fix(combat): summon spawns only on passable cells

src/pf1e_simulator/combat.py

@@ -2040,8 +2040,7 @@ class CombatEngine:
                 if dr == 0 and dc == 0:
                     continue
                 pos = (center[0] + dr, center[1] + dc)
-                if (0 <= pos[0] < self._grid.height and
+                if (self._grid.passable(pos) and
-                    0 <= pos[1] < self._grid.width and
                     not any(s.pos == pos for s in self._states if s.active)):
                     spawn_pos = pos
                     break

tests/test_summoning.py

@@ -163,6 +163,75 @@ class TestSummonedCreatureActs:
         )
 
 
+def _build_engine_with_walls(seed: int = 42, duration_rounds: int = 2) -> CombatEngine:
+    """Caster at (1,1) under a walled row 0, like sample_arena's border walls.
+
+    The spawn search must skip wall cells and pick the first passable one.
+    """
+    caster = _make_caster()
+    enemy = _make_enemy()
+    c = CombatantState(
+        combatant=caster, side="players", pos=(1, 1), hp=caster.hp_max,
+    )
+    e = CombatantState(
+        combatant=enemy, side="monsters", pos=(9, 1), hp=enemy.hp_max,
+    )
+    legend = {
+        ".": TerrainType(type="floor", move_cost=1),
+        "#": TerrainType(type="wall", move_cost=None),
+    }
+    terrain = tuple(
+        "#" * 12 if r == 0 else "#..........." if r == 1 else "." * 12
+        for r in range(12)
+    )
+    spec = MapSpec(name="test", terrain=terrain, legend=legend)
+    grid = Grid.from_spec(spec)
+    reg = {"Summon Monster II": _make_summon_spell(duration_rounds)}
+    return CombatEngine(
+        SeededRng(seed), grid, [c, e],
+        policy=_summon_policy,
+        spell_registry=reg,
+    )
+
+
+class TestSummonSpawnsOnPassableCell:
+    """Given: a caster whose adjacent ring contains wall cells (arena border)
+    When: a summons resolves
+    Then: the creature spawns on a passable cell and acts (not just waits)."""
+
+    def test_summon_spawns_on_passable_cell_and_acts(self) -> None:
+        engine = _build_engine_with_walls(seed=42)
+        result = engine.run()
+
+        wolf_lines = [
+            line for line in result.transcript if "celestial_wolf" in line
+        ]
+        spawn_line = next(
+            (ln for ln in wolf_lines if "summon celestial_wolf at" in ln),
+            None,
+        )
+        assert spawn_line is not None, (
+            f"Wolf was never summoned. Wolf lines: {wolf_lines}"
+        )
+        # "summon celestial_wolf at (r, c) (2r)" — parse the spawn position.
+        pos_str = spawn_line.split("at (")[1].split(")")[0]
+        spawn_pos = tuple(int(part) for part in pos_str.split(", "))
+        assert engine._grid.passable(spawn_pos), (
+            f"Wolf spawned on impassable cell {spawn_pos}: {spawn_line!r}"
+        )
+
+        action_keywords = (
+            "charge", "attack", "move", "full_attack", "bite", "5-foot",
+        )
+        acted_lines = [
+            line for line in wolf_lines
+            if any(kw in line for kw in action_keywords)
+        ]
+        assert len(acted_lines) >= 1, (
+            f"Wolf never acted (only waited). Wolf lines: {wolf_lines}"
+        )
+
+
 class TestSummonedCreatureExpires:
     """Given: a caster who summons with duration 2
     When: enough rounds pass