diff --git a/backend/Cargo.lock b/backend/Cargo.lock
index a193c9815..df170437b 100644
--- a/backend/Cargo.lock
+++ b/backend/Cargo.lock
@@ -1121,6 +1121,7 @@ dependencies = [
  "async-trait",
  "axum",
  "base64",
+ "bytes",
  "chrono",
  "futures",
  "gateway-admin",
@@ -1142,6 +1143,7 @@ name = "gateway-core"
 version = "0.1.0"
 dependencies = [
  "async-trait",
+ "bytes",
  "chrono",
  "futures",
  "futures-timer",
diff --git a/backend/crates/gateway-api/Cargo.toml b/backend/crates/gateway-api/Cargo.toml
index c9fbdbe41..23e54e825 100644
--- a/backend/crates/gateway-api/Cargo.toml
+++ b/backend/crates/gateway-api/Cargo.toml
@@ -14,6 +14,7 @@ path = "tests/main.rs"
 [dependencies]
 axum = { version = "0.8.9", default-features = false, features = ["json", "query", "ws"] }
 base64 = "0.22.1"
+bytes = "1.11.1"
 chrono = { version = "0.4.45", features = ["serde"] }
 futures = "0.3.32"
 gateway-admin = { path = "../gateway-admin" }
diff --git a/backend/crates/gateway-api/src/openai/responses/http.rs b/backend/crates/gateway-api/src/openai/responses/http.rs
index 561c6903d..856b0ae44 100644
--- a/backend/crates/gateway-api/src/openai/responses/http.rs
+++ b/backend/crates/gateway-api/src/openai/responses/http.rs
@@ -19,7 +19,7 @@ use gateway_core::engine::execution::{ClientTransport, ExecutionSession, Started
 use gateway_core::error::{GatewayError, GatewayErrorKind};
 use gateway_core::event::{ProviderEvent, ProviderResponseHeader};
 use gateway_core::lifecycle::ConnectionGuard;
-use gateway_protocol::openai::sse::{DONE_SSE_FRAME, response_failed_sse_event};
+use gateway_protocol::openai::sse::{DONE_SSE_FRAME, response_failed_sse_event_with_id};
 
 use crate::ApiState;
 use crate::openai::{
@@ -468,13 +468,13 @@ impl ResponsesStreamState {
     fn new(
         session: Box<dyn ExecutionSession>,
         encoder: OpenAiResponsesEncoder,
-        initial_frames: Vec<String>,
+        initial_frames: Vec<Bytes>,
         connection_guard: Option<Box<dyn ConnectionGuard>>,
     ) -> Self {
         Self {
             session: Some(session),
             encoder,
-            pending: initial_frames.into_iter().map(Bytes::from).collect(),
+            pending: initial_frames.into_iter().collect(),
             output_finished: false,
             execution_terminal: false,
             _connection_guard: connection_guard,
@@ -526,7 +526,13 @@ impl ResponsesStreamState {
                     .session
                     .as_ref()
                     .is_some_and(|session| session.is_finalized());
-                self.finish_with_gateway_error(gateway_error_from_engine(&error));
+                if self.encoder.has_wire_failure() {
+                    self.pending
+                        .push_back(Bytes::from_static(DONE_SSE_FRAME.as_bytes()));
+                    self.output_finished = true;
+                } else {
+                    self.finish_with_gateway_error(gateway_error_from_engine(&error));
+                }
             }
         }
     }
@@ -537,7 +543,7 @@ impl ResponsesStreamState {
                 if self.encoder.is_completed() {
                     self.finish_completed(frames).await;
                 } else {
-                    self.pending.extend(frames.into_iter().map(Bytes::from));
+                    self.pending.extend(frames);
                 }
             }
             Err(error) => {
@@ -547,7 +553,7 @@ impl ResponsesStreamState {
         }
     }
 
-    async fn finish_completed(&mut self, frames: Vec<String>) {
+    async fn finish_completed(&mut self, frames: Vec<Bytes>) {
         let next = match self.session.as_mut() {
             Some(session) => session.next_event().await,
             None => {
@@ -565,7 +571,7 @@ impl ResponsesStreamState {
                     .as_ref()
                     .is_some_and(|session| session.is_finalized()) =>
             {
-                self.pending.extend(frames.into_iter().map(Bytes::from));
+                self.pending.extend(frames);
                 self.execution_terminal = true;
                 self.pending
                     .push_back(Bytes::from_static(DONE_SSE_FRAME.as_bytes()));
@@ -608,7 +614,8 @@ impl ResponsesStreamState {
     fn finish_with_gateway_error(&mut self, error: GatewayError) {
         let (_, default_type, default_code) = gateway_error_contract(error.kind());
         self.pending
-            .push_back(Bytes::from(response_failed_sse_event(
+            .push_back(Bytes::from(response_failed_sse_event_with_id(
+                self.encoder.response_id(),
                 error.client_error_type().unwrap_or(default_type),
                 error.client_error_code().unwrap_or(default_code),
                 error.client_message(),
@@ -621,7 +628,8 @@ impl ResponsesStreamState {
     fn finish_with_encode_error(&mut self, error: ResponseEncodeError) {
         let protocol = error.protocol_body().error;
         self.pending
-            .push_back(Bytes::from(response_failed_sse_event(
+            .push_back(Bytes::from(response_failed_sse_event_with_id(
+                self.encoder.response_id(),
                 protocol.kind,
                 protocol.code,
                 &protocol.message,
diff --git a/backend/crates/gateway-api/src/openai/responses/response.rs b/backend/crates/gateway-api/src/openai/responses/response.rs
index 83610b3a1..5454589be 100644
--- a/backend/crates/gateway-api/src/openai/responses/response.rs
+++ b/backend/crates/gateway-api/src/openai/responses/response.rs
@@ -2,6 +2,7 @@
 
 use std::collections::BTreeMap;
 
+use bytes::Bytes;
 use gateway_core::accounting::Usage;
 use gateway_core::event::{
     CompactionOutput, ContentItem, ContentKind, EventSequenceValidator, FinishReason, GatewayEvent,
@@ -21,14 +22,6 @@ enum ResponseRepresentation {
     OpenAiWire,
 }
 
-#[derive(Debug)]
-struct PendingWireEvent {
-    event_type: Option<String>,
-    data: Value,
-    sse_id: Option<String>,
-    sse_retry: Option<u64>,
-}
-
 /// Provider event 封套到 OpenAI Responses wire 的唯一表达边界。
 ///
 /// Provider 已提供 OpenAI wire 时只下发该 wire；否则由 [`ResponsesCollector`]
@@ -37,10 +30,9 @@ struct PendingWireEvent {
 pub struct OpenAiResponsesEncoder {
     canonical: ResponsesCollector,
     representation: ResponseRepresentation,
-    upstream_response_id: Option<String>,
-    gateway_response_id: Option<String>,
+    response_id: Option<String>,
     wire_terminal: Option<Value>,
-    pending_wire: Vec<PendingWireEvent>,
+    wire_failure: bool,
     canonical_completed: bool,
 }
 
@@ -51,10 +43,9 @@ impl OpenAiResponsesEncoder {
         Self {
             canonical: ResponsesCollector::new(created_at),
             representation: ResponseRepresentation::Undecided,
-            upstream_response_id: None,
-            gateway_response_id: None,
+            response_id: None,
             wire_terminal: None,
-            pending_wire: Vec::new(),
+            wire_failure: false,
             canonical_completed: false,
         }
     }
@@ -64,8 +55,29 @@ impl OpenAiResponsesEncoder {
     /// # Errors
     ///
     /// canonical 顺序无效、响应身份变化或表达模式混用时返回错误。
-    pub fn push_sse(&mut self, event: &ProviderEvent) -> Result<Vec<String>, ResponseEncodeError> {
-        self.push(event, WireEncoding::Sse)
+    pub fn push_sse(&mut self, event: &ProviderEvent) -> Result<Vec<Bytes>, ResponseEncodeError> {
+        let openai_wire = self.select_representation(event)?;
+        if self.representation == ResponseRepresentation::OpenAiWire {
+            let Some(wire) = openai_wire else {
+                return Ok(Vec::new());
+            };
+            self.observe_wire_terminal(wire);
+            if let Some(raw_sse_frame) = wire.raw_sse_frame() {
+                return Ok(vec![raw_sse_frame.clone()]);
+            }
+            return Ok(vec![Bytes::from(encode_sse_event_with_metadata(
+                wire.event_type().unwrap_or_default(),
+                &wire.data().to_string(),
+                wire.sse_id(),
+                wire.sse_retry(),
+            ))]);
+        }
+
+        Ok(self
+            .push_canonical(event)?
+            .into_iter()
+            .map(Bytes::from)
+            .collect())
     }
 
     /// 消费一个 Provider event，并返回 WebSocket JSON messages。
@@ -77,7 +89,28 @@ impl OpenAiResponsesEncoder {
         &mut self,
         event: &ProviderEvent,
     ) -> Result<Vec<String>, ResponseEncodeError> {
-        self.push(event, WireEncoding::WebSocket)
+        let openai_wire = self.select_representation(event)?;
+        if self.representation == ResponseRepresentation::OpenAiWire {
+            let Some(wire) = openai_wire else {
+                return Ok(Vec::new());
+            };
+            if !wire.has_json_data() {
+                return Ok(Vec::new());
+            }
+            self.observe_wire_terminal(wire);
+            return Ok(vec![wire.data().to_string()]);
+        }
+
+        self.push_canonical(event)?
+            .into_iter()
+            .map(|frame| {
+                frame
+                    .lines()
+                    .find_map(|line| line.strip_prefix("data: "))
+                    .map(ToOwned::to_owned)
+                    .ok_or(ResponseEncodeError::InvalidEventEncoding)
+            })
+            .collect()
     }
 
     /// 返回是否已经观察到 canonical 或 wire 终态。
@@ -87,10 +120,16 @@ impl OpenAiResponsesEncoder {
             || self.canonical.final_response.is_some()
     }
 
-    /// 返回 Core 冻结并已写入客户端事件的网关响应 ID。
+    /// 返回是否已把 Provider 原生失败 event 交付给客户端。
     #[must_use]
-    pub fn gateway_response_id(&self) -> Option<&str> {
-        self.gateway_response_id.as_deref()
+    pub const fn has_wire_failure(&self) -> bool {
+        self.wire_failure
+    }
+
+    /// 返回 Core 已观察到的客户端可见 Provider 原生响应 ID。
+    #[must_use]
+    pub fn response_id(&self) -> Option<&str> {
+        self.response_id.as_deref()
     }
 
     /// 校验完整响应并返回非流式 JSON。
@@ -110,11 +149,10 @@ impl OpenAiResponsesEncoder {
         }
     }
 
-    fn push(
+    fn select_representation<'event>(
         &mut self,
-        event: &ProviderEvent,
-        encoding: WireEncoding,
-    ) -> Result<Vec<String>, ResponseEncodeError> {
+        event: &'event ProviderEvent,
+    ) -> Result<Option<&'event gateway_core::event::ProtocolWireEvent>, ResponseEncodeError> {
         self.observe_identity(event)?;
         let openai_wire = event
             .wire_event()
@@ -130,70 +168,18 @@ impl OpenAiResponsesEncoder {
             self.representation = ResponseRepresentation::Canonical;
         }
 
-        if self.representation == ResponseRepresentation::OpenAiWire {
-            let Some(wire) = openai_wire else {
-                return Ok(Vec::new());
-            };
-            self.pending_wire.push(PendingWireEvent {
-                event_type: wire.event_type().map(ToOwned::to_owned),
-                data: wire.data().clone(),
-                sse_id: wire.sse_id().map(ToOwned::to_owned),
-                sse_retry: wire.sse_retry(),
-            });
-            if self.gateway_response_id.is_none() {
-                return Ok(Vec::new());
-            }
-            let pending = std::mem::take(&mut self.pending_wire);
-            return pending
-                .into_iter()
-                .map(|pending| {
-                    let PendingWireEvent {
-                        event_type,
-                        mut data,
-                        sse_id,
-                        sse_retry,
-                    } = pending;
-                    self.rewrite_wire_identity(&mut data);
-                    let effective_type = event_type
-                        .as_deref()
-                        .or_else(|| data.get("type").and_then(Value::as_str));
-                    if matches!(
-                        effective_type,
-                        Some("response.completed" | "response.incomplete")
-                    ) {
-                        self.wire_terminal = data.get("response").cloned();
-                    }
-                    Ok(match encoding {
-                        WireEncoding::Sse => encode_sse_event_with_metadata(
-                            event_type.as_deref().unwrap_or_default(),
-                            &data.to_string(),
-                            sse_id.as_deref(),
-                            sse_retry,
-                        ),
-                        WireEncoding::WebSocket => data.to_string(),
-                    })
-                })
-                .collect();
-        }
+        Ok(openai_wire)
+    }
 
+    fn push_canonical(
+        &mut self,
+        event: &ProviderEvent,
+    ) -> Result<Vec<String>, ResponseEncodeError> {
         let mut canonical_frames = Vec::new();
         for fact in event.canonical_facts() {
             canonical_frames.extend(self.canonical.push(fact)?);
         }
-
-        match encoding {
-            WireEncoding::Sse => Ok(canonical_frames),
-            WireEncoding::WebSocket => canonical_frames
-                .into_iter()
-                .map(|frame| {
-                    frame
-                        .lines()
-                        .find_map(|line| line.strip_prefix("data: "))
-                        .map(ToOwned::to_owned)
-                        .ok_or(ResponseEncodeError::InvalidEventEncoding)
-                })
-                .collect(),
-        }
+        Ok(canonical_frames)
     }
 
     fn observe_identity(&mut self, event: &ProviderEvent) -> Result<(), ResponseEncodeError> {
@@ -206,67 +192,33 @@ impl OpenAiResponsesEncoder {
                 }
                 _ => continue,
             };
-            let Some(upstream) = metadata.upstream_response_id() else {
-                continue;
-            };
             if self
-                .upstream_response_id
+                .response_id
                 .as_deref()
-                .is_some_and(|current| current != upstream.as_str())
-                || self
-                    .gateway_response_id
-                    .as_deref()
-                    .is_some_and(|current| current != metadata.response_id())
+                .is_some_and(|current| current != metadata.response_id())
             {
                 return Err(ResponseEncodeError::WireIdentityChanged);
             }
-            self.upstream_response_id = Some(upstream.as_str().to_owned());
-            self.gateway_response_id = Some(metadata.response_id().to_owned());
+            self.response_id = Some(metadata.response_id().to_owned());
         }
         Ok(())
     }
 
-    fn rewrite_wire_identity(&self, data: &mut Value) {
-        let (Some(upstream), Some(gateway)) = (
-            self.upstream_response_id.as_deref(),
-            self.gateway_response_id.as_deref(),
-        ) else {
+    fn observe_wire_terminal(&mut self, wire: &gateway_core::event::ProtocolWireEvent) {
+        if !wire.has_json_data() {
             return;
-        };
-        rewrite_response_identity(data, upstream, gateway);
-    }
-}
-
-#[derive(Debug, Clone, Copy)]
-enum WireEncoding {
-    Sse,
-    WebSocket,
-}
-
-fn rewrite_response_identity(value: &mut Value, upstream: &str, gateway: &str) {
-    match value {
-        Value::Array(values) => {
-            for value in values {
-                rewrite_response_identity(value, upstream, gateway);
-            }
         }
-        Value::Object(object) => {
-            if let Some(Value::String(response_id)) = object.get_mut("response_id")
-                && response_id == upstream
-            {
-                *response_id = gateway.to_owned();
-            }
-            if let Some(Value::Object(response)) = object.get_mut("response")
-                && let Some(Value::String(response_id)) = response.get_mut("id")
-                && response_id == upstream
-            {
-                *response_id = gateway.to_owned();
-            }
-            for value in object.values_mut() {
-                rewrite_response_identity(value, upstream, gateway);
-            }
+        let effective_type = wire
+            .event_type()
+            .or_else(|| wire.data().get("type").and_then(Value::as_str));
+        if matches!(
+            effective_type,
+            Some("response.completed" | "response.incomplete")
+        ) {
+            self.wire_terminal = wire.data().get("response").cloned();
+        } else if matches!(effective_type, Some("response.failed" | "error")) {
+            self.wire_failure = true;
         }
-        _ => {}
     }
 }
 
diff --git a/backend/crates/gateway-api/src/openai/responses/websocket.rs b/backend/crates/gateway-api/src/openai/responses/websocket.rs
index 551352585..d93d1570e 100644
--- a/backend/crates/gateway-api/src/openai/responses/websocket.rs
+++ b/backend/crates/gateway-api/src/openai/responses/websocket.rs
@@ -428,6 +428,10 @@ async fn forward_execution(
                 return send_gateway_error(socket, &error, &request_id).await;
             }
             ActiveInput::Event(Err(error)) => {
+                if encoder.has_wire_failure() {
+                    execution.disarm();
+                    return ForwardOutcome::Continue;
+                }
                 let error = gateway_error_from_engine(&error);
                 return send_gateway_error(socket, &error, &request_id).await;
             }
@@ -446,7 +450,7 @@ fn commit_connection_replay(
     encoder: &OpenAiResponsesEncoder,
     provider_state: Option<ProviderSessionState>,
 ) -> Result<(), GatewayError> {
-    let response_id = encoder.gateway_response_id().ok_or_else(|| {
+    let response_id = encoder.response_id().ok_or_else(|| {
         GatewayError::new(
             GatewayErrorKind::Internal,
             "gateway completed a response without an identity",
diff --git a/backend/crates/gateway-api/tests/openai/responses/http.rs b/backend/crates/gateway-api/tests/openai/responses/http.rs
index bf5c32516..8d5861cdf 100644
--- a/backend/crates/gateway-api/tests/openai/responses/http.rs
+++ b/backend/crates/gateway-api/tests/openai/responses/http.rs
@@ -10,6 +10,7 @@ use axum::{
     extract::connect_info::ConnectInfo,
     http::{HeaderMap, Request, StatusCode, header::AUTHORIZATION},
 };
+use bytes::Bytes;
 use futures::future::{BoxFuture, pending};
 use gateway_core::engine::execution::{
     AuthenticatedClient, ClientAuthenticationError, ExecutionService, ExecutionSession,
@@ -642,17 +643,19 @@ async fn streaming_response_forwards_only_allowlisted_provider_headers() {
 }
 
 #[tokio::test]
-async fn streaming_commit_batch_encodes_pre_identity_wire_before_committing() {
+async fn streaming_commit_batch_preserves_pre_identity_wire_before_committing() {
     let trace = Arc::new(Trace::default());
-    let upstream_id = SafeUpstreamValue::new("resp_upstream").expect("upstream response ID");
-    let metadata =
-        ResponseMeta::new("resp_gateway", "public-model").with_upstream_response_id(upstream_id);
+    let metadata = ResponseMeta::new("resp_upstream", "public-model");
+    let raw_future = Bytes::from_static(
+        b"id: evt_before_identity\r\nevent: response.future_metadata\r\nretry: 3000\r\ndata: { \"type\": \"response.future_metadata\", \"opaque\": true }\r\n\r\n",
+    );
     let events = vec![
         ProviderEvent::wire(
-            ProtocolWireEvent::json_with_sse_metadata(
+            ProtocolWireEvent::json_with_raw_sse_metadata(
                 "openai",
                 Some("response.future_metadata".to_owned()),
                 json!({"type":"response.future_metadata","opaque":true}),
+                raw_future.clone(),
                 Some("evt_before_identity".to_owned()),
                 Some(3_000),
             )
@@ -700,10 +703,8 @@ async fn streaming_commit_batch_encodes_pre_identity_wire_before_committing() {
     let created = body.find("response.created").expect("created event");
     let completed = body.find("response.completed").expect("completed event");
     assert!(future < created && created < completed);
-    assert!(body.contains("id: evt_before_identity\n"));
-    assert!(body.contains("retry: 3000\n"));
-    assert!(body.contains("resp_gateway"));
-    assert!(!body.contains("resp_upstream"));
+    assert!(body.as_bytes().starts_with(raw_future.as_ref()));
+    assert!(body.contains("resp_upstream"));
     assert!(body.ends_with("data: [DONE]\n\n"));
     assert_eq!(trace.client_statuses(), vec![200]);
     assert_eq!(trace.snapshot(), vec!["next_event", "commit", "next_end"]);
@@ -921,6 +922,90 @@ async fn streaming_error_should_emit_client_visible_upstream_details() {
     assert!(body.ends_with("data: [DONE]\n\n"));
 }
 
+#[tokio::test]
+async fn streaming_upstream_wire_failure_should_not_be_rewritten_as_a_gateway_error() {
+    let trace = Arc::new(Trace::default());
+    let raw_failure = Bytes::from_static(
+        b"event: response.failed\r\ndata: { \"type\": \"response.failed\", \"response\": { \"id\": \"resp_test\", \"status\": \"failed\", \"error\": { \"code\": \"rate_limit_exceeded\", \"message\": \"upstream raw failure marker\" } } }\r\n\r\n",
+    );
+    let wire_failure = ProviderEvent::wire(
+        ProtocolWireEvent::json_with_raw_sse_metadata(
+            "openai",
+            Some("response.failed".to_owned()),
+            json!({
+                "type": "response.failed",
+                "response": {
+                    "id": "resp_test",
+                    "status": "failed",
+                    "error": {
+                        "code": "rate_limit_exceeded",
+                        "message": "upstream raw failure marker"
+                    }
+                }
+            }),
+            raw_failure.clone(),
+            None,
+            None,
+        )
+        .expect("valid upstream failure wire"),
+    );
+    let started_wire = ProviderEvent::canonical_with_wire(
+        vec![started()],
+        ProtocolWireEvent::json(
+            "openai",
+            Some("response.created".to_owned()),
+            json!({
+                "type": "response.created",
+                "response": {
+                    "id": "resp_test",
+                    "model": "public-model",
+                    "status": "in_progress"
+                }
+            }),
+        )
+        .expect("valid upstream started wire"),
+    );
+    let session = FakeSession::streaming(
+        Arc::clone(&trace),
+        vec![
+            NextStep::Event(CoordinatedEvent::single(
+                started_wire,
+                CommitRequirement::CommitBeforeDelivery,
+            )),
+            NextStep::Event(CoordinatedEvent::single(
+                wire_failure,
+                CommitRequirement::AlreadyCommitted,
+            )),
+            NextStep::Error(EngineError::Provider(ProviderError::new(
+                ProviderErrorKind::RateLimited,
+                UpstreamSendState::Sent,
+            ))),
+        ],
+    );
+
+    let response = stream_execution_response(Box::new(session), 1, None).await;
+    let body = to_bytes(response.into_body(), usize::MAX)
+        .await
+        .expect("read SSE body");
+
+    assert!(
+        body.windows(raw_failure.len())
+            .any(|frame| frame == raw_failure.as_ref())
+    );
+    assert_eq!(
+        String::from_utf8_lossy(&body)
+            .matches("upstream raw failure marker")
+            .count(),
+        1
+    );
+    assert!(!String::from_utf8_lossy(&body).contains("resp_proxy_"));
+    assert!(String::from_utf8_lossy(&body).ends_with("data: [DONE]\n\n"));
+    assert_eq!(
+        trace.snapshot(),
+        vec!["next_event", "commit", "next_event", "next_error"]
+    );
+}
+
 #[tokio::test]
 async fn streaming_second_commit_request_should_fail_and_finalize_once() {
     let trace = Arc::new(Trace::default());
diff --git a/backend/crates/gateway-api/tests/openai/responses/mod.rs b/backend/crates/gateway-api/tests/openai/responses/mod.rs
index 620f61a70..ceb99f6b5 100644
--- a/backend/crates/gateway-api/tests/openai/responses/mod.rs
+++ b/backend/crates/gateway-api/tests/openai/responses/mod.rs
@@ -2,6 +2,7 @@ mod http;
 mod websocket;
 
 use axum::http::HeaderMap;
+use bytes::Bytes;
 use gateway_api::openai::responses::{
     ContinuationIntent, DecodedResponsesRequest, OpenAiRequestHeaders, OpenAiResponsesEncoder,
     RequestDecodeError, ResponseCreateFrameError, ResponseEncodeError, ResponsesCollector,
@@ -9,7 +10,6 @@ use gateway_api::openai::responses::{
 };
 use gateway_core::{
     accounting::{CalculatedCost, ProviderReportedCost, Usage},
-    error::SafeUpstreamValue,
     event::{
         CompactionOutput, CompactionSummary, ContentItem, ContentKind, EventSequenceError,
         FinishReason, GatewayEvent, ProtocolWireEvent, ProviderEvent, ReasoningDelta, ResponseMeta,
@@ -804,11 +804,17 @@ fn websocket_events_should_reuse_the_exact_sse_event_json() {
         let websocket_events = websocket_encoder
             .push_websocket(&provider_event)
             .expect("WebSocket event encoding");
-        let parsed = parse_sse_events(&sse_frames.join(""))
-            .expect("generated SSE frames remain parseable")
-            .into_iter()
-            .map(|event| event.data)
+        let sse_body = sse_frames
+            .iter()
+            .flat_map(|frame| frame.as_ref().iter().copied())
             .collect::<Vec<_>>();
+        let parsed = parse_sse_events(
+            std::str::from_utf8(&sse_body).expect("generated SSE frames remain UTF-8"),
+        )
+        .expect("generated SSE frames remain parseable")
+        .into_iter()
+        .map(|event| event.data)
+        .collect::<Vec<_>>();
 
         assert_eq!(websocket_events, parsed);
     }
@@ -1070,17 +1076,14 @@ fn collector_should_reject_unrepresentable_media_output() {
 }
 
 #[test]
-fn openai_wire_encoder_should_preserve_unknown_media_events_and_hide_upstream_response_id() {
+fn openai_wire_encoder_should_preserve_unknown_media_events_and_upstream_response_id() {
     let upstream_id = "resp_upstream_private";
-    let gateway_id = "resp_gateway_public";
-    let started = ResponseMeta::new(gateway_id, "gpt-test").with_upstream_response_id(
-        SafeUpstreamValue::new(upstream_id).expect("safe upstream response ID"),
+    let started = ResponseMeta::new(upstream_id, "gpt-test");
+    let completed =
+        ResponseMeta::new(upstream_id, "gpt-test").with_finish_reason(FinishReason::Stop);
+    let raw_partial_image = Bytes::from_static(
+        b"id: evt_partial_image\r\nevent: response.image_generation_call.partial_image\r\nretry: 2000\r\ndata: { \"type\": \"response.image_generation_call.partial_image\", \"response_id\": \"resp_upstream_private\", \"partial_image_b64\": \"opaque-image-fragment\" }\r\n\r\n",
     );
-    let completed = ResponseMeta::new(gateway_id, "gpt-test")
-        .with_finish_reason(FinishReason::Stop)
-        .with_upstream_response_id(
-            SafeUpstreamValue::new(upstream_id).expect("safe upstream response ID"),
-        );
     let events = [
         openai_wire_event(
             vec![GatewayEvent::Started(started)],
@@ -1091,7 +1094,7 @@ fn openai_wire_encoder_should_preserve_unknown_media_events_and_hide_upstream_re
             }),
         ),
         ProviderEvent::wire(
-            ProtocolWireEvent::json_with_sse_metadata(
+            ProtocolWireEvent::json_with_raw_sse_metadata(
                 "openai",
                 Some("response.image_generation_call.partial_image".to_owned()),
                 json!({
@@ -1099,6 +1102,7 @@ fn openai_wire_encoder_should_preserve_unknown_media_events_and_hide_upstream_re
                     "response_id": upstream_id,
                     "partial_image_b64": "opaque-image-fragment"
                 }),
+                raw_partial_image.clone(),
                 Some("evt_partial_image".to_owned()),
                 Some(2_000),
             )
@@ -1123,7 +1127,12 @@ fn openai_wire_encoder_should_preserve_unknown_media_events_and_hide_upstream_re
         .flat_map(|event| encoder.push_sse(event).expect("wire event should encode"))
         .collect::<Vec<_>>();
     let response = encoder.finish().expect("wire response should finish");
-    let parsed = parse_sse_events(&frames.join("")).expect("wire SSE should parse");
+    let body = frames
+        .iter()
+        .flat_map(|frame| frame.as_ref().iter().copied())
+        .collect::<Vec<_>>();
+    let body_text = std::str::from_utf8(&body).expect("wire SSE should be UTF-8");
+    let parsed = parse_sse_events(body_text).expect("wire SSE should parse");
 
     assert_eq!(parsed.len(), 3);
     assert_eq!(parsed[1].id.as_deref(), Some("evt_partial_image"));
@@ -1134,8 +1143,12 @@ fn openai_wire_encoder_should_preserve_unknown_media_events_and_hide_upstream_re
             .get("partial_image_b64"),
         Some(&json!("opaque-image-fragment"))
     );
-    assert_eq!(response.get("id"), Some(&json!(gateway_id)));
-    assert!(!frames.join("").contains(upstream_id));
+    assert_eq!(response.get("id"), Some(&json!(upstream_id)));
+    assert!(body_text.contains(upstream_id));
+    assert!(
+        body.windows(raw_partial_image.len())
+            .any(|frame| frame == raw_partial_image.as_ref())
+    );
 }
 
 fn openai_wire_event(canonical: Vec<GatewayEvent>, event_type: &str, data: Value) -> ProviderEvent {
diff --git a/backend/crates/gateway-core/Cargo.toml b/backend/crates/gateway-core/Cargo.toml
index 7b308ab37..0cb416a0e 100644
--- a/backend/crates/gateway-core/Cargo.toml
+++ b/backend/crates/gateway-core/Cargo.toml
@@ -13,6 +13,7 @@ path = "tests/main.rs"
 
 [dependencies]
 async-trait = "0.1.89"
+bytes = "1.11.1"
 chrono = "0.4.45"
 futures = "0.3.32"
 futures-timer = "3.0.3"
diff --git a/backend/crates/gateway-core/src/engine/coordinator.rs b/backend/crates/gateway-core/src/engine/coordinator.rs
index def828225..6ca107a35 100644
--- a/backend/crates/gateway-core/src/engine/coordinator.rs
+++ b/backend/crates/gateway-core/src/engine/coordinator.rs
@@ -5,10 +5,6 @@ use std::num::NonZeroU32;
 use std::sync::Arc;
 use std::time::{Duration, SystemTime};
 
-use futures::{FutureExt, StreamExt, pin_mut, select_biased};
-use futures_timer::Delay;
-use uuid::Uuid;
-
 use crate::accounting::{CostEstimate, CostSource, Usage};
 use crate::engine::continuation::ContinuationBinding;
 use crate::engine::provider::{Provider, ProviderCallMetadata, ProviderRequest, ProviderStream};
@@ -25,6 +21,8 @@ use crate::event::{
 };
 use crate::operation::{Operation, RetrySafety};
 use crate::routing::RoutingPlan;
+use futures::{FutureExt, StreamExt, pin_mut, select_biased};
+use futures_timer::Delay;
 
 /// Request 级协调器；不会创建或写入 `request_attempts`。
 pub struct AttemptCoordinator<S: ?Sized> {
@@ -60,7 +58,6 @@ where
         let client_api_key_ref = request.client_api_key_ref.clone();
         let request_started_at = request.started_at;
         let deadline = request.deadline_at;
-        let gateway_response_id = format!("resp_{}", Uuid::now_v7().simple());
         let account_state_owner = continuation
             .as_ref()
             .and_then(ContinuationBinding::pinned)
@@ -103,7 +100,6 @@ where
             image_generation_requested,
             cost: CostEstimate::unavailable(),
             timings: ModelRequestTimings::default(),
-            gateway_response_id,
             client_response_id: None,
             upstream_response_id: None,
             last_account_exhaustion: None,
@@ -182,7 +178,6 @@ pub struct ResponseExecutionSession<S: ?Sized> {
     image_generation_requested: bool,
     cost: CostEstimate,
     timings: ModelRequestTimings,
-    gateway_response_id: String,
     client_response_id: Option<String>,
     upstream_response_id: Option<String>,
     last_account_exhaustion: Option<ProviderError>,
@@ -408,8 +403,8 @@ where
                         continue;
                     }
                     let mut identity_error = None;
-                    for fact in event.canonical_facts_mut() {
-                        if let Err(error) = self.freeze_response_identity(fact) {
+                    for fact in event.canonical_facts() {
+                        if let Err(error) = self.observe_response_identity(fact) {
                             identity_error = Some(error);
                             break;
                         }
@@ -735,27 +730,32 @@ where
         Ok(())
     }
 
-    fn freeze_response_identity(&mut self, event: &mut GatewayEvent) -> Result<(), ProviderError> {
-        let upstream_response_id = event
-            .freeze_gateway_response_id(&self.gateway_response_id)
-            .map_err(|_| {
-                ProviderError::new(ProviderErrorKind::Protocol, UpstreamSendState::Sent)
-            })?;
-        let Some(upstream_response_id) = upstream_response_id else {
-            return Ok(());
+    fn observe_response_identity(&mut self, event: &GatewayEvent) -> Result<(), ProviderError> {
+        let metadata = match event {
+            GatewayEvent::Started(metadata) | GatewayEvent::Completed(metadata) => metadata,
+            _ => return Ok(()),
         };
+        let response_id = crate::error::SafeUpstreamValue::new(metadata.response_id().to_owned())
+            .map_err(|_| {
+            ProviderError::new(ProviderErrorKind::Protocol, UpstreamSendState::Sent)
+        })?;
+        let response_id = response_id.as_str();
+        if response_id.is_empty() {
+            return Ok(());
+        }
         if self
             .upstream_response_id
             .as_deref()
-            .is_some_and(|expected| expected != upstream_response_id)
+            .is_some_and(|expected| expected != response_id)
         {
             return Err(ProviderError::new(
                 ProviderErrorKind::Protocol,
                 UpstreamSendState::Sent,
             ));
         }
-        self.client_response_id = Some(self.gateway_response_id.clone());
-        self.upstream_response_id = Some(upstream_response_id);
+        let response_id = response_id.to_owned();
+        self.client_response_id = Some(response_id.clone());
+        self.upstream_response_id = Some(response_id);
         Ok(())
     }
 
diff --git a/backend/crates/gateway-core/src/event.rs b/backend/crates/gateway-core/src/event.rs
index a287385c5..cdb12d7c0 100644
--- a/backend/crates/gateway-core/src/event.rs
+++ b/backend/crates/gateway-core/src/event.rs
@@ -3,6 +3,7 @@
 use std::collections::BTreeMap;
 use std::fmt;
 
+use bytes::Bytes;
 use serde_json::Value;
 use thiserror::Error;
 
@@ -17,7 +18,6 @@ pub struct ResponseMeta {
     response_id: String,
     model: String,
     finish_reason: Option<FinishReason>,
-    upstream_response_id: Option<SafeUpstreamValue>,
 }
 
 impl ResponseMeta {
@@ -28,7 +28,6 @@ impl ResponseMeta {
             response_id: response_id.into(),
             model: model.into(),
             finish_reason: None,
-            upstream_response_id: None,
         }
     }
 
@@ -39,7 +38,7 @@ impl ResponseMeta {
         self
     }
 
-    /// 返回网关响应 ID。
+    /// 返回客户端可见的 Provider 原生响应 ID。
     #[must_use]
     pub fn response_id(&self) -> &str {
         &self.response_id
@@ -56,19 +55,6 @@ impl ResponseMeta {
     pub const fn finish_reason(&self) -> Option<FinishReason> {
         self.finish_reason
     }
-
-    /// 附加 adapter 已分类为非 bearer 的上游 response ID。
-    #[must_use]
-    pub fn with_upstream_response_id(mut self, response_id: SafeUpstreamValue) -> Self {
-        self.upstream_response_id = Some(response_id);
-        self
-    }
-
-    /// 返回仅供 attempt 遥测持久化的安全上游 response ID。
-    #[must_use]
-    pub const fn upstream_response_id(&self) -> Option<&SafeUpstreamValue> {
-        self.upstream_response_id.as_ref()
-    }
 }
 
 /// 规范化终止原因。
@@ -273,6 +259,8 @@ pub struct ProtocolWireEvent {
     protocol: String,
     event_type: Option<String>,
     data: Value,
+    has_json_data: bool,
+    raw_sse_frame: Option<Bytes>,
     sse_id: Option<String>,
     sse_retry: Option<u64>,
 }
@@ -318,11 +306,59 @@ impl ProtocolWireEvent {
             protocol,
             event_type,
             data,
+            has_json_data: true,
+            raw_sse_frame: None,
             sse_id,
             sse_retry,
         })
     }
 
+    /// 创建携带未经改写 SSE 原始帧的协议 JSON event。
+    ///
+    /// `data` 只供 Core 旁路观测；客户端 SSE 输出必须优先使用 `raw_sse_frame`。
+    ///
+    /// # Errors
+    ///
+    /// 与 [`Self::json_with_sse_metadata`] 相同。
+    pub fn json_with_raw_sse_metadata(
+        protocol: impl Into<String>,
+        event_type: Option<String>,
+        data: Value,
+        raw_sse_frame: Bytes,
+        sse_id: Option<String>,
+        sse_retry: Option<u64>,
+    ) -> Result<Self, IdentifierError> {
+        let mut event =
+            Self::json_with_sse_metadata(protocol, event_type, data, sse_id, sse_retry)?;
+        event.raw_sse_frame = Some(raw_sse_frame);
+        Ok(event)
+    }
+
+    /// 创建只有原始 SSE 字节、没有可解析 JSON 的协议 event。
+    ///
+    /// 例如 keep-alive 注释和未知的非 JSON SSE 帧仍须原样透传，但不会参与
+    /// WebSocket JSON 输出或旁路观测。
+    ///
+    /// # Errors
+    ///
+    /// 协议名不满足 wire 安全约束时返回错误。
+    pub fn raw_sse(
+        protocol: impl Into<String>,
+        raw_sse_frame: Bytes,
+    ) -> Result<Self, IdentifierError> {
+        let protocol = protocol.into();
+        validate_text(&protocol, 64, true, None)?;
+        Ok(Self {
+            protocol,
+            event_type: None,
+            data: Value::Null,
+            has_json_data: false,
+            raw_sse_frame: Some(raw_sse_frame),
+            sse_id: None,
+            sse_retry: None,
+        })
+    }
+
     /// 返回客户端协议名称。
     #[must_use]
     pub fn protocol(&self) -> &str {
@@ -353,6 +389,18 @@ impl ProtocolWireEvent {
         &self.data
     }
 
+    /// 返回该 event 是否携带可供旁路观测的 JSON 数据。
+    #[must_use]
+    pub const fn has_json_data(&self) -> bool {
+        self.has_json_data
+    }
+
+    /// 返回可直接写给 SSE 客户端的未经改写原始帧。
+    #[must_use]
+    pub const fn raw_sse_frame(&self) -> Option<&Bytes> {
+        self.raw_sse_frame.as_ref()
+    }
+
     /// 拆出协议原生 JSON 数据。
     #[must_use]
     pub fn into_data(self) -> Value {
@@ -366,6 +414,8 @@ impl fmt::Debug for ProtocolWireEvent {
             .debug_struct("ProtocolWireEvent")
             .field("protocol", &self.protocol)
             .field("event_type", &self.event_type)
+            .field("has_json_data", &self.has_json_data)
+            .field("has_raw_sse_frame", &self.raw_sse_frame.is_some())
             .field("has_sse_id", &self.sse_id.is_some())
             .field("sse_retry", &self.sse_retry)
             .field("data", &"<not included in Debug>")
@@ -760,24 +810,6 @@ impl GatewayEvent {
                 | Self::Completed(_)
         )
     }
-
-    /// 冻结客户端可见的网关 response ID，并返回 Provider 原生 response ID。
-    ///
-    /// 只有 Coordinator 会调用该边界；Provider 产生的 ID 永远不会直接下发。
-    pub(crate) fn freeze_gateway_response_id(
-        &mut self,
-        gateway_response_id: &str,
-    ) -> Result<Option<String>, crate::error::IdentifierError> {
-        let metadata = match self {
-            Self::Started(metadata) | Self::Completed(metadata) => metadata,
-            _ => return Ok(None),
-        };
-        let upstream_response_id = SafeUpstreamValue::new(metadata.response_id.clone())?;
-        let upstream_response_id_text = upstream_response_id.as_str().to_owned();
-        metadata.response_id = gateway_response_id.to_owned();
-        metadata.upstream_response_id = Some(upstream_response_id);
-        Ok(Some(upstream_response_id_text))
-    }
 }
 
 /// Canonical event 顺序错误。
diff --git a/backend/crates/gateway-core/tests/engine/coordinator.rs b/backend/crates/gateway-core/tests/engine/coordinator.rs
index 557810c67..534ba963b 100644
--- a/backend/crates/gateway-core/tests/engine/coordinator.rs
+++ b/backend/crates/gateway-core/tests/engine/coordinator.rs
@@ -343,11 +343,10 @@ fn complete_stream(total_tokens: Option<u64>) -> Vec<Result<GatewayEvent, Provid
             ..Usage::new()
         })));
     }
-    events.push(Ok(GatewayEvent::Completed(
-        ResponseMeta::new("response-1", "gpt-5").with_upstream_response_id(
-            SafeUpstreamValue::new("upstream-response").expect("safe response id"),
-        ),
-    )));
+    events.push(Ok(GatewayEvent::Completed(ResponseMeta::new(
+        "response-1",
+        "gpt-5",
+    ))));
     events
 }
 
@@ -505,9 +504,8 @@ fn success_updates_one_model_request_and_persists_usage() {
         GatewayEvent::Completed(metadata) => metadata.response_id(),
         event => panic!("unexpected final event: {event:?}"),
     };
-    assert!(started_id.starts_with("resp_"));
+    assert_eq!(started_id, "response-1");
     assert_eq!(started_id, completed_id);
-    assert_ne!(started_id, "response-1");
     assert!(!session.is_finalized());
     block_on(session.commit_downstream(Some(200))).expect("commit response");
 
diff --git a/backend/crates/gateway-protocol/src/openai/sse.rs b/backend/crates/gateway-protocol/src/openai/sse.rs
index 122e30b53..02fef6364 100644
--- a/backend/crates/gateway-protocol/src/openai/sse.rs
+++ b/backend/crates/gateway-protocol/src/openai/sse.rs
@@ -1,5 +1,7 @@
 //! SSE 事件解析与编码。
 
+use std::fmt;
+
 use serde_json::json;
 use thiserror::Error;
 
@@ -16,6 +18,50 @@ pub struct SseEvent {
     pub retry: Option<u64>,
 }
 
+/// 保留完整原始字节与旁路解析结果的单个 SSE 帧。
+///
+/// 这用于需要原样转发的 transport；`events` 只供旁路观测，不能反过来重建
+/// `raw`。
+#[derive(Clone, PartialEq, Eq)]
+pub struct SseFrame {
+    raw: Vec<u8>,
+    events: Vec<SseEvent>,
+}
+
+impl SseFrame {
+    fn new(raw: Vec<u8>, events: Vec<SseEvent>) -> Self {
+        Self { raw, events }
+    }
+
+    /// 返回未经改写的完整 SSE 帧字节。
+    #[must_use]
+    pub fn raw(&self) -> &[u8] {
+        &self.raw
+    }
+
+    /// 返回从同一原始帧旁路解析出的事件。
+    #[must_use]
+    pub fn events(&self) -> &[SseEvent] {
+        &self.events
+    }
+
+    /// 拆出原始帧与旁路解析事件。
+    #[must_use]
+    pub fn into_parts(self) -> (Vec<u8>, Vec<SseEvent>) {
+        (self.raw, self.events)
+    }
+}
+
+impl fmt::Debug for SseFrame {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter
+            .debug_struct("SseFrame")
+            .field("raw_len", &self.raw.len())
+            .field("events", &self.events)
+            .finish()
+    }
+}
+
 /// 单事件缓冲上限。
 pub const MAX_SSE_EVENT_BUFFER_BYTES: usize = 64 * 1024 * 1024;
 
@@ -54,6 +100,38 @@ impl SseEventDecoder {
         Ok(events)
     }
 
+    /// 追加一个字节块，保留每个完整 SSE 帧的原始字节及其旁路解析结果。
+    ///
+    /// 与 [`Self::push`] 相比，此方法仅应由需要原样转发的 transport 使用；普通
+    /// 解析路径无需为原始帧额外分配内存。旁路解析失败时仍保留原始帧，并以空
+    /// event 列表表示不可观测，避免观测失败截断客户端字节流。
+    pub fn push_frames(&mut self, chunk: &[u8]) -> Result<Vec<SseFrame>, SseError> {
+        self.pending.extend_from_slice(chunk);
+        let mut frames = Vec::new();
+        let mut consumed = 0usize;
+
+        while let Some(frame_len) = sse_frame_end(&self.pending[consumed..]) {
+            let end = consumed.saturating_add(frame_len);
+            let raw = self.pending[consumed..end].to_vec();
+            let events = std::str::from_utf8(&raw)
+                .ok()
+                .and_then(|frame| parse_sse_events(frame).ok())
+                .unwrap_or_default();
+            frames.push(SseFrame::new(raw, events));
+            consumed = end;
+        }
+
+        if consumed != 0 {
+            self.pending.drain(..consumed);
+        }
+        if self.pending.len() > MAX_SSE_EVENT_BUFFER_BYTES {
+            return Err(SseError::BufferExceeded {
+                max_bytes: MAX_SSE_EVENT_BUFFER_BYTES,
+            });
+        }
+        Ok(frames)
+    }
+
     /// 流结束时解析尚未带空行分隔符的最后一帧。
     pub fn finish(&mut self) -> Result<Vec<SseEvent>, SseError> {
         if self.pending.is_empty() {
@@ -64,6 +142,21 @@ impl SseEventDecoder {
             .map_err(|error| SseError::ParseError(error.to_string()))?;
         parse_sse_events(frame)
     }
+
+    /// 在流结束时返回未带空行分隔符的最后一帧及其旁路解析结果。
+    ///
+    /// 与 [`Self::push_frames`] 一致，旁路解析失败不会丢弃原始帧。
+    pub fn finish_frames(&mut self) -> Result<Vec<SseFrame>, SseError> {
+        if self.pending.is_empty() {
+            return Ok(Vec::new());
+        }
+        let raw = std::mem::take(&mut self.pending);
+        let events = std::str::from_utf8(&raw)
+            .ok()
+            .and_then(|frame| parse_sse_events(frame).ok())
+            .unwrap_or_default();
+        Ok(vec![SseFrame::new(raw, events)])
+    }
 }
 
 /// 编码 OpenAI Responses `response.failed` SSE 事件。
@@ -116,6 +209,17 @@ pub fn sse_frame_end(bytes: &[u8]) -> Option<usize> {
     sse_frame_separator_bytes(bytes).map(|(position, separator_len)| position + separator_len)
 }
 
+/// 判断完整 SSE 帧是否是单个 `[DONE]` 控制帧。
+#[must_use]
+pub fn sse_frame_is_done(frame: &str) -> bool {
+    let mut data = frame.lines().filter_map(|raw_line| {
+        let line = raw_line.strip_suffix('\r').unwrap_or(raw_line);
+        let (field, value) = split_sse_field(line);
+        (field == "data").then_some(value)
+    });
+    matches!((data.next(), data.next()), (Some("[DONE]"), None))
+}
+
 /// SSE 解析错误。
 #[derive(Debug, Error, PartialEq, Eq)]
 pub enum SseError {
diff --git a/backend/crates/gateway-protocol/tests/openai/sse.rs b/backend/crates/gateway-protocol/tests/openai/sse.rs
index 11fd54f3d..bee85ae24 100644
--- a/backend/crates/gateway-protocol/tests/openai/sse.rs
+++ b/backend/crates/gateway-protocol/tests/openai/sse.rs
@@ -1,20 +1,9 @@
 use gateway_protocol::openai::sse::{
     DONE_SSE_FRAME, MAX_SSE_EVENT_BUFFER_BYTES, SseError, SseEvent, SseEventDecoder,
     encode_sse_event, encode_sse_event_with_metadata, parse_sse_events, response_failed_sse_event,
-    response_failed_sse_event_with_id, sse_frame_end,
+    response_failed_sse_event_with_id, sse_frame_end, sse_frame_is_done,
 };
 
-fn sse_frame_is_done(frame: &str) -> bool {
-    let mut data = frame.lines().filter_map(|raw_line| {
-        let line = raw_line.strip_suffix('\r').unwrap_or(raw_line);
-        let (field, value) = line.split_once(':').map_or((line, ""), |(field, value)| {
-            (field, value.strip_prefix(' ').unwrap_or(value))
-        });
-        (field == "data").then_some(value)
-    });
-    matches!((data.next(), data.next()), (Some("[DONE]"), None))
-}
-
 fn sse_body_has_done(body: &str) -> bool {
     body.trim_end_matches(['\r', '\n'])
         .ends_with(DONE_SSE_FRAME.trim_end_matches(['\r', '\n']))
@@ -118,6 +107,69 @@ fn incremental_decoder_should_decode_across_arbitrary_chunk_boundaries() {
     );
 }
 
+#[test]
+fn raw_frame_decoder_should_preserve_exact_frame_across_chunk_boundaries() {
+    let raw = b": keep-alive\r\nid: evt_1\r\nevent: response.future\r\nretry: 250\r\ndata: { \"type\": \"response.future\", \"opaque\": true }\r\n\r\n";
+    let mut decoder = SseEventDecoder::default();
+
+    assert!(
+        decoder
+            .push_frames(&raw[..37])
+            .expect("partial raw frame")
+            .is_empty()
+    );
+    let frames = decoder.push_frames(&raw[37..]).expect("complete raw frame");
+
+    assert_eq!(frames.len(), 1);
+    assert_eq!(frames[0].raw(), raw);
+    assert_eq!(
+        frames[0].events()[0].event.as_deref(),
+        Some("response.future")
+    );
+    assert_eq!(
+        frames[0].events()[0].data,
+        r#"{ "type": "response.future", "opaque": true }"#
+    );
+}
+
+#[test]
+fn raw_frame_decoder_should_preserve_unparseable_frames_for_transparent_transport() {
+    let invalid_retry = b"retry: later\ndata: opaque\n\n";
+    let non_utf8 = b"data: \xff\n\n";
+    let mut decoder = SseEventDecoder::default();
+
+    let frames = decoder
+        .push_frames(invalid_retry)
+        .expect("raw frame remains deliverable");
+    assert_eq!(frames[0].raw(), invalid_retry);
+    assert!(frames[0].events().is_empty());
+
+    let frames = decoder
+        .push_frames(non_utf8)
+        .expect("non-UTF-8 raw frame remains deliverable");
+    assert_eq!(frames[0].raw(), non_utf8);
+    assert!(frames[0].events().is_empty());
+}
+
+#[test]
+fn raw_frame_decoder_finish_should_preserve_unparseable_trailing_frame() {
+    let raw = b"retry: later\ndata: opaque";
+    let mut decoder = SseEventDecoder::default();
+
+    assert!(
+        decoder
+            .push_frames(raw)
+            .expect("unfinished raw frame remains buffered")
+            .is_empty()
+    );
+    let frames = decoder
+        .finish_frames()
+        .expect("trailing raw frame remains deliverable");
+
+    assert_eq!(frames[0].raw(), raw);
+    assert!(frames[0].events().is_empty());
+}
+
 #[test]
 fn incremental_decoder_finish_should_decode_unterminated_final_frame() {
     let mut decoder = SseEventDecoder::default();
diff --git a/backend/crates/providers/openai/src/provider.rs b/backend/crates/providers/openai/src/provider.rs
index 1bd16015f..a7512255d 100644
--- a/backend/crates/providers/openai/src/provider.rs
+++ b/backend/crates/providers/openai/src/provider.rs
@@ -797,6 +797,9 @@ fn cold_response_stream(response: ColdResponse) -> EventStream {
         let failure_rate_limit_headers = response.rate_limit_headers.clone();
         let rate_limit_updates = response.rate_limit_header_updates;
         let mut decoder = CodexCanonicalDecoder::new(upstream_model.as_str());
+        if response.transport == CodexBackendTransport::HttpSse {
+            decoder = decoder.with_raw_sse_passthrough();
+        }
         loop {
             let Some(stream_deadline) = remaining(context.deadline()) else {
                 Err(provider_error(ProviderErrorKind::Timeout, UpstreamSendState::Sent))?;
diff --git a/backend/crates/providers/openai/src/transport/canonical.rs b/backend/crates/providers/openai/src/transport/canonical.rs
index e8d19f7a9..e64f9dccf 100644
--- a/backend/crates/providers/openai/src/transport/canonical.rs
+++ b/backend/crates/providers/openai/src/transport/canonical.rs
@@ -5,6 +5,7 @@ use std::{
     fmt,
 };
 
+use bytes::Bytes;
 use gateway_core::accounting::Usage;
 use gateway_core::engine::UpstreamSendState;
 use gateway_core::error::{ProviderError, ProviderErrorKind};
@@ -13,7 +14,7 @@ use gateway_core::event::{
     ReasoningDelta, ResponseMeta, TextDelta, ToolCallDelta,
 };
 use gateway_protocol::openai::events::{TokenUsage, extract_usage};
-use gateway_protocol::openai::sse::{SseEvent, SseEventDecoder};
+use gateway_protocol::openai::sse::{SseEvent, SseEventDecoder, SseFrame, sse_frame_is_done};
 use serde_json::Value;
 use thiserror::Error;
 
@@ -38,6 +39,7 @@ pub struct CodexCanonicalDecoder {
     reasoning_output_seen: BTreeSet<u32>,
     usage_emitted: bool,
     semantic_output_seen: bool,
+    raw_sse_passthrough: bool,
 }
 
 /// 上游 Responses 事件的两类失败：协议损坏，或上游明确报告业务失败。
@@ -130,10 +132,32 @@ impl CodexCanonicalDecoder {
             reasoning_output_seen: BTreeSet::new(),
             usage_emitted: false,
             semantic_output_seen: false,
+            raw_sse_passthrough: false,
         }
     }
 
+    /// 让 HTTP SSE 上游帧以原始字节随 wire event 向下游传递。
+    ///
+    /// JSON 投影仍只供 canonical facts、计费与亲和旁路读取；不会用于重建 SSE。
+    #[must_use]
+    pub fn with_raw_sse_passthrough(mut self) -> Self {
+        self.raw_sse_passthrough = true;
+        self
+    }
+
     pub fn push(&mut self, chunk: &[u8]) -> CodexCanonicalOutcome {
+        if self.raw_sse_passthrough {
+            let frames = match self.decoder.push_frames(chunk) {
+                Ok(frames) => frames,
+                Err(error) => {
+                    return self.failure(
+                        Vec::new(),
+                        CodexCanonicalError::Protocol(protocol_error(error)),
+                    );
+                }
+            };
+            return self.decode_frames(frames);
+        }
         let events = match self.decoder.push(chunk) {
             Ok(events) => events,
             Err(error) => {
@@ -147,6 +171,18 @@ impl CodexCanonicalDecoder {
     }
 
     pub fn finish(&mut self) -> CodexCanonicalOutcome {
+        if self.raw_sse_passthrough {
+            let frames = match self.decoder.finish_frames() {
+                Ok(frames) => frames,
+                Err(error) => {
+                    return self.failure(
+                        Vec::new(),
+                        CodexCanonicalError::Protocol(protocol_error(error)),
+                    );
+                }
+            };
+            return self.decode_frames(frames);
+        }
         let events = match self.decoder.finish() {
             Ok(events) => events,
             Err(error) => {
@@ -162,51 +198,108 @@ impl CodexCanonicalDecoder {
     fn decode(&mut self, events: Vec<SseEvent>) -> CodexCanonicalOutcome {
         let mut output = Vec::new();
         for event in events {
-            if event.data.trim() == "[DONE]" {
+            if let Err(error) = self.decode_one(event, None, &mut output) {
+                return self.failure(output, error);
+            }
+        }
+        CodexCanonicalOutcome::Events(output)
+    }
+
+    fn decode_frames(&mut self, frames: Vec<SseFrame>) -> CodexCanonicalOutcome {
+        let mut output = Vec::new();
+        for frame in frames {
+            let done = std::str::from_utf8(frame.raw()).is_ok_and(sse_frame_is_done);
+            let (raw, events) = frame.into_parts();
+            if done {
                 continue;
             }
-            let value = match serde_json::from_str::<Value>(&event.data) {
-                Ok(value) => value,
-                // P1 恢复 raw bytes 后会连该帧原样交付；当前 event carrier 只能承载
-                // JSON，所以先跳过这条无法投影的帧，继续读取后续上游事件。
-                Err(_) => continue,
-            };
-            let event_type = event
-                .event
-                .as_deref()
-                .or_else(|| value.get("type").and_then(Value::as_str));
-            if matches!(event_type, Some("response.failed" | "error")) {
-                return self.failure(
-                    output,
-                    CodexCanonicalError::Upstream(ResponsesSseFailure::from_event(
-                        event_type.unwrap_or_default(),
-                        &value,
-                    )),
-                );
+            let raw = Bytes::from(raw);
+            if events.is_empty() {
+                if let Ok(wire) = ProtocolWireEvent::raw_sse("openai", raw) {
+                    output.push(ProviderEvent::wire(wire));
+                }
+                continue;
             }
-            let mut canonical = Vec::new();
-            if let Some(event_type) = event_type {
-                let _ = self.decode_event(event_type, &value, &mut canonical);
+            for (index, event) in events.into_iter().enumerate() {
+                let raw_sse_frame = (index == 0).then(|| raw.clone());
+                if let Err(error) = self.decode_one(event, raw_sse_frame, &mut output) {
+                    return self.failure(output, error);
+                }
             }
-            let semantic_output = response_event_signals(event_type, &value).semantic_output;
-            let wire = match ProtocolWireEvent::json_with_sse_metadata(
+        }
+        CodexCanonicalOutcome::Events(output)
+    }
+
+    fn decode_one(
+        &mut self,
+        event: SseEvent,
+        raw_sse_frame: Option<Bytes>,
+        output: &mut Vec<ProviderEvent>,
+    ) -> Result<(), CodexCanonicalError> {
+        if event.data.trim() == "[DONE]" {
+            return Ok(());
+        }
+        let value = match serde_json::from_str::<Value>(&event.data) {
+            Ok(value) => value,
+            Err(_) => {
+                if let Some(raw_sse_frame) = raw_sse_frame
+                    && let Ok(wire) = ProtocolWireEvent::raw_sse("openai", raw_sse_frame)
+                {
+                    output.push(ProviderEvent::wire(wire));
+                }
+                return Ok(());
+            }
+        };
+        let event_type = event
+            .event
+            .as_deref()
+            .or_else(|| value.get("type").and_then(Value::as_str));
+        if matches!(event_type, Some("response.failed" | "error")) {
+            let failure = ResponsesSseFailure::from_event(event_type.unwrap_or_default(), &value);
+            if let Ok(wire) = Self::wire_for_event(event, value, raw_sse_frame) {
+                output.push(ProviderEvent::wire(wire));
+            }
+            return Err(CodexCanonicalError::Upstream(failure));
+        }
+        let mut canonical = Vec::new();
+        if let Some(event_type) = event_type {
+            let _ = self.decode_event(event_type, &value, &mut canonical);
+        }
+        let semantic_output = response_event_signals(event_type, &value).semantic_output;
+        let Ok(wire) = Self::wire_for_event(event, value, raw_sse_frame) else {
+            return Ok(());
+        };
+        output.push(if canonical.is_empty() {
+            ProviderEvent::wire(wire)
+        } else {
+            ProviderEvent::canonical_with_wire(canonical, wire)
+        });
+        self.semantic_output_seen |= semantic_output;
+        Ok(())
+    }
+
+    fn wire_for_event(
+        event: SseEvent,
+        value: Value,
+        raw_sse_frame: Option<Bytes>,
+    ) -> Result<ProtocolWireEvent, gateway_core::error::IdentifierError> {
+        match raw_sse_frame {
+            Some(raw_sse_frame) => ProtocolWireEvent::json_with_raw_sse_metadata(
+                "openai",
+                event.event,
+                value,
+                raw_sse_frame,
+                event.id,
+                event.retry,
+            ),
+            None => ProtocolWireEvent::json_with_sse_metadata(
                 "openai",
                 event.event,
                 value,
                 event.id,
                 event.retry,
-            ) {
-                Ok(wire) => wire,
-                Err(_) => continue,
-            };
-            output.push(if canonical.is_empty() {
-                ProviderEvent::wire(wire)
-            } else {
-                ProviderEvent::canonical_with_wire(canonical, wire)
-            });
-            self.semantic_output_seen |= semantic_output;
+            ),
         }
-        CodexCanonicalOutcome::Events(output)
     }
 
     fn failure(
diff --git a/backend/crates/providers/openai/tests/transport/canonical.rs b/backend/crates/providers/openai/tests/transport/canonical.rs
index ea5e7d737..04c88e001 100644
--- a/backend/crates/providers/openai/tests/transport/canonical.rs
+++ b/backend/crates/providers/openai/tests/transport/canonical.rs
@@ -29,6 +29,57 @@ fn decoder_should_preserve_existing_metadata_fixture_as_openai_wire() {
     ));
 }
 
+#[test]
+fn raw_sse_passthrough_should_keep_original_bytes_alongside_canonical_facts() {
+    let heartbeat = ": keep-alive\r\n\r\n";
+    let created = concat!(
+        "id: evt_created\r\n",
+        "event: response.created\r\n",
+        "retry: 250\r\n",
+        "data: { \"type\": \"response.created\", \"response\": { \"id\": \"resp_raw\", \"model\": \"gpt-test\" } }\r\n\r\n",
+    );
+    let body = format!("{heartbeat}{created}");
+
+    let events = CodexCanonicalDecoder::new("fallback")
+        .with_raw_sse_passthrough()
+        .push(body.as_bytes())
+        .expect("raw SSE should remain deliverable");
+    let heartbeat_wire = events[0].wire_event().expect("heartbeat wire");
+    let created_wire = events[1].wire_event().expect("created wire");
+
+    assert!(!heartbeat_wire.has_json_data());
+    assert_eq!(
+        heartbeat_wire.raw_sse_frame().map(AsRef::as_ref),
+        Some(heartbeat.as_bytes())
+    );
+    assert!(created_wire.has_json_data());
+    assert_eq!(
+        created_wire.raw_sse_frame().map(AsRef::as_ref),
+        Some(created.as_bytes())
+    );
+    assert!(matches!(
+        events[1].canonical_facts(),
+        [GatewayEvent::Started(metadata)] if metadata.response_id() == "resp_raw"
+    ));
+}
+
+#[test]
+fn raw_sse_passthrough_should_forward_unparseable_frames_without_failure() {
+    let raw = b"retry: later\ndata: opaque\n\n";
+
+    let events = CodexCanonicalDecoder::new("fallback")
+        .with_raw_sse_passthrough()
+        .push(raw)
+        .expect("unparseable frame must not abort transparent transport");
+    let wire = events[0].wire_event().expect("raw wire event");
+
+    assert!(!wire.has_json_data());
+    assert_eq!(
+        wire.raw_sse_frame().map(AsRef::as_ref),
+        Some(raw.as_slice())
+    );
+}
+
 #[test]
 fn decoder_should_emit_calculated_cost_for_complete_known_model_usage() {
     let body = concat!(
@@ -328,6 +379,29 @@ fn decoder_should_classify_official_cyber_policy_as_an_invalid_request() {
     assert_failed_event("cyber_policy", "policy-secret-marker");
 }
 
+#[test]
+fn raw_sse_failure_should_keep_the_original_frame_before_reporting_the_typed_failure() {
+    let raw = concat!(
+        "event: response.failed\r\n",
+        "data: { \"type\": \"response.failed\", \"response\": { \"id\": \"resp_raw_failed\", \"status\": \"failed\", \"error\": { \"code\": \"rate_limit_exceeded\", \"message\": \"raw failure marker\" } } }\r\n\r\n",
+    );
+
+    let failure = CodexCanonicalDecoder::new("fallback")
+        .with_raw_sse_passthrough()
+        .push(raw.as_bytes())
+        .expect_err("response.failed remains a typed lifecycle failure");
+    let wire = failure.events()[0]
+        .wire_event()
+        .expect("upstream failure wire remains deliverable");
+
+    assert_eq!(wire.event_type(), Some("response.failed"));
+    assert_eq!(
+        wire.raw_sse_frame().map(|frame| frame.as_ref()),
+        Some(raw.as_bytes())
+    );
+    assert!(!format!("{failure:?}").contains("raw failure marker"));
+}
+
 #[test]
 fn decoder_should_preserve_same_chunk_output_before_typed_failure() {
     let marker = "same-chunk-secret-marker";
@@ -365,7 +439,8 @@ fn decoder_should_preserve_same_chunk_output_before_typed_failure() {
         vec![
             "response.created",
             "response.content_part.added",
-            "response.output_text.delta"
+            "response.output_text.delta",
+            "response.failed"
         ]
     );
     assert!(!format!("{failure:?}").contains(marker));