fix(snowflake): reject invalid Claude tool_choice strings

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: arpan sahu <28574248+arpansahu@users.noreply.github.com>

litellm/llms/snowflake/chat/transformation.py

@@ -322,7 +322,12 @@ class SnowflakeConfig(SnowflakeBaseConfig, OpenAIGPTConfig):
                 "required": {"type": "any"},
                 "none": {"type": "none"},
             }
-            return mapping.get(tool_choice, {"type": "auto"})
+            if tool_choice not in mapping:
+                raise ValueError(
+                    "Unsupported tool_choice value for Snowflake Claude model: "
+                    f"{tool_choice!r}. Expected one of: auto, required, none."
+                )
+            return mapping[tool_choice]
         elif isinstance(tool_choice, dict):
             if tool_choice.get("type") == "function":
                 func: Final = tool_choice.get("function", {})

tests/test_litellm/llms/snowflake/chat/test_snowflake_chat_transformation.py

@@ -118,6 +118,21 @@ class TestSnowflakeToolTransformation:
                 f"got {transformed_request['tool_choice']}"
             )
 
+    def test_claude_rejects_invalid_string_tool_choice(self):
+        """
+        Test that invalid string tool_choice values are not silently downgraded to auto.
+        """
+        config = SnowflakeConfig()
+
+        with pytest.raises(ValueError, match="Unsupported tool_choice value"):
+            config.transform_request(
+                model="snowflake/claude-sonnet-4-5",
+                messages=[{"role": "user", "content": "Test"}],
+                optional_params={"tool_choice": "requried"},
+                litellm_params={},
+                headers={},
+            )
+
     def test_transform_response_with_tool_calls(self):
         """
         Test that standard OpenAI tool_calls response format is parsed correctly.