feat(rust): encode LiteLLM response ids on native responses (#46572)

Native Responses now hands back the same managed ids as Python: the
resp_ id carries the provider and deployment, encrypted-content items get
encitem_ ids and wrapped content under affinity routing, and container ids
become cntr_ ids. Encoded encrypted-content items in the input are restored
before the provider request. The codec lives in inference-responses with
goldens taken from litellm/responses/utils.py

litellm-rust/Cargo.lock

@@ -4083,6 +4083,7 @@ dependencies = [
 name = "litellm-inference-responses"
 version = "0.1.0"
 dependencies = [
+ "base64 0.22.1",
  "bytes",
  "futures-util",
  "litellm-auth",

litellm-rust/crates/inference-responses/AGENTS.md

@@ -2,3 +2,4 @@
 - This crate owns Responses API call orchestration. Payloads belong in `litellm-llms-types`, transformations in `llms/src/base_llm/responses` and `llms/src/<provider>/responses`
 - The HTTP route returns `litellm_host::call::CallOutput`: a completed response, or a stream head and chunks, cached through `litellm_inference::caching::execute_streaming`
 - WebSocket sessions (`src/websocket.rs`) stay separate from the HTTP call driver because a connection can accept multiple requests while receiving events
+- `src/ids.rs` owns the LiteLLM-managed ids handed back to callers (`resp_`, `encitem_`, `litellm_enc:`, `cntr_`) and must stay fully compatible with `litellm/responses/utils.py`

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

@@ -6,6 +6,7 @@ license.workspace = true
 repository.workspace = true
 
 [dependencies]
+base64.workspace = true
 bytes.workspace = true
 futures-util.workspace = true
 litellm-auth = { workspace = true, features = ["aws", "azure", "gcp"] }

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

@@ -0,0 +1,499 @@
+//! LiteLLM-managed identifiers on Responses payloads, fully compatible with `litellm/responses/utils.py`
+//!
+//! LiteLLM rewrites some ids in a Responses API result before handing it back, so that a later
+//! request carrying those ids can be routed to the provider and deployment that produced them,
+//! and then restored to what the provider originally issued. The native and Python paths serve
+//! the same traffic, so an id minted by either one must decode on the other.
+//!
+//! Each managed id is a fixed prefix followed by standard, padded base64 of a `;`-separated
+//! plaintext:
+//!
+//! | Id | Applied to | Decoded plaintext |
+//! |---|---|---|
+//! | `resp_<b64>` | the response `id` | `litellm:custom_llm_provider:{provider};model_id:{model_id};response_id:{id}` |
+//! | `encitem_<b64>` | the `id` of an output item with `encrypted_content` | `litellm:model_id:{model_id};item_id:{id}` |
+//! | `litellm_enc:<b64>;{content}` | that item's `encrypted_content` | `<b64>` is `model_id:{model_id}`, and the original content follows the `;` unencoded |
+//! | `cntr_<b64>` | `container_id` on output items, `code_interpreter_call`, and message annotations | `litellm:custom_llm_provider:{provider};model_id:{model_id};container_id:{id}` |
+//!
+//! For example, OpenAI's `resp_0a1b2c3d4e5f` served without a deployment id becomes
+//! `resp_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOm9wZW5haTttb2RlbF9pZDpOb25lO3Jlc3BvbnNlX2lkOnJlc3BfMGExYjJjM2Q0ZTVm`,
+//! which decodes to `litellm:custom_llm_provider:openai;model_id:None;response_id:resp_0a1b2c3d4e5f`.
+//!
+//! How they fit together:
+//! - `resp_` lets a follow-up's `previous_response_id` find the provider and deployment again.
+//!   [`encode_response`] stamps it on every response, unless the id is already managed.
+//! - `encitem_` and `litellm_enc:` carry encrypted-content affinity: encrypted reasoning only
+//!   decrypts under the API key that produced it, so the router pins replays to that deployment.
+//!   They are stamped only when the router sets `encrypted_content_affinity_enabled` and a
+//!   deployment `model_id` is known (see [`IdScope`]). Items without an `id`, such as Codex's,
+//!   carry the deployment in the wrapped content alone.
+//! - `cntr_` lets container calls find the provider and deployment that own a container. A
+//!   container id that already names a provider is left as it is.
+//! - On the way in, [`restore_input`] turns `encitem_` ids and `litellm_enc:` content in the
+//!   request input back into the provider's own bytes before the request is sent. The routing
+//!   decision itself stays in Python's `EncryptedContentAffinityCheck`.
+//!
+//! Python's quirks are kept on purpose:
+//! - A missing provider or `model_id` is written as `None` in `resp_` ids (an f-string of
+//!   `None`), but as an empty string in `cntr_` ids. [`decode_container_id`] reads both as absent.
+//! - Decoding follows Python's non-strict `base64.b64decode`: characters outside the alphabet
+//!   are skipped, trailing bits are allowed, and padding stripped in transit is added back.
+//! - A `resp_` id counts as managed when it decodes to at least three `;`-separated parts.
+
+use base64::{
+    Engine, alphabet,
+    engine::{GeneralPurpose, general_purpose::PAD},
+};
+use litellm_llms_types::formats::responses::ResponsesApiResponse;
+use serde_json::{Map, Value};
+
+const RESPONSE_PREFIX: &str = "resp_";
+const ITEM_PREFIX: &str = "encitem_";
+const CONTAINER_PREFIX: &str = "cntr_";
+const WRAPPED_CONTENT_PREFIX: &str = "litellm_enc:";
+
+/// Python's non-strict `base64.b64decode`: characters outside the alphabet are skipped and
+/// non-zero trailing bits are accepted
+const LENIENT: GeneralPurpose = GeneralPurpose::new(
+    &alphabet::STANDARD,
+    PAD.with_decode_allow_trailing_bits(true),
+);
+
+/// Where a response came from, as encoded into the ids LiteLLM hands back
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct IdScope {
+    pub provider: Option<String>,
+    pub model_id: Option<String>,
+    pub encrypted_content_affinity: bool,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct DecodedContainerId {
+    pub provider: Option<String>,
+    pub model_id: Option<String>,
+    pub container_id: String,
+}
+
+/// Rewrites the response id, encrypted-content items and container ids the way the Python
+/// Responses path does before returning to the caller. An already managed id is left untouched
+pub fn encode_response(response: &mut ResponsesApiResponse, scope: &IdScope) {
+    if is_managed_response_id(&response.id) {
+        return;
+    }
+    response.id = response_id(scope, &response.id);
+    if let Some(model_id) = scope
+        .model_id
+        .as_deref()
+        .filter(|_| scope.encrypted_content_affinity)
+        .filter(|model_id| !model_id.is_empty())
+    {
+        response
+            .output
+            .iter_mut()
+            .filter_map(Value::as_object_mut)
+            .for_each(|item| encode_encrypted_item(item, model_id));
+    }
+    response
+        .output
+        .iter_mut()
+        .for_each(|item| encode_containers(item, scope));
+}
+
+/// Restores encrypted-content item ids and contents that LiteLLM encoded on an earlier response,
+/// so the provider receives what it originally issued
+pub fn restore_input(input: &mut Value) {
+    let Some(items) = input.as_array_mut() else {
+        return;
+    };
+    for item in items.iter_mut().filter_map(Value::as_object_mut) {
+        if let Some(Value::String(id)) = item.get_mut("id")
+            && let Some((_, original)) = decode_encrypted_item_id(id)
+        {
+            *id = original;
+        }
+        if let Some(Value::String(content)) = item.get_mut("encrypted_content")
+            && let Some(original) = unwrap_encrypted_content(content)
+        {
+            *content = original;
+        }
+    }
+}
+
+pub fn response_id(scope: &IdScope, id: &str) -> String {
+    let assembled = format!(
+        "litellm:custom_llm_provider:{};model_id:{};response_id:{id}",
+        python_str(scope.provider.as_deref()),
+        python_str(scope.model_id.as_deref()),
+    );
+    format!("{RESPONSE_PREFIX}{}", LENIENT.encode(assembled))
+}
+
+pub fn is_managed_response_id(id: &str) -> bool {
+    decode_text(&id.replace(RESPONSE_PREFIX, ""))
+        .is_some_and(|decoded| decoded.split(';').count() >= 3)
+}
+
+pub fn encrypted_item_id(model_id: &str, id: &str) -> String {
+    format!(
+        "{ITEM_PREFIX}{}",
+        LENIENT.encode(format!("litellm:model_id:{model_id};item_id:{id}"))
+    )
+}
+
+pub fn decode_encrypted_item_id(id: &str) -> Option<(String, String)> {
+    let decoded = decode_text(&padded(id.strip_prefix(ITEM_PREFIX)?))?;
+    let (model_id, item_id) = decoded.split_once(';')?;
+    Some((
+        model_id.replace("litellm:model_id:", ""),
+        item_id.replace("item_id:", ""),
+    ))
+}
+
+pub fn wrap_encrypted_content(content: &str, model_id: &str) -> String {
+    format!(
+        "{WRAPPED_CONTENT_PREFIX}{};{content}",
+        LENIENT.encode(format!("model_id:{model_id}"))
+    )
+}
+
+/// The original content of a wrapped `encrypted_content`, or `None` when it is not wrapped
+pub fn unwrap_encrypted_content(content: &str) -> Option<String> {
+    if !content.starts_with(WRAPPED_CONTENT_PREFIX) {
+        return None;
+    }
+    let (metadata, original) = content.split_once(';')?;
+    decode_text(&padded(&metadata.replace(WRAPPED_CONTENT_PREFIX, "")))?;
+    Some(original.to_owned())
+}
+
+pub fn container_id(scope: &IdScope, id: &str) -> String {
+    let assembled = format!(
+        "litellm:custom_llm_provider:{};model_id:{};container_id:{id}",
+        scope.provider.as_deref().unwrap_or_default(),
+        scope.model_id.as_deref().unwrap_or_default(),
+    );
+    format!("{CONTAINER_PREFIX}{}", LENIENT.encode(assembled))
+}
+
+pub fn decode_container_id(id: &str) -> DecodedContainerId {
+    let unmanaged = || DecodedContainerId {
+        provider: None,
+        model_id: None,
+        container_id: id.to_owned(),
+    };
+    if !id.starts_with(CONTAINER_PREFIX) {
+        return unmanaged();
+    }
+    let Some(decoded) = decode_text(&id.replace(CONTAINER_PREFIX, "")) else {
+        return unmanaged();
+    };
+    let parsed = decoded
+        .strip_prefix("litellm:custom_llm_provider:")
+        .and_then(|rest| rest.split_once(';'))
+        .and_then(|(provider, rest)| {
+            let (model_id, rest) = rest.strip_prefix("model_id:")?.split_once(';')?;
+            let container_id = rest.strip_prefix("container_id:")?;
+            (!container_id.is_empty() && !container_id.contains('\n')).then_some((
+                provider,
+                model_id,
+                container_id,
+            ))
+        });
+    let Some((provider, model_id, container_id)) = parsed else {
+        return unmanaged();
+    };
+    let present = |value: &str| (!matches!(value, "" | "None")).then(|| value.to_owned());
+    DecodedContainerId {
+        provider: present(provider),
+        model_id: present(model_id),
+        container_id: container_id.to_owned(),
+    }
+}
+
+fn encode_encrypted_item(item: &mut Map<String, Value>, model_id: &str) {
+    let Some(Value::String(content)) = item.get_mut("encrypted_content") else {
+        return;
+    };
+    if content.is_empty() {
+        return;
+    }
+    *content = wrap_encrypted_content(content, model_id);
+    if let Some(Value::String(id)) = item.get_mut("id")
+        && !id.is_empty()
+    {
+        *id = encrypted_item_id(model_id, id);
+    }
+}
+
+fn encode_containers(item: &mut Value, scope: &IdScope) {
+    let Some(item) = item.as_object_mut() else {
+        return;
+    };
+    encode_container_field(item, scope);
+    if let Some(nested) = item
+        .get_mut("code_interpreter_call")
+        .and_then(Value::as_object_mut)
+    {
+        encode_container_field(nested, scope);
+    }
+    if item.get("type").and_then(Value::as_str) != Some("message") {
+        return;
+    }
+    let Some(content) = item.get_mut("content").and_then(Value::as_array_mut) else {
+        return;
+    };
+    content
+        .iter_mut()
+        .filter_map(|part| part.get_mut("annotations").and_then(Value::as_array_mut))
+        .flatten()
+        .for_each(|annotation| encode_containers(annotation, scope));
+}
+
+fn encode_container_field(item: &mut Map<String, Value>, scope: &IdScope) {
+    if let Some(Value::String(id)) = item.get_mut("container_id")
+        && decode_container_id(id).provider.is_none()
+    {
+        *id = container_id(scope, id);
+    }
+}
+
+fn python_str(value: Option<&str>) -> &str {
+    value.unwrap_or("None")
+}
+
+fn padded(value: &str) -> String {
+    let missing = value.len() % 4;
+    let padding = if missing == 0 { 0 } else { 4 - missing };
+    format!("{value}{}", "=".repeat(padding))
+}
+
+fn decode_text(value: &str) -> Option<String> {
+    let alphabet: String = value
+        .chars()
+        .filter(|character| {
+            character.is_ascii_alphanumeric() || matches!(character, '+' | '/' | '=')
+        })
+        .collect();
+    String::from_utf8(LENIENT.decode(alphabet).ok()?).ok()
+}
+
+#[cfg(test)]
+mod tests {
+    use rstest::rstest;
+    use serde_json::json;
+
+    use super::*;
+
+    fn scope(provider: Option<&str>, model_id: Option<&str>, affinity: bool) -> IdScope {
+        IdScope {
+            provider: provider.map(str::to_owned),
+            model_id: model_id.map(str::to_owned),
+            encrypted_content_affinity: affinity,
+        }
+    }
+
+    fn response(id: &str, output: Value) -> ResponsesApiResponse {
+        serde_json::from_value(json!({"id": id, "model": "gpt-6.1-sol", "output": output})).unwrap()
+    }
+
+    #[rstest]
+    #[case::openai_without_model_id(
+        Some("openai"),
+        None,
+        "resp_0a1b2c3d4e5f",
+        "resp_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOm9wZW5haTttb2RlbF9pZDpOb25lO3Jlc3BvbnNlX2lkOnJlc3BfMGExYjJjM2Q0ZTVm"
+    )]
+    #[case::openrouter_with_model_id(
+        Some("openrouter"),
+        Some("deploy-1"),
+        "gen-123",
+        "resp_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOm9wZW5yb3V0ZXI7bW9kZWxfaWQ6ZGVwbG95LTE7cmVzcG9uc2VfaWQ6Z2VuLTEyMw=="
+    )]
+    fn response_ids_match_python(
+        #[case] provider: Option<&str>,
+        #[case] model_id: Option<&str>,
+        #[case] id: &str,
+        #[case] expected: &str,
+    ) {
+        assert_eq!(response_id(&scope(provider, model_id, false), id), expected);
+    }
+
+    #[rstest]
+    #[case::raw_short_id("resp_0a1b2c3d4e5f", false)]
+    #[case::raw_long_id("resp_68a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3", false)]
+    #[case::two_segments("resp_YTti", false)]
+    #[case::three_segments("resp_YTtiO2M=", true)]
+    #[case::managed(
+        "resp_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOm9wZW5haTttb2RlbF9pZDpOb25lO3Jlc3BvbnNlX2lkOng=",
+        true
+    )]
+    fn managed_response_ids_match_python(#[case] id: &str, #[case] expected: bool) {
+        assert_eq!(is_managed_response_id(id), expected);
+    }
+
+    #[test]
+    fn encrypted_items_match_python() {
+        assert_eq!(
+            encrypted_item_id("deploy-1", "rs_0a1b"),
+            "encitem_bGl0ZWxsbTptb2RlbF9pZDpkZXBsb3ktMTtpdGVtX2lkOnJzXzBhMWI="
+        );
+        assert_eq!(
+            wrap_encrypted_content("gAAAA", "deploy-1"),
+            "litellm_enc:bW9kZWxfaWQ6ZGVwbG95LTE=;gAAAA"
+        );
+    }
+
+    #[rstest]
+    #[case::padded("encitem_bGl0ZWxsbTptb2RlbF9pZDpkZXBsb3ktMTtpdGVtX2lkOnJzXzBhMWI=", Some(("deploy-1", "rs_0a1b")))]
+    #[case::padding_stripped_in_transit("encitem_bGl0ZWxsbTptb2RlbF9pZDptO2l0ZW1faWQ6cnNfMQ", Some(("m", "rs_1")))]
+    #[case::not_base64("encitem_notbase64!", None)]
+    #[case::unmanaged("rs_0a1b", None)]
+    fn encrypted_item_ids_decode_like_python(
+        #[case] id: &str,
+        #[case] expected: Option<(&str, &str)>,
+    ) {
+        assert_eq!(
+            decode_encrypted_item_id(id),
+            expected.map(|(model_id, item_id)| (model_id.to_owned(), item_id.to_owned()))
+        );
+    }
+
+    #[rstest]
+    #[case::unpadded_metadata("litellm_enc:bW9kZWxfaWQ6bQ;gAAAA", Some("gAAAA"))]
+    #[case::no_separator("litellm_enc:nosemicolon", None)]
+    #[case::unwrapped("gAAAA", None)]
+    fn encrypted_content_unwraps_like_python(
+        #[case] content: &str,
+        #[case] expected: Option<&str>,
+    ) {
+        assert_eq!(unwrap_encrypted_content(content).as_deref(), expected);
+    }
+
+    #[rstest]
+    #[case::with_model_id(
+        Some("deploy-1"),
+        "cntr_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOm9wZW5haTttb2RlbF9pZDpkZXBsb3ktMTtjb250YWluZXJfaWQ6Y250cl9hYmM="
+    )]
+    #[case::without_model_id(
+        None,
+        "cntr_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOm9wZW5haTttb2RlbF9pZDo7Y29udGFpbmVyX2lkOmNudHJfYWJj"
+    )]
+    fn container_ids_match_python(#[case] model_id: Option<&str>, #[case] expected: &str) {
+        assert_eq!(
+            container_id(&scope(Some("openai"), model_id, false), "cntr_abc"),
+            expected
+        );
+    }
+
+    #[rstest]
+    #[case::raw("cntr_abc", None, None, "cntr_abc")]
+    #[case::managed(
+        "cntr_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOm9wZW5haTttb2RlbF9pZDptO2NvbnRhaW5lcl9pZDpjbnRyXzE=",
+        Some("openai"),
+        Some("m"),
+        "cntr_1"
+    )]
+    #[case::empty_segments(
+        "cntr_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOjttb2RlbF9pZDo7Y29udGFpbmVyX2lkOmNudHJfMQ==",
+        None,
+        None,
+        "cntr_1"
+    )]
+    #[case::python_none_provider(
+        "cntr_bGl0ZWxsbTpjdXN0b21fbGxtX3Byb3ZpZGVyOk5vbmU7bW9kZWxfaWQ6O2NvbnRhaW5lcl9pZDp4",
+        None,
+        None,
+        "x"
+    )]
+    fn container_ids_decode_like_python(
+        #[case] id: &str,
+        #[case] provider: Option<&str>,
+        #[case] model_id: Option<&str>,
+        #[case] container_id: &str,
+    ) {
+        assert_eq!(
+            decode_container_id(id),
+            DecodedContainerId {
+                provider: provider.map(str::to_owned),
+                model_id: model_id.map(str::to_owned),
+                container_id: container_id.to_owned(),
+            }
+        );
+    }
+
+    #[test]
+    fn encodes_response_items_under_affinity() {
+        let mut encoded = response(
+            "resp_1",
+            json!([
+                {"type": "reasoning", "id": "rs_0a1b", "encrypted_content": "gAAAA", "summary": []},
+                {"type": "reasoning", "encrypted_content": "gBBBB", "summary": []},
+                {"type": "code_interpreter_call", "id": "ci_1", "container_id": "cntr_abc"},
+                {"type": "message", "id": "msg_1", "content": [{"type": "output_text", "text": "", "annotations": [
+                    {"type": "container_file_citation", "container_id": "cntr_abc"}
+                ]}]}
+            ]),
+        );
+        let scope = scope(Some("openai"), Some("deploy-1"), true);
+        encode_response(&mut encoded, &scope);
+        let container = container_id(&scope, "cntr_abc");
+        assert_eq!(encoded.id, response_id(&scope, "resp_1"));
+        assert_eq!(
+            Value::Array(encoded.output),
+            json!([
+                {
+                    "type": "reasoning",
+                    "id": "encitem_bGl0ZWxsbTptb2RlbF9pZDpkZXBsb3ktMTtpdGVtX2lkOnJzXzBhMWI=",
+                    "encrypted_content": "litellm_enc:bW9kZWxfaWQ6ZGVwbG95LTE=;gAAAA",
+                    "summary": []
+                },
+                {"type": "reasoning", "encrypted_content": "litellm_enc:bW9kZWxfaWQ6ZGVwbG95LTE=;gBBBB", "summary": []},
+                {"type": "code_interpreter_call", "id": "ci_1", "container_id": container},
+                {"type": "message", "id": "msg_1", "content": [{"type": "output_text", "text": "", "annotations": [
+                    {"type": "container_file_citation", "container_id": container}
+                ]}]}
+            ])
+        );
+    }
+
+    #[rstest]
+    #[case::affinity_disabled(scope(Some("openai"), Some("deploy-1"), false))]
+    #[case::no_model_id(scope(Some("openai"), None, true))]
+    fn leaves_encrypted_items_without_affinity(#[case] scope: IdScope) {
+        let output = json!([{"type": "reasoning", "id": "rs_1", "encrypted_content": "gAAAA", "summary": []}]);
+        let mut encoded = response("resp_1", output.clone());
+        encode_response(&mut encoded, &scope);
+        assert_eq!(Value::Array(encoded.output), output);
+    }
+
+    #[test]
+    fn leaves_managed_responses_untouched() {
+        let scope = scope(Some("openai"), Some("deploy-1"), true);
+        let id = response_id(&scope, "resp_1");
+        let output = json!([{"type": "code_interpreter_call", "container_id": "cntr_abc"}]);
+        let mut encoded = response(&id, output.clone());
+        encode_response(&mut encoded, &scope);
+        assert_eq!((encoded.id, Value::Array(encoded.output)), (id, output));
+    }
+
+    #[test]
+    fn restores_encrypted_items_in_input() {
+        let mut input = json!([
+            {
+                "type": "reasoning",
+                "id": "encitem_bGl0ZWxsbTptb2RlbF9pZDpkZXBsb3ktMTtpdGVtX2lkOnJzXzBhMWI=",
+                "encrypted_content": "litellm_enc:bW9kZWxfaWQ6ZGVwbG95LTE=;gAAAA",
+                "summary": []
+            },
+            {"role": "user", "content": "hi"}
+        ]);
+        restore_input(&mut input);
+        assert_eq!(
+            input,
+            json!([
+                {"type": "reasoning", "id": "rs_0a1b", "encrypted_content": "gAAAA", "summary": []},
+                {"role": "user", "content": "hi"}
+            ])
+        );
+    }
+}

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

@@ -1,6 +1,7 @@
 use litellm_host::observation::ObservationSender;
 pub use litellm_inference::RouteError as Error;
 
+pub mod ids;
 pub mod route;
 pub mod types;
 pub mod websocket;

litellm-rust/crates/python-bridge/src/routes/responses/host.rs

@@ -1,22 +1,41 @@
 use std::convert::Infallible;
 
 use crate::routes::inference::InferenceHost;
-use litellm_host_python::{InvokeError, PythonBinding, PythonHostCalls, PythonOwned};
-use litellm_inference_responses::{Error, route::Responses, types::ResponsesCall};
+use litellm_core_utils::get_llm_provider_logic::get_custom_llm_provider;
+use litellm_host_python::{InvokeError, PythonBinding, PythonHostCalls, PythonOwned, from_py};
+use litellm_inference_responses::{
+    Error,
+    ids::{self, IdScope},
+    route::Responses,
+    types::ResponsesCall,
+};
 use pyo3::{
     gc::{PyTraverseError, PyVisit},
     prelude::*,
     types::PyDict,
 };
 
-pub(super) struct ResponsesPythonHost(pub InferenceHost);
+pub(super) struct ResponsesPythonHost {
+    host: InferenceHost,
+    ids: IdScope,
+}
+
+impl ResponsesPythonHost {
+    pub fn new(host: InferenceHost) -> Self {
+        Self {
+            host,
+            ids: IdScope::default(),
+        }
+    }
+}
 
 pub(super) fn project(
     host: &mut InferenceHost,
     py: Python<'_>,
     arguments: &Bound<'_, PyDict>,
 ) -> PyResult<ResponsesCall> {
-    let call = host.project(py, arguments, "input")?;
+    let mut call = host.project(py, arguments, "input")?;
+    ids::restore_input(&mut call.input);
     let optional_params = call
         .params
         .into_iter()
@@ -50,6 +69,39 @@ pub(super) fn project(
     })
 }
 
+/// The provider and deployment Python encodes into the ids it returns: the resolved provider and
+/// `litellm_metadata.model_info.id`
+fn id_scope(
+    host: &InferenceHost,
+    py: Python<'_>,
+    arguments: &Bound<'_, PyDict>,
+    call: &ResponsesCall,
+) -> PyResult<IdScope> {
+    let metadata = host.argument(py, arguments, "litellm_metadata")?;
+    let encrypted_content_affinity = match &metadata {
+        Some(metadata) => metadata
+            .call_method1("get", ("encrypted_content_affinity_enabled",))?
+            .is_truthy()?,
+        None => false,
+    };
+    let metadata = metadata
+        .map(|value| from_py::<serde_json::Value>(&value))
+        .transpose()?
+        .unwrap_or_default();
+    let model_id = match metadata.pointer("/model_info/id") {
+        None | Some(serde_json::Value::Null) => None,
+        Some(serde_json::Value::String(id)) => Some(id.clone()),
+        Some(other) => Some(other.to_string()),
+    };
+    Ok(IdScope {
+        provider: get_custom_llm_provider(&call.model, call.custom_llm_provider.as_deref())
+            .map(|resolved| resolved.custom_llm_provider.to_owned())
+            .or_else(|| call.custom_llm_provider.clone()),
+        model_id,
+        encrypted_content_affinity,
+    })
+}
+
 impl PythonBinding for ResponsesPythonHost {
     type Protocol = Responses;
     type Failure = PyErr;
@@ -59,7 +111,8 @@ impl PythonBinding for ResponsesPythonHost {
         py: Python<'_>,
         arguments: &Bound<'_, PyDict>,
     ) -> Result<ResponsesCall, InvokeError<Error>> {
-        let call = project(&mut self.0, py, arguments).map_err(InvokeError::Python)?;
+        let call = project(&mut self.host, py, arguments).map_err(InvokeError::Python)?;
+        self.ids = id_scope(&self.host, py, arguments, &call).map_err(InvokeError::Python)?;
         if call
             .optional_params
             .get("stream")
@@ -77,7 +130,9 @@ impl PythonBinding for ResponsesPythonHost {
         py: Python<'_>,
         response: <Responses as litellm_host::protocol::Protocol>::Response,
     ) -> PyResult<Py<PyAny>> {
-        self.0.response(py, &response)
+        let mut response = response;
+        ids::encode_response(&mut response, &self.ids);
+        self.host.response(py, &response)
     }
 
     fn encode_stream_head(
@@ -103,7 +158,7 @@ impl PythonBinding for ResponsesPythonHost {
     }
 
     fn map_error(&self, py: Python<'_>, error: Error) -> PyResult<PyErr> {
-        self.0.error(py, error)
+        self.host.error(py, error)
     }
     fn host_error(error: &PyErr) -> Error {
         Error::InvalidRequest(error.to_string().into())
@@ -122,9 +177,9 @@ impl PythonHostCalls<Responses> for ResponsesPythonHost {
 
 impl PythonOwned for ResponsesPythonHost {
     fn close(&mut self, _: Python<'_>) {
-        self.0.close();
+        self.host.close();
     }
     fn traverse(&self, visit: &PyVisit<'_>) -> Result<(), PyTraverseError> {
-        self.0.traverse(visit)
+        self.host.traverse(visit)
     }
 }

litellm-rust/crates/python-bridge/src/routes/responses/mod.rs

@@ -62,7 +62,7 @@ fn run_responses(py: Python<'_>, call: NativeCall<'_>, asynchronous: bool) -> Py
         ));
     }
     let host = InferenceHost::new(call.view()?, ROUTE_HOST_MODULE);
-    run_inference::<ResponsesRoute, _>(py, call, asynchronous, ResponsesPythonHost(host))
+    run_inference::<ResponsesRoute, _>(py, call, asynchronous, ResponsesPythonHost::new(host))
 }
 
 #[pyfunction]

tests/rust-python-harness/strategies/e2e_parity/sdk/responses/test_native_parity.py

@@ -44,6 +44,16 @@ _COMPARED_LOG_FIELDS: Final = (
     "status",
 )
 
+TEXT_MESSAGE: Final[Mapping[str, JsonValue]] = MappingProxyType(
+    {
+        "id": "msg_0a1b2c3d4e5f",
+        "type": "message",
+        "status": "completed",
+        "role": "assistant",
+        "content": [{"type": "output_text", "annotations": [], "logprobs": [], "text": "Paris"}],
+    }
+)
+
 TEXT_RESPONSE: Final[Mapping[str, JsonValue]] = MappingProxyType(
     {
         "id": "resp_0a1b2c3d4e5f",
@@ -61,13 +71,7 @@ TEXT_RESPONSE: Final[Mapping[str, JsonValue]] = MappingProxyType(
                 "type": "reasoning",
                 "summary": [],
             },
-            {
-                "id": "msg_0a1b2c3d4e5f",
-                "type": "message",
-                "status": "completed",
-                "role": "assistant",
-                "content": [{"type": "output_text", "annotations": [], "logprobs": [], "text": "Paris"}],
-            },
+            dict(TEXT_MESSAGE),
         ],
         "parallel_tool_calls": True,
         "previous_response_id": None,
@@ -122,6 +126,36 @@ WEATHER_TOOL: Final[Mapping[str, JsonValue]] = MappingProxyType(
 )
 
 
+ENCRYPTED_REASONING_RESPONSE: Final[Mapping[str, JsonValue]] = MappingProxyType(
+    {
+        **TEXT_RESPONSE,
+        "output": [
+            {"id": "rs_0a1b2c3d4e5f", "type": "reasoning", "summary": [], "encrypted_content": "gAAAAB0a1b2c3d"},
+            {
+                "id": "ci_0a1b2c3d4e5f",
+                "type": "code_interpreter_call",
+                "status": "completed",
+                "code": "print(1)",
+                "container_id": "cntr_0a1b2c3d4e5f",
+                "outputs": [],
+            },
+            dict(TEXT_MESSAGE),
+        ],
+    }
+)
+
+AFFINITY_REPLAY_INPUT: Final[list[JsonValue]] = [
+    {
+        "type": "reasoning",
+        "id": ResponsesAPIRequestUtils._build_encrypted_item_id("deploy-1", "rs_0a1b2c3d4e5f"),  # pyright: ignore[reportPrivateUsage]  # the encoder Python applies on the way out
+        "summary": [],
+        "encrypted_content": ResponsesAPIRequestUtils.wrap_encrypted_content_with_model_id(
+            "gAAAAB0a1b2c3d", "deploy-1"
+        ),
+    },
+    {"role": "user", "content": "And Germany?"},
+]
+
 REASONING_REPLAY_INPUT: Final[list[JsonValue]] = [
     {"type": "reasoning", "id": "rs_0a1b2c3d4e5f", "summary": [], "status": None},
     {"role": "user", "content": "And Germany?"},
@@ -157,30 +191,28 @@ class Case:
             yield pytest.param(self, aspect, id=f"{self.name}-{aspect}", marks=marks)
 
 
-ID_ENCODING_GAP: Final = MappingProxyType(
-    {"response": "native responses return the provider's raw response id instead of LiteLLM's encoded resp_ id"}
+DEPLOYMENT_METADATA: Final = MappingProxyType(
+    {"model_info": {"id": "deploy-1"}, "encrypted_content_affinity_enabled": True}
 )
 
 
-def _gaps(**request_gaps: str) -> Mapping[str, str]:
-    return MappingProxyType({**ID_ENCODING_GAP, **request_gaps})
+def _gaps(**gaps: str) -> Mapping[str, str]:
+    return MappingProxyType(gaps)
 
 
 CASES: Final = (
-    Case("plain_text", {"input": "What is the capital of France?"}, gaps=_gaps()),
+    Case("plain_text", {"input": "What is the capital of France?"}),
     Case(
         "instructions_and_input_items",
         {
             "instructions": "Answer in one word",
             "input": [{"role": "user", "content": [{"type": "input_text", "text": "Capital of France?"}]}],
         },
-        gaps=_gaps(),
     ),
     Case(
         "function_tool",
         {"input": "Weather in Paris?", "tools": [dict(WEATHER_TOOL)], "tool_choice": "auto"},
         upstream=FUNCTION_CALL_RESPONSE,
-        gaps=_gaps(),
     ),
     Case(
         "encoded_previous_response_id",
@@ -190,7 +222,16 @@ CASES: Final = (
                 custom_llm_provider="openai", model_id=None, response_id="resp_6f5e4d3c2b1a"
             ),
         },
-        gaps=_gaps(),
+    ),
+    Case(
+        "deployment_scoped_ids",
+        {"input": "hi", "litellm_metadata": dict(DEPLOYMENT_METADATA)},
+        upstream=ENCRYPTED_REASONING_RESPONSE,
+    ),
+    Case(
+        "affinity_encoded_reasoning_replay",
+        {"input": AFFINITY_REPLAY_INPUT, "litellm_metadata": dict(DEPLOYMENT_METADATA)},
+        upstream=ENCRYPTED_REASONING_RESPONSE,
     ),
     Case(
         "warm_up_probe_below_minimum_max_output_tokens",
@@ -215,7 +256,6 @@ CASES: Final = (
             ],
             "tools": [{**WEATHER_TOOL, "cache_control": {"type": "ephemeral"}}],
         },
-        gaps=_gaps(),
     ),
     Case(
         "reasoning_replay_without_status",