feat(rust): add native OpenRouter Responses (#46000)

The Responses route now resolves openrouter alongside openai. The
OpenRouter config reuses the OpenAI request and response transforms and
owns only its bearer credential (OPENROUTER_API_KEY, then OR_API_KEY) and
base URL (OPENROUTER_API_BASE). Wire model ids follow Python's
get_llm_provider, including the openrouter/auto native id with an
explicit provider. The Python route host no longer hands litellm.openai_key
to OpenRouter.

The OpenRouter live test lives in tests/live/openrouter.rs and returns
early when the provider key is not exported, so cargo test stays offline
by default instead of hiding it behind --ignored.

Co-authored-by: nate-berri <nate@berri.ai>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

litellm-rust/AGENTS.md

@@ -15,6 +15,7 @@ Use the derived conversions directly (`<&'static str>::from(x)` / `.into()`, `st
 - `crates/<crate>/tests/` is only for tests that drive several modules together end to end, such as a full request through a route. A test of one type or function never goes there
 - A helper shared by several inline test modules goes in a `#[cfg(test)] mod test_support;` at the crate root, and only once a second module needs it
 - A test for another crate's item belongs in that crate, not in a downstream one
+- Tests that call a real provider go in `crates/<crate>/tests/live/<provider>.rs` behind a `tests/live/main.rs`. Each reads the provider's key from the environment through an `Option` fixture and returns early when it is unset, never `#[ignore]`, so `cargo test` stays offline until the key is exported
 - Never set `autotests = false` or hand-list `[[test]]` targets. Every file directly under `tests/` is discovered by cargo, and a shared helper goes in `tests/<name>/mod.rs` or `tests/<subject>/support.rs` so it is not picked up as a test crate of its own
 
 ## Test fixtures and cases

litellm-rust/Cargo.lock

@@ -4089,6 +4089,7 @@ dependencies = [
  "litellm-cache",
  "litellm-cache-memory",
  "litellm-cache-response",
+ "litellm-core-utils",
  "litellm-host",
  "litellm-host-native",
  "litellm-http",

litellm-rust/crates/inference-responses/Cargo.toml

@@ -10,6 +10,7 @@ bytes.workspace = true
 futures-util.workspace = true
 litellm-auth = { workspace = true, features = ["aws", "azure", "gcp"] }
 litellm-cache-response.workspace = true
+litellm-core-utils.workspace = true
 litellm-host.workspace = true
 litellm-http.workspace = true
 litellm-inference.workspace = true

litellm-rust/crates/inference-responses/src/prepare.rs

@@ -1,7 +1,11 @@
-use litellm_host::interceptors::RequestContext;
+use litellm_core_utils::get_llm_provider_logic::{
+    CustomLlmProvider, LlmProviders, get_custom_llm_provider,
+};
+use litellm_host::interceptors::{ProviderIdentity, RequestContext};
 use litellm_llms::{
     base_llm::responses::transformation::BaseResponsesApiConfig,
     openai::responses::transformation::OpenAiResponsesApiConfig,
+    openrouter::responses::transformation::OPENROUTER_RESPONSES_CONFIG,
 };
 use litellm_secrets::source::SecretSource;
 use serde_json::Value;
@@ -16,10 +20,10 @@ pub(super) async fn prepare(
     call: ResponsesCall,
     secrets: &dyn SecretSource,
 ) -> Result<ProviderResponsesRequest, Error> {
-    let identity = resolve_provider(&call.model, call.custom_llm_provider.as_deref())?;
+    let ResponsesProvider { identity, config } =
+        resolve_provider(&call.model, call.custom_llm_provider.as_deref())?;
     let provider = identity.provider.as_str();
     let model = identity.model.as_str();
-    let config: &'static dyn BaseResponsesApiConfig = &OpenAiResponsesApiConfig;
     let snapshot = secrets
         .resolve(config.secret_names(call.api_key.as_deref(), call.api_base.as_deref()))
         .await?;
@@ -52,20 +56,107 @@ pub(super) async fn prepare(
     })
 }
 
+pub(super) struct ResponsesProvider {
+    pub identity: ProviderIdentity,
+    pub config: &'static dyn BaseResponsesApiConfig,
+}
+
+/// Python's `get_llm_provider`: a bare model is OpenAI's, and with an explicit OpenRouter
+/// provider a model without a vendor segment keeps the `openrouter/` prefix as its wire id.
 pub(super) fn resolve_provider(
     model: &str,
     custom_llm_provider: Option<&str>,
-) -> Result<litellm_host::interceptors::ProviderIdentity, Error> {
-    let provider = custom_llm_provider.unwrap_or("openai");
-    if provider != "openai" {
-        return Err(Error::Unsupported("native HTTP responses provider"));
-    }
-    let resolved = model.strip_prefix("openai/").unwrap_or(model);
-    if resolved.is_empty() || resolved.contains('/') {
+) -> Result<ResponsesProvider, Error> {
+    let explicit = custom_llm_provider.filter(|provider| !provider.is_empty());
+    let (provider, resolved) = match get_custom_llm_provider(model, explicit) {
+        Some(CustomLlmProvider {
+            model,
+            custom_llm_provider,
+        }) => (custom_llm_provider, model),
+        None => ("openai", model),
+    };
+    if resolved.is_empty() {
         return Err(Error::InvalidProvider(model.into()));
     }
-    Ok(litellm_host::interceptors::ProviderIdentity {
-        model: resolved.into(),
-        provider: provider.into(),
+    let (config, wire_model): (&'static dyn BaseResponsesApiConfig, String) =
+        match provider.parse::<LlmProviders>() {
+            Ok(LlmProviders::Openai) if resolved.contains('/') => {
+                return Err(Error::InvalidProvider(model.into()));
+            }
+            Ok(LlmProviders::Openai) => (&OpenAiResponsesApiConfig, resolved.into()),
+            Ok(LlmProviders::Openrouter) if explicit.is_some() && !resolved.contains('/') => (
+                &OPENROUTER_RESPONSES_CONFIG,
+                format!("openrouter/{resolved}"),
+            ),
+            Ok(LlmProviders::Openrouter) => (&OPENROUTER_RESPONSES_CONFIG, resolved.into()),
+            _ => return Err(Error::Unsupported("native HTTP responses provider")),
+        };
+    Ok(ResponsesProvider {
+        identity: ProviderIdentity {
+            model: wire_model,
+            provider: provider.into(),
+        },
+        config,
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use rstest::rstest;
+
+    use super::*;
+
+    /// Pinned against Python's `get_llm_provider` on 2026-10-11.
+    #[rstest]
+    #[case::bare("gpt-5", None, "openai", "gpt-5")]
+    #[case::openai_prefix("openai/gpt-5", None, "openai", "gpt-5")]
+    #[case::openai_explicit("gpt-5", Some("openai"), "openai", "gpt-5")]
+    #[case::openrouter_prefix(
+        "openrouter/anthropic/claude",
+        None,
+        "openrouter",
+        "anthropic/claude"
+    )]
+    #[case::openrouter_explicit(
+        "openrouter/anthropic/claude",
+        Some("openrouter"),
+        "openrouter",
+        "anthropic/claude"
+    )]
+    #[case::openrouter_explicit_unprefixed(
+        "anthropic/claude",
+        Some("openrouter"),
+        "openrouter",
+        "anthropic/claude"
+    )]
+    #[case::openrouter_native_id(
+        "openrouter/auto",
+        Some("openrouter"),
+        "openrouter",
+        "openrouter/auto"
+    )]
+    #[case::openrouter_native_id_implicit("openrouter/auto", None, "openrouter", "auto")]
+    fn providers_and_wire_models_match_python(
+        #[case] model: &str,
+        #[case] custom_llm_provider: Option<&str>,
+        #[case] provider: &str,
+        #[case] wire_model: &str,
+    ) {
+        let resolved = resolve_provider(model, custom_llm_provider).unwrap();
+        assert_eq!(resolved.identity.provider, provider);
+        assert_eq!(resolved.identity.model, wire_model);
+    }
+
+    #[rstest]
+    #[case::other_prefix("other/model", None)]
+    #[case::other_explicit("model", Some("other"))]
+    #[case::openai_with_vendor_segment("openai/other/model", None)]
+    #[case::empty_model("openai/", None)]
+    #[case::conflicting_prefix("openrouter/anthropic/claude", Some("openai"))]
+    fn everything_else_is_rejected(#[case] model: &str, #[case] custom_llm_provider: Option<&str>) {
+        assert!(matches!(
+            resolve_provider(model, custom_llm_provider),
+            Err(Error::InvalidProvider(_) | Error::Unsupported(_))
+        ));
+    }
+}

litellm-rust/crates/inference-responses/tests/live/main.rs

@@ -0,0 +1,7 @@
+//! Real provider calls, one module per provider. Each test skips when its provider's key is not
+//! in the environment, so `cargo test` stays offline by default.
+
+#[path = "../support/mod.rs"]
+mod support;
+
+mod openrouter;

litellm-rust/crates/inference-responses/tests/live/openrouter.rs

@@ -0,0 +1,98 @@
+use std::{sync::Arc, time::Duration};
+
+use futures_util::TryStreamExt;
+use litellm_inference_responses::types::{ResponsesCall, ResponsesOutput};
+use litellm_inference_testing::RecordingSecrets;
+use litellm_llms::base_llm::responses::streaming::decode;
+use litellm_llms_types::formats::responses::streaming::ResponsesEventType;
+use rstest::{fixture, rstest};
+use serde_json::json;
+
+use crate::support::responses_route;
+
+const DEFAULT_MODEL: &str = "openrouter/openai/gpt-5.5";
+
+/// `OPENROUTER_API_KEY` as a secret source; tests skip when it is unset.
+#[fixture]
+fn secrets() -> Option<Arc<RecordingSecrets>> {
+    let key = std::env::var("OPENROUTER_API_KEY").ok()?;
+    Some(Arc::new(RecordingSecrets::new([(
+        "OPENROUTER_API_KEY",
+        key.as_str(),
+    )])))
+}
+
+fn call(stream: bool) -> ResponsesCall {
+    ResponsesCall {
+        model: std::env::var("OPENROUTER_LIVE_MODEL").unwrap_or_else(|_| DEFAULT_MODEL.into()),
+        input: json!("Reply with the single word: pong"),
+        optional_params: json!({"max_output_tokens": 32, "stream": stream})
+            .as_object()
+            .unwrap()
+            .clone(),
+        api_key: None,
+        api_base: None,
+        custom_llm_provider: None,
+        extra_headers: None,
+        timeout: Some(Duration::from_secs(60)),
+    }
+}
+
+#[rstest]
+#[tokio::test]
+async fn a_complete_response_carries_output_and_usage(secrets: Option<Arc<RecordingSecrets>>) {
+    let Some(secrets) = secrets else { return };
+    let output = responses_route(secrets)
+        .execute(call(false), &(), None)
+        .await
+        .unwrap();
+    let ResponsesOutput::Complete(response) = output else {
+        panic!("expected a complete response");
+    };
+    let body = serde_json::to_value(response).unwrap();
+    let text = body["output"]
+        .as_array()
+        .into_iter()
+        .flatten()
+        .filter_map(|item| item["content"].as_array())
+        .flatten()
+        .filter_map(|part| part["text"].as_str())
+        .collect::<String>();
+    assert!(text.to_ascii_lowercase().contains("pong"), "{body}");
+    assert!(
+        body["usage"]["total_tokens"].as_u64().unwrap() > 0,
+        "{body}"
+    );
+}
+
+#[rstest]
+#[tokio::test]
+async fn a_stream_ends_with_response_completed(secrets: Option<Arc<RecordingSecrets>>) {
+    let Some(secrets) = secrets else { return };
+    let output = responses_route(secrets)
+        .execute(call(true), &(), None)
+        .await
+        .unwrap();
+    let ResponsesOutput::Stream { chunks, .. } = output else {
+        panic!("expected SSE");
+    };
+    let wire = chunks.try_collect::<Vec<_>>().await.unwrap().concat();
+    let events = decode(&wire).unwrap();
+    assert_eq!(
+        events.first().map(|event| &event.event_type),
+        Some(&ResponsesEventType::ResponseCreated)
+    );
+    assert!(
+        events
+            .iter()
+            .any(|event| event.event_type == ResponsesEventType::OutputTextDelta)
+    );
+    let last = events.last().unwrap();
+    assert_eq!(last.event_type, ResponsesEventType::ResponseCompleted);
+    assert!(
+        last.data["response"]["usage"]["total_tokens"]
+            .as_u64()
+            .unwrap()
+            > 0
+    );
+}

litellm-rust/crates/inference-responses/tests/openrouter.rs

@@ -0,0 +1,150 @@
+use std::sync::Arc;
+
+use futures_util::TryStreamExt;
+use litellm_inference_responses::{
+    Error,
+    types::{ResponsesCall, ResponsesOutput},
+};
+use litellm_inference_testing::{RecordingSecrets, no_secrets};
+use rstest::{fixture, rstest};
+use serde_json::json;
+use wiremock::ResponseTemplate;
+
+mod support;
+use support::*;
+
+#[fixture]
+fn call() -> ResponsesCall {
+    ResponsesCall {
+        model: "openrouter/anthropic/test-model".into(),
+        input: json!("hello"),
+        optional_params: Default::default(),
+        api_key: None,
+        api_base: None,
+        custom_llm_provider: None,
+        extra_headers: None,
+        timeout: None,
+    }
+}
+
+fn response_body() -> serde_json::Value {
+    json!({"id": "resp_1", "model": "anthropic/test-model", "output": [{"type": "message", "content": []}], "usage": {"total_tokens": 7, "cost": 0.00017}})
+}
+
+#[rstest]
+#[case::explicit_key(Some("explicit"), &[], "Bearer explicit")]
+#[case::managed_key(None, &[("OPENROUTER_API_KEY", "managed")], "Bearer managed")]
+#[case::legacy_name(None, &[("OR_API_KEY", "legacy")], "Bearer legacy")]
+#[tokio::test]
+async fn the_payload_goes_to_the_openrouter_responses_endpoint_with_a_bearer(
+    call: ResponsesCall,
+    #[case] api_key: Option<&str>,
+    #[case] secrets: &[(&str, &str)],
+    #[case] expected: &str,
+) {
+    let upstream = upstream([json_response(response_body())]).await;
+    let output = responses_route(Arc::new(RecordingSecrets::new(secrets.iter().copied())))
+        .execute(
+            ResponsesCall {
+                api_key: api_key.map(str::to_owned),
+                api_base: Some(format!("{}/api/v1", upstream.uri())),
+                optional_params: json!({"max_output_tokens": 16})
+                    .as_object()
+                    .unwrap()
+                    .clone(),
+                ..call
+            },
+            &(),
+            None,
+        )
+        .await
+        .unwrap();
+    let ResponsesOutput::Complete(response) = output else {
+        panic!("expected a complete response");
+    };
+    assert_eq!(serde_json::to_value(response).unwrap(), response_body());
+    let request = only_request(&upstream).await;
+    assert_eq!(request.url.path(), "/api/v1/responses");
+    assert_eq!(request.header("authorization"), Some(expected));
+    assert_eq!(
+        request.json(),
+        json!({"max_output_tokens": 16, "model": "anthropic/test-model", "input": "hello"})
+    );
+}
+
+#[rstest]
+#[tokio::test]
+async fn the_secret_manager_supplies_the_base_and_key(call: ResponsesCall) {
+    let upstream = upstream([json_response(response_body())]).await;
+    let base = format!("{}/api/v1/", upstream.uri());
+    let secrets = Arc::new(RecordingSecrets::new([
+        ("OPENROUTER_API_KEY", "managed"),
+        ("OPENROUTER_API_BASE", base.as_str()),
+    ]));
+    responses_route(secrets.clone())
+        .execute(call, &(), None)
+        .await
+        .unwrap();
+    assert_eq!(
+        secrets.requested(),
+        ["OPENROUTER_API_KEY", "OR_API_KEY", "OPENROUTER_API_BASE"]
+    );
+    let request = only_request(&upstream).await;
+    assert_eq!(request.url.path(), "/api/v1/responses");
+    assert_eq!(request.header("authorization"), Some("Bearer managed"));
+}
+
+#[rstest]
+#[tokio::test]
+async fn a_missing_key_fails_before_transport(call: ResponsesCall) {
+    let upstream = upstream([json_response(response_body())]).await;
+    let result = responses_route(no_secrets())
+        .execute(
+            ResponsesCall {
+                api_base: Some(upstream.uri()),
+                ..call
+            },
+            &(),
+            None,
+        )
+        .await;
+    assert!(matches!(
+        result,
+        Err(Error::Auth(litellm_auth::Error::MissingApiKey {
+            provider: "OpenRouter",
+            ..
+        }))
+    ));
+    assert!(received(&upstream).await.is_empty());
+}
+
+#[rstest]
+#[tokio::test]
+async fn streaming_relays_every_openrouter_event_untouched(call: ResponsesCall) {
+    let sse = "data: {\"type\":\"response.created\",\"response\":{\"id\":\"resp_1\"}}\n\ndata: {\"type\":\"response.output_text.delta\",\"delta\":\"hi\"}\n\ndata: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp_1\",\"usage\":{\"cost\":0.0002}}}\n\n";
+    let upstream =
+        upstream([ResponseTemplate::new(200).set_body_raw(sse, "text/event-stream")]).await;
+    let output = responses_route(no_secrets())
+        .execute(
+            ResponsesCall {
+                api_key: Some("key".into()),
+                api_base: Some(upstream.uri()),
+                optional_params: json!({"stream": true}).as_object().unwrap().clone(),
+                ..call
+            },
+            &(),
+            None,
+        )
+        .await
+        .unwrap();
+    let ResponsesOutput::Stream { chunks, .. } = output else {
+        panic!("expected SSE");
+    };
+    assert_eq!(
+        chunks.try_collect::<Vec<_>>().await.unwrap().concat(),
+        sse.as_bytes()
+    );
+    let request = only_request(&upstream).await;
+    assert_eq!(request.json()["stream"], true);
+    assert_eq!(request.json()["model"], "anthropic/test-model");
+}

litellm-rust/crates/llms/AGENTS.md

@@ -58,6 +58,7 @@
 
 - `AnthropicConfig`, `AmazonConverseConfig` and the non-OCR base traits are partial. Preserve their acceptance gates, passthrough and host fallback contracts
 - `OpenAiResponsesApiConfig` implements WebSocket transformations and direct HTTP Responses, without Python's model-specific param rewriting or Responses-to-Chat emulation
+- OpenAI-compatible Responses hosts (`openrouter`) reuse the OpenAI request and response transforms as free functions and own only their credentials and base URL
 - Chat `supported_openai_param_mappings` lists OpenAI/provider name pairs, unlike Python's name-only list. Audio `map_transcription_params` is a Rust filtering helper
 - Auth resolution is split between configs and route preparation in `inference-<format>`
 

litellm-rust/crates/llms/src/openai/responses/transformation.rs

@@ -165,34 +165,46 @@ impl BaseResponsesApiConfig for OpenAiResponsesApiConfig {
         input: Value,
         params: Map<String, Value>,
     ) -> Result<Value, Error> {
-        if !input.is_string() && !input.is_array() {
-            return Err(Error::InvalidRequest(
-                "responses input must be a string or an array".into(),
-            ));
-        }
-        if params
-            .get("stream")
-            .is_some_and(|stream| !stream.is_boolean())
-        {
-            return Err(Error::InvalidRequest("stream must be a boolean".into()));
-        }
-        Ok(Value::Object(
-            params
-                .into_iter()
-                .chain([
-                    ("model".into(), Value::String(model.into())),
-                    ("input".into(), input),
-                ])
-                .collect(),
-        ))
+        responses_request(model, input, params)
     }
 
     fn transform_response_api_response(&self, body: Value) -> Result<ResponsesApiResponse, Error> {
-        serde_json::from_value(body)
-            .map_err(|error| Error::InvalidResponse(error.to_string().into()))
+        responses_response(body)
     }
 }
 
+/// The OpenAI Responses request body, shared by every OpenAI-compatible host.
+pub fn responses_request(
+    model: &str,
+    input: Value,
+    params: Map<String, Value>,
+) -> Result<Value, Error> {
+    if !input.is_string() && !input.is_array() {
+        return Err(Error::InvalidRequest(
+            "responses input must be a string or an array".into(),
+        ));
+    }
+    if params
+        .get("stream")
+        .is_some_and(|stream| !stream.is_boolean())
+    {
+        return Err(Error::InvalidRequest("stream must be a boolean".into()));
+    }
+    Ok(Value::Object(
+        params
+            .into_iter()
+            .chain([
+                ("model".into(), Value::String(model.into())),
+                ("input".into(), input),
+            ])
+            .collect(),
+    ))
+}
+
+pub fn responses_response(body: Value) -> Result<ResponsesApiResponse, Error> {
+    serde_json::from_value(body).map_err(|error| Error::InvalidResponse(error.to_string().into()))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

litellm-rust/crates/llms/src/openrouter/mod.rs

@@ -1 +1,2 @@
 pub mod messages;
+pub mod responses;

litellm-rust/crates/llms/src/openrouter/responses/AGENTS.md

@@ -0,0 +1,10 @@
+# rules
+
+- Send the OpenAI Responses payload to `/api/v1/responses` and relay the OpenAI SSE events
+- Authenticate with a bearer token from `OPENROUTER_API_KEY`, falling back to `OR_API_KEY`
+- Only `OPENROUTER_API_BASE` overrides the default base, never the OpenAI base variables
+- No native WebSocket mode
+
+# references
+
+- https://openrouter.ai/docs/api_reference/responses/overview

litellm-rust/crates/llms/src/openrouter/responses/mod.rs

@@ -0,0 +1 @@
+pub mod transformation;

litellm-rust/crates/llms/src/openrouter/responses/transformation.rs

@@ -0,0 +1,174 @@
+use litellm_auth::{CredentialPlacement, SecretValue};
+use litellm_core_utils::settings::resolve_non_empty;
+use litellm_llms_types::formats::responses::ResponsesApiResponse;
+use serde_json::{Map, Value};
+
+use crate::{
+    Error,
+    base_llm::{
+        auth::{AuthScheme, ValidatedEnvironment},
+        responses::transformation::BaseResponsesApiConfig,
+    },
+    openai::responses::transformation::{responses_request, responses_response},
+};
+
+const API_KEY_ENVS: [&str; 2] = ["OPENROUTER_API_KEY", "OR_API_KEY"];
+const API_BASE_ENV: &str = "OPENROUTER_API_BASE";
+const DEFAULT_BASE: &str = "https://openrouter.ai/api/v1";
+const RESPONSES_PATH: &str = "/responses";
+
+pub struct OpenRouterResponsesApiConfig;
+pub const OPENROUTER_RESPONSES_CONFIG: OpenRouterResponsesApiConfig = OpenRouterResponsesApiConfig;
+
+impl BaseResponsesApiConfig for OpenRouterResponsesApiConfig {
+    fn secret_names(
+        &self,
+        api_key: Option<&str>,
+        api_base: Option<&str>,
+    ) -> &'static [&'static str] {
+        match (
+            api_key.is_some_and(|key| !key.trim().is_empty()),
+            api_base.is_some_and(|base| !base.trim().is_empty()),
+        ) {
+            (true, true) => &[],
+            (true, false) => &[API_BASE_ENV],
+            (false, true) => &API_KEY_ENVS,
+            (false, false) => &["OPENROUTER_API_KEY", "OR_API_KEY", API_BASE_ENV],
+        }
+    }
+
+    fn validate_environment(
+        &self,
+        headers: Vec<(String, String)>,
+        api_key: Option<&str>,
+        lookup: &dyn Fn(&str) -> Option<String>,
+    ) -> Result<ValidatedEnvironment, Error> {
+        let key = resolve_non_empty(api_key, lookup, &API_KEY_ENVS).ok_or(
+            litellm_auth::Error::MissingApiKey {
+                provider: "OpenRouter",
+                environment_variable: API_KEY_ENVS[0],
+            },
+        )?;
+        Ok(ValidatedEnvironment {
+            headers: litellm_http::request::with_default_headers(
+                headers,
+                &[("content-type", "application/json")],
+            ),
+            auth: AuthScheme::Credential {
+                placement: CredentialPlacement::Bearer,
+                secret: SecretValue::new(key),
+            },
+        })
+    }
+
+    fn get_complete_url(
+        &self,
+        api_base: Option<&str>,
+        lookup: &dyn Fn(&str) -> Option<String>,
+    ) -> String {
+        let base = resolve_non_empty(api_base, lookup, &[API_BASE_ENV])
+            .unwrap_or_else(|| DEFAULT_BASE.into());
+        format!("{}{RESPONSES_PATH}", base.trim_end_matches('/'))
+    }
+
+    fn transform_responses_api_request(
+        &self,
+        model: &str,
+        input: Value,
+        params: Map<String, Value>,
+    ) -> Result<Value, Error> {
+        responses_request(model, input, params)
+    }
+
+    fn transform_response_api_response(&self, body: Value) -> Result<ResponsesApiResponse, Error> {
+        responses_response(body)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use rstest::rstest;
+
+    use super::*;
+
+    fn env(values: &'static [(&'static str, &'static str)]) -> impl Fn(&str) -> Option<String> {
+        move |name| {
+            values
+                .iter()
+                .find(|(key, _)| *key == name)
+                .map(|(_, value)| (*value).to_owned())
+        }
+    }
+
+    #[rstest]
+    #[case::default(None, &[], "https://openrouter.ai/api/v1/responses")]
+    #[case::explicit(Some("https://proxy.test/api/v1"), &[], "https://proxy.test/api/v1/responses")]
+    #[case::trailing_slash(Some("https://proxy.test/api/v1/"), &[], "https://proxy.test/api/v1/responses")]
+    #[case::blank_falls_to_secret(Some(" "), &[("OPENROUTER_API_BASE", "https://secret.test/v1")], "https://secret.test/v1/responses")]
+    #[case::openai_base_is_ignored(None, &[("OPENAI_BASE_URL", "https://openai.test/v1")], "https://openrouter.ai/api/v1/responses")]
+    fn url_is_the_base_plus_responses(
+        #[case] api_base: Option<&str>,
+        #[case] secrets: &'static [(&'static str, &'static str)],
+        #[case] expected: &str,
+    ) {
+        assert_eq!(
+            OPENROUTER_RESPONSES_CONFIG.get_complete_url(api_base, &env(secrets)),
+            expected
+        );
+    }
+
+    #[rstest]
+    #[case::explicit(Some("explicit"), &[("OPENROUTER_API_KEY", "managed")], "explicit")]
+    #[case::managed(None, &[("OPENROUTER_API_KEY", "managed"), ("OR_API_KEY", "legacy")], "managed")]
+    #[case::legacy_name(None, &[("OR_API_KEY", "legacy")], "legacy")]
+    #[case::blank_explicit(Some(" "), &[("OR_API_KEY", "legacy")], "legacy")]
+    fn bearer_comes_from_the_call_then_either_secret_name(
+        #[case] api_key: Option<&str>,
+        #[case] secrets: &'static [(&'static str, &'static str)],
+        #[case] expected: &str,
+    ) {
+        let environment = OPENROUTER_RESPONSES_CONFIG
+            .validate_environment(vec![], api_key, &env(secrets))
+            .unwrap();
+        let AuthScheme::Credential { placement, secret } = environment.auth else {
+            panic!("expected a credential");
+        };
+        assert_eq!(placement, CredentialPlacement::Bearer);
+        assert_eq!(secret.expose(), expected);
+        assert_eq!(
+            environment.headers,
+            vec![("content-type".to_owned(), "application/json".to_owned())]
+        );
+    }
+
+    #[rstest]
+    #[case::nothing(&[])]
+    #[case::openai_key_only(&[("OPENAI_API_KEY", "openai")])]
+    fn a_missing_key_names_the_primary_variable(
+        #[case] secrets: &'static [(&'static str, &'static str)],
+    ) {
+        assert!(matches!(
+            OPENROUTER_RESPONSES_CONFIG.validate_environment(vec![], None, &env(secrets)),
+            Err(Error::Auth(litellm_auth::Error::MissingApiKey {
+                provider: "OpenRouter",
+                environment_variable: "OPENROUTER_API_KEY",
+            }))
+        ));
+    }
+
+    #[rstest]
+    #[case::both_given(Some("key"), Some("base"), &[])]
+    #[case::key_given(Some("key"), None, &["OPENROUTER_API_BASE"])]
+    #[case::base_given(None, Some("base"), &["OPENROUTER_API_KEY", "OR_API_KEY"])]
+    #[case::neither(None, None, &["OPENROUTER_API_KEY", "OR_API_KEY", "OPENROUTER_API_BASE"])]
+    fn only_missing_settings_are_looked_up(
+        #[case] api_key: Option<&str>,
+        #[case] api_base: Option<&str>,
+        #[case] expected: &[&str],
+    ) {
+        assert_eq!(
+            OPENROUTER_RESPONSES_CONFIG.secret_names(api_key, api_base),
+            expected
+        );
+    }
+}

litellm/rust_bridge/responses/route_host.py

@@ -12,8 +12,9 @@ from litellm.types.llms.openai import ResponsesAPIOptionalRequestParams, Respons
 PARAMETERS: Final = tuple(ResponsesAPIOptionalRequestParams.__annotations__)
 
 
-def connection_defaults(_provider: str) -> tuple[str | None, str | None]:
-    return litellm.api_key or litellm.openai_key, litellm.api_base
+def connection_defaults(provider: str) -> tuple[str | None, str | None]:
+    provider_key: Final = litellm.openai_key if provider == "openai" else None
+    return litellm.api_key or provider_key, litellm.api_base
 
 
 def response(value: Mapping[str, object]) -> ResponsesAPIResponse:

tests/unit/rust_bridge/responses/test_route_host.py

@@ -59,6 +59,16 @@ def test_connection_defaults_preserve_openai_precedence(
     assert connection_defaults("openai") == (expected, litellm.api_base)
 
 
+@pytest.mark.parametrize(("global_key", "expected"), (("global", "global"), (None, None)))
+def test_connection_defaults_keep_the_openai_key_away_from_openrouter(
+    monkeypatch: pytest.MonkeyPatch, global_key: str | None, expected: str | None
+) -> None:
+    monkeypatch.setattr(litellm, "api_key", global_key)
+    monkeypatch.setattr(litellm, "openai_key", "openai-only")
+    monkeypatch.setattr(litellm, "api_base", None)
+    assert connection_defaults("openrouter") == (expected, None)
+
+
 class _UpstreamFailure(Exception):
     headers: Final = ()