diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index 3631f3afb..b8568a104 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -82,6 +82,8 @@ use crate::model_provider_info::ModelProviderInfo;
 use crate::model_provider_info::WireApi;
 use crate::tools::spec::create_tools_json_for_responses_api;
 
+pub const OPENAI_BETA_HEADER: &str = "OpenAI-Beta";
+pub const OPENAI_BETA_RESPONSES_WEBSOCKETS: &str = "responses_websockets=2026-02-04";
 pub const X_CODEX_TURN_STATE_HEADER: &str = "x-codex-turn-state";
 pub const X_CODEX_TURN_METADATA_HEADER: &str = "x-codex-turn-metadata";
 pub const X_RESPONSESAPI_INCLUDE_TIMING_METRICS_HEADER: &str =
@@ -477,14 +479,8 @@ impl ModelClientSession {
         };
 
         if needs_new {
-            let mut headers = options.extra_headers.clone();
-            headers.extend(build_conversation_headers(options.conversation_id.clone()));
-            if self.client.state.include_timing_metrics {
-                headers.insert(
-                    X_RESPONSESAPI_INCLUDE_TIMING_METRICS_HEADER,
-                    HeaderValue::from_static("true"),
-                );
-            }
+            let headers =
+                build_websocket_connect_headers(options, self.client.state.include_timing_metrics);
             let websocket_telemetry = Self::build_websocket_telemetry(otel_manager);
             let new_conn: ApiWebSocketConnection =
                 ApiWebSocketResponsesClient::new(api_provider, api_auth)
@@ -787,6 +783,25 @@ fn build_responses_headers(
     headers
 }
 
+fn build_websocket_connect_headers(
+    options: &ApiResponsesOptions,
+    include_timing_metrics: bool,
+) -> ApiHeaderMap {
+    let mut headers = options.extra_headers.clone();
+    headers.extend(build_conversation_headers(options.conversation_id.clone()));
+    headers.insert(
+        OPENAI_BETA_HEADER,
+        HeaderValue::from_static(OPENAI_BETA_RESPONSES_WEBSOCKETS),
+    );
+    if include_timing_metrics {
+        headers.insert(
+            X_RESPONSESAPI_INCLUDE_TIMING_METRICS_HEADER,
+            HeaderValue::from_static("true"),
+        );
+    }
+    headers
+}
+
 fn map_response_stream<S>(api_stream: S, otel_manager: OtelManager) -> ResponseStream
 where
     S: futures::Stream<Item = std::result::Result<ResponseEvent, ApiError>>
diff --git a/codex-rs/core/tests/suite/client_websockets.rs b/codex-rs/core/tests/suite/client_websockets.rs
index e58a512f9..76a1f0b3c 100644
--- a/codex-rs/core/tests/suite/client_websockets.rs
+++ b/codex-rs/core/tests/suite/client_websockets.rs
@@ -40,6 +40,8 @@ use tempfile::TempDir;
 use tracing_test::traced_test;
 
 const MODEL: &str = "gpt-5.2-codex";
+const OPENAI_BETA_HEADER: &str = "OpenAI-Beta";
+const OPENAI_BETA_RESPONSES_WEBSOCKETS: &str = "responses_websockets=2026-02-04";
 
 struct WebsocketTestHarness {
     _codex_home: TempDir,
@@ -74,6 +76,11 @@ async fn responses_websocket_streams_request() {
     assert_eq!(body["model"].as_str(), Some(MODEL));
     assert_eq!(body["stream"], serde_json::Value::Bool(true));
     assert_eq!(body["input"].as_array().map(Vec::len), Some(1));
+    let handshake = server.single_handshake();
+    assert_eq!(
+        handshake.header(OPENAI_BETA_HEADER),
+        Some(OPENAI_BETA_RESPONSES_WEBSOCKETS.to_string())
+    );
 
     server.shutdown().await;
 }