diff --git a/packages/sdk-python/src/qwen_code_sdk/validation.py b/packages/sdk-python/src/qwen_code_sdk/validation.py
index 5e144da4d1e..d52dc9c7942 100644
--- a/packages/sdk-python/src/qwen_code_sdk/validation.py
+++ b/packages/sdk-python/src/qwen_code_sdk/validation.py
@@ -135,9 +135,7 @@ def validate_query_options(options: QueryOptions) -> None:
         )
 
     if options.max_session_turns is not None and (
-        isinstance(options.max_session_turns, bool)
-        or not isinstance(options.max_session_turns, int)
-        or options.max_session_turns < -1
+        not _is_int(options.max_session_turns) or options.max_session_turns < -1
     ):
         raise ValidationError("max_session_turns must be -1 or a non-negative integer")
 
@@ -147,13 +145,16 @@ def validate_query_options(options: QueryOptions) -> None:
     ):
         raise ValidationError("path_to_qwen_executable cannot be empty")
 
-    if options.max_tool_calls is not None and options.max_tool_calls < -1:
+    if options.max_tool_calls is not None and (
+        not _is_int(options.max_tool_calls) or options.max_tool_calls < -1
+    ):
         raise ValidationError("max_tool_calls must be -1 or a non-negative integer")
 
-    if options.max_subagent_depth is not None and not (
-        1 <= options.max_subagent_depth <= 100
+    if options.max_subagent_depth is not None and (
+        not _is_int(options.max_subagent_depth)
+        or not (1 <= options.max_subagent_depth <= 100)
     ):
-        raise ValidationError("max_subagent_depth must be between 1 and 100")
+        raise ValidationError("max_subagent_depth must be an integer between 1 and 100")
 
     if options.agents:
         for i, agent in enumerate(options.agents):
@@ -205,6 +206,15 @@ def validate_query_options(options: QueryOptions) -> None:
         raise ValidationError("proxy cannot be empty")
 
 
+def _is_int(value: object) -> bool:
+    """True for a real integer.
+
+    ``bool`` subclasses ``int``, so ``isinstance(True, int)`` is True and a
+    bare isinstance check would let ``max_tool_calls=True`` through as 1.
+    """
+    return isinstance(value, int) and not isinstance(value, bool)
+
+
 def _validate_optional_callable(
     value: object,
     validator: Callable[[object, type[ValidationError]], None],
diff --git a/packages/sdk-python/tests/unit/test_validation.py b/packages/sdk-python/tests/unit/test_validation.py
index 10bdfd1d05c..25ad4cf65fa 100644
--- a/packages/sdk-python/tests/unit/test_validation.py
+++ b/packages/sdk-python/tests/unit/test_validation.py
@@ -188,6 +188,31 @@ def test_rejects_invalid_max_subagent_depth() -> None:
         validate_query_options(QueryOptions(max_subagent_depth=0))
 
 
+@pytest.mark.parametrize("value", [True, False, 0.5])
+def test_rejects_non_integer_max_tool_calls(value: object) -> None:
+    # The error message promises "-1 or a non-negative integer", and the value
+    # is stringified straight onto the CLI, so `True` would become
+    # `--max-tool-calls True`.
+    with pytest.raises(ValidationError, match="max_tool_calls"):
+        validate_query_options(QueryOptions(max_tool_calls=cast(Any, value)))
+
+
+@pytest.mark.parametrize("value", [True, False, 2.5])
+def test_rejects_non_integer_max_subagent_depth(value: object) -> None:
+    with pytest.raises(ValidationError, match="max_subagent_depth"):
+        validate_query_options(QueryOptions(max_subagent_depth=cast(Any, value)))
+
+
+def test_accepts_valid_integer_limits() -> None:
+    # The in-range integers these options are documented to take must survive.
+    validate_query_options(
+        QueryOptions(max_tool_calls=-1, max_session_turns=-1, max_subagent_depth=1)
+    )
+    validate_query_options(
+        QueryOptions(max_tool_calls=0, max_session_turns=0, max_subagent_depth=100)
+    )
+
+
 def test_rejects_agents_missing_required_fields() -> None:
     with pytest.raises(ValidationError, match="missing required field"):
         validate_query_options(QueryOptions(agents=[{"name": "test"}]))