Propagate caller metadata to rendezvous connections (#39073)

## What changed

- Add `x-cluster-name` from `OPENAI_CLUSTER` and
  `x-openai-internal-caller` from `DD_SERVICE` to rendezvous WebSocket
  handshakes when the environment values are nonempty and valid HTTP header
  values.
- Apply the rendezvous headers to both client and remote executor connections
  while preserving the existing W3C trace context headers.

GitOrigin-RevId: fead0244ba24fa208990b92d2170a9ae76ff2ceb

codex-rs/exec-server/src/client_transport.rs

@@ -34,7 +34,7 @@ use crate::noise_relay::NoiseHarnessConnectionArgs;
 use crate::noise_relay::noise_harness_connection_from_websocket;
 use crate::noise_relay::noise_relay_websocket_config;
 use crate::relay::harness_connection_from_websocket;
-use crate::trace_context::current_trace_context_headers;
+use crate::trace_context::current_rendezvous_headers;
 
 const ENVIRONMENT_CLIENT_NAME: &str = "codex-environment";
 
@@ -342,9 +342,7 @@ impl ExecServerClient {
                 url: diagnostic_url.clone(),
                 source,
             })?;
-        request
-            .headers_mut()
-            .extend(current_trace_context_headers());
+        request.headers_mut().extend(current_rendezvous_headers());
         let (stream, _) = timeout(
             connect_timeout,
             WebSocketConnector::new_with_tls_mode(

codex-rs/exec-server/src/remote.rs

@@ -44,6 +44,7 @@ use crate::relay::HarnessKeyValidator;
 use crate::relay::run_multiplexed_environment;
 use crate::server::ConnectionProcessor;
 use crate::server::RequestDispatchMode;
+use crate::trace_context::current_rendezvous_headers;
 use crate::trace_context::current_trace_context_headers;
 
 const ERROR_BODY_PREVIEW_BYTES: usize = 4096;
@@ -673,9 +674,7 @@ async fn connect_rendezvous(
     let started_at = Instant::now();
     let result = async {
         let mut request = url.into_client_request()?;
-        request
-            .headers_mut()
-            .extend(current_trace_context_headers());
+        request.headers_mut().extend(current_rendezvous_headers());
         let connector = WebSocketConnector::new_with_tls_mode(
             http_client_factory,
             WebSocketTlsMode::TungsteniteDefault,

codex-rs/exec-server/src/trace_context.rs

@@ -1,6 +1,22 @@
 use http::HeaderMap;
 use http::HeaderValue;
 
+pub(crate) fn current_rendezvous_headers() -> HeaderMap {
+    let mut headers = current_trace_context_headers();
+    for (header, variable) in [
+        ("x-cluster-name", "OPENAI_CLUSTER"),
+        ("x-openai-internal-caller", "DD_SERVICE"),
+    ] {
+        if let Ok(value) = std::env::var(variable)
+            && !value.is_empty()
+            && let Ok(value) = HeaderValue::try_from(value)
+        {
+            headers.insert(header, value);
+        }
+    }
+    headers
+}
+
 pub(crate) fn current_trace_context_headers() -> HeaderMap {
     let mut headers = HeaderMap::new();
     let Some(trace) = codex_otel::current_span_w3c_trace_context() else {