fix(rust): clarify Bedrock bridge configuration

Co-Authored-By: Ishaan Jaffer <155045088+ishaan-berri@users.noreply.github.com>

litellm-rust/crates/ai-gateway/src/messages/prepare.rs

@@ -1,6 +1,7 @@
 use litellm_core::CoreError;
 use litellm_core::CoreResult;
 use litellm_core::messages::transformation::MessagesAuthStrategy;
+use litellm_core::providers::bedrock::AWS_REGION_NAME;
 use litellm_core::routing_utils::provider::{CustomLlmProvider, get_custom_llm_provider};
 use serde_json::Value;
 
@@ -29,10 +30,10 @@ pub(super) fn prepare_messages_call(
 
     let config = messages_provider_config(provider)
         .ok_or_else(|| CoreError::InvalidProvider(provider.to_string()))?;
+    let region_override = request.aws_region_name;
     let env_lookup = |key: &str| {
-        if key == "AWS_REGION_NAME" {
-            return request
-                .aws_region_name
+        if key == AWS_REGION_NAME {
+            return region_override
                 .map(str::to_string)
                 .or_else(|| std::env::var(key).ok());
         }

litellm-rust/crates/core/src/messages/types.rs

@@ -45,7 +45,7 @@ pub struct AnthropicMessage {
 
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
 pub struct AnthropicMessagesRequest {
-    #[serde(skip_serializing_if = "String::is_empty")]
+    #[serde(default, skip_serializing_if = "String::is_empty")]
     pub model: String,
     pub messages: Vec<AnthropicMessage>,
     #[serde(skip_serializing_if = "Option::is_none")]

litellm-rust/crates/core/src/providers/bedrock/mod.rs

@@ -6,4 +6,5 @@
 pub mod audio_transcription;
 pub mod aws_base;
 mod constants;
+pub use constants::AWS_REGION_NAME;
 pub mod messages;

litellm/llms/custom_httpx/llm_http_handler.py

@@ -2283,7 +2283,6 @@ class BaseLLMHTTPHandler:
         from litellm.rust_bridge import messages as rust_messages_bridge
 
         upstream_body = {key: value for key, value in request_body.items() if key != "stream"}
-        upstream_body.setdefault("model", model)
         try:
             rust_response = await rust_messages_bridge.amessages(
                 model=model,

litellm/rust_bridge/messages.py

@@ -111,7 +111,7 @@ def messages(
         custom_llm_provider=custom_llm_provider,
         extra_headers=extra_headers,
         timeout_seconds=timeout_to_seconds(timeout),
-        **({"aws_region_name": aws_region_name} if aws_region_name is not None else {}),
+        aws_region_name=aws_region_name,
     )
 
 
@@ -137,5 +137,5 @@ async def amessages(
         custom_llm_provider=custom_llm_provider,
         extra_headers=extra_headers,
         timeout_seconds=timeout_to_seconds(timeout),
-        **({"aws_region_name": aws_region_name} if aws_region_name is not None else {}),
+        aws_region_name=aws_region_name,
     )

tests/test_litellm/anthropic_interface/test_rust_bridge_messages.py

@@ -46,6 +46,7 @@ class RecordingMessages:
         custom_llm_provider: str | None,
         extra_headers: dict[str, object] | None,
         timeout_seconds: float | None,
+        aws_region_name: str | None,
     ) -> dict[str, object]:
         self.calls.append(
             {
@@ -56,6 +57,7 @@ class RecordingMessages:
                 "custom_llm_provider": custom_llm_provider,
                 "extra_headers": extra_headers,
                 "timeout_seconds": timeout_seconds,
+                "aws_region_name": aws_region_name,
             }
         )
         return dict(FAKE_MESSAGES_RESPONSE)
@@ -74,6 +76,7 @@ class RecordingAsyncMessages:
         custom_llm_provider: str | None,
         extra_headers: dict[str, object] | None,
         timeout_seconds: float | None,
+        aws_region_name: str | None,
     ) -> dict[str, object]:
         self.calls.append(
             {
@@ -84,6 +87,7 @@ class RecordingAsyncMessages:
                 "custom_llm_provider": custom_llm_provider,
                 "extra_headers": extra_headers,
                 "timeout_seconds": timeout_seconds,
+                "aws_region_name": aws_region_name,
             }
         )
         return dict(FAKE_MESSAGES_RESPONSE)
@@ -192,6 +196,7 @@ def test_messages_wrapper_forwards_args_and_converts_timeout():
         "custom_llm_provider": "azure_ai",
         "extra_headers": {"anthropic-beta": "token-efficient-tools-2025-02-19"},
         "timeout_seconds": 42.0,
+        "aws_region_name": None,
     }
 
 
@@ -213,6 +218,7 @@ async def test_amessages_wrapper_forwards_args():
     assert response == FAKE_MESSAGES_RESPONSE
     assert bridge.calls[0]["model"] == "claude-sonnet-4-5"
     assert bridge.calls[0]["timeout_seconds"] == 12.5
+    assert bridge.calls[0]["aws_region_name"] is None
 
 
 def _gate(**overrides):
@@ -248,6 +254,7 @@ async def test_gate_invokes_rust_and_marks_response_header():
     assert call["api_base"] == "https://resource.services.ai.azure.com/anthropic"
     assert call["extra_headers"] == {"x-api-key": "sk-azure", "anthropic-version": "2023-06-01"}
     assert call["timeout_seconds"] == 30.0
+    assert call["aws_region_name"] is None
 
 
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