fix(bedrock_mantle): source per-request AWS credential params from litellm_params when signing chat completions

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/llms/custom_httpx/llm_http_handler.py

@@ -5,7 +5,7 @@ import ssl
 from collections.abc import AsyncIterator, Coroutine, Iterator, Mapping
 from contextlib import asynccontextmanager
 from functools import lru_cache
-from types import ModuleType
+from types import MappingProxyType, ModuleType
 from typing import TYPE_CHECKING, Any, Final, Literal, Optional, TypedDict, TypeVar, Union, cast, get_type_hints
 from urllib.parse import parse_qs, urlencode, urlparse, urlunparse
 
@@ -20,6 +20,7 @@ from litellm._logging import _redact_string, verbose_logger
 from litellm.anthropic_beta_headers_manager import update_headers_with_filtered_beta
 from litellm.constants import REALTIME_WEBSOCKET_MAX_MESSAGE_SIZE_BYTES
 from litellm.litellm_core_utils.asyncify import run_async_function
+from litellm.litellm_core_utils.get_litellm_params import AWS_CREDENTIAL_KWARGS_KEYS
 from litellm.litellm_core_utils.realtime_streaming import RealTimeStreaming
 from litellm.litellm_core_utils.url_utils import encode_url_path_segment
 from litellm.llms.base_llm.anthropic_messages.transformation import (
@@ -252,6 +253,24 @@ def _has_pre_call_deployment_hook(logging_obj: LiteLLMLoggingObj) -> bool:
     return False
 
 
+def _aws_signing_overrides(
+    optional_params: Mapping[str, Any], litellm_params: Mapping[str, Any]
+) -> Mapping[str, Any]:
+    """AWS credential params for SigV4 signers that read them off optional_params.
+
+    Only `bedrock`/`sagemaker` keep `aws_*` in optional_params: every other provider
+    spreads optional_params into the request body, so the params are stripped there
+    and survive on litellm_params alone.
+    """
+    return MappingProxyType(
+        {
+            key: litellm_params[key]
+            for key in AWS_CREDENTIAL_KWARGS_KEYS
+            if optional_params.get(key) is None and litellm_params.get(key) is not None
+        }
+    )
+
+
 class BaseLLMHTTPHandler:
     async def _make_common_async_call(
         self,
@@ -495,7 +514,10 @@ class BaseLLMHTTPHandler:
 
         headers, signed_json_body = provider_config.sign_request(
             headers=headers,
-            optional_params=optional_params,
+            optional_params={
+                **optional_params,
+                **_aws_signing_overrides(optional_params, litellm_params),
+            },
             request_data=data,
             api_base=api_base,
             api_key=api_key,

tests/test_litellm/llms/bedrock_mantle/test_bedrock_mantle_transformation.py

@@ -489,6 +489,83 @@ class TestBedrockMantleChatAuth:
         assert "/us-east-2/bedrock/aws4_request" in authorization
         assert requests[0]["url"].startswith("https://bedrock-mantle.us-east-2.api.aws")
 
+    def test_completion_per_request_role_reaches_signer_and_not_the_body(
+        self, monkeypatch
+    ):
+        # Per-request aws_role_name/aws_session_name are stripped from optional_params
+        # for non-bedrock providers, so they must be sourced from litellm_params at
+        # signing time, and must never be serialized into the provider request body.
+        from botocore.credentials import Credentials
+
+        from litellm.llms.bedrock.base_aws_llm import BaseAWSLLM
+
+        for var in (
+            "BEDROCK_MANTLE_API_KEY",
+            "AWS_BEARER_TOKEN_BEDROCK",
+            "BEDROCK_MANTLE_API_BASE",
+        ):
+            monkeypatch.delenv(var, raising=False)
+
+        credential_calls = []
+
+        def fake_get_credentials(self, **kwargs):
+            credential_calls.append(kwargs)
+            return Credentials(
+                access_key="ASIAEXAMPLE",
+                secret_key="YXNzdW1lZC1yb2xlLXNlY3JldC1hc3N1bWVk",
+                token="assumed-session-token",
+            )
+
+        monkeypatch.setattr(BaseAWSLLM, "get_credentials", fake_get_credentials)
+
+        requests = []
+
+        def mock_post(self, url, data=None, headers=None, **kwargs):
+            raw_body = data.decode("utf-8") if isinstance(data, bytes) else data
+            requests.append({"headers": headers or {}, "body": json.loads(raw_body or "{}")})
+            return httpx.Response(
+                status_code=200,
+                json={
+                    "id": "chatcmpl-test",
+                    "object": "chat.completion",
+                    "created": 1733529600,
+                    "model": "google.gemma-4-31b",
+                    "choices": [
+                        {
+                            "index": 0,
+                            "message": {"role": "assistant", "content": "ok"},
+                            "finish_reason": "stop",
+                        }
+                    ],
+                    "usage": {
+                        "prompt_tokens": 1,
+                        "completion_tokens": 1,
+                        "total_tokens": 2,
+                    },
+                },
+                request=httpx.Request("POST", url),
+            )
+
+        with patch(
+            "litellm.llms.custom_httpx.http_handler.HTTPHandler.post", mock_post
+        ):
+            litellm.completion(
+                model="bedrock_mantle/google.gemma-4-31b",
+                messages=[{"role": "user", "content": "hello"}],
+                aws_role_name="arn:aws:iam::000000000000:role/attributed-role",
+                aws_session_name="user-123",
+                aws_region_name="us-east-1",
+            )
+
+        assert len(credential_calls) == 1
+        assert (
+            credential_calls[0]["aws_role_name"]
+            == "arn:aws:iam::000000000000:role/attributed-role"
+        )
+        assert credential_calls[0]["aws_session_name"] == "user-123"
+        assert requests[0]["headers"]["Authorization"].startswith("AWS4-HMAC-SHA256")
+        assert not [key for key in requests[0]["body"] if key.startswith("aws_")]
+
 
 class TestBedrockMantleProjectHeader:
     def test_validate_environment_sets_openai_project_header(self):

tests/test_litellm/llms/custom_httpx/test_llm_http_handler.py

@@ -2071,3 +2071,22 @@ async def test_anthropic_invalid_thinking_signature_retry_resigns_bedrock_reques
     retry_authorization = posts[1]["headers"]["Authorization"]
     assert retry_authorization.startswith("AWS4-HMAC-SHA256")
     assert retry_authorization != first_attempt_headers["Authorization"]
+
+
+def test_aws_signing_overrides_only_fills_missing_credentials():
+    from litellm.llms.custom_httpx.llm_http_handler import _aws_signing_overrides
+
+    overrides = _aws_signing_overrides(
+        {"temperature": 0.2, "aws_region_name": "us-west-2"},
+        {
+            "aws_role_name": "arn:aws:iam::000000000000:role/attributed",
+            "aws_session_name": "user-123",
+            "aws_region_name": "us-east-1",
+            "api_key": "not-an-aws-param",
+        },
+    )
+
+    assert dict(overrides) == {
+        "aws_role_name": "arn:aws:iam::000000000000:role/attributed",
+        "aws_session_name": "user-123",
+    }