diff --git a/crates/app-tauri/src/chat.rs b/crates/app-tauri/src/chat.rs
index a0ae1675..6170e86d 100644
--- a/crates/app-tauri/src/chat.rs
+++ b/crates/app-tauri/src/chat.rs
@@ -35,6 +35,11 @@ use domain::ports::{
 };
 
 use crate::dto::{ReplyChunk, ReplyProgressDto, ReplyProgressKindDto, ReplyProgressStageDto};
+
+/// Visible terminal message when a structured stream ends without the authoritative
+/// `ReplyEvent::Final`.
+pub const MODEL_RESPONSE_NOT_FINALIZED_MESSAGE: &str =
+    "La réponse du modèle n'a pas pu être finalisée.";
 use crate::stream::TauriChannelSink;
 
 /// Maximum number of recent chat chunks retained for transport reattach replay.
@@ -338,3 +343,12 @@ pub fn chunk_from_event(event: ReplyEvent) -> Option<ReplyChunk> {
         ReplyEvent::RateLimited { .. } => None,
     }
 }
+
+/// Terminal wire chunk for an exhausted structured stream that never produced the
+/// authoritative `ReplyEvent::Final`.
+#[must_use]
+pub fn unfinished_turn_chunk() -> ReplyChunk {
+    ReplyChunk::Error {
+        message: MODEL_RESPONSE_NOT_FINALIZED_MESSAGE.to_owned(),
+    }
+}
diff --git a/crates/app-tauri/src/commands.rs b/crates/app-tauri/src/commands.rs
index 80b258ca..73dc7d26 100644
--- a/crates/app-tauri/src/commands.rs
+++ b/crates/app-tauri/src/commands.rs
@@ -2512,7 +2512,6 @@ pub async fn agent_send(
     let meta = state.structured_sessions.meta_for_session(&sid);
     std::thread::spawn(move || {
         let mut terminal_visible = false;
-        let mut streamed_text = String::new();
         let mut settler = crate::chat::ProgressSettler::default();
         for event in stream {
             // Non-terminal, sans contenu chat : un signal de limite alimente le service
@@ -2543,9 +2542,6 @@ pub async fn agent_send(
             let Some(chunk) = crate::chat::chunk_from_event(event) else {
                 continue;
             };
-            if let ReplyChunk::TextDelta { text } = &chunk {
-                streamed_text.push_str(text);
-            }
             if matches!(chunk, ReplyChunk::Final { .. } | ReplyChunk::Error { .. }) {
                 terminal_visible = true;
             }
@@ -2556,15 +2552,7 @@ pub async fn agent_send(
             let _ = bridge.send_output_settled(&sid, &mut settler, chunk);
         }
         if !terminal_visible {
-            let chunk = if streamed_text.trim().is_empty() {
-                ReplyChunk::Error {
-                    message: "Le modèle n'a renvoyé aucune réponse.".to_owned(),
-                }
-            } else {
-                ReplyChunk::Final {
-                    content: streamed_text,
-                }
-            };
+            let chunk = crate::chat::unfinished_turn_chunk();
             let _ = bridge.send_output_settled(&sid, &mut settler, chunk);
         }
         bridge.detach_if(&sid, gen);
diff --git a/crates/app-tauri/tests/chat_bridge.rs b/crates/app-tauri/tests/chat_bridge.rs
index 23b70dcb..35ee19d9 100644
--- a/crates/app-tauri/tests/chat_bridge.rs
+++ b/crates/app-tauri/tests/chat_bridge.rs
@@ -14,8 +14,8 @@ use std::sync::{Arc, Mutex};
 use tauri::ipc::{Channel, InvokeResponseBody};
 
 use app_tauri_lib::chat::{
-    chunk_from_event, ChatBridge, ProgressSettler, MAX_CHAT_SCROLLBACK_BYTES,
-    MAX_CHAT_SCROLLBACK_CHUNKS,
+    chunk_from_event, unfinished_turn_chunk, ChatBridge, ProgressSettler,
+    MAX_CHAT_SCROLLBACK_BYTES, MAX_CHAT_SCROLLBACK_CHUNKS, MODEL_RESPONSE_NOT_FINALIZED_MESSAGE,
 };
 use app_tauri_lib::dto::{
     ReplyChunk, ReplyProgressDto, ReplyProgressKindDto, ReplyProgressSourceDto,
@@ -233,13 +233,9 @@ fn chunk_from_event_drops_heartbeat() {
 /// end. This is the body of the spawned pump thread, run inline.
 fn pump_turn(bridge: &ChatBridge, session: &SessionId, gen: u64, events: Vec<ReplyEvent>) {
     let mut terminal_visible = false;
-    let mut streamed_text = String::new();
     for event in events {
         // Mirror the real pump: heartbeats map to no chunk and are skipped.
         if let Some(chunk) = chunk_from_event(event) {
-            if let ReplyChunk::TextDelta { text } = &chunk {
-                streamed_text.push_str(text);
-            }
             if matches!(chunk, ReplyChunk::Final { .. } | ReplyChunk::Error { .. }) {
                 terminal_visible = true;
             }
@@ -247,12 +243,7 @@ fn pump_turn(bridge: &ChatBridge, session: &SessionId, gen: u64, events: Vec<Rep
         }
     }
     if !terminal_visible {
-        let chunk = if streamed_text.trim().is_empty() {
-            error_chunk("Le modèle n'a renvoyé aucune réponse.")
-        } else {
-            final_chunk(&streamed_text)
-        };
-        let _ = bridge.send_output(session, chunk);
+        let _ = bridge.send_output(session, unfinished_turn_chunk());
     }
     bridge.detach_if(session, gen);
 }
@@ -313,7 +304,7 @@ fn pump_with_only_a_final_delivers_just_the_final() {
 }
 
 #[test]
-fn pump_with_text_deltas_then_eof_synthesizes_final_not_no_reply() {
+fn pump_with_text_deltas_then_eof_emits_not_finalized_error() {
     let bridge = ChatBridge::new();
     let session = sid();
     let sink = Arc::new(Mutex::new(Vec::new()));
@@ -331,12 +322,20 @@ fn pump_with_text_deltas_then_eof_synthesizes_final_not_no_reply() {
 
     assert_eq!(
         sink.lock().unwrap().as_slice(),
-        &[delta("Hel"), delta("lo"), final_chunk("Hello")]
+        &[
+            delta("Hel"),
+            delta("lo"),
+            error_chunk(MODEL_RESPONSE_NOT_FINALIZED_MESSAGE)
+        ]
     );
     assert_eq!(
         bridge.scrollback(&session),
-        vec![delta("Hel"), delta("lo"), final_chunk("Hello")],
-        "reattach replays the synthesized terminal chunk instead of no-reply"
+        vec![
+            delta("Hel"),
+            delta("lo"),
+            error_chunk(MODEL_RESPONSE_NOT_FINALIZED_MESSAGE)
+        ],
+        "reattach replays the explicit not-finalized terminal chunk"
     );
 }
 
@@ -351,7 +350,7 @@ fn pump_with_heartbeat_then_eof_emits_visible_error() {
 
     assert_eq!(
         sink.lock().unwrap().as_slice(),
-        &[error_chunk("Le modèle n'a renvoyé aucune réponse.")]
+        &[error_chunk(MODEL_RESPONSE_NOT_FINALIZED_MESSAGE)]
     );
 }
 
@@ -593,7 +592,7 @@ fn detach_view_keeps_session_scrollback_and_later_reattach_replays_absent_chunks
 }
 
 #[test]
-fn detached_turn_with_text_eof_replays_final_without_no_reply_on_reattach() {
+fn detached_turn_with_text_eof_replays_not_finalized_error_on_reattach() {
     let bridge = ChatBridge::new();
     let session = sid();
     let first_sink = Arc::new(Mutex::new(Vec::new()));
@@ -618,13 +617,11 @@ fn detached_turn_with_text_eof_replays_final_without_no_reply_on_reattach() {
     );
     assert_eq!(
         bridge.scrollback(&session),
-        vec![delta("off"), delta("screen"), final_chunk("offscreen")]
-    );
-    assert!(
-        !bridge
-            .scrollback(&session)
-            .iter()
-            .any(|chunk| matches!(chunk, ReplyChunk::Error { message } if message == "Le modèle n'a renvoyé aucune réponse."))
+        vec![
+            delta("off"),
+            delta("screen"),
+            error_chunk(MODEL_RESPONSE_NOT_FINALIZED_MESSAGE)
+        ]
     );
 }
 
diff --git a/crates/app-tauri/tests/dto.rs b/crates/app-tauri/tests/dto.rs
index d54a9abc..8b74c1f0 100644
--- a/crates/app-tauri/tests/dto.rs
+++ b/crates/app-tauri/tests/dto.rs
@@ -183,6 +183,13 @@ fn error_dto_carries_stable_code_and_message() {
     assert!(v.get("message").is_some());
 }
 
+#[test]
+fn error_dto_preserves_structured_no_final_code() {
+    let dto = ErrorDto::from(AppError::TargetReturnedNoReply("architect".into()));
+    assert_eq!(dto.code, "TARGET_RETURNED_NO_REPLY");
+    assert!(dto.message.contains("structured Final response"));
+}
+
 #[test]
 fn domain_event_relay_name_is_frozen() {
     assert_eq!(DOMAIN_EVENT, "domain://event");