diff --git a/codex-rs/app-server-protocol/src/protocol/thread_history.rs b/codex-rs/app-server-protocol/src/protocol/thread_history.rs
index 04cd1190bc..ba1e6261cc 100644
--- a/codex-rs/app-server-protocol/src/protocol/thread_history.rs
+++ b/codex-rs/app-server-protocol/src/protocol/thread_history.rs
@@ -1,5 +1,6 @@
 use crate::protocol::v2::ThreadItem;
 use crate::protocol::v2::Turn;
+use crate::protocol::v2::TurnError;
 use crate::protocol::v2::TurnStatus;
 use crate::protocol::v2::UserInput;
 use codex_protocol::protocol::AgentReasoningEvent;
@@ -142,6 +143,7 @@ impl ThreadHistoryBuilder {
         PendingTurn {
             id: self.next_turn_id(),
             items: Vec::new(),
+            error: None,
             status: TurnStatus::Completed,
         }
     }
@@ -190,6 +192,7 @@ impl ThreadHistoryBuilder {
 struct PendingTurn {
     id: String,
     items: Vec<ThreadItem>,
+    error: Option<TurnError>,
     status: TurnStatus,
 }
 
@@ -198,6 +201,7 @@ impl From<PendingTurn> for Turn {
         Self {
             id: value.id,
             items: value.items,
+            error: value.error,
             status: value.status,
         }
     }
diff --git a/codex-rs/app-server-protocol/src/protocol/v2.rs b/codex-rs/app-server-protocol/src/protocol/v2.rs
index 3772607420..fc25493e78 100644
--- a/codex-rs/app-server-protocol/src/protocol/v2.rs
+++ b/codex-rs/app-server-protocol/src/protocol/v2.rs
@@ -875,8 +875,9 @@ pub struct Turn {
     /// For all other responses and notifications returning a Turn,
     /// the items field will be an empty list.
     pub items: Vec<ThreadItem>,
-    #[serde(flatten)]
     pub status: TurnStatus,
+    /// Only populated when the Turn's status is failed.
+    pub error: Option<TurnError>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS, Error)]
@@ -898,12 +899,12 @@ pub struct ErrorNotification {
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
-#[serde(tag = "status", rename_all = "camelCase")]
-#[ts(tag = "status", export_to = "v2/")]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
 pub enum TurnStatus {
     Completed,
     Interrupted,
-    Failed { error: TurnError },
+    Failed,
     InProgress,
 }
 
diff --git a/codex-rs/app-server-test-client/src/main.rs b/codex-rs/app-server-test-client/src/main.rs
index f75f3f98a8..8c2a38e46c 100644
--- a/codex-rs/app-server-test-client/src/main.rs
+++ b/codex-rs/app-server-test-client/src/main.rs
@@ -563,7 +563,9 @@ impl CodexClient {
                 ServerNotification::TurnCompleted(payload) => {
                     if payload.turn.id == turn_id {
                         println!("\n< turn/completed notification: {:?}", payload.turn.status);
-                        if let TurnStatus::Failed { error } = &payload.turn.status {
+                        if payload.turn.status == TurnStatus::Failed
+                            && let Some(error) = payload.turn.error
+                        {
                             println!("[turn error] {}", error.message);
                         }
                         break;
diff --git a/codex-rs/app-server/src/bespoke_event_handling.rs b/codex-rs/app-server/src/bespoke_event_handling.rs
index 00757c8a94..b4dd16b9a6 100644
--- a/codex-rs/app-server/src/bespoke_event_handling.rs
+++ b/codex-rs/app-server/src/bespoke_event_handling.rs
@@ -718,6 +718,7 @@ async fn emit_turn_completed_with_status(
     conversation_id: ConversationId,
     event_turn_id: String,
     status: TurnStatus,
+    error: Option<TurnError>,
     outgoing: &OutgoingMessageSender,
 ) {
     let notification = TurnCompletedNotification {
@@ -725,6 +726,7 @@ async fn emit_turn_completed_with_status(
         turn: Turn {
             id: event_turn_id,
             items: vec![],
+            error,
             status,
         },
     };
@@ -813,13 +815,12 @@ async fn handle_turn_complete(
 ) {
     let turn_summary = find_and_remove_turn_summary(conversation_id, turn_summary_store).await;
 
-    let status = if let Some(error) = turn_summary.last_error {
-        TurnStatus::Failed { error }
-    } else {
-        TurnStatus::Completed
+    let (status, error) = match turn_summary.last_error {
+        Some(error) => (TurnStatus::Failed, Some(error)),
+        None => (TurnStatus::Completed, None),
     };
 
-    emit_turn_completed_with_status(conversation_id, event_turn_id, status, outgoing).await;
+    emit_turn_completed_with_status(conversation_id, event_turn_id, status, error, outgoing).await;
 }
 
 async fn handle_turn_interrupted(
@@ -834,6 +835,7 @@ async fn handle_turn_interrupted(
         conversation_id,
         event_turn_id,
         TurnStatus::Interrupted,
+        None,
         outgoing,
     )
     .await;
@@ -1306,6 +1308,7 @@ mod tests {
             OutgoingMessage::AppServerNotification(ServerNotification::TurnCompleted(n)) => {
                 assert_eq!(n.turn.id, event_turn_id);
                 assert_eq!(n.turn.status, TurnStatus::Completed);
+                assert_eq!(n.turn.error, None);
             }
             other => bail!("unexpected message: {other:?}"),
         }
@@ -1346,6 +1349,7 @@ mod tests {
             OutgoingMessage::AppServerNotification(ServerNotification::TurnCompleted(n)) => {
                 assert_eq!(n.turn.id, event_turn_id);
                 assert_eq!(n.turn.status, TurnStatus::Interrupted);
+                assert_eq!(n.turn.error, None);
             }
             other => bail!("unexpected message: {other:?}"),
         }
@@ -1385,14 +1389,13 @@ mod tests {
         match msg {
             OutgoingMessage::AppServerNotification(ServerNotification::TurnCompleted(n)) => {
                 assert_eq!(n.turn.id, event_turn_id);
+                assert_eq!(n.turn.status, TurnStatus::Failed);
                 assert_eq!(
-                    n.turn.status,
-                    TurnStatus::Failed {
-                        error: TurnError {
-                            message: "bad".to_string(),
-                            codex_error_info: Some(V2CodexErrorInfo::Other),
-                        }
-                    }
+                    n.turn.error,
+                    Some(TurnError {
+                        message: "bad".to_string(),
+                        codex_error_info: Some(V2CodexErrorInfo::Other),
+                    })
                 );
             }
             other => bail!("unexpected message: {other:?}"),
@@ -1653,14 +1656,13 @@ mod tests {
         match msg {
             OutgoingMessage::AppServerNotification(ServerNotification::TurnCompleted(n)) => {
                 assert_eq!(n.turn.id, a_turn1);
+                assert_eq!(n.turn.status, TurnStatus::Failed);
                 assert_eq!(
-                    n.turn.status,
-                    TurnStatus::Failed {
-                        error: TurnError {
-                            message: "a1".to_string(),
-                            codex_error_info: Some(V2CodexErrorInfo::BadRequest),
-                        }
-                    }
+                    n.turn.error,
+                    Some(TurnError {
+                        message: "a1".to_string(),
+                        codex_error_info: Some(V2CodexErrorInfo::BadRequest),
+                    })
                 );
             }
             other => bail!("unexpected message: {other:?}"),
@@ -1674,14 +1676,13 @@ mod tests {
         match msg {
             OutgoingMessage::AppServerNotification(ServerNotification::TurnCompleted(n)) => {
                 assert_eq!(n.turn.id, b_turn1);
+                assert_eq!(n.turn.status, TurnStatus::Failed);
                 assert_eq!(
-                    n.turn.status,
-                    TurnStatus::Failed {
-                        error: TurnError {
-                            message: "b1".to_string(),
-                            codex_error_info: None,
-                        }
-                    }
+                    n.turn.error,
+                    Some(TurnError {
+                        message: "b1".to_string(),
+                        codex_error_info: None,
+                    })
                 );
             }
             other => bail!("unexpected message: {other:?}"),
@@ -1696,6 +1697,7 @@ mod tests {
             OutgoingMessage::AppServerNotification(ServerNotification::TurnCompleted(n)) => {
                 assert_eq!(n.turn.id, a_turn2);
                 assert_eq!(n.turn.status, TurnStatus::Completed);
+                assert_eq!(n.turn.error, None);
             }
             other => bail!("unexpected message: {other:?}"),
         }
diff --git a/codex-rs/app-server/src/codex_message_processor.rs b/codex-rs/app-server/src/codex_message_processor.rs
index 95d53c7202..3619260aac 100644
--- a/codex-rs/app-server/src/codex_message_processor.rs
+++ b/codex-rs/app-server/src/codex_message_processor.rs
@@ -2453,6 +2453,7 @@ impl CodexMessageProcessor {
                 let turn = Turn {
                     id: turn_id.clone(),
                     items: vec![],
+                    error: None,
                     status: TurnStatus::InProgress,
                 };
 
@@ -2494,6 +2495,7 @@ impl CodexMessageProcessor {
         Turn {
             id: turn_id,
             items,
+            error: None,
             status: TurnStatus::InProgress,
         }
     }