diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index 3c21552dcb..14dba39e29 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -31,6 +31,7 @@ use crate::client_common::Prompt;
 use crate::client_common::ResponseEvent;
 use crate::client_common::ResponseStream;
 use crate::client_common::ResponsesApiRequest;
+use crate::client_common::TurnType;
 use crate::client_common::create_reasoning_param_for_request;
 use crate::client_common::create_text_param_for_request;
 use crate::config::Config;
@@ -244,7 +245,7 @@ impl ModelClient {
         let max_attempts = self.provider.request_max_retries();
         for attempt in 0..=max_attempts {
             match self
-                .attempt_stream_responses(attempt, &payload_json, &auth_manager)
+                .attempt_stream_responses(attempt, &payload_json, &auth_manager, prompt.turn_type)
                 .await
             {
                 Ok(stream) => {
@@ -272,6 +273,7 @@ impl ModelClient {
         attempt: u64,
         payload_json: &Value,
         auth_manager: &Option<Arc<AuthManager>>,
+        turn_type: TurnType,
     ) -> std::result::Result<ResponseStream, StreamAttemptError> {
         // Always fetch the latest auth in case a prior attempt refreshed the token.
         let auth = auth_manager.as_ref().and_then(|m| m.auth());
@@ -293,6 +295,13 @@ impl ModelClient {
             // Send session_id for compatibility.
             .header("conversation_id", self.conversation_id.to_string())
             .header("session_id", self.conversation_id.to_string())
+            .header(
+                "action_kind",
+                match turn_type {
+                    TurnType::Review => "review",
+                    TurnType::Regular => "turn",
+                },
+            )
             .header(reqwest::header::ACCEPT, "text/event-stream")
             .json(payload_json);
 
diff --git a/codex-rs/core/src/client_common.rs b/codex-rs/core/src/client_common.rs
index d30da5192a..f25a2093b4 100644
--- a/codex-rs/core/src/client_common.rs
+++ b/codex-rs/core/src/client_common.rs
@@ -23,6 +23,13 @@ use tokio::sync::mpsc;
 /// Review thread system prompt. Edit `core/src/review_prompt.md` to customize.
 pub const REVIEW_PROMPT: &str = include_str!("../review_prompt.md");
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum TurnType {
+    #[default]
+    Regular,
+    Review,
+}
+
 /// API request payload for a single model turn
 #[derive(Default, Debug, Clone)]
 pub struct Prompt {
@@ -41,6 +48,9 @@ pub struct Prompt {
 
     /// Optional the output schema for the model's response.
     pub output_schema: Option<Value>,
+
+    /// The type of turn being executed
+    pub turn_type: TurnType,
 }
 
 impl Prompt {
diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index d11a53b59a..4d3e4cf9d6 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -42,6 +42,7 @@ use crate::apply_patch::convert_apply_patch_to_protocol;
 use crate::client::ModelClient;
 use crate::client_common::Prompt;
 use crate::client_common::ResponseEvent;
+use crate::client_common::TurnType;
 use crate::config::Config;
 use crate::config_types::ShellEnvironmentPolicy;
 use crate::conversation_history::ConversationHistory;
@@ -1933,6 +1934,13 @@ async fn run_turn(
     sub_id: String,
     input: Vec<ResponseItem>,
 ) -> CodexResult<TurnRunResult> {
+    fn resolve_turn_type(turn_context: &TurnContext) -> TurnType {
+        if turn_context.is_review_mode {
+            TurnType::Review
+        } else {
+            TurnType::Regular
+        }
+    }
     let mcp_tools = sess.services.mcp_connection_manager.list_all_tools();
     let router = Arc::new(ToolRouter::from_config(
         &turn_context.tools_config,
@@ -1950,6 +1958,7 @@ async fn run_turn(
         parallel_tool_calls,
         base_instructions_override: turn_context.base_instructions.clone(),
         output_schema: turn_context.final_output_json_schema.clone(),
+        turn_type: resolve_turn_type(&turn_context),
     };
 
     let mut retries = 0;
diff --git a/codex-rs/core/tests/suite/client.rs b/codex-rs/core/tests/suite/client.rs
index eb14dabb81..29dc5f6b81 100644
--- a/codex-rs/core/tests/suite/client.rs
+++ b/codex-rs/core/tests/suite/client.rs
@@ -349,12 +349,14 @@ async fn includes_conversation_id_and_model_headers_in_request() {
     let request_conversation_id = request.headers.get("conversation_id").unwrap();
     let request_authorization = request.headers.get("authorization").unwrap();
     let request_originator = request.headers.get("originator").unwrap();
+    let turn_kind = request.headers.get("action_kind").unwrap();
 
     assert_eq!(
         request_conversation_id.to_str().unwrap(),
         conversation_id.to_string()
     );
     assert_eq!(request_originator.to_str().unwrap(), "codex_cli_rs");
+    assert_eq!(turn_kind.to_str().unwrap(), "turn");
     assert_eq!(
         request_authorization.to_str().unwrap(),
         "Bearer Test API Key"
diff --git a/codex-rs/core/tests/suite/review.rs b/codex-rs/core/tests/suite/review.rs
index f3eeb3a310..61fe1f198e 100644
--- a/codex-rs/core/tests/suite/review.rs
+++ b/codex-rs/core/tests/suite/review.rs
@@ -338,6 +338,78 @@ async fn review_uses_custom_review_model_from_config() {
     server.verify().await;
 }
 
+/// Ensure the client marks review turns with `action_kind: review` on the
+/// outbound Responses API request.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn review_sends_action_kind_header() {
+    skip_if_no_network!();
+
+    // Minimal stream: just a completed event
+    let sse_raw = r#"[
+        {"type":"response.completed", "response": {"id": "__ID__"}}
+    ]"#;
+    // Expect 2 requests total: first the review thread, then a follow-up turn.
+    let server = start_responses_server_with_sse(sse_raw, 2).await;
+    let codex_home = TempDir::new().unwrap();
+    let codex = new_conversation_for_server(&server, &codex_home, |_| {}).await;
+
+    codex
+        .submit(Op::Review {
+            review_request: ReviewRequest {
+                prompt: "check action_kind header".to_string(),
+                user_facing_hint: "check action_kind header".to_string(),
+            },
+        })
+        .await
+        .unwrap();
+
+    // Wait for completion to ensure the request was sent.
+    let _entered = wait_for_event(&codex, |ev| matches!(ev, EventMsg::EnteredReviewMode(_))).await;
+    let _closed = wait_for_event(&codex, |ev| matches!(ev, EventMsg::ExitedReviewMode(_))).await;
+    let _complete = wait_for_event(&codex, |ev| matches!(ev, EventMsg::TaskComplete(_))).await;
+
+    // Assert the outbound request included the correct header for the review request.
+    let mut requests = server.received_requests().await.unwrap();
+    assert!(
+        !requests.is_empty(),
+        "expected at least one request (review)"
+    );
+    let review_req = &requests[0];
+    let review_kind = review_req.headers.get("action_kind");
+    assert!(
+        review_kind.is_some(),
+        "expected action_kind header on review"
+    );
+    assert_eq!(review_kind.unwrap().to_str().unwrap(), "review");
+
+    // Now send a normal follow-up turn and ensure its header is "turn".
+    codex
+        .submit(Op::UserInput {
+            items: vec![InputItem::Text {
+                text: "follow-up after review".to_string(),
+            }],
+        })
+        .await
+        .unwrap();
+    let _complete2 = wait_for_event(&codex, |ev| matches!(ev, EventMsg::TaskComplete(_))).await;
+
+    requests = server.received_requests().await.unwrap();
+    assert_eq!(
+        requests.len(),
+        2,
+        "expected 2 requests (review + follow-up)"
+    );
+    let follow_req = &requests[1];
+    let follow_kind = follow_req.headers.get("action_kind");
+    assert!(
+        follow_kind.is_some(),
+        "expected action_kind header on follow-up"
+    );
+    assert_eq!(follow_kind.unwrap().to_str().unwrap(), "turn");
+
+    server.verify().await;
+}
+
 /// When a review session begins, it must not prepend prior chat history from
 /// the parent session. The request `input` should contain only the review
 /// prompt from the user.