diff --git a/litellm-rust/crates/inference-messages/src/common_utils.rs b/litellm-rust/crates/inference-messages/src/common_utils.rs
index e5ece2837d8..d0f109c1e99 100644
--- a/litellm-rust/crates/inference-messages/src/common_utils.rs
+++ b/litellm-rust/crates/inference-messages/src/common_utils.rs
@@ -1,5 +1,5 @@
 use litellm_core_utils::get_llm_provider_logic::LlmProviders;
-use litellm_http::request::string_headers as shared_string_headers;
+use litellm_llms::ErrorDetail;
 use litellm_llms::tencent::messages::transformation::TENCENT_MESSAGES_CONFIG;
 use litellm_llms::{
     anthropic::messages::transformation::ANTHROPIC_MESSAGES_CONFIG,
@@ -19,8 +19,6 @@ use serde_json::{Map, Value};
 
 use super::Error;
 
-const HEADER_CONTEXT: &str = "messages";
-
 #[derive(Clone, Copy)]
 pub(crate) struct MessagesProvider {
     provider: LlmProviders,
@@ -75,7 +73,52 @@ pub(crate) fn messages_provider(provider: LlmProviders, model: &str) -> Option<M
 pub(super) fn string_headers(
     extra_headers: Option<Map<String, Value>>,
 ) -> Result<Vec<(String, String)>, Error> {
-    shared_string_headers(HEADER_CONTEXT, extra_headers).map_err(Error::from)
+    extra_headers
+        .unwrap_or_default()
+        .into_iter()
+        .map(|(name, value)| match value {
+            Value::String(value) => Ok((name, value)),
+            value => Err(Error::invalid_request(ErrorDetail::invalid(
+                "extra_headers",
+                NonStringHeader {
+                    actual: python_type_name(&value),
+                    name,
+                },
+            ))),
+        })
+        .collect()
+}
+
+/// A header value the caller set to something other than a string, named by its Python type
+/// since the caller wrote it in Python.
+#[derive(Debug)]
+struct NonStringHeader {
+    name: String,
+    actual: &'static str,
+}
+
+impl std::fmt::Display for NonStringHeader {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            formatter,
+            "header {} must be a string, got {}",
+            self.name, self.actual
+        )
+    }
+}
+
+impl std::error::Error for NonStringHeader {}
+
+fn python_type_name(value: &Value) -> &'static str {
+    match value {
+        Value::Null => "NoneType",
+        Value::Bool(_) => "bool",
+        Value::Number(number) if number.is_f64() => "float",
+        Value::Number(_) => "int",
+        Value::String(_) => "str",
+        Value::Array(_) => "list",
+        Value::Object(_) => "dict",
+    }
 }
 
 #[cfg(test)]
@@ -85,7 +128,6 @@ mod tests {
     use rstest::rstest;
 
     use super::{messages_provider, string_headers};
-    use crate::Error;
     use litellm_core_utils::get_llm_provider_logic::LlmProviders;
 
     #[rstest]
@@ -113,17 +155,28 @@ mod tests {
         assert!(messages_provider(provider, model).is_none());
     }
 
-    #[test]
-    fn string_headers_rejects_non_string_values() {
-        let headers = json!({"x-count": 3}).as_object().unwrap().clone();
-        let err = string_headers(Some(headers)).expect_err("non-string header rejected");
+    #[rstest]
+    #[case::int(json!(12345), "int")]
+    #[case::float(json!(1.5), "float")]
+    #[case::bool(json!(true), "bool")]
+    #[case::null(json!(null), "NoneType")]
+    #[case::list(json!([1]), "list")]
+    #[case::dict(json!({"a": 1}), "dict")]
+    fn non_string_header_is_a_bad_request_naming_the_header_and_its_type(
+        #[case] value: serde_json::Value,
+        #[case] python_type: &str,
+    ) {
+        let headers = json!({"x-kept": "v", "x-count": value})
+            .as_object()
+            .unwrap()
+            .clone();
+        let error = string_headers(Some(headers)).expect_err("non-string header refused");
+        assert!(error.is_request(), "{error:?}");
+        assert_eq!(error.upstream_response(), None);
+        let rejection = error.rejected_request().expect("a rejected request");
         assert_eq!(
-            err,
-            Error::Headers(litellm_http::request::HeaderError {
-                context: "messages",
-                name: "x-count".to_string(),
-                actual: "number",
-            })
+            litellm_error::Report::new(rejection).to_string(),
+            format!("invalid extra_headers: header x-count must be a string, got {python_type}")
         );
     }
 }
diff --git a/litellm-rust/crates/inference-messages/src/handler.rs b/litellm-rust/crates/inference-messages/src/handler.rs
index 5ab171076ff..5eb017ddfc5 100644
--- a/litellm-rust/crates/inference-messages/src/handler.rs
+++ b/litellm-rust/crates/inference-messages/src/handler.rs
@@ -26,10 +26,10 @@ use litellm_llms_types::formats::messages::{
 };
 use litellm_secrets::source::Secrets;
 use litellm_tracing::ByteChunk;
-use serde_json::Value;
+use serde_json::{Map, Value};
 
 use super::{
-    Error, MessagesCall, MessagesCallResponse, MessagesRoute,
+    Error, MessagesBody, MessagesCall, MessagesCallResponse, MessagesRoute,
     common_utils::{MessagesProvider, merge_messages_header_sources, string_headers},
     constants::MESSAGES_TIMEOUT_SECS,
     route::Messages,
@@ -85,7 +85,10 @@ pub(super) async fn execute(
         ),
     };
     let reported = match &output {
-        MessagesCallResponse::Complete(response) => provider.config().reported_cost(response),
+        MessagesCallResponse::Complete(response) => match response {
+            MessagesBody::Message(message) => provider.config().reported_cost(message),
+            MessagesBody::Unchecked(_) => None,
+        },
         MessagesCallResponse::Stream { .. } => None,
     };
     context
@@ -347,8 +350,7 @@ async fn call_provider(
         // body it cannot parse, and the public mapping classifies it by that status.
         return Err(litellm_http::Error::upstream(status, text).into());
     }
-    decode_response(config, &identity.model, &text)
-        .map(|message| MessagesCallResponse::Complete(Box::new(message)))
+    decode_response(config, &identity.model, &text).map(MessagesCallResponse::Complete)
 }
 
 fn serialize_failure(err: serde_json::Error) -> Error {
@@ -412,15 +414,23 @@ fn decode_response(
     config: &dyn BaseMessagesConfig,
     model: &str,
     text: &str,
-) -> Result<MessagesResponse, Error> {
-    let response = serde_json::from_str(text).map_err(|err| {
-        Error::invalid_response(litellm_llms::ErrorDetail::invalid(
-            "messages response JSON",
-            err,
-        ))
-    })?;
+) -> Result<MessagesBody, Error> {
+    let response = match serde_json::from_str::<MessagesResponse>(text) {
+        Ok(response) => response,
+        Err(err) => {
+            let Ok(mut body) = serde_json::from_str::<Map<String, Value>>(text) else {
+                return Err(Error::invalid_response(litellm_llms::ErrorDetail::invalid(
+                    "messages response JSON",
+                    err,
+                )));
+            };
+            body.entry("stop_sequence").or_insert(Value::Null);
+            return Ok(MessagesBody::Unchecked(body));
+        }
+    };
     config
         .transform_anthropic_messages_response(model, response)
+        .map(|message| MessagesBody::Message(Box::new(message)))
         .map_err(Error::from)
         .map_err(Error::after_send)
 }
diff --git a/litellm-rust/crates/inference-messages/src/lib.rs b/litellm-rust/crates/inference-messages/src/lib.rs
index 745442d0314..25ebeaacb49 100644
--- a/litellm-rust/crates/inference-messages/src/lib.rs
+++ b/litellm-rust/crates/inference-messages/src/lib.rs
@@ -17,8 +17,8 @@ use crate::common_utils::messages_provider;
 pub use common_utils::merge_messages_header_sources;
 pub use litellm_inference::Error;
 pub use types::{
-    MessagesCall, MessagesCallResponse, MessagesSettings, MessagesShaping, litellm_params,
-    messages_body,
+    MessagesBody, MessagesCall, MessagesCallResponse, MessagesSettings, MessagesShaping,
+    litellm_params, messages_body,
 };
 
 #[derive(Clone)]
diff --git a/litellm-rust/crates/inference-messages/src/route.rs b/litellm-rust/crates/inference-messages/src/route.rs
index 7ff886689da..5f06d16d49f 100644
--- a/litellm-rust/crates/inference-messages/src/route.rs
+++ b/litellm-rust/crates/inference-messages/src/route.rs
@@ -5,11 +5,10 @@ use litellm_host::{
     call::{HostedCompletion, HostedMachine, hosted_call},
     protocol::Protocol,
 };
-use litellm_llms_types::formats::messages::MessagesResponse;
 
-use super::{Error, MessagesCall};
+use super::{Error, MessagesBody, MessagesCall};
 
-pub type MessagesOutput = HostedCompletion<Box<MessagesResponse>>;
+pub type MessagesOutput = HostedCompletion<MessagesBody>;
 
 /// The upstream response as the caller sees it at stream hand-off, before any chunk.
 pub struct MessagesStreamHead {
@@ -19,7 +18,7 @@ pub struct MessagesStreamHead {
 pub struct Messages;
 
 impl Protocol for Messages {
-    type Response = Box<MessagesResponse>;
+    type Response = MessagesBody;
     type Error = Error;
     type Request = MessagesCall;
     type HostCall = Infallible;
diff --git a/litellm-rust/crates/inference-messages/src/types.rs b/litellm-rust/crates/inference-messages/src/types.rs
index ece17b3380c..772ea6f7292 100644
--- a/litellm-rust/crates/inference-messages/src/types.rs
+++ b/litellm-rust/crates/inference-messages/src/types.rs
@@ -42,7 +42,16 @@ pub(super) fn invalid_request(err: serde_json::Error) -> Error {
 }
 
 pub type MessagesCallResponse =
-    CallOutput<Box<MessagesResponse>, super::route::MessagesStreamHead, Bytes, Error>;
+    CallOutput<MessagesBody, super::route::MessagesStreamHead, Bytes, Error>;
+
+// Python's `transform_anthropic_messages_response` returns any JSON object the provider sends
+// with a 200, message or not, so one that is not a message passes through as sent.
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum MessagesBody {
+    Message(Box<MessagesResponse>),
+    Unchecked(Map<String, Value>),
+}
 
 #[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
 pub struct MessagesShaping {
diff --git a/litellm-rust/crates/inference-messages/tests/bedrock_native/main.rs b/litellm-rust/crates/inference-messages/tests/bedrock_native/main.rs
index f91d5c79f7c..5207f4e9d58 100644
--- a/litellm-rust/crates/inference-messages/tests/bedrock_native/main.rs
+++ b/litellm-rust/crates/inference-messages/tests/bedrock_native/main.rs
@@ -1,7 +1,9 @@
 use std::{sync::Arc, time::Duration};
 
 use futures_util::TryStreamExt;
-use litellm_inference_messages::{Error, MessagesCall, MessagesCallResponse, MessagesShaping};
+use litellm_inference_messages::{
+    Error, MessagesBody, MessagesCall, MessagesCallResponse, MessagesShaping,
+};
 use litellm_inference_testing::{RecordingSecrets, no_secrets};
 use litellm_llms_types::formats::messages::{MessagesRequest, MessagesResponse};
 use rstest::{fixture, rstest};
@@ -74,7 +76,10 @@ async fn run(call: MessagesCall) -> Result<MessagesCallResponse, Error> {
 
 async fn run_message(call: MessagesCall) -> MessagesResponse {
     match run(call).await.unwrap() {
-        MessagesCallResponse::Complete(message) => *message,
+        MessagesCallResponse::Complete(message) => match message {
+            MessagesBody::Message(message) => *message,
+            MessagesBody::Unchecked(_) => panic!("expected a message"),
+        },
         MessagesCallResponse::Stream { .. } => panic!("expected a completed message"),
     }
 }
diff --git a/litellm-rust/crates/inference-messages/tests/caching.rs b/litellm-rust/crates/inference-messages/tests/caching.rs
index 663c87453a9..787501a8fed 100644
--- a/litellm-rust/crates/inference-messages/tests/caching.rs
+++ b/litellm-rust/crates/inference-messages/tests/caching.rs
@@ -50,42 +50,47 @@ async fn messages_cache_identity_includes_provider_native_parameters(
     #[case] original: Value,
     #[case] changed: Value,
 ) {
-    use litellm_inference_messages::route::Messages;
+    use litellm_inference_messages::{MessagesBody, route::Messages};
     use litellm_llms_types::formats::messages::MessagesResponse;
 
     let calls = AtomicUsize::new(0);
     for (value, expected_call) in [(original.clone(), 0), (changed, 1), (original, 0)] {
-        let response =
-            execute_unary::<Messages, _, _>(
-                CacheRequest::from_wire(
-                    ProviderIdentity {
-                        model: "test".into(),
-                        provider: "anthropic".into(),
-                    },
-                    Some(&WireRequest {
-                        url: "https://example.test/v1/messages".into(),
-                        headers: vec![],
-                        body: json!({
-                            "model":"test", "messages":[{"role":"user","content":"hello"}],
-                            "max_tokens":32, (field):value
-                        }),
-                    }),
-                ),
-                Some(cache.clone()),
-                Some(CacheOptions::new(CacheScope::Shared)),
-                &(),
-                None,
-                || async {
-                    let call = calls.fetch_add(1, Ordering::SeqCst);
-                    Ok(Box::new(serde_json::from_value::<MessagesResponse>(json!({
-                    "id":call.to_string(), "type":"message", "role":"assistant", "model":"test",
-                    "content":[{"type":"text","text":format!("answer {call}")}],
-                    "stop_reason":"end_turn", "stop_sequence":null
-                })).unwrap()))
+        let response = execute_unary::<Messages, _, _>(
+            CacheRequest::from_wire(
+                ProviderIdentity {
+                    model: "test".into(),
+                    provider: "anthropic".into(),
                 },
-            )
-            .await
-            .unwrap();
+                Some(&WireRequest {
+                    url: "https://example.test/v1/messages".into(),
+                    headers: vec![],
+                    body: json!({
+                        "model":"test", "messages":[{"role":"user","content":"hello"}],
+                        "max_tokens":32, (field):value
+                    }),
+                }),
+            ),
+            Some(cache.clone()),
+            Some(CacheOptions::new(CacheScope::Shared)),
+            &(),
+            None,
+            || async {
+                let call = calls.fetch_add(1, Ordering::SeqCst);
+                Ok(MessagesBody::Message(Box::new(
+                    serde_json::from_value::<MessagesResponse>(json!({
+                        "id":call.to_string(), "type":"message", "role":"assistant", "model":"test",
+                        "content":[{"type":"text","text":format!("answer {call}")}],
+                        "stop_reason":"end_turn", "stop_sequence":null
+                    }))
+                    .unwrap(),
+                )))
+            },
+        )
+        .await
+        .unwrap();
+        let MessagesBody::Message(response) = response else {
+            panic!("expected a message");
+        };
         assert_eq!(response.id, expected_call.to_string());
         assert_eq!(
             response.content[0]["text"],
@@ -253,7 +258,7 @@ async fn provider_reported_cost_is_delivered_once_and_never_charged_for_a_cache_
     #[case] cost: Value,
     #[case] expected: Option<f64>,
 ) {
-    use litellm_inference_messages::{MessagesCall, MessagesCallResponse};
+    use litellm_inference_messages::{MessagesBody, MessagesCall, MessagesCallResponse};
     let response = json!({"id": "msg_cost", "type": "message", "role": "assistant", "model": "native-test",
         "content": [{"type": "text", "text": "answer"}], "stop_reason": "end_turn", "stop_sequence": null,
         "usage": {"input_tokens": 3, "output_tokens": 2}, "cost": cost});
@@ -277,6 +282,9 @@ async fn provider_reported_cost_is_delivered_once_and_never_charged_for_a_cache_
         panic!("expected Messages responses");
     };
     assert_eq!(first, second);
+    let MessagesBody::Message(first) = first else {
+        panic!("expected a message");
+    };
     assert_eq!(first.extra.get("cost"), Some(&cost));
     assert_eq!(support::received(&upstream).await.len(), 1);
     let facts = hooks.facts.lock().unwrap();
diff --git a/litellm-rust/crates/inference-messages/tests/live/support.rs b/litellm-rust/crates/inference-messages/tests/live/support.rs
index 81e295e34ad..52684928f1f 100644
--- a/litellm-rust/crates/inference-messages/tests/live/support.rs
+++ b/litellm-rust/crates/inference-messages/tests/live/support.rs
@@ -4,7 +4,9 @@ use futures_util::{FutureExt, TryStreamExt};
 use litellm_host::interceptors::{
     ExecutionFacts, Interceptors, RawResponse, RequestContext, ResultSource, WireRequest,
 };
-use litellm_inference_messages::{Error, MessagesCall, MessagesCallResponse, MessagesRoute};
+use litellm_inference_messages::{
+    Error, MessagesBody, MessagesCall, MessagesCallResponse, MessagesRoute,
+};
 use litellm_inference_testing::live::{LiveResources, model, within_deadline};
 use litellm_llms_types::formats::messages::MessagesResponse;
 use serde_json::{Value, json};
@@ -111,7 +113,10 @@ pub(super) fn call(provider: &str, payload: Value) -> MessagesCall {
 
 pub(super) fn complete(response: MessagesCallResponse) -> Box<MessagesResponse> {
     match response {
-        MessagesCallResponse::Complete(message) => message,
+        MessagesCallResponse::Complete(message) => match message {
+            MessagesBody::Message(message) => message,
+            MessagesBody::Unchecked(_) => panic!("a complete request returned no message"),
+        },
         MessagesCallResponse::Stream { .. } => panic!("a complete request returned a stream"),
     }
 }
diff --git a/litellm-rust/crates/inference-messages/tests/messages/host.rs b/litellm-rust/crates/inference-messages/tests/messages/host.rs
index e8df20e7dcb..20f6a97aa37 100644
--- a/litellm-rust/crates/inference-messages/tests/messages/host.rs
+++ b/litellm-rust/crates/inference-messages/tests/messages/host.rs
@@ -6,7 +6,7 @@ use litellm_host::{
     interceptors::{ExecutionFacts, RequestContext, ResultSource, WireRequest},
     lifecycle::CallEvent,
 };
-use litellm_inference_messages::{MessagesCallResponse, route::Messages};
+use litellm_inference_messages::{MessagesBody, MessagesCallResponse, route::Messages};
 use litellm_inference_testing::{RecordingSecrets, no_secrets};
 use litellm_llms::base_llm::messages::context::{
     MessagesModelCapabilities as AnthropicModelCapabilities, SupportedEffortTiers,
@@ -340,7 +340,10 @@ async fn response_mode_follows_the_intercepted_request(
                 }
                 MessagesCallResponse::Complete(message) => {
                     assert_eq!(expected_stream, Some(false));
-                    assert_eq!(*message, serde_json::from_value(message_body()).unwrap());
+                    assert_eq!(
+                        message,
+                        MessagesBody::Message(serde_json::from_value(message_body()).unwrap())
+                    );
                 }
             }
             Ok::<_, Error>(())
diff --git a/litellm-rust/crates/inference-messages/tests/messages/main.rs b/litellm-rust/crates/inference-messages/tests/messages/main.rs
index a01e571ec75..fe203287766 100644
--- a/litellm-rust/crates/inference-messages/tests/messages/main.rs
+++ b/litellm-rust/crates/inference-messages/tests/messages/main.rs
@@ -5,7 +5,7 @@ use std::{
 
 use litellm_http::{HttpSettings, Resolution};
 use litellm_inference_messages::{
-    Error, MessagesCall, MessagesSettings, MessagesShaping,
+    Error, MessagesBody, MessagesCall, MessagesSettings, MessagesShaping,
     route::{Messages, MessagesMachine, MessagesOutput},
 };
 use litellm_inference_testing::RecordingSecrets;
@@ -119,7 +119,10 @@ async fn run(call: MessagesCall) -> Result<MessagesOutput, Error> {
 
 async fn run_message(call: MessagesCall) -> MessagesResponse {
     match run(call).await.expect("messages call succeeds") {
-        MessagesOutput::Complete(message) => *message,
+        MessagesOutput::Complete(message) => match message {
+            MessagesBody::Message(message) => *message,
+            MessagesBody::Unchecked(_) => panic!("a call returned no message"),
+        },
         MessagesOutput::StreamEnded | MessagesOutput::Detached => {
             panic!("a non-streaming call returned a stream")
         }
diff --git a/litellm-rust/crates/inference-messages/tests/messages/response.rs b/litellm-rust/crates/inference-messages/tests/messages/response.rs
index 76813fe0a34..f978da5e995 100644
--- a/litellm-rust/crates/inference-messages/tests/messages/response.rs
+++ b/litellm-rust/crates/inference-messages/tests/messages/response.rs
@@ -2,7 +2,7 @@ use litellm_host::{
     interceptors::{ExecutionFacts, ResultSource},
     lifecycle::ExecutionEvent,
 };
-use litellm_inference_messages::{MessagesCallResponse, messages_body};
+use litellm_inference_messages::{MessagesBody, MessagesCallResponse, messages_body};
 use litellm_inference_testing::{
     RecordingSecrets, http_config, no_secrets, provider_http, resources,
 };
@@ -48,6 +48,9 @@ async fn calls_defer_execution_until_polled(
     let MessagesCallResponse::Complete(response) = future.await.unwrap() else {
         panic!("expected a completed message");
     };
+    let MessagesBody::Message(response) = response else {
+        panic!("expected a message");
+    };
     assert_eq!(
         response.content,
         message_body()["content"].as_array().unwrap().as_slice()
@@ -240,10 +243,42 @@ async fn an_unparseable_success_body_is_reported_as_the_upstream_answer(call: Me
     assert_eq!(error.upstream_response(), Some((200, "not json")));
 }
 
+#[rstest]
+#[case::error_object(
+    json!({"type": "error", "error": {"type": "overloaded_error", "message": "Overloaded"}}),
+    json!({"type": "error", "error": {"type": "overloaded_error", "message": "Overloaded"},
+        "stop_sequence": null}),
+)]
+#[case::message_missing_id(
+    json!({"type": "message", "content": [], "stop_sequence": "###"}),
+    json!({"type": "message", "content": [], "stop_sequence": "###"}),
+)]
+#[tokio::test]
+async fn a_success_body_that_is_not_a_message_passes_through(
+    call: MessagesCall,
+    #[case] body: Value,
+    #[case] expected: Value,
+) {
+    let upstream = upstream([json_response(body)]).await;
+
+    let response = run(MessagesCall {
+        api_key: Some("sk".into()),
+        api_base: Some(upstream.uri()),
+        ..call
+    })
+    .await
+    .expect("any JSON object is returned");
+
+    let MessagesOutput::Complete(response) = response else {
+        panic!("expected a completed response");
+    };
+    assert_eq!(serde_json::to_value(response).unwrap(), expected);
+}
+
 #[rstest]
 #[tokio::test]
 async fn an_unreadable_success_body_is_an_invalid_response(call: MessagesCall) {
-    let upstream = upstream([json_response(json!({"unexpected": true}))]).await;
+    let upstream = upstream([json_response(json!(["unexpected"]))]).await;
 
     let error = run(MessagesCall {
         api_key: Some("sk".into()),
@@ -320,6 +355,9 @@ async fn the_facade_sends_through_the_injected_http_pool_configuration(call: Mes
     let MessagesCallResponse::Complete(message) = response else {
         panic!("a non-streaming request returns a message");
     };
+    let MessagesBody::Message(message) = message else {
+        panic!("expected a message");
+    };
     assert_eq!(message.id, "msg_1");
     let sent = only_request(&upstream).await;
     assert_eq!(sent.header("x-api-key"), Some("sk-ant"));
@@ -412,6 +450,9 @@ async fn route_uses_injected_dependencies_and_optional_cache(
         else {
             panic!("expected a completed message");
         };
+        let MessagesBody::Message(response) = response else {
+            panic!("expected a message");
+        };
         assert_eq!(
             response.content,
             message_body()["content"].as_array().unwrap().as_slice()
@@ -484,6 +525,9 @@ async fn cache_overrides_preserve_the_routes_isolated_scope(call: MessagesCall)
         else {
             panic!("expected a completed message");
         };
+        let MessagesBody::Message(response) = response else {
+            panic!("expected a message");
+        };
         assert_eq!(response.id, expected["id"].as_str().unwrap());
     }
     assert_eq!(received(&upstream).await.len(), 2);
diff --git a/litellm-rust/crates/python-bridge/src/routes/messages/host.rs b/litellm-rust/crates/python-bridge/src/routes/messages/host.rs
index af614f17360..e92daa67be4 100644
--- a/litellm-rust/crates/python-bridge/src/routes/messages/host.rs
+++ b/litellm-rust/crates/python-bridge/src/routes/messages/host.rs
@@ -239,9 +239,9 @@ impl PythonBinding for MessagesPythonHost {
     fn encode_response(
         &mut self,
         py: Python<'_>,
-        response: Box<litellm_llms_types::formats::messages::MessagesResponse>,
+        response: litellm_inference_messages::MessagesBody,
     ) -> PyResult<Py<PyAny>> {
-        public_response(py, ROUTE_HOST_MODULE, response.as_ref())
+        public_response(py, ROUTE_HOST_MODULE, &response)
     }
 
     fn encode_stream_head(
diff --git a/tests/test_litellm_rust/messages/test_callbacks.py b/tests/test_litellm_rust/messages/test_callbacks.py
index 3073c1cf7dd..0550b530913 100644
--- a/tests/test_litellm_rust/messages/test_callbacks.py
+++ b/tests/test_litellm_rust/messages/test_callbacks.py
@@ -284,6 +284,23 @@ async def test_pre_call_deployment_rejection_logs_failure_without_provider_io(se
     assert not {"log_pre_api_call", "log_success_event", "async_log_success_event"} & set(recorder.names)
 
 
+@pytest.mark.asyncio
+async def test_non_string_header_is_a_bad_request_refused_before_the_provider_call(server: RecordingServer) -> None:
+    recorder: Final = RecordingLogger()
+
+    with rebound(litellm, "callbacks", [recorder]):
+        with pytest.raises(
+            litellm.BadRequestError, match=r"invalid extra_headers: header x-org must be a string, got int"
+        ) as raised:
+            await call(server, extra_headers={"x-org": 12345})
+        failures: Final = await recorder.wait_for_async("async_log_failure_event")
+
+    assert raised.value.status_code == 400
+    assert not server.requests
+    assert "log_pre_api_call" not in recorder.names
+    assert _OBJECT.validate_python(failures[0].kwargs)["exception"] is raised.value
+
+
 @pytest.mark.asyncio
 async def test_pre_call_deployment_hook_can_delete_keywords(server: RecordingServer) -> None:
     class DropKeywords(CustomLogger):
diff --git a/tests/test_litellm_rust/messages/test_requests.py b/tests/test_litellm_rust/messages/test_requests.py
index 92031e72aee..3e486bbe9e6 100644
--- a/tests/test_litellm_rust/messages/test_requests.py
+++ b/tests/test_litellm_rust/messages/test_requests.py
@@ -4,7 +4,7 @@ import pytest
 
 import litellm
 from tests.test_litellm_rust.messages.data import MESSAGES, MESSAGES_RESPONSE, call
-from tests.test_litellm_rust.support.recording_server import RecordingServer
+from tests.test_litellm_rust.support.recording_server import RecordingServer, ResponseSpec
 from tests.test_litellm_rust.support.routing import assert_served_natively
 
 pytestmark = pytest.mark.requires_rust_extension
@@ -57,6 +57,21 @@ async def test_replayed_tool_ids_are_sanitized_before_they_reach_the_provider(se
     ]
 
 
+@pytest.mark.asyncio
+async def test_a_success_body_that_is_not_a_message_passes_through(server: RecordingServer) -> None:
+    overloaded: Final = {"type": "error", "error": {"type": "overloaded_error", "message": "Overloaded"}}
+    server.default_response = ResponseSpec(body=overloaded)
+
+    response: Final = await call(server)
+
+    assert_served_natively(server, response)
+    assert isinstance(response, dict)
+    assert {name: value for name, value in response.items() if name != "_hidden_params"} == {
+        **overloaded,
+        "stop_sequence": None,
+    }
+
+
 @pytest.mark.asyncio
 async def test_provider_specific_headers_scoped_to_anthropic_reach_the_wire(server: RecordingServer) -> None:
     await call(