diff --git a/litellm/router.py b/litellm/router.py
index 8175a5c5c40..c47eea31f81 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -431,7 +431,7 @@ def _anthropic_stream_raised_error_status(error: Exception) -> int | None:
 
 
 def _anthropic_stream_fallback_error_for_raised(
-    error: Exception, model: str, llm_provider: str, has_generated_content: bool
+    error: Exception, model: str, has_generated_content: bool
 ) -> "MidStreamFallbackError | None":
     """
     A provider iterator that fails mid-stream by raising (Bedrock surfaces
@@ -454,7 +454,7 @@ def _anthropic_stream_fallback_error_for_raised(
     return MidStreamFallbackError(
         message=str(error),
         model=model,
-        llm_provider=llm_provider,
+        llm_provider="anthropic",
         original_exception=error,
         is_pre_first_chunk=True,
     )
@@ -5059,8 +5059,6 @@ class Router:
             has_generated_content = False  # rebind-ok: set once real content is seen, or the buffer cap is hit
             buffered_lifecycle_chunks: tuple[bytes, ...] = ()  # rebind-ok: flushed once committed or on decline
             model: Final = cast(str, initial_kwargs.get("model"))  # cast-ok: kwargs always carries the model group
-            custom_llm_provider: Final = initial_kwargs.get("custom_llm_provider")
-            llm_provider: Final = custom_llm_provider if isinstance(custom_llm_provider, str) else "anthropic"
             try:
                 async for chunk in source_iterator:
                     if _anthropic_stream_forwards_ping_live(
@@ -5109,7 +5107,6 @@ class Router:
                     has_generated_content,
                     buffered_lifecycle_chunks,
                     model,
-                    llm_provider,
                     initial_kwargs,
                     wrapper,
                 ):
@@ -5130,7 +5127,6 @@ class Router:
         has_generated_content: bool,
         buffered_lifecycle_chunks: tuple[bytes, ...],
         model: str,
-        llm_provider: str,
         initial_kwargs: dict[str, Any],  # mutable-ok: handed to _aanthropic_messages_fallback_attempt, which mutates it
         wrapper: "FallbackAwareAnthropicMessagesStream",
     ) -> AsyncGenerator[bytes, None]:
@@ -5158,7 +5154,7 @@ class Router:
         fallback_error: Final = (
             stream_error
             if isinstance(stream_error, MidStreamFallbackError)
-            else _anthropic_stream_fallback_error_for_raised(stream_error, model, llm_provider, has_generated_content)
+            else _anthropic_stream_fallback_error_for_raised(stream_error, model, has_generated_content)
         )
         if fallback_error is None:
             raise stream_error
diff --git a/tests/test_litellm/test_router.py b/tests/test_litellm/test_router.py
index bb0ab43ead9..752bbf942d1 100644
--- a/tests/test_litellm/test_router.py
+++ b/tests/test_litellm/test_router.py
@@ -4,6 +4,7 @@ import json
 import logging
 import os
 import threading
+from types import SimpleNamespace
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import httpx
@@ -10264,14 +10265,28 @@ async def test_anthropic_messages_raised_provider_error_before_content_triggers_
     assert source.closed is True
 
 
+class _AnthropicMessagesStringStatusError(Exception):
+    def __init__(self):
+        super().__init__("bad request")
+        self.status_code = "400"
+
+
+class _AnthropicMessagesResponseOnlyStatusError(Exception):
+    def __init__(self):
+        super().__init__("bad request")
+        self.response = SimpleNamespace(status_code=400)
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "raised_error",
     [
         BedrockError(status_code=400, message='validationException {"message": "Malformed input"}'),
         BedrockError(status_code=424, message='modelStreamErrorException {"message": "Model stream error"}'),
+        _AnthropicMessagesStringStatusError(),
+        _AnthropicMessagesResponseOnlyStatusError(),
     ],
-    ids=["400", "424"],
+    ids=["400", "424", "str-400", "response-only-400"],
 )
 async def test_anthropic_messages_raised_non_retriable_provider_error_propagates_unchanged(raised_error):
     """A raised 4xx (other than 429) is a client error no other deployment can
@@ -10295,7 +10310,7 @@ async def test_anthropic_messages_raised_non_retriable_provider_error_propagates
             async for chunk in wrapped:
                 collected.append(chunk)
 
-        with pytest.raises(BedrockError) as exc_info:
+        with pytest.raises(type(raised_error)) as exc_info:
             await _consume()
 
     assert collected == []