diff --git a/desktop/src-tauri/src/dictation.rs b/desktop/src-tauri/src/dictation.rs
index 7295506..ef7a6af 100644
--- a/desktop/src-tauri/src/dictation.rs
+++ b/desktop/src-tauri/src/dictation.rs
@@ -4,8 +4,9 @@
 
 use parking_lot::Mutex;
 use serde_json::{json, Value};
-use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
 use std::sync::mpsc;
+use std::sync::Arc;
 use std::time::{Duration, Instant};
 use tauri::{AppHandle, Emitter, EventTarget, Manager};
 use tokio::sync::Notify;
@@ -24,12 +25,14 @@ pub struct DictationState {
 }
 
 struct Session {
-    id: String,
     /// 会话代际（18A/18B）：每次 start 自增，on_server_msg / 收尾任务校验后才生效。
     epoch: u64,
     capture: Option<crate::audio::Capture>,
     started: Instant,
     got_first_partial: bool,
+    /// 收尾语义（true=取消）：stop() 在停采集前写入，转发线程排空音频后据此
+    /// 发 Stop/Cancel 帧，保证控制帧在全部音频帧之后到网关（尾部不丢，见 stop）。
+    canceled: Arc<AtomicBool>,
 }
 
 pub fn start(app: &AppHandle) {
@@ -71,23 +74,42 @@ pub fn start(app: &AppHandle) {
             None
         }
     };
+    // 收尾语义标志：stop() 停采集前写入；转发线程排空音频后读取并发控制帧。
+    let canceled = Arc::new(AtomicBool::new(false));
     {
         let ws = ws.clone();
+        let sid = session_id.clone();
+        let canceled = canceled.clone();
         std::thread::spawn(move || {
-            while let Ok(frame) = rx.recv() {
-                if ws.send(crate::ws::WsCmd::Audio(frame)).is_err() {
-                    break;
+            // 排空音频通道：capture 被 drop（stop 里）→ tx 关闭 → 这里 recv 收完
+            // 剩余缓冲帧后返回 Err。ws 写入失败则直接退出，不再补发控制帧。
+            loop {
+                match rx.recv() {
+                    Ok(frame) => {
+                        if ws.send(crate::ws::WsCmd::Audio(frame)).is_err() {
+                            return;
+                        }
+                    }
+                    Err(_) => break,
                 }
             }
+            // 音频已全部入队，最后才发 Stop/Cancel——保证控制帧排在所有音频帧之后，
+            // 网关先收完音频再收 stop，尾部半秒不再被截断（竞态修复）。
+            let cmd = if canceled.load(Ordering::SeqCst) {
+                crate::ws::WsCmd::Cancel { session_id: sid }
+            } else {
+                crate::ws::WsCmd::Stop { session_id: sid }
+            };
+            let _ = ws.send(cmd);
         });
     }
 
     *state.inner.lock() = Some(Session {
-        id: session_id,
         epoch,
         capture,
         started: Instant::now(),
         got_first_partial: false,
+        canceled,
     });
 }
 
@@ -104,7 +126,11 @@ pub fn stop(app: &AppHandle, canceled: bool) {
     let epoch = sess.epoch;
     emit_overlay(app, "hotkey", json!({"state": "up"}));
     set_tray_tooltip(app, "dudu — 就绪");
-    sess.capture.take(); // 停止采集
+
+    // 先写收尾语义，再停采集：转发线程排空音频后据此发 Stop/Cancel，
+    // 保证控制帧排在所有音频帧之后（尾部不被截断）。不在此处直接发控制帧。
+    sess.canceled.store(canceled, Ordering::SeqCst);
+    sess.capture.take(); // 停止采集 → 关音频通道 → 转发线程排空后补发控制帧
 
     let buf = app.state::<CommitBuffer>();
     if canceled {
@@ -112,14 +138,6 @@ pub fn stop(app: &AppHandle, canceled: bool) {
         buf.discard(epoch);
     }
 
-    let ws = (*app.state::<crate::ws::WsHandle>()).clone();
-    let cmd = if canceled {
-        crate::ws::WsCmd::Cancel { session_id: sess.id.clone() }
-    } else {
-        crate::ws::WsCmd::Stop { session_id: sess.id.clone() }
-    };
-    let _ = ws.send(cmd);
-
     // 取尾部 final 完成信号（事件驱动注入，18C）。
     let finalized = buf.finalize_signal();