Fix converse handling for parallel_tool_calls

litellm/llms/bedrock/chat/converse_transformation.py

@@ -1217,15 +1217,15 @@ class AmazonConverseConfig(BaseConfig):
 
         # Handle parallel_tool_calls configuration
         parallel_tool_use_config = additional_request_params.pop("_parallel_tool_use_config", None)
-        if parallel_tool_use_config is not None:
+        if parallel_tool_use_config is not None and is_claude_4_5_on_bedrock(model):
-            # Merge the tool_choice config from parallel_tool_calls into additional_request_params
             for key, value in parallel_tool_use_config.items():
                 if key in additional_request_params and isinstance(additional_request_params[key], dict) and isinstance(value, dict):
-                    # Merge dictionaries
                     additional_request_params[key].update(value)
                 else:
                     additional_request_params[key] = value
 
+        additional_request_params.pop("parallel_tool_calls", None)
+
         # Only set the topK value in for models that support it
         additional_request_params.update(
             self._handle_top_k_value(model, inference_params)

tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py

@@ -3382,59 +3382,78 @@ def test_output_config_applies_additional_properties():
 
 
 
-def test_parallel_tool_calls_in_request_transformation():
+_TOOL_PARAM = [
-    """Test that parallel_tool_calls is correctly placed in additionalModelRequestFields after full transformation"""
+    {
-    config = AmazonConverseConfig()
+        "type": "function",
-    
+        "function": {
-    messages = [
+            "name": "get_weather",
-        {"role": "user", "content": "What's the weather in SF and NYC?"}
+            "description": "Get the weather",
-    ]
+            "parameters": {
-    
+                "type": "object",
-    non_default_params = {
+                "properties": {
-        "parallel_tool_calls": False,
+                    "location": {
-        "tools": [
+                        "type": "string",
-            {
+                        "description": "The location to get weather for",
-                "type": "function",
-                "function": {
-                    "name": "get_weather",
-                    "description": "Get the weather",
-                    "parameters": {
-                        "type": "object",
-                        "properties": {
-                            "location": {
-                                "type": "string",
-                                "description": "The location to get weather for"
-                            }
-                        },
-                        "required": ["location"]
                     }
-                }
+                },
-            }
+                "required": ["location"],
-        ],
+            },
-        "max_tokens": 100,
+        },
     }
-    
+]
+
+
+def test_parallel_tool_calls_newer_model_adds_disable_flag():
+    """Newer Claude models (4.5+) should get disable_parallel_tool_use in additionalModelRequestFields."""
+    config = AmazonConverseConfig()
+    model = "anthropic.claude-sonnet-4-5-20250929-v1:0"
+    messages = [{"role": "user", "content": "What's the weather in SF and NYC?"}]
+
     optional_params = config.map_openai_params(
-        non_default_params=non_default_params,
+        non_default_params={"parallel_tool_calls": False, "tools": _TOOL_PARAM},
         optional_params={},
-        model="anthropic.claude-sonnet-4-5-v2:0",
+        model=model,
         drop_params=False,
     )
-    
+
-    # Transform the request
     request_data = config.transform_request(
-        model="anthropic.claude-sonnet-4-5-v2:0",
+        model=model,
         messages=messages,
         optional_params=optional_params,
         litellm_params={},
         headers={},
     )
-    
+
-    # Verify the structure
     assert "additionalModelRequestFields" in request_data
     assert "tool_choice" in request_data["additionalModelRequestFields"]
-    assert "disable_parallel_tool_use" in request_data["additionalModelRequestFields"]["tool_choice"]
     assert request_data["additionalModelRequestFields"]["tool_choice"]["disable_parallel_tool_use"] is True
+    assert "parallel_tool_calls" not in request_data["additionalModelRequestFields"]
+
+
+def test_parallel_tool_calls_older_model_drops_disable_flag():
+    """Older Claude models (pre-4.5) must NOT receive disable_parallel_tool_use — Bedrock rejects it."""
+    config = AmazonConverseConfig()
+    model = "anthropic.claude-3-5-sonnet-20241022-v2:0"
+    messages = [{"role": "user", "content": "What's the weather in SF and NYC?"}]
+
+    optional_params = config.map_openai_params(
+        non_default_params={"parallel_tool_calls": False, "tools": _TOOL_PARAM},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+
+    request_data = config.transform_request(
+        model=model,
+        messages=messages,
+        optional_params=optional_params,
+        litellm_params={},
+        headers={},
+    )
+
+    additional = request_data.get("additionalModelRequestFields", {})
+    assert "tool_choice" not in additional
+    assert "parallel_tool_calls" not in additional
 
 
 class TestBedrockMinThinkingBudgetTokens: