[Fix] Ensure /messages works when using `bedrock/converse/<model> with LiteLLM (#13627)

* get_bedrock_provider_config_for_messages_api

* fixes for get_bedrock_provider_config_for_messages_api

* test_anthropic_messages_litellm_router_bedrock

* fix merge conflicts

* fix - refactor based on jugal's comment

litellm/llms/bedrock/common_utils.py

@@ -4,11 +4,14 @@ Common utilities used across bedrock chat/embedding/image generation
 
 import json
 import os
-from typing import TYPE_CHECKING, List, Literal, Optional, Union
+from typing import TYPE_CHECKING, Dict, List, Literal, Optional, Union
 
 import httpx
 
 import litellm
+from litellm.llms.base_llm.anthropic_messages.transformation import (
+    BaseAnthropicMessagesConfig,
+)
 from litellm.llms.base_llm.base_utils import BaseLLMModelInfo
 from litellm.llms.base_llm.chat.transformation import BaseLLMException
 from litellm.secret_managers.main import get_secret
@@ -443,23 +446,82 @@ class BedrockModelInfo(BaseLLMModelInfo):
         """
         Get the bedrock route for the given model.
         """
+        route_mappings: Dict[str, Literal["invoke", "converse_like", "converse", "agent"]] = {
+            "invoke/": "invoke",
+            "converse_like/": "converse_like", 
+            "converse/": "converse",
+            "agent/": "agent"
+        }
+        
+        # Check explicit routes first
+        for prefix, route_type in route_mappings.items():
+            if prefix in model:
+                return route_type
+        
         base_model = BedrockModelInfo.get_base_model(model)
         alt_model = BedrockModelInfo.get_non_litellm_routing_model_name(model=model)
-        if "invoke/" in model:
-            return "invoke"
-        elif "converse_like" in model:
-            return "converse_like"
-        elif "converse/" in model:
-            return "converse"
-        elif "agent/" in model:
-            return "agent"
-        elif (
+        if (
             base_model in litellm.bedrock_converse_models
             or alt_model in litellm.bedrock_converse_models
         ):
             return "converse"
         return "invoke"
+    
+    @staticmethod
+    def _explicit_converse_route(model: str) -> bool:
+        """
+        Check if the model is an explicit converse route.
+        """
+        return "converse/" in model
+    
+    @staticmethod
+    def _explicit_invoke_route(model: str) -> bool:
+        """
+        Check if the model is an explicit invoke route.
+        """
+        return "invoke/" in model
+    
+    @staticmethod
+    def _explicit_agent_route(model: str) -> bool:
+        """
+        Check if the model is an explicit agent route.
+        """
+        return "agent/" in model
+    
+    @staticmethod
+    def _explicit_converse_like_route(model: str) -> bool:
+        """
+        Check if the model is an explicit converse like route.
+        """
+        return "converse_like/" in model
+    
 
+    @staticmethod
+    def get_bedrock_provider_config_for_messages_api(model: str) -> Optional[BaseAnthropicMessagesConfig]:
+        """
+        Get the bedrock provider config for the given model.
+
+        Only route to AmazonAnthropicClaude3MessagesConfig() for BaseMessagesConfig
+
+        All other routes should return None since they will go through litellm.completion
+        """
+
+        #########################################################
+        # Converse routes should go through litellm.completion()
+        if BedrockModelInfo._explicit_converse_route(model):
+            return None
+        
+        #########################################################
+        # This goes through litellm.AmazonAnthropicClaude3MessagesConfig()
+        # Since bedrock Invoke supports Native Anthropic Messages API
+        #########################################################
+        if "claude" in model:
+            return litellm.AmazonAnthropicClaudeMessagesConfig()
+        
+        #########################################################
+        # These routes will go through litellm.completion()
+        #########################################################
+        return None
 
 class BedrockEventStreamDecoderBase:
     """

litellm/proxy/proxy_config.yaml

@@ -2,3 +2,9 @@ model_list:
   - model_name: vertex_ai/*
     litellm_params:
       model: vertex_ai/*
+  - model_name: bedrock/converse/us.anthropic.claude-sonnet-4-20250514-v1:0
+    litellm_params:
+      model: bedrock/converse/us.anthropic.claude-sonnet-4-20250514-v1:0
+  - model_name: bedrock/us.anthropic.claude-sonnet-4-20250514-v1:0
+    litellm_params:
+      model: bedrock/us.anthropic.claude-sonnet-4-20250514-v1:0

litellm/utils.py

@@ -7071,7 +7071,8 @@ class ProviderConfigManager:
         # The 'BEDROCK' provider corresponds to Amazon's implementation of Anthropic Claude v3.
         # This mapping ensures that the correct configuration is returned for BEDROCK.
         elif litellm.LlmProviders.BEDROCK == provider:
-            return litellm.AmazonAnthropicClaudeMessagesConfig()
+            from litellm.llms.bedrock.common_utils import BedrockModelInfo
+            return BedrockModelInfo.get_bedrock_provider_config_for_messages_api(model)
         elif litellm.LlmProviders.VERTEX_AI == provider:
             if "claude" in model:
                 from litellm.llms.vertex_ai.vertex_ai_partner_models.anthropic.experimental_pass_through.transformation import (

tests/pass_through_unit_tests/test_bedrock_anthropic_messages_test.py

@@ -0,0 +1,68 @@
+
+import json
+import os
+import sys
+from datetime import datetime
+from typing import AsyncIterator, Dict, Any
+import asyncio
+import unittest.mock
+from unittest.mock import AsyncMock, MagicMock
+import pytest
+from litellm.router import Router
+
+sys.path.insert(
+    0, os.path.abspath("../../..")
+)  # Adds the parent directory to the system path
+import litellm
+from base_anthropic_unified_messages_test import BaseAnthropicMessagesTest
+
+INSTANCE_BASE_ANTHROPIC_MESSAGES_TEST = BaseAnthropicMessagesTest()
+
+@pytest.mark.asyncio
+async def test_anthropic_messages_litellm_router_bedrock():
+    """
+    Test the anthropic_messages with non-streaming request
+    """
+
+    litellm._turn_on_debug()
+    router = Router(
+        model_list=[
+            {
+                "model_name": "bedrock/converse/us.anthropic.claude-sonnet-4-20250514-v1:0",
+                "litellm_params": {
+                    "model": "bedrock/converse/us.anthropic.claude-sonnet-4-20250514-v1:0",
+                },
+            },
+            {
+                "model_name": "bedrock/us.anthropic.claude-sonnet-4-20250514-v1:0",
+                "litellm_params": {
+                    "model": "bedrock/us.anthropic.claude-sonnet-4-20250514-v1:0",
+                },
+            }
+        ]
+    )
+    
+    # Set up test parameters
+    messages = [{"role": "user", "content": "Hello, can you tell me a short joke?"}]
+
+    # Call 1 using bedrock/converse/us.anthropic.claude-sonnet-4-20250514-v1:0
+    response = await router.aanthropic_messages(
+        messages=messages,
+        model="bedrock/converse/us.anthropic.claude-sonnet-4-20250514-v1:0",
+        max_tokens=100,
+    )
+
+    # Verify response
+    INSTANCE_BASE_ANTHROPIC_MESSAGES_TEST._validate_response(response)
+
+    # Call 2 using bedrock/us.anthropic.claude-sonnet-4-20250514-v1:0
+    response = await router.aanthropic_messages(
+        messages=messages,
+        model="bedrock/us.anthropic.claude-sonnet-4-20250514-v1:0",
+        max_tokens=100,
+    )
+
+    # Verify response
+    INSTANCE_BASE_ANTHROPIC_MESSAGES_TEST._validate_response(response)
+
+