fix(bedrock/realtime): mint response/item ids so toolUse is not dropped

Nova Sonic starts tool turns with contentStart role=TOOL, so ASSISTANT-only
id init never runs and transform_tool_use_event used to return empty events
even after parsing content. Mint resp_/item_ ids when missing so
function_call_arguments.done reaches the client with non-empty args

litellm/llms/bedrock/realtime/transformation.py

@@ -1026,11 +1026,9 @@ class BedrockRealtimeConfig(BaseRealtimeConfig):
         verbose_logger.debug("Handling toolUse")
         tool_use = event["toolUse"]
 
-        if not current_output_item_id or not current_response_id:
+        response_id = current_response_id or f"resp_{uuid.uuid4()}"
-            return [], "", ""
+        item_id = current_output_item_id or f"item_{uuid.uuid4()}"
 
-        # Parse the tool input. Nova 2 Sonic sends arguments in `content`;
-        # fall back to `input` for backward compatibility.
         tool_input = {}
         raw_input = tool_use["content"] if "content" in tool_use else tool_use.get("input")
         if raw_input:
@@ -1042,15 +1040,13 @@ class BedrockRealtimeConfig(BaseRealtimeConfig):
         tool_call_id = tool_use.get("toolUseId", "")
         tool_name = tool_use.get("toolName", "")
 
-        # Create a function call arguments done event
-        # This is a custom event format that matches what clients expect
         from typing import cast
 
         function_call_event: dict[str, Any] = {
             "type": "response.function_call_arguments.done",
             "event_id": f"event_{uuid.uuid4()}",
-            "response_id": current_response_id,
+            "response_id": response_id,
-            "item_id": current_output_item_id,
+            "item_id": item_id,
             "output_index": 0,
             "call_id": tool_call_id,
             "name": tool_name,

tests/test_litellm/llms/bedrock/realtime/test_bedrock_realtime_transformation.py

@@ -614,16 +614,30 @@ class TestBedrockRealtimeResponseTransformation:
         assert args["location"] == "San Francisco"
 
     def test_transform_tool_use_event_directly(self):
-        """Test transform_tool_use_event directly for guard clause and input parsing"""
+        """Test transform_tool_use_event directly for input parsing and missing IDs"""
         config = BedrockRealtimeConfig()
 
-        # Guard clause: missing IDs returns empty result
+        # Missing IDs still emit a function call (Nova Sonic starts tools with role=TOOL)
         events, tool_call_id, tool_name = config.transform_tool_use_event(
-            {"toolUse": {}}, None, "resp_123"
+            {
+                "toolUse": {
+                    "toolUseId": "tool_call_no_ids",
+                    "toolName": "get_weather",
+                    "content": json.dumps({"location": "Seattle"}),
+                }
+            },
+            None,
+            None,
         )
-        assert events == []
+        assert len(events) == 1
-        assert tool_call_id == ""
+        assert events[0]["type"] == "response.function_call_arguments.done"
-        assert tool_name == ""
+        assert events[0]["call_id"] == "tool_call_no_ids"
+        assert events[0]["name"] == "get_weather"
+        assert events[0]["response_id"].startswith("resp_")
+        assert events[0]["item_id"].startswith("item_")
+        assert json.loads(events[0]["arguments"]) == {"location": "Seattle"}
+        assert tool_call_id == "tool_call_no_ids"
+        assert tool_name == "get_weather"
 
         # JSON string content is parsed and converted to a function call event
         events, tool_call_id, tool_name = config.transform_tool_use_event(
@@ -641,6 +655,8 @@ class TestBedrockRealtimeResponseTransformation:
         assert events[0]["type"] == "response.function_call_arguments.done"
         assert events[0]["call_id"] == "tool_call_123"
         assert events[0]["name"] == "get_weather"
+        assert events[0]["response_id"] == "resp_123"
+        assert events[0]["item_id"] == "item_123"
         assert json.loads(events[0]["arguments"]) == {"location": "San Francisco"}
 
         # Invalid JSON content falls back to empty arguments