Move compression into the request builder

codex-rs/codex-api/src/endpoint/chat.rs

@@ -8,6 +8,8 @@ use crate::error::ApiError;
 use crate::provider::Provider;
 use crate::provider::RequestCompression;
 use crate::provider::WireApi;
+use crate::requests::body::encode_body;
+use crate::requests::body::insert_compression_headers;
 use crate::sse::chat::spawn_chat_stream;
 use crate::telemetry::SseTelemetry;
 use codex_client::HttpTransport;
@@ -87,14 +89,11 @@ impl<T: HttpTransport, A: AuthProvider> ChatClient<T, A> {
         extra_headers: HeaderMap,
         request_compression: RequestCompression,
     ) -> Result<ResponseStream, ApiError> {
+        let mut headers = extra_headers;
+        insert_compression_headers(&mut headers, request_compression);
+        let encoded_body = encode_body(&body, request_compression)?;
         self.streaming
-            .stream(
-                self.path(),
-                body,
-                extra_headers,
-                request_compression,
-                spawn_chat_stream,
-            )
+            .stream(self.path(), encoded_body, headers, spawn_chat_stream)
             .await
     }
 }

codex-rs/codex-api/src/endpoint/responses.rs

@@ -16,7 +16,6 @@ use codex_client::HttpTransport;
 use codex_client::RequestTelemetry;
 use codex_protocol::protocol::SessionSource;
 use http::HeaderMap;
-use serde_json::Value;
 use std::sync::Arc;
 use tracing::instrument;
 
@@ -57,10 +56,8 @@ impl<T: HttpTransport, A: AuthProvider> ResponsesClient<T, A> {
     pub async fn stream_request(
         &self,
         request: ResponsesRequest,
-        request_compression: RequestCompression,
     ) -> Result<ResponseStream, ApiError> {
-        self.stream(request.body, request.headers, request_compression)
-            .await
+        self.stream(request).await
     }
 
     #[instrument(level = "trace", skip_all, err)]
@@ -93,9 +90,10 @@ impl<T: HttpTransport, A: AuthProvider> ResponsesClient<T, A> {
             .session_source(session_source)
             .store_override(store_override)
             .extra_headers(extra_headers)
+            .request_compression(request_compression)
             .build(self.streaming.provider())?;
 
-        self.stream_request(request, request_compression).await
+        self.stream_request(request).await
     }
 
     fn path(&self) -> &'static str {
@@ -105,18 +103,12 @@ impl<T: HttpTransport, A: AuthProvider> ResponsesClient<T, A> {
         }
     }
 
-    pub async fn stream(
-        &self,
-        body: Value,
-        extra_headers: HeaderMap,
-        request_compression: RequestCompression,
-    ) -> Result<ResponseStream, ApiError> {
+    pub async fn stream(&self, request: ResponsesRequest) -> Result<ResponseStream, ApiError> {
         self.streaming
             .stream(
                 self.path(),
-                body,
-                extra_headers,
-                request_compression,
+                request.body,
+                request.headers,
                 spawn_response_stream,
             )
             .await

codex-rs/codex-api/src/endpoint/streaming.rs

@@ -3,10 +3,8 @@ use crate::auth::add_auth_headers;
 use crate::common::ResponseStream;
 use crate::error::ApiError;
 use crate::provider::Provider;
-use crate::provider::RequestCompression;
 use crate::telemetry::SseTelemetry;
 use crate::telemetry::run_with_request_telemetry;
-use bytes::Bytes;
 use codex_client::Body;
 use codex_client::HttpTransport;
 use codex_client::RequestTelemetry;
@@ -15,14 +13,9 @@ use http::HeaderMap;
 use http::HeaderValue;
 use http::Method;
 use http::header::ACCEPT;
-use http::header::CONTENT_ENCODING;
 use http::header::CONTENT_TYPE;
-use serde_json::Value;
 use std::sync::Arc;
 use std::time::Duration;
-use std::time::Instant;
-use tracing::info;
-use zstd::stream::encode_all;
 
 pub(crate) struct StreamingClient<T: HttpTransport, A: AuthProvider> {
     transport: T,
@@ -60,14 +53,10 @@ impl<T: HttpTransport, A: AuthProvider> StreamingClient<T, A> {
     pub(crate) async fn stream(
         &self,
         path: &str,
-        body: Value,
+        body: Body,
         extra_headers: HeaderMap,
-        request_compression: RequestCompression,
         spawner: fn(StreamResponse, Duration, Option<Arc<dyn SseTelemetry>>) -> ResponseStream,
     ) -> Result<ResponseStream, ApiError> {
-        let content_encoding = matches!(request_compression, RequestCompression::Zstd);
-        let encoded_body = encode_body(&body, request_compression).map_err(ApiError::Stream)?;
-
         let builder = || {
             let mut req = self.provider.build_request(Method::POST, path);
             req.headers.extend(extra_headers.clone());
@@ -76,11 +65,7 @@ impl<T: HttpTransport, A: AuthProvider> StreamingClient<T, A> {
             req.headers
                 .entry(CONTENT_TYPE)
                 .or_insert_with(|| HeaderValue::from_static("application/json"));
-            if content_encoding {
-                req.headers
-                    .insert(CONTENT_ENCODING, HeaderValue::from_static("zstd"));
-            }
-            req.body = Some(encoded_body.clone());
+            req.body = Some(body.clone());
             add_auth_headers(&self.auth, req)
         };
 
@@ -99,24 +84,3 @@ impl<T: HttpTransport, A: AuthProvider> StreamingClient<T, A> {
         ))
     }
 }
-
-fn encode_body(body: &Value, compression: RequestCompression) -> Result<Body, String> {
-    match compression {
-        RequestCompression::None => Ok(Body::Json(body.clone())),
-        RequestCompression::Zstd => {
-            let json = serde_json::to_vec(body)
-                .map_err(|err| format!("failed to encode request body as json: {err}"))?;
-            let started_at = Instant::now();
-            let compressed = encode_all(json.as_slice(), 0)
-                .map_err(|err| format!("failed to compress request body: {err}"))?;
-            let elapsed = started_at.elapsed();
-            info!(
-                input_bytes = json.len(),
-                output_bytes = compressed.len(),
-                elapsed_ms = elapsed.as_millis(),
-                "compressed request body"
-            );
-            Ok(Body::Bytes(Bytes::from(compressed)))
-        }
-    }
-}

codex-rs/codex-api/src/requests/body.rs

@@ -0,0 +1,40 @@
+use crate::error::ApiError;
+use crate::provider::RequestCompression;
+use bytes::Bytes;
+use codex_client::Body;
+use http::HeaderMap;
+use http::HeaderValue;
+use http::header::CONTENT_ENCODING;
+use serde_json::Value;
+use std::time::Instant;
+use tracing::info;
+use zstd::stream::encode_all;
+
+pub(crate) fn encode_body(body: &Value, compression: RequestCompression) -> Result<Body, ApiError> {
+    match compression {
+        RequestCompression::None => Ok(Body::Json(body.clone())),
+        RequestCompression::Zstd => {
+            let json = serde_json::to_vec(body).map_err(|err| {
+                ApiError::Stream(format!("failed to encode request body as json: {err}"))
+            })?;
+            let started_at = Instant::now();
+            let compressed = encode_all(json.as_slice(), 0).map_err(|err| {
+                ApiError::Stream(format!("failed to compress request body: {err}"))
+            })?;
+            let elapsed = started_at.elapsed();
+            info!(
+                input_bytes = json.len(),
+                output_bytes = compressed.len(),
+                elapsed_ms = elapsed.as_millis(),
+                "compressed request body"
+            );
+            Ok(Body::Bytes(Bytes::from(compressed)))
+        }
+    }
+}
+
+pub(crate) fn insert_compression_headers(headers: &mut HeaderMap, compression: RequestCompression) {
+    if matches!(compression, RequestCompression::Zstd) {
+        headers.insert(CONTENT_ENCODING, HeaderValue::from_static("zstd"));
+    }
+}

codex-rs/codex-api/src/requests/mod.rs

@@ -1,3 +1,4 @@
+pub(crate) mod body;
 pub mod chat;
 pub(crate) mod headers;
 pub mod responses;

codex-rs/codex-api/src/requests/responses.rs

@@ -3,9 +3,13 @@ use crate::common::ResponsesApiRequest;
 use crate::common::TextControls;
 use crate::error::ApiError;
 use crate::provider::Provider;
+use crate::provider::RequestCompression;
+use crate::requests::body::encode_body;
+use crate::requests::body::insert_compression_headers;
 use crate::requests::headers::build_conversation_headers;
 use crate::requests::headers::insert_header;
 use crate::requests::headers::subagent_header;
+use codex_client::Body;
 use codex_protocol::models::ResponseItem;
 use codex_protocol::protocol::SessionSource;
 use http::HeaderMap;
@@ -13,7 +17,7 @@ use serde_json::Value;
 
 /// Assembled request body plus headers for a Responses stream request.
 pub struct ResponsesRequest {
-    pub body: Value,
+    pub body: Body,
     pub headers: HeaderMap,
 }
 
@@ -32,6 +36,7 @@ pub struct ResponsesRequestBuilder<'a> {
     session_source: Option<SessionSource>,
     store_override: Option<bool>,
     headers: HeaderMap,
+    request_compression: RequestCompression,
 }
 
 impl<'a> ResponsesRequestBuilder<'a> {
@@ -94,6 +99,11 @@ impl<'a> ResponsesRequestBuilder<'a> {
         self
     }
 
+    pub fn request_compression(mut self, request_compression: RequestCompression) -> Self {
+        self.request_compression = request_compression;
+        self
+    }
+
     pub fn build(self, provider: &Provider) -> Result<ResponsesRequest, ApiError> {
         let model = self
             .model
@@ -137,6 +147,8 @@ impl<'a> ResponsesRequestBuilder<'a> {
         if let Some(subagent) = subagent_header(&self.session_source) {
             insert_header(&mut headers, "x-openai-subagent", &subagent);
         }
+        insert_compression_headers(&mut headers, self.request_compression);
+        let body = encode_body(&body, self.request_compression)?;
 
         Ok(ResponsesRequest { body, headers })
     }
@@ -175,6 +187,7 @@ mod tests {
 
     use crate::provider::RetryConfig;
     use crate::provider::WireApi;
+    use codex_client::Body;
     use codex_protocol::protocol::SubAgentSource;
     use http::HeaderValue;
     use pretty_assertions::assert_eq;
@@ -220,10 +233,12 @@ mod tests {
             .build(&provider)
             .expect("request");
 
-        assert_eq!(request.body.get("store"), Some(&Value::Bool(true)));
+        let Body::Json(body) = &request.body else {
+            panic!("expected json body for responses request");
+        };
+        assert_eq!(body.get("store"), Some(&Value::Bool(true)));
 
-        let ids: Vec<Option<String>> = request
-            .body
+        let ids: Vec<Option<String>> = body
             .get("input")
             .and_then(|v| v.as_array())
             .into_iter()