diff --git a/packages/gds-framework/gds/parameters.py b/packages/gds-framework/gds/parameters.py
index 8899fba..ca4ba34 100644
--- a/packages/gds-framework/gds/parameters.py
+++ b/packages/gds-framework/gds/parameters.py
@@ -37,8 +37,11 @@ def check_value(self, value: Any) -> bool:
         if not self.typedef.check_value(value):
             return False
         if self.bounds is not None:
-            low, high = self.bounds
-            if not (low <= value <= high):
+            try:
+                low, high = self.bounds
+                if not (low <= value <= high):
+                    return False
+            except Exception:
                 return False
         return True
 
diff --git a/packages/gds-framework/gds/types/typedef.py b/packages/gds-framework/gds/types/typedef.py
index 78e56a1..dae0336 100644
--- a/packages/gds-framework/gds/types/typedef.py
+++ b/packages/gds-framework/gds/types/typedef.py
@@ -32,7 +32,12 @@ def check_value(self, value: Any) -> bool:
         """Check if a value satisfies this type definition."""
         if not isinstance(value, self.python_type):
             return False
-        return self.constraint is None or self.constraint(value)
+        if self.constraint is None:
+            return True
+        try:
+            return bool(self.constraint(value))
+        except Exception:
+            return False
 
 
 # ── Built-in types ──────────────────────────────────────────
diff --git a/packages/gds-framework/tests/test_types.py b/packages/gds-framework/tests/test_types.py
index 8e914a2..d54cf61 100644
--- a/packages/gds-framework/tests/test_types.py
+++ b/packages/gds-framework/tests/test_types.py
@@ -180,6 +180,34 @@ def test_frozen(self):
         with pytest.raises(ValidationError):
             t.name = "Other"  # type: ignore[misc]
 
+    def test_constraint_exception_returns_false(self):
+        """Constraint that raises should return False, not propagate."""
+        t = TypeDef(
+            name="Bad",
+            python_type=float,
+            constraint=lambda x: 1 / 0,  # ZeroDivisionError
+        )
+        assert t.check_value(1.0) is False
+
+    def test_constraint_type_error_returns_false(self):
+        """Constraint that raises TypeError should return False."""
+        t = TypeDef(
+            name="Bad",
+            python_type=float,
+            constraint=lambda x: x > "not a number",  # TypeError
+        )
+        assert t.check_value(1.0) is False
+
+    def test_constraint_returns_truthy_non_bool(self):
+        """Constraint returning truthy non-bool value should work."""
+        t = TypeDef(
+            name="Truthy",
+            python_type=str,
+            constraint=lambda x: x,  # non-empty string is truthy
+        )
+        assert t.check_value("hello") is True
+        assert t.check_value("") is False
+
 
 # ── Built-in types ───────────────────────────────────────────