has_cover(grid, (1, 0), (1, 4), ranged=False, occupied=occupied) is False
+
+
+def test_soft_cover_creature_behind_target_ignored() -> None:
+    """A creature behind the target does not grant cover."""
+    grid = make_grid(["......", "......"])
+    occupied = frozenset({(1, 5)})
+    assert has_cover(grid, (1, 0), (1, 4), ranged=True, occupied=occupied) is False
+
+
+def test_soft_cover_creature_off_axis_ignored() -> None:
+    """A creature off the attack line does not grant cover."""
+    grid = make_grid([".....", "....."])
+    occupied = frozenset({(0, 2)})
+    assert has_cover(grid, (1, 0), (1, 4), ranged=True, occupied=occupied) is False