fix(utils): keep a non-string tool_choice type a 400, not a TypeError

A list or dict in tool_choice["type"] is unhashable, so the hosted tool lookup needs the string check first. The bridge test that used file_search as an untranslatable choice now uses a type that really is unknown.

litellm/utils.py

@@ -9758,9 +9758,12 @@ def validate_chat_completion_tool_choice(
             )
 
         # Standard OpenAI format: {"type": "function", "function": {...}}
+        forces_hosted_tool: Final[bool] = (
+            isinstance(tool_choice_type, str) and tool_choice_type in HOSTED_TOOL_CHOICE_TYPES
+        )
         if (
             tool_choice_type != "allowed_tools"
-            and tool_choice_type not in HOSTED_TOOL_CHOICE_TYPES
+            and not forces_hosted_tool
             and (tool_choice_type is None or tool_choice.get("function") is None)
         ):
             raise BadRequestError(

tests/unit/responses/litellm_completion_transformation/test_litellm_completion_responses.py

@@ -5949,12 +5949,12 @@ async def test_bridge_rejects_untranslatable_tool_choice_with_a_400(stream: bool
             model="anthropic/claude-haiku-4-5",
             input="Which fruit is red?",
             tools=[{"type": "function", "name": "lookup_fruit", "parameters": {"type": "object"}}],
-            tool_choice={"type": "file_search"},
+            tool_choice={"type": "web_search_tool"},
             stream=stream,
             api_key="sk-unused",
         )
     assert exc_info.value.status_code == 400
-    assert "tool_choice={'type': 'file_search'}" in str(exc_info.value)
+    assert "tool_choice={'type': 'web_search_tool'}" in str(exc_info.value)
 
 
 def test_cache_control_on_user_message():

tests/unit/test_utils.py

@@ -8810,6 +8810,7 @@ def test_validate_tool_choice_cursor_format():
         {"type": "function"},
         {"name": "lookup_fruit"},
         {"type": "web_search_tool"},
+        {"type": ["web_search"]},
     ],
 )
 def test_validate_tool_choice_invalid_dict_is_a_400(tool_choice):