diff --git a/src/pf1e_simulator/loaders/combatant.py b/src/pf1e_simulator/loaders/combatant.py
index 9716113..4b013b3 100644
--- a/src/pf1e_simulator/loaders/combatant.py
+++ b/src/pf1e_simulator/loaders/combatant.py
@@ -19,7 +19,7 @@ import logging
 import re
 from typing import TYPE_CHECKING
 
-from pydantic import ValidationError
+from pydantic import TypeAdapter, ValidationError
 
 if TYPE_CHECKING:
     from pathlib import Path
@@ -187,6 +187,25 @@ class CombatantLoadError(Exception):
         self.reason = reason
 
 
+_LEVEL_ADAPTER: TypeAdapter[int] = TypeAdapter(int)
+
+
+def _parse_level(raw_level: Json, path: Path) -> int:
+    """Coerce the JSON ``level`` with the same lax rules Pydantic applies.
+
+    Feat resolution (Toughness) needs the level before model validation;
+    reading it with a bare ``isinstance(int)`` check disagreed with
+    Pydantic, which also accepts numeric strings ("4") and lossless
+    floats (4.0) -- the feat then silently used level 1 on a level-4
+    sheet.  A value Pydantic would reject raises CombatantLoadError here.
+    """
+    try:
+        return _LEVEL_ADAPTER.validate_python(raw_level)
+    except ValidationError as exc:
+        msg = f"level must be an integer, got {raw_level!r}"
+        raise CombatantLoadError(path, msg) from exc
+
+
 def _resolve_features(
     raw_features: list[Json], level: int, path: Path
 ) -> list[AbilitySpec]:
@@ -301,8 +320,7 @@ def load_combatant(path: Path) -> Combatant:
     # Resolve features (list of strings → list of AbilitySpec).  A present
     # but non-list value (e.g. a bare string) used to be popped and dropped
     # silently, so the combatant lost every feat; it is now a data error.
-    raw_level = data.get("level")
-    level = raw_level if isinstance(raw_level, int) and not isinstance(raw_level, bool) else 1
+    level = _parse_level(data.get("level", 1), path)
     had_features = "features" in data
     raw_features = data.pop("features", None)
     if had_features and not isinstance(raw_features, list):
diff --git a/tests/test_combatant_loader.py b/tests/test_combatant_loader.py
index 4b1ebe6..d71af16 100644
--- a/tests/test_combatant_loader.py
+++ b/tests/test_combatant_loader.py
@@ -146,6 +146,28 @@ class TestFeatures:
         c = load_combatant(_write(tmp_path, data))
         assert c.features[0].effects == toughness(7).effects
 
+    def test_toughness_numeric_string_level(self, tmp_path: Path) -> None:
+        data = _minimal_payload(level="4", features=["Toughness"])
+        c = load_combatant(_write(tmp_path, data))
+        assert c.level == 4
+        assert c.features[0].effects == toughness(4).effects
+
+    def test_toughness_lossless_float_level(self, tmp_path: Path) -> None:
+        data = _minimal_payload(level=4.0, features=["Toughness"])
+        c = load_combatant(_write(tmp_path, data))
+        assert c.level == 4
+        assert c.features[0].effects == toughness(4).effects
+
+    def test_non_numeric_level_raises(self, tmp_path: Path) -> None:
+        data = _minimal_payload(level="abc", features=["Toughness"])
+        with pytest.raises(CombatantLoadError, match="level must be an integer"):
+            load_combatant(_write(tmp_path, data))
+
+    def test_fractional_level_raises(self, tmp_path: Path) -> None:
+        data = _minimal_payload(level=4.5, features=["Toughness"])
+        with pytest.raises(CombatantLoadError, match="level must be an integer"):
+            load_combatant(_write(tmp_path, data))
+
     def test_level_default_one(self, tmp_path: Path) -> None:
         data = _minimal_payload(level=1, features=["Toughness"])
         c = load_combatant(_write(tmp_path, data))