Add timeout for remote compaction requests (#23451)

## Why

Remote compaction currently sends a unary `POST /responses/compact` and
waits for the full response before replacing history or emitting the
completed `ContextCompaction` item. Unlike normal `/responses` streaming
requests, this unary compact request had no timeout boundary. If the
backend accepts the request and then stalls before returning a body, the
existing request retry policy never sees a transport error, so the
compact turn can remain stuck after the started item with no completion
or actionable error.

That matches the reported hang shape in issues such as #18363, where
logs show `responses/compact` was posted but no corresponding compact
completion followed. A bounded request timeout gives the existing retry
policy a concrete timeout error to retry instead of letting the user sit
indefinitely on automatic context compaction.

## What

- Add a request timeout to legacy `/responses/compact` calls.
- Size that timeout from the provider stream idle timeout with a
conservative multiplier, so the default compact attempt gets 20 minutes
rather than the 5 minute stream idle window.
- Map API transport timeouts to a request timeout error instead of the
child-process timeout message.

## Testing

- Not run (per request; CI will cover).

codex-rs/codex-api/src/api_bridge.rs

@@ -123,7 +123,7 @@ pub fn map_api_error(err: ApiError) -> CodexErr {
                 status: http::StatusCode::INTERNAL_SERVER_ERROR,
                 request_id: None,
             }),
-            TransportError::Timeout => CodexErr::Timeout,
+            TransportError::Timeout => CodexErr::RequestTimeout,
             TransportError::Network(msg) | TransportError::Build(msg) => {
                 CodexErr::Stream(msg, None)
             }

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

@@ -11,6 +11,7 @@ use http::Method;
 use serde::Deserialize;
 use serde_json::to_value;
 use std::sync::Arc;
+use std::time::Duration;
 
 pub struct CompactClient<T: HttpTransport> {
     session: EndpointSession<T>,
@@ -37,10 +38,19 @@ impl<T: HttpTransport> CompactClient<T> {
         &self,
         body: serde_json::Value,
         extra_headers: HeaderMap,
+        request_timeout: Duration,
     ) -> Result<Vec<ResponseItem>, ApiError> {
         let resp = self
             .session
-            .execute(Method::POST, Self::path(), extra_headers, Some(body))
+            .execute_with(
+                Method::POST,
+                Self::path(),
+                extra_headers,
+                Some(body),
+                |req| {
+                    req.timeout = Some(request_timeout);
+                },
+            )
             .await?;
         let parsed: CompactHistoryResponse =
             serde_json::from_slice(&resp.body).map_err(|e| ApiError::Stream(e.to_string()))?;
@@ -51,10 +61,11 @@ impl<T: HttpTransport> CompactClient<T> {
         &self,
         input: &CompactionInput<'_>,
         extra_headers: HeaderMap,
+        request_timeout: Duration,
     ) -> Result<Vec<ResponseItem>, ApiError> {
         let body = to_value(input)
             .map_err(|e| ApiError::Stream(format!("failed to encode compaction input: {e}")))?;
-        self.compact(body, extra_headers).await
+        self.compact(body, extra_headers, request_timeout).await
     }
 }
 

codex-rs/core/src/client.rs

@@ -146,6 +146,9 @@ const X_CODEX_WS_STREAM_REQUEST_START_MS_CLIENT_METADATA_KEY: &str =
 const RESPONSES_WEBSOCKETS_V2_BETA_HEADER_VALUE: &str = "responses_websockets=2026-02-06";
 const RESPONSES_ENDPOINT: &str = "/responses";
 const RESPONSES_COMPACT_ENDPOINT: &str = "/responses/compact";
+// `/responses/compact` is unary, so the timeout covers the full response rather than one idle
+// period between stream events.
+const COMPACT_REQUEST_TIMEOUT_IDLE_MULTIPLIER: u32 = 4;
 const MEMORIES_SUMMARIZE_ENDPOINT: &str = "/memories/trace_summarize";
 #[cfg(test)]
 pub(crate) const WEBSOCKET_CONNECT_TIMEOUT: Duration =
@@ -502,12 +505,16 @@ impl ModelClient {
         if let Some(header_value) = self.generate_attestation_header_for().await {
             extra_headers.insert(X_OAI_ATTESTATION_HEADER, header_value);
         }
+        let compact_request_timeout = client_setup
+            .api_provider
+            .stream_idle_timeout
+            .saturating_mul(COMPACT_REQUEST_TIMEOUT_IDLE_MULTIPLIER);
         let client =
             ApiCompactClient::new(transport, client_setup.api_provider, client_setup.api_auth)
                 .with_telemetry(Some(request_telemetry));
         let trace_attempt = compaction_trace.start_attempt(&payload);
         let result = client
-            .compact_input(&payload, extra_headers)
+            .compact_input(&payload, extra_headers, compact_request_timeout)
             .await
             .map_err(map_api_error);
         trace_attempt.record_result(result.as_deref());

codex-rs/protocol/src/error.rs

@@ -89,6 +89,8 @@ pub enum CodexErr {
     /// Returned by run_command_stream when the spawned child process timed out (10s).
     #[error("timeout waiting for child process to exit")]
     Timeout,
+    #[error("request timed out")]
+    RequestTimeout,
     /// Returned by run_command_stream when the child could not be spawned (its stdout/stderr pipes
     /// could not be captured). Analogous to the previous `CodexError::Spawn` variant.
     #[error("spawn failed: child stdout/stderr not captured")]
@@ -192,6 +194,7 @@ impl CodexErr {
             | CodexErr::CyberPolicy { .. } => false,
             CodexErr::Stream(..)
             | CodexErr::Timeout
+            | CodexErr::RequestTimeout
             | CodexErr::UnexpectedStatus(_)
             | CodexErr::ResponseStreamFailed(_)
             | CodexErr::ConnectionFailed(_)