Terminal utf8 and reconnect (#14895)

* fix: handle incomplete UTF-8 sequences in terminal output, rework on https://github.com/rustdesk/rustdesk/pull/14736

* Fix terminal auto-reconnect freeze:  reconnect resumes terminal output, while multi-tab reconnect avoids restoring duplicate tabs for terminals that are already open.

* fix(terminal): subtract with overflow

```
thread '<unnamed>' panicked at src\server\terminal_service.rs:476:17:
attempt to subtract with overflow
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'tokio-runtime-worker' panicked at src\server\terminal_service.rs:1576:50:
called `Result::unwrap()` on an `Err` value: PoisonError { .. }
[2026-04-25T07:17:34Z ERROR librustdesk::server::service] Failed to join thread for service ts_9badd3fe-2411-4996-9f40-93c979009edd, Any { .. }
```

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix ios enter: https://github.com/rustdesk/rustdesk/issues/14907

* fix(terminal): reconnect, error handling

1. Terminal shows "^[[1;1R^[[2;2R^[[>0;0;0c"
2. NaN

```
[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Converting object to an encodable object failed: NaN
...
```

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): dialog, close window

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): close terminal window on disconnect dialog

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): merge reconnect backlog into replay output

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): avoid reconnect stalls and delayed layout writes

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): remove invalid test

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): schedule frame before flushing buffered output

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): windows&macos, charset utf-8

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): reconnect suppress next output

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix: cap terminal reconnect replay output

  - split reconnect replay backlog into capped chunks
  - mark terminal data replay chunks for client-side suppression
  - avoid using open-message text to suppress xterm replies
  - reuse default terminal padding value
  - remove misleading Enter-key normalization PR link

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): env en_US.UTF-8

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): reconnect, refactor

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): flag, retry output

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): update hbb_common

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): comments

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): comments utf-8 chunk accumulator

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(terminal): update hbb_common

Signed-off-by: fufesou <linlong1266@gmail.com>

---------

Signed-off-by: fufesou <linlong1266@gmail.com>
Co-authored-by: fufesou <linlong1266@gmail.com>

flutter/lib/common.dart

@@ -716,6 +716,17 @@ closeConnection({String? id}) {
       stateGlobal.isInMainPage = true;
     } else {
       final controller = Get.find<DesktopTabController>();
+      if (controller.tabType == DesktopTabType.terminal &&
+          controller.onCloseWindow != null) {
+        // Terminal windows are scoped to one peer. The optional id passed to
+        // closeConnection() is that peer id, not a terminal tab key
+        // (${peerId}_${terminalId}). Closing from terminal dialogs should close
+        // the peer's whole terminal window, including all terminal tabs.
+        unawaited(controller.onCloseWindow!().catchError((e, _) {
+          debugPrint('[closeConnection] Failed to close terminal window: $e');
+        }));
+        return;
+      }
       controller.closeBy(id);
     }
   }
@@ -4179,8 +4190,7 @@ Widget? buildAvatarWidget({
       width: size,
       height: size,
       fit: BoxFit.cover,
-      errorBuilder: (_, __, ___) =>
-          fallback ?? SizedBox.shrink(),
+      errorBuilder: (_, __, ___) => fallback ?? SizedBox.shrink(),
     ),
   );
 }

flutter/lib/desktop/pages/terminal_page.dart

@@ -27,6 +27,7 @@ class TerminalPage extends StatefulWidget {
   final bool? isSharedPassword;
   final String? connToken;
   final int terminalId;
+
   /// Tab key for focus management, passed from parent to avoid duplicate construction
   final String tabKey;
   final SimpleWrapper<State<TerminalPage>?> _lastState = SimpleWrapper(null);
@@ -43,6 +44,9 @@ class TerminalPage extends StatefulWidget {
 
 class _TerminalPageState extends State<TerminalPage>
     with AutomaticKeepAliveClientMixin {
+  static const EdgeInsets _defaultTerminalPadding =
+      EdgeInsets.symmetric(horizontal: 5.0, vertical: 2.0);
+
   late FFI _ffi;
   late TerminalModel _terminalModel;
   double? _cellHeight;
@@ -155,13 +159,27 @@ class _TerminalPageState extends State<TerminalPage>
   // extra space left after dividing the available height by the height of a single
   // terminal row (`_cellHeight`) and distributing it evenly as top and bottom padding.
   EdgeInsets _calculatePadding(double heightPx) {
-    if (_cellHeight == null) {
-      return const EdgeInsets.symmetric(horizontal: 5.0, vertical: 2.0);
+    final cellHeight = _cellHeight;
+    if (!heightPx.isFinite ||
+        heightPx <= 0 ||
+        cellHeight == null ||
+        !cellHeight.isFinite ||
+        cellHeight <= 0) {
+      return _defaultTerminalPadding;
+    }
+    final rows = (heightPx / cellHeight).floor();
+    if (rows <= 0) {
+      return _defaultTerminalPadding;
+    }
+    final extraSpace = heightPx - rows * cellHeight;
+    if (!extraSpace.isFinite || extraSpace < 0) {
+      return _defaultTerminalPadding;
     }
-    final rows = (heightPx / _cellHeight!).floor();
-    final extraSpace = heightPx - rows * _cellHeight!;
     final topBottom = extraSpace / 2.0;
-    return EdgeInsets.symmetric(horizontal: 5.0, vertical: topBottom);
+    return EdgeInsets.symmetric(
+      horizontal: _defaultTerminalPadding.horizontal / 2,
+      vertical: topBottom,
+    );
   }
 
   @override

flutter/lib/desktop/pages/terminal_tab_page.dart

@@ -46,6 +46,7 @@ class _TerminalTabPageState extends State<TerminalTabPage> {
           .setTitle(getWindowNameWithId(id));
     };
     tabController.onRemoved = (_, id) => onRemoveId(id);
+    tabController.onCloseWindow = _closeWindowFromConnection;
     final terminalId = params['terminalId'] ?? _nextTerminalId++;
     tabController.add(_createTerminalTab(
       peerId: params['id'],
@@ -144,6 +145,8 @@ class _TerminalTabPageState extends State<TerminalTabPage> {
     _windowClosing = true;
     final tabKeys = tabController.state.value.tabs.map((t) => t.key).toList();
     // Remove all UI tabs immediately (same instant behavior as the old tabController.clear())
+    // Keep the cleanup target lookup below synchronous before its first await:
+    // it relies on the current frame still retaining each TerminalPage's FFI/model.
     tabController.clear();
     // Run session cleanup in parallel with bounded timeout (closeTerminal() has internal 3s timeout).
     // Skip tabs already being closed by a concurrent _closeTab() to avoid duplicate FFI calls.
@@ -368,8 +371,34 @@ class _TerminalTabPageState extends State<TerminalTabPage> {
     final persistentSessions =
         args['persistent_sessions'] as List<dynamic>? ?? [];
     final sortedSessions = persistentSessions.whereType<int>().toList()..sort();
+    var peerId = args['peer_id'] as String? ?? '';
+    if (peerId.isEmpty) {
+      if (tabController.state.value.tabs.isEmpty ||
+          tabController.state.value.selected >=
+              tabController.state.value.tabs.length) {
+        debugPrint('[TerminalTabPage] Skip restore: no selected tab');
+        return;
+      }
+      final currentTab = tabController.state.value.selectedTabInfo;
+      final parsed = _parseTabKey(currentTab.key);
+      if (parsed == null) return;
+      peerId = parsed.$1;
+    }
+    final existingTerminalIds = tabController.state.value.tabs
+        .map((tab) => _parseTabKey(tab.key))
+        .where((parsed) => parsed != null && parsed.$1 == peerId)
+        .map((parsed) => parsed!.$2)
+        .toSet();
+    if (existingTerminalIds.isEmpty) {
+      debugPrint(
+          '[TerminalTabPage] Skip restore: no seed tab for peer $peerId');
+      return;
+    }
     for (final terminalId in sortedSessions) {
-      _addNewTerminalForCurrentPeer(terminalId: terminalId);
+      if (!existingTerminalIds.add(terminalId)) {
+        continue;
+      }
+      _addNewTerminal(peerId, terminalId: terminalId);
       // A delay is required to ensure the UI has sufficient time to update
       // before adding the next terminal. Without this delay, `_TerminalPageState::dispose()`
       // may be called prematurely while the tab widget is still in the tab controller.
@@ -546,6 +575,11 @@ class _TerminalTabPageState extends State<TerminalTabPage> {
     }
   }
 
+  Future<void> _closeWindowFromConnection() async {
+    await _closeAllTabs();
+    await WindowController.fromWindowId(windowId()).close();
+  }
+
   int windowId() {
     return widget.params["windowId"];
   }

flutter/lib/desktop/widgets/tabbar_widget.dart

@@ -99,6 +99,7 @@ class DesktopTabController {
   /// index, key
   Function(int, String)? onRemoved;
   Function(String)? onSelected;
+  Future<void> Function()? onCloseWindow;
 
   DesktopTabController(
       {required this.tabType, this.onRemoved, this.onSelected});

flutter/lib/models/terminal_model.dart

@@ -27,25 +27,30 @@ class TerminalModel with ChangeNotifier {
   // Buffer for output data received before terminal view has valid dimensions.
   // This prevents NaN errors when writing to terminal before layout is complete.
   final _pendingOutputChunks = <String>[];
+  final _pendingOutputSuppressFlags = <bool>[];
   int _pendingOutputSize = 0;
   static const int _kMaxOutputBufferChars = 8 * 1024;
   // View ready state: true when terminal has valid dimensions, safe to write
   bool _terminalViewReady = false;
-
-  bool get isPeerWindows => parent.ffiModel.pi.platform == kPeerPlatformWindows;
+  bool _markViewReadyScheduled = false;
+  bool _suppressTerminalOutput = false;
+  bool _suppressNextTerminalDataOutput = false;
 
   void Function(int w, int h, int pw, int ph)? onResizeExternal;
 
   Future<void> _handleInput(String data) async {
-    // If we press the `Enter` button on Android,
-    // `data` can be '\r' or '\n' when using different keyboards.
-    // Android -> Windows. '\r' works, but '\n' does not. '\n' is just a newline.
-    // Android -> Linux. Both '\r' and '\n' work as expected (execute a command).
-    // So when we receive '\n', we may need to convert it to '\r' to ensure compatibility.
-    // Desktop -> Desktop works fine.
-    // Check if we are on mobile or web(mobile), and convert '\n' to '\r'.
+    // Soft keyboards (notably iOS) emit '\n' when Enter is pressed, while a
+    // real keyboard's Enter sends '\r'. Some Android keyboards also emit '\n'.
+    // - Peer Windows: '\r' works, '\n' is just a newline.
+    // - Peer Linux: canonical-mode shells accept both, but raw-mode apps
+    //   (readline, prompt_toolkit, vim, TUI frameworks) expect '\r'.
+    // - Peer macOS: same as Linux, raw-mode apps expect '\r'
+    //   (https://github.com/rustdesk/rustdesk/issues/14907).
+    // So on mobile / web-mobile, always normalize a lone '\n' to '\r'.
+    // We deliberately do not touch multi-character payloads (e.g. pasted text)
+    // so embedded newlines in pasted content are preserved.
     final isMobileOrWebMobile = (isMobile || (isWeb && !isWebDesktop));
-    if (isMobileOrWebMobile && isPeerWindows && data == '\n') {
+    if (isMobileOrWebMobile && data == '\n') {
       data = '\r';
     }
     if (_terminalOpened) {
@@ -70,7 +75,10 @@ class TerminalModel with ChangeNotifier {
     terminalController = TerminalController();
 
     // Setup terminal callbacks
-    terminal.onOutput = _handleInput;
+    terminal.onOutput = (data) {
+      if (_suppressTerminalOutput) return;
+      _handleInput(data);
+    };
 
     terminal.onResize = (w, h, pw, ph) async {
       // Validate all dimensions before using them
@@ -84,7 +92,7 @@ class TerminalModel with ChangeNotifier {
         // Mark terminal view as ready and flush any buffered output on first valid resize.
         // Must be after onResizeExternal so the view layer has valid dimensions before flushing.
         if (!_terminalViewReady) {
-          _markViewReady();
+          _scheduleMarkViewReady();
         }
 
         if (_terminalOpened) {
@@ -110,14 +118,16 @@ class TerminalModel with ChangeNotifier {
   void onReady() {
     parent.dialogManager.dismissAll();
 
-    // Fire and forget - don't block onReady
-    openTerminal().catchError((e) {
+    // Fire and forget - don't block onReady. If the transport reconnects while
+    // this model is still open, re-send OpenTerminal so the remote service marks
+    // the persistent session active again and resumes output streaming.
+    openTerminal(force: _terminalOpened).catchError((e) {
       debugPrint('[TerminalModel] Error opening terminal: $e');
     });
   }
 
-  Future<void> openTerminal() async {
-    if (_terminalOpened) return;
+  Future<void> openTerminal({bool force = false}) async {
+    if (_terminalOpened && !force) return;
     // Request the remote side to open a terminal with default shell
     // The remote side will decide which shell to use based on its OS
 
@@ -275,9 +285,12 @@ class TerminalModel with ChangeNotifier {
     if (success) {
       _terminalOpened = true;
 
-      // On reconnect ("Reconnected to existing terminal"), server may replay recent output.
-      // If this TerminalView instance is reused (not rebuilt), duplicate lines can appear.
-      // We intentionally accept this tradeoff for now to keep logic simple.
+      // On reconnect, the server may replay recent output. That replay can include
+      // terminal queries like DSR/DA; xterm answers them through onOutput as
+      // "^[[1;1R^[[2;2R^[[>0;0;0c", which must not be sent back to the peer.
+      final replayTerminalOutput = evt['replay_terminal_output'];
+      _suppressNextTerminalDataOutput = replayTerminalOutput == true ||
+          message == 'Reconnected to existing terminal with pending output';
 
       // Fallback: if terminal view is not yet ready but already has valid
       // dimensions (e.g. layout completed before open response arrived),
@@ -285,7 +298,7 @@ class TerminalModel with ChangeNotifier {
       if (!_terminalViewReady &&
           terminal.viewWidth > 0 &&
           terminal.viewHeight > 0) {
-        _markViewReady();
+        _scheduleMarkViewReady();
       }
 
       // Process any buffered input
@@ -297,12 +310,16 @@ class TerminalModel with ChangeNotifier {
       });
 
       final persistentSessions =
-          evt['persistent_sessions'] as List<dynamic>? ?? [];
+          (evt['persistent_sessions'] as List<dynamic>? ?? [])
+              .whereType<int>()
+              .where((id) => !parent.terminalModels.containsKey(id))
+              .toList();
       if (kWindowId != null && persistentSessions.isNotEmpty) {
         DesktopMultiWindow.invokeMethod(
             kWindowId!,
             kWindowEventRestoreTerminalSessions,
             jsonEncode({
+              'peer_id': id,
               'persistent_sessions': persistentSessions,
             }));
       }
@@ -332,6 +349,8 @@ class TerminalModel with ChangeNotifier {
     final data = evt['data'];
 
     if (data != null) {
+      final suppressTerminalOutput = _suppressNextTerminalDataOutput;
+      _suppressNextTerminalDataOutput = false;
       try {
         String text = '';
         if (data is String) {
@@ -351,7 +370,7 @@ class TerminalModel with ChangeNotifier {
           return;
         }
 
-        _writeToTerminal(text);
+        _writeToTerminal(text, suppressTerminalOutput: suppressTerminalOutput);
       } catch (e) {
         debugPrint('[TerminalModel] Failed to process terminal data: $e');
       }
@@ -361,7 +380,10 @@ class TerminalModel with ChangeNotifier {
   /// Write text to terminal, buffering if the view is not yet ready.
   /// All terminal output should go through this method to avoid NaN errors
   /// from writing before the terminal view has valid layout dimensions.
-  void _writeToTerminal(String text) {
+  void _writeToTerminal(
+    String text, {
+    bool suppressTerminalOutput = false,
+  }) {
     if (!_terminalViewReady) {
       // If a single chunk exceeds the cap, keep only its tail.
       // Note: truncation may split a multi-byte ANSI escape sequence,
@@ -373,34 +395,73 @@ class TerminalModel with ChangeNotifier {
         _pendingOutputChunks
           ..clear()
           ..add(truncated);
+        _pendingOutputSuppressFlags
+          ..clear()
+          ..add(suppressTerminalOutput);
         _pendingOutputSize = truncated.length;
       } else {
         _pendingOutputChunks.add(text);
+        _pendingOutputSuppressFlags.add(suppressTerminalOutput);
         _pendingOutputSize += text.length;
         // Drop oldest chunks if exceeds limit (whole chunks to preserve ANSI sequences)
         while (_pendingOutputSize > _kMaxOutputBufferChars &&
             _pendingOutputChunks.length > 1) {
           final removed = _pendingOutputChunks.removeAt(0);
+          _pendingOutputSuppressFlags.removeAt(0);
           _pendingOutputSize -= removed.length;
         }
       }
       return;
     }
-    terminal.write(text);
+    _writeTerminalChunk(text, suppressTerminalOutput: suppressTerminalOutput);
   }
 
   void _flushOutputBuffer() {
     if (_pendingOutputChunks.isEmpty) return;
     debugPrint(
         '[TerminalModel] Flushing $_pendingOutputSize buffered chars (${_pendingOutputChunks.length} chunks)');
-    for (final chunk in _pendingOutputChunks) {
-      terminal.write(chunk);
+    for (var i = 0; i < _pendingOutputChunks.length; i++) {
+      _writeTerminalChunk(
+        _pendingOutputChunks[i],
+        suppressTerminalOutput: _pendingOutputSuppressFlags[i],
+      );
     }
     _pendingOutputChunks.clear();
+    _pendingOutputSuppressFlags.clear();
     _pendingOutputSize = 0;
   }
 
+  void _writeTerminalChunk(
+    String text, {
+    required bool suppressTerminalOutput,
+  }) {
+    if (!suppressTerminalOutput) {
+      terminal.write(text);
+      return;
+    }
+    final previous = _suppressTerminalOutput;
+    _suppressTerminalOutput = true;
+    try {
+      terminal.write(text);
+    } finally {
+      _suppressTerminalOutput = previous;
+    }
+  }
+
   /// Mark terminal view as ready and flush buffered output.
+  void _scheduleMarkViewReady() {
+    if (_disposed || _terminalViewReady || _markViewReadyScheduled) return;
+    _markViewReadyScheduled = true;
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      _markViewReadyScheduled = false;
+      if (_disposed || _terminalViewReady) return;
+      if (terminal.viewWidth > 0 && terminal.viewHeight > 0) {
+        _markViewReady();
+      }
+    });
+    WidgetsBinding.instance.ensureVisualUpdate();
+  }
+
   void _markViewReady() {
     if (_terminalViewReady) return;
     _terminalViewReady = true;
@@ -426,7 +487,10 @@ class TerminalModel with ChangeNotifier {
     // Clear buffers to free memory
     _inputBuffer.clear();
     _pendingOutputChunks.clear();
+    _pendingOutputSuppressFlags.clear();
     _pendingOutputSize = 0;
+    _markViewReadyScheduled = false;
+    _suppressNextTerminalDataOutput = false;
     // Terminal cleanup is handled server-side when service closes
     super.dispose();
   }

src/client.rs

@@ -1745,6 +1745,9 @@ pub struct LoginConfigHandler {
     pub direct: Option<bool>,
     pub received: bool,
     switch_uuid: Option<String>,
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    switch_back_allowed: bool,
     pub save_ab_password_to_recent: bool, // true: connected with ab password
     pub other_server: Option<(String, String, String)>,
     pub custom_fps: Arc<Mutex<Option<usize>>>,
@@ -1861,6 +1864,11 @@ impl LoginConfigHandler {
 
         self.direct = None;
         self.received = false;
+        #[cfg(feature = "flutter")]
+        #[cfg(not(any(target_os = "android", target_os = "ios")))]
+        {
+            self.switch_back_allowed = false;
+        }
         self.switch_uuid = switch_uuid;
         self.adapter_luid = adapter_luid;
         self.selected_windows_session_id = None;
@@ -1874,6 +1882,23 @@ impl LoginConfigHandler {
         self.is_terminal_admin = is_terminal_admin;
     }
 
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    pub fn allow_switch_back_once(&mut self) {
+        self.switch_back_allowed = true;
+    }
+
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    pub fn consume_switch_back_permission(&mut self) -> bool {
+        if self.switch_back_allowed {
+            self.switch_back_allowed = false;
+            true
+        } else {
+            false
+        }
+    }
+
     /// Check if the client should auto login.
     /// Return password if the client should auto login, otherwise return empty string.
     pub fn should_auto_login(&self) -> String {
@@ -3377,6 +3402,36 @@ pub fn handle_login_error(
     }
 }
 
+#[cfg(feature = "flutter")]
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+async fn consume_local_switch_sides_uuid(id: &str, uuid: &Uuid) -> bool {
+    let Ok(mut conn) = crate::ipc::connect(1000, "").await else {
+        return false;
+    };
+    let uuid = uuid.to_string();
+    if conn
+        .send(&crate::ipc::Data::SwitchSidesUuid(
+            uuid.clone(),
+            id.to_owned(),
+            None,
+        ))
+        .await
+        .is_err()
+    {
+        return false;
+    }
+    match conn.next_timeout(1000).await {
+        Ok(Some(crate::ipc::Data::SwitchSidesUuid(
+            returned_uuid,
+            returned_id,
+            Some(true),
+        ))) => {
+            returned_uuid == uuid && returned_id == id
+        }
+        _ => false,
+    }
+}
+
 /// Handle hash message sent by peer.
 /// Hash will be used for login.
 ///
@@ -3397,14 +3452,24 @@ pub async fn handle_hash(
     // Take care of password application order
 
     // switch_uuid
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    {
         let uuid = lc.write().unwrap().switch_uuid.take();
         if let Some(uuid) = uuid {
             if let Ok(uuid) = uuid::Uuid::from_str(&uuid) {
+                let id = lc.read().unwrap().id.clone();
+                if !consume_local_switch_sides_uuid(&id, &uuid).await {
+                    log::warn!("Ignored untrusted switch_uuid");
+                } else {
+                    lc.write().unwrap().allow_switch_back_once();
                     send_switch_login_request(lc.clone(), peer, uuid).await;
                     lc.write().unwrap().password_source = Default::default();
                     return;
                 }
             }
+        }
+    }
     // last password
     let mut password = lc.read().unwrap().password.clone();
     // preset password

src/client/io_loop.rs

@@ -1923,9 +1923,23 @@ impl<T: InvokeUiSession> Remote<T> {
                             );
                         }
                     }
-                    Some(misc::Union::SwitchBack(_)) => {
                     #[cfg(feature = "flutter")]
+                    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+                    Some(misc::Union::SwitchBack(_)) => {
+                        let allow_switch_back = self
+                            .handler
+                            .lc
+                            .write()
+                            .unwrap()
+                            .consume_switch_back_permission();
+                        if allow_switch_back {
                             self.handler.switch_back(&self.handler.get_id());
+                        } else {
+                            log::warn!(
+                                "Ignored unsolicited SwitchBack from {}",
+                                self.handler.get_id()
+                            );
+                        }
                     }
                     #[cfg(all(feature = "flutter", feature = "plugin_framework"))]
                     #[cfg(not(any(target_os = "android", target_os = "ios")))]

src/flutter.rs

@@ -1135,6 +1135,10 @@ impl InvokeUiSession for FlutterHandler {
                     ("message", json!(&opened.message)),
                     ("pid", json!(opened.pid)),
                     ("service_id", json!(&opened.service_id)),
+                    (
+                        "replay_terminal_output",
+                        json!(opened.replay_terminal_output),
+                    ),
                 ];
                 if !opened.persistent_sessions.is_empty() {
                     event_data.push(("persistent_sessions", json!(opened.persistent_sessions)));

src/flutter_ffi.rs

@@ -2213,7 +2213,7 @@ pub fn cm_elevate_portable(conn_id: i32) {
 }
 
 pub fn cm_switch_back(conn_id: i32) {
-    #[cfg(not(any(target_os = "ios")))]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
     crate::ui_cm_interface::switch_back(conn_id);
 }
 

src/ipc.rs

@@ -285,7 +285,14 @@ pub enum Data {
     Empty,
     Disconnected,
     DataPortableService(DataPortableService),
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
     SwitchSidesRequest(String),
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
+    SwitchSidesUuid(String, String, Option<bool>),
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
     SwitchSidesBack,
     UrlLink(String),
     VoiceCallIncoming,
@@ -771,6 +778,8 @@ async fn handle(data: Data, stream: &mut Connection) {
         Data::TestRendezvousServer => {
             crate::test_rendezvous_server();
         }
+        #[cfg(feature = "flutter")]
+        #[cfg(not(any(target_os = "android", target_os = "ios")))]
         Data::SwitchSidesRequest(id) => {
             let uuid = uuid::Uuid::new_v4();
             crate::server::insert_switch_sides_uuid(id, uuid.clone());
@@ -780,6 +789,19 @@ async fn handle(data: Data, stream: &mut Connection) {
                     .await
             );
         }
+        #[cfg(feature = "flutter")]
+        #[cfg(not(any(target_os = "android", target_os = "ios")))]
+        Data::SwitchSidesUuid(uuid, id, None) => {
+            let allowed = uuid
+                .parse::<uuid::Uuid>()
+                .map(|uuid| crate::server::remove_pending_switch_sides_uuid(&id, &uuid))
+                .unwrap_or(false);
+            allow_err!(
+                stream
+                    .send(&Data::SwitchSidesUuid(uuid, id, Some(allowed)))
+                    .await
+            );
+        }
         #[cfg(all(feature = "flutter", feature = "plugin_framework"))]
         #[cfg(not(any(target_os = "android", target_os = "ios")))]
         Data::Plugin(plugin) => crate::plugin::ipc::handle_plugin(plugin, stream).await,

src/lang/de.rs

@@ -743,6 +743,6 @@ pub static ref T: std::collections::HashMap<&'static str, &'static str> =
         ("Display Name", "Anzeigename"),
         ("password-hidden-tip", "Ein permanentes Passwort wurde festgelegt (ausgeblendet)."),
         ("preset-password-in-use-tip", "Das voreingestellte Passwort wird derzeit verwendet."),
-        ("Enable privacy mode", ""),
+        ("Enable privacy mode", "Datenschutzmodus aktivieren"),
     ].iter().cloned().collect();
 }

src/lang/fr.rs

@@ -743,6 +743,6 @@ pub static ref T: std::collections::HashMap<&'static str, &'static str> =
         ("Display Name", "Nom d’affichage"),
         ("password-hidden-tip", "Le mot de passe permanent est défini (masqué)."),
         ("preset-password-in-use-tip", "Le mot de passe prédéfini est actuellement utilisé."),
-        ("Enable privacy mode", ""),
+        ("Enable privacy mode", "Activer le mode de confidentialité"),
     ].iter().cloned().collect();
 }

src/lang/it.rs

@@ -743,6 +743,6 @@ pub static ref T: std::collections::HashMap<&'static str, &'static str> =
         ("Display Name", "Visualizza nome"),
         ("password-hidden-tip", "È impostata una password permanente (nascosta)."),
         ("preset-password-in-use-tip", "È attualmente in uso la password preimpostata."),
-        ("Enable privacy mode", ""),
+        ("Enable privacy mode", "Abilita modalità privacy"),
     ].iter().cloned().collect();
 }

src/lang/ru.rs

@@ -743,6 +743,6 @@ pub static ref T: std::collections::HashMap<&'static str, &'static str> =
         ("Display Name", "Отображаемое имя"),
         ("password-hidden-tip", "Установлен постоянный пароль (скрытый)."),
         ("preset-password-in-use-tip", "Установленный пароль сейчас используется."),
-        ("Enable privacy mode", ""),
+        ("Enable privacy mode", "Использовать режим конфиденциальности"),
     ].iter().cloned().collect();
 }

src/lang/tr.rs

@@ -741,8 +741,8 @@ pub static ref T: std::collections::HashMap<&'static str, &'static str> =
         ("keep-awake-during-incoming-sessions-label", "Gelen oturumlar süresince ekranı açık tutun"),
         ("Continue with {}", "{} ile devam et"),
         ("Display Name", "Görünen Ad"),
-        ("password-hidden-tip", "Şifre gizli"),
-        ("preset-password-in-use-tip", "Önceden ayarlanmış şifre kullanılıyor"),
-        ("Enable privacy mode", ""),
+        ("password-hidden-tip", "Parola gizli"),
+        ("preset-password-in-use-tip", "Önceden ayarlanmış parola kullanılıyor"),
+        ("Enable privacy mode", "Gizlilik modunu etkinleştir"),
     ].iter().cloned().collect();
 }

src/server/connection.rs

@@ -73,11 +73,17 @@ lazy_static::lazy_static! {
     static ref ALIVE_CONNS: Arc::<Mutex<Vec<i32>>> = Default::default();
     pub static ref AUTHED_CONNS: Arc::<Mutex<Vec<AuthedConn>>> = Default::default();
     pub static ref CONTROL_PERMISSIONS_ARRAY: Arc::<Mutex<Vec<(i32, ControlPermissions)>>> = Default::default();
-    static ref SWITCH_SIDES_UUID: Arc::<Mutex<HashMap<String, (Instant, uuid::Uuid)>>> = Default::default();
     static ref WAKELOCK_SENDER: Arc::<Mutex<std::sync::mpsc::Sender<(usize, usize)>>> = Arc::new(Mutex::new(start_wakelock_thread()));
     static ref WAKELOCK_KEEP_AWAKE_OPTION: Arc::<Mutex<Option<bool>>> = Default::default();
 }
 
+#[cfg(feature = "flutter")]
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+lazy_static::lazy_static! {
+    static ref SWITCH_SIDES_UUID: Arc::<Mutex<HashMap<String, (Instant, uuid::Uuid)>>> = Default::default();
+    static ref PENDING_SWITCH_SIDES_UUID: Arc::<Mutex<HashMap<String, (Instant, uuid::Uuid)>>> = Default::default();
+}
+
 fn constant_time_eq(a: &[u8], b: &[u8]) -> bool {
     if a.len() != b.len() {
         return false;
@@ -775,6 +781,8 @@ impl Connection {
                                 log::error!("Failed to start portable service from cm: {:?}", e);
                             }
                         }
+                        #[cfg(feature = "flutter")]
+                        #[cfg(not(any(target_os = "android", target_os = "ios")))]
                         ipc::Data::SwitchSidesBack => {
                             let mut misc = Misc::new();
                             misc.set_switch_back(SwitchBack::default());
@@ -2579,6 +2587,7 @@ impl Connection {
             }
         } else if let Some(message::Union::SwitchSidesResponse(_s)) = msg.union {
             #[cfg(feature = "flutter")]
+            #[cfg(not(any(target_os = "android", target_os = "ios")))]
             if let Some(lr) = _s.lr.clone().take() {
                 self.handle_login_request_without_validation(&lr).await;
                 SWITCH_SIDES_UUID
@@ -3294,8 +3303,13 @@ impl Connection {
                         }
                     }
                     #[cfg(feature = "flutter")]
+                    #[cfg(not(any(target_os = "android", target_os = "ios")))]
                     Some(misc::Union::SwitchSidesRequest(s)) => {
                         if let Ok(uuid) = uuid::Uuid::from_slice(&s.uuid.to_vec()[..]) {
+                            crate::server::insert_pending_switch_sides_uuid(
+                                self.lr.my_id.clone(),
+                                uuid.clone(),
+                            );
                             crate::run_me(vec![
                                 "--connect",
                                 &self.lr.my_id,
@@ -4938,6 +4952,8 @@ impl Connection {
     }
 }
 
+#[cfg(feature = "flutter")]
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
 pub fn insert_switch_sides_uuid(id: String, uuid: uuid::Uuid) {
     SWITCH_SIDES_UUID
         .lock()
@@ -4945,6 +4961,27 @@ pub fn insert_switch_sides_uuid(id: String, uuid: uuid::Uuid) {
         .insert(id, (tokio::time::Instant::now(), uuid));
 }
 
+#[cfg(feature = "flutter")]
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+pub fn insert_pending_switch_sides_uuid(id: String, uuid: uuid::Uuid) {
+    let mut uuids = PENDING_SWITCH_SIDES_UUID.lock().unwrap();
+    uuids.retain(|_, (instant, _)| instant.elapsed() < Duration::from_secs(10));
+    uuids.insert(id, (tokio::time::Instant::now(), uuid));
+}
+
+#[cfg(feature = "flutter")]
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
+pub fn remove_pending_switch_sides_uuid(id: &str, uuid: &uuid::Uuid) -> bool {
+    let mut uuids = PENDING_SWITCH_SIDES_UUID.lock().unwrap();
+    uuids.retain(|_, (instant, _)| instant.elapsed() < Duration::from_secs(10));
+    if uuids.get(id).map(|(_, stored_uuid)| stored_uuid == uuid) == Some(true) {
+        uuids.remove(id);
+        true
+    } else {
+        false
+    }
+}
+
 #[cfg(not(any(target_os = "android", target_os = "ios")))]
 async fn start_ipc(
     mut rx_to_cm: mpsc::UnboundedReceiver<ipc::Data>,

src/server/terminal_helper.rs

@@ -318,6 +318,35 @@ pub fn get_default_shell() -> String {
     std::env::var("COMSPEC").unwrap_or_else(|_| "cmd.exe".to_string())
 }
 
+fn utf8_shell_args(shell: &str) -> Vec<String> {
+    let name = std::path::Path::new(shell)
+        .file_name()
+        .and_then(|name| name.to_str())
+        .unwrap_or(shell)
+        .to_ascii_lowercase();
+
+    if name == "cmd.exe" || name == "cmd" {
+        return vec!["/K".to_string(), "chcp 65001 >NUL".to_string()];
+    }
+
+    if name == "pwsh.exe" || name == "pwsh" || name == "powershell.exe" {
+        return vec![
+            "-NoLogo".to_string(),
+            "-NoExit".to_string(),
+            "-Command".to_string(),
+            "chcp.com 65001 > $null; [Console]::InputEncoding = [System.Text.Encoding]::UTF8; [Console]::OutputEncoding = [System.Text.Encoding]::UTF8".to_string(),
+        ];
+    }
+
+    Vec::new()
+}
+
+pub fn configure_utf8_shell_command(shell: &str, cmd: &mut CommandBuilder) {
+    for arg in utf8_shell_args(shell) {
+        cmd.arg(arg);
+    }
+}
+
 /// Get the SID of the user from a token.
 /// Returns a Vec<u8> containing the SID bytes.
 pub fn get_user_sid_from_token(user_token: UserToken) -> Result<Vec<u8>> {
@@ -831,7 +860,8 @@ pub fn run_terminal_helper(args: &[String]) -> Result<()> {
     let shell = get_default_shell();
     log::debug!("Using shell: {}", shell);
 
-    let cmd = CommandBuilder::new(&shell);
+    let mut cmd = CommandBuilder::new(&shell);
+    configure_utf8_shell_command(&shell, &mut cmd);
     let mut child = pty_pair
         .slave
         .spawn_command(cmd)

src/server/terminal_service.rs

@@ -20,10 +20,11 @@ use std::{
 // Windows-specific imports from terminal_helper module
 #[cfg(target_os = "windows")]
 use super::terminal_helper::{
-    create_named_pipe_server, encode_helper_message, encode_resize_message,
-    is_helper_process_running, launch_terminal_helper_with_token, wait_for_pipe_connection,
-    HelperProcessGuard, OwnedHandle, SendableHandle, WinCloseHandle, WinTerminateProcess,
-    WinWaitForSingleObject, MSG_TYPE_DATA, PIPE_CONNECTION_TIMEOUT_MS, WIN_WAIT_OBJECT_0,
+    configure_utf8_shell_command, create_named_pipe_server, encode_helper_message,
+    encode_resize_message, is_helper_process_running, launch_terminal_helper_with_token,
+    wait_for_pipe_connection, HelperProcessGuard, OwnedHandle, SendableHandle, WinCloseHandle,
+    WinTerminateProcess, WinWaitForSingleObject, MSG_TYPE_DATA, PIPE_CONNECTION_TIMEOUT_MS,
+    WIN_WAIT_OBJECT_0,
 };
 
 const MAX_OUTPUT_BUFFER_SIZE: usize = 1024 * 1024; // 1MB per terminal
@@ -133,6 +134,26 @@ fn get_default_shell() -> String {
     }
 }
 
+#[cfg(target_os = "macos")]
+fn locale_value_is_utf8(value: &str) -> bool {
+    let value = value.to_ascii_uppercase();
+    value.contains("UTF-8") || value.contains("UTF8")
+}
+
+#[cfg(target_os = "macos")]
+fn should_force_process_utf8_ctype() -> bool {
+    if let Ok(value) = std::env::var("LC_ALL") {
+        return !locale_value_is_utf8(&value);
+    }
+    if let Ok(value) = std::env::var("LC_CTYPE") {
+        return !locale_value_is_utf8(&value);
+    }
+    if let Ok(value) = std::env::var("LANG") {
+        return !locale_value_is_utf8(&value);
+    }
+    true
+}
+
 pub fn is_service_specified_user(service_id: &str) -> Option<bool> {
     get_service(service_id).map(|s| s.lock().unwrap().is_specified_user)
 }
@@ -435,6 +456,7 @@ impl OutputBuffer {
                 // Find first newline in new data
                 if let Some(newline_pos) = data.iter().position(|&b| b == b'\n') {
                     last_line.extend_from_slice(&data[..=newline_pos]);
+                    self.total_size += newline_pos + 1;
                     start = newline_pos + 1;
                     self.last_line_incomplete = false;
                 } else {
@@ -473,8 +495,29 @@ impl OutputBuffer {
         // Trim old data if buffer is too large
         while self.total_size > MAX_OUTPUT_BUFFER_SIZE || self.lines.len() > MAX_BUFFER_LINES {
             if let Some(removed) = self.lines.pop_front() {
+                if removed.len() > self.total_size {
+                    log::error!(
+                        "OutputBuffer total_size underflow avoided: total_size={}, removed_len={}, lines_len={}",
+                        self.total_size,
+                        removed.len(),
+                        self.lines.len()
+                    );
+                    self.total_size = self.lines.iter().map(|line| line.len()).sum();
+                } else {
                     self.total_size -= removed.len();
                 }
+                if self.lines.is_empty() {
+                    self.last_line_incomplete = false;
+                }
+            } else {
+                log::error!(
+                    "OutputBuffer trim invariant broken: total_size={}, lines_len=0",
+                    self.total_size
+                );
+                self.total_size = 0;
+                self.last_line_incomplete = false;
+                break;
+            }
         }
     }
 
@@ -531,6 +574,97 @@ impl OutputBuffer {
     }
 }
 
+/// Find the largest prefix of `buf` that does not end in the middle of a UTF-8
+/// code point. Invalid bytes are treated as complete so they can continue
+/// downstream and be rendered with replacement characters if needed.
+fn find_utf8_split_point(buf: &[u8]) -> usize {
+    if buf.is_empty() {
+        return 0;
+    }
+
+    let start = buf.len().saturating_sub(3);
+    for i in (start..buf.len()).rev() {
+        let b = buf[i];
+        if b & 0x80 == 0 {
+            return buf.len();
+        }
+        if b & 0xC0 == 0x80 {
+            continue;
+        }
+
+        let seq_len = if b & 0xE0 == 0xC0 {
+            2
+        } else if b & 0xF0 == 0xE0 {
+            3
+        } else if b & 0xF8 == 0xF0 {
+            4
+        } else {
+            return buf.len();
+        };
+
+        return if buf.len() - i >= seq_len {
+            buf.len()
+        } else {
+            i
+        };
+    }
+
+    buf.len()
+}
+
+// Terminal output currently follows a UTF-8 text model end to end: the service
+// keeps replay buffers on UTF-8 boundaries, and Flutter decodes payload bytes as
+// UTF-8 before writing to xterm. This accumulator only prevents splitting a
+// trailing UTF-8 code point across PTY reads. Supporting non-UTF-8 terminals
+// would need a separate design covering remote encoding detection, Flutter
+// decoding, replay truncation, and input transcoding.
+#[derive(Default)]
+struct Utf8ChunkAccumulator {
+    remainder: Vec<u8>,
+}
+
+impl Utf8ChunkAccumulator {
+    fn push_chunk(&mut self, mut data: Vec<u8>) -> Option<Vec<u8>> {
+        if data.is_empty() {
+            return None;
+        }
+
+        let had_remainder = !self.remainder.is_empty();
+        if had_remainder {
+            let mut combined = std::mem::take(&mut self.remainder);
+            combined.extend_from_slice(&data);
+            data = combined;
+        }
+
+        let split = find_utf8_split_point(&data);
+        if split == data.len() {
+            return Some(data);
+        }
+
+        // Only hold back a candidate incomplete suffix when we have evidence that
+        // the bytes before it are already UTF-8 text. If split is 0, the whole
+        // read may be the start of a UTF-8 character, so keep it for the next read.
+        if !had_remainder && split > 0 && std::str::from_utf8(&data[..split]).is_err() {
+            return Some(data);
+        }
+
+        self.remainder = data.split_off(split);
+        if data.is_empty() {
+            None
+        } else {
+            Some(data)
+        }
+    }
+
+    fn finish(&mut self) -> Option<Vec<u8>> {
+        if self.remainder.is_empty() {
+            None
+        } else {
+            Some(std::mem::take(&mut self.remainder))
+        }
+    }
+}
+
 /// Try to send data through the output channel with rate-limited drop logging.
 /// Returns `true` if the caller should break out of the read loop (channel disconnected).
 fn try_send_output(
@@ -570,7 +704,11 @@ fn try_send_output(
             false
         }
         Err(mpsc::TrySendError::Disconnected(_)) => {
-            log::debug!("Terminal {}{} output channel disconnected", terminal_id, label);
+            log::debug!(
+                "Terminal {}{} output channel disconnected",
+                terminal_id,
+                label
+            );
             true
         }
     }
@@ -937,15 +1075,35 @@ impl TerminalServiceProxy {
         if let Some(session_arc) = service.sessions.get(&open.terminal_id) {
             // Reconnect to existing terminal
             let mut session = session_arc.lock().unwrap();
-            // Directly enter Active state with pending buffer for immediate streaming.
-            // Historical buffer is sent first by read_outputs(), then real-time data follows.
-            // No overlap: pending_buffer comes from output_buffer (pre-disconnect history),
-            // while received_data in read_outputs() comes from the channel (post-reconnect).
-            // During disconnect, the run loop (sp.ok()) exits so read_outputs() stops being
-            // called; output_buffer is not updated, and channel data may be lost if it fills up.
-            let buffer = session
+            // Directly enter Active state with pending replay for immediate streaming.
+            // The replay combines output_buffer history and the channel backlog that was
+            // already pending at reconnect time so the client can suppress stale xterm
+            // query answers without requiring a protobuf schema change.
+            // During disconnect, read_outputs() is not called; channel data can still be lost
+            // if output_rx fills before reconnect drains it.
+            let mut buffer = session
                 .output_buffer
                 .get_recent(DEFAULT_RECONNECT_BUFFER_BYTES);
+            let mut reconnect_backlog = Vec::new();
+            if let Some(output_rx) = &session.output_rx {
+                // Cap reconnect-time drain so a chatty PTY cannot keep OpenTerminal
+                // inside this loop indefinitely. Remaining output is drained by read_outputs().
+                for _ in 0..CHANNEL_BUFFER_SIZE {
+                    let Ok(data) = output_rx.try_recv() else {
+                        break;
+                    };
+                    reconnect_backlog.push(data);
+                }
+            }
+            let has_reconnect_backlog = !reconnect_backlog.is_empty();
+            for data in reconnect_backlog {
+                session.output_buffer.append(&data);
+            }
+            if has_reconnect_backlog {
+                buffer = session
+                    .output_buffer
+                    .get_recent(DEFAULT_RECONNECT_BUFFER_BYTES);
+            }
             let has_pending = !buffer.is_empty();
             session.state = SessionState::Active {
                 pending_buffer: if has_pending { Some(buffer) } else { None },
@@ -959,9 +1117,14 @@ impl TerminalServiceProxy {
             let mut opened = TerminalOpened::new();
             opened.terminal_id = open.terminal_id;
             opened.success = true;
-            opened.message = "Reconnected to existing terminal".to_string();
+            opened.message = if has_pending {
+                "Reconnected to existing terminal with pending output".to_string()
+            } else {
+                "Reconnected to existing terminal".to_string()
+            };
             opened.pid = session.pid;
             opened.service_id = self.service_id.clone();
+            opened.replay_terminal_output = has_pending;
             if service.needs_session_sync {
                 if service.sessions.len() > 1 {
                     // No need to include the current terminal in the list.
@@ -1016,6 +1179,9 @@ impl TerminalServiceProxy {
         #[allow(unused_mut)]
         let mut cmd = CommandBuilder::new(&shell);
 
+        #[cfg(target_os = "windows")]
+        configure_utf8_shell_command(&shell, &mut cmd);
+
         // macOS-specific terminal configuration
         // 1. Use login shell (-l) to load user's shell profile (~/.zprofile, ~/.bash_profile)
         //    This ensures PATH includes Homebrew paths (/opt/homebrew/bin, /usr/local/bin)
@@ -1036,6 +1202,12 @@ impl TerminalServiceProxy {
             };
             cmd.env("TERM", term);
             log::debug!("Set TERM={} for macOS PTY", term);
+
+            if should_force_process_utf8_ctype() {
+                cmd.env_remove("LC_ALL");
+                cmd.env("LC_CTYPE", "en_US.UTF-8");
+                log::debug!("Set LC_CTYPE=en_US.UTF-8 for macOS PTY");
+            }
         }
 
         // Note: On Windows with user_token, we use helper mode (handle_open_with_helper)
@@ -1086,6 +1258,7 @@ impl TerminalServiceProxy {
         let reader_thread = thread::spawn(move || {
             let mut reader = reader;
             let mut buf = vec![0u8; 4096];
+            let mut utf8_chunks = Utf8ChunkAccumulator::default();
             let mut drop_count: u64 = 0;
             // Initialize to > 5s ago so the first drop triggers a warning immediately.
             let mut last_drop_warn = Instant::now() - Duration::from_secs(6);
@@ -1095,13 +1268,25 @@ impl TerminalServiceProxy {
                         // EOF
                         // This branch can be reached when the child process exits on macOS.
                         // But not on Linux and Windows in my tests.
+                        if let Some(data) = utf8_chunks.finish() {
+                            let _ = try_send_output(
+                                &output_tx,
+                                data,
+                                terminal_id,
+                                "",
+                                &mut drop_count,
+                                &mut last_drop_warn,
+                            );
+                        }
                         break;
                     }
                     Ok(n) => {
                         if exiting.load(Ordering::SeqCst) {
                             break;
                         }
-                        let data = buf[..n].to_vec();
+                        let Some(data) = utf8_chunks.push_chunk(buf[..n].to_vec()) else {
+                            continue;
+                        };
                         // Use try_send to avoid blocking the reader thread when channel is full.
                         // During disconnect, the run loop (sp.ok()) stops and read_outputs() is
                         // no longer called, so the channel won't be drained. Blocking send would
@@ -1308,12 +1493,23 @@ impl TerminalServiceProxy {
         let terminal_id = open.terminal_id;
         let reader_thread = thread::spawn(move || {
             let mut buf = vec![0u8; 4096];
+            let mut utf8_chunks = Utf8ChunkAccumulator::default();
             let mut drop_count: u64 = 0;
             // Initialize to > 5s ago so the first drop triggers a warning immediately.
             let mut last_drop_warn = Instant::now() - Duration::from_secs(6);
             loop {
                 match output_pipe.read(&mut buf) {
                     Ok(0) => {
+                        if let Some(data) = utf8_chunks.finish() {
+                            let _ = try_send_output(
+                                &output_tx,
+                                data,
+                                terminal_id,
+                                " (helper)",
+                                &mut drop_count,
+                                &mut last_drop_warn,
+                            );
+                        }
                         // EOF - helper process exited
                         log::debug!("Terminal {} helper output EOF", terminal_id);
                         break;
@@ -1322,7 +1518,9 @@ impl TerminalServiceProxy {
                         if exiting.load(Ordering::SeqCst) {
                             break;
                         }
-                        let data = buf[..n].to_vec();
+                        let Some(data) = utf8_chunks.push_chunk(buf[..n].to_vec()) else {
+                            continue;
+                        };
                         // Use try_send to avoid blocking the reader thread (same as direct PTY mode)
                         if try_send_output(
                             &output_tx,
@@ -1462,9 +1660,10 @@ impl TerminalServiceProxy {
         data: &TerminalData,
     ) -> Result<Option<TerminalResponse>> {
         if let Some(session_arc) = session {
+            let input = {
                 let mut session = session_arc.lock().unwrap();
                 session.update_activity();
-            if let Some(input_tx) = &session.input_tx {
+                if let Some(input_tx) = session.input_tx.clone() {
                     // Encode data for helper mode or send raw for direct PTY mode
                     #[cfg(target_os = "windows")]
                     let msg = if session.is_helper_mode {
@@ -1475,7 +1674,14 @@ impl TerminalServiceProxy {
                     #[cfg(not(target_os = "windows"))]
                     let msg = data.data.to_vec();
 
-                // Send data to writer thread
+                    Some((input_tx, msg))
+                } else {
+                    None
+                }
+            };
+
+            if let Some((input_tx, msg)) = input {
+                // Send outside the session lock; SyncSender::send can block when full.
                 if let Err(e) = input_tx.send(msg) {
                     log::error!(
                         "Failed to send data to terminal {}: {}",
@@ -1683,10 +1889,6 @@ impl TerminalServiceProxy {
                     }
                 }
 
-                if has_activity {
-                    session.update_activity();
-                }
-
                 // Update buffer (always buffer for reconnection support)
                 for data in &received_data {
                     session.output_buffer.append(data);
@@ -1696,7 +1898,7 @@ impl TerminalServiceProxy {
                 // Data is already buffered above and will be sent on next reconnection.
                 // Use a scoped block to limit the mutable borrow of session.state,
                 // so we can immutably borrow other session fields afterwards.
-                let sigwinch_action = {
+                let (replay_buffer, sigwinch_action) = {
                     let (pending_buffer, sigwinch) = match &mut session.state {
                         SessionState::Active {
                             pending_buffer,
@@ -1705,19 +1907,12 @@ impl TerminalServiceProxy {
                         _ => continue,
                     };
 
-                    // Send pending buffer response first (set on reconnection in handle_open).
-                    // This ensures historical buffer is sent before any real-time data.
-                    if let Some(buffer) = pending_buffer.take() {
-                        if !buffer.is_empty() {
-                            responses
-                                .push(Self::create_terminal_data_response(terminal_id, buffer));
-                        }
-                    }
+                    let replay_buffer = pending_buffer.take();
 
                     // Two-phase SIGWINCH: see SigwinchPhase doc comments for rationale.
                     // Each phase is a single PTY resize, spaced ~30ms apart by the polling
                     // interval, ensuring the TUI app sees a real size change on each signal.
-                    match sigwinch {
+                    let sigwinch_action = match sigwinch {
                         SigwinchPhase::TempResize { retries } => {
                             if *retries == 0 {
                                 log::warn!(
@@ -1745,8 +1940,19 @@ impl TerminalServiceProxy {
                             }
                         }
                         SigwinchPhase::Idle => None,
-                    }
                     };
+                    (replay_buffer, sigwinch_action)
+                };
+
+                if let Some(buffer) = replay_buffer {
+                    if !buffer.is_empty() {
+                        responses.push(Self::create_terminal_data_response(terminal_id, buffer));
+                    }
+                }
+
+                if has_activity {
+                    session.update_activity();
+                }
 
                 // Execute SIGWINCH resize outside the mutable borrow scope of session.state.
                 if let Some(action) = sigwinch_action {
@@ -1845,3 +2051,116 @@ impl TerminalServiceProxy {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{find_utf8_split_point, OutputBuffer, Utf8ChunkAccumulator, MAX_BUFFER_LINES};
+
+    #[test]
+    fn utf8_split_point_returns_full_len_for_complete_input() {
+        assert_eq!(find_utf8_split_point(b"hello"), 5);
+        assert_eq!(find_utf8_split_point("中文".as_bytes()), "中文".len());
+        assert_eq!(find_utf8_split_point("😀".as_bytes()), "😀".len());
+    }
+
+    #[test]
+    fn utf8_split_point_detects_incomplete_trailing_sequence() {
+        let data = [b'a', 0xE4, 0xB8];
+        assert_eq!(find_utf8_split_point(&data), 1);
+    }
+
+    #[test]
+    fn utf8_split_point_keeps_malformed_prefix_but_buffers_trailing_lead_byte() {
+        let data = [0xFF, 0xE4];
+        assert_eq!(find_utf8_split_point(&data), 1);
+    }
+
+    #[test]
+    fn utf8_split_point_treats_orphan_continuations_as_complete() {
+        let data = [0x80, 0x81, 0x82];
+        assert_eq!(find_utf8_split_point(&data), data.len());
+    }
+
+    #[test]
+    fn utf8_chunk_accumulator_reassembles_split_multibyte_output() {
+        let full = "你好世界".as_bytes();
+        let mut chunker = Utf8ChunkAccumulator::default();
+        let mut output = Vec::new();
+
+        for chunk in full.chunks(5) {
+            if let Some(data) = chunker.push_chunk(chunk.to_vec()) {
+                output.extend_from_slice(&data);
+            }
+        }
+
+        if let Some(data) = chunker.finish() {
+            output.extend_from_slice(&data);
+        }
+
+        assert_eq!(output, full);
+    }
+
+    #[test]
+    fn utf8_chunk_accumulator_buffers_leading_split_multibyte_output() {
+        let mut chunker = Utf8ChunkAccumulator::default();
+
+        assert!(chunker.push_chunk(vec![0xE4]).is_none());
+        assert!(chunker.push_chunk(vec![0xB8]).is_none());
+        assert_eq!(
+            chunker.push_chunk(vec![0xAD]),
+            Some("中".as_bytes().to_vec())
+        );
+        assert!(chunker.finish().is_none());
+    }
+
+    #[test]
+    fn utf8_chunk_accumulator_flushes_incomplete_tail_on_finish() {
+        let mut chunker = Utf8ChunkAccumulator::default();
+        assert_eq!(chunker.push_chunk(vec![b'a', 0xE4]), Some(vec![b'a']));
+        assert_eq!(chunker.finish(), Some(vec![0xE4]));
+        assert!(chunker.finish().is_none());
+    }
+
+    #[test]
+    fn utf8_chunk_accumulator_does_not_stall_on_malformed_bytes() {
+        let mut chunker = Utf8ChunkAccumulator::default();
+        assert_eq!(chunker.push_chunk(vec![0xFF]), Some(vec![0xFF]));
+        assert!(chunker.finish().is_none());
+    }
+
+    #[test]
+    fn utf8_chunk_accumulator_buffers_lone_utf8_lead_bytes() {
+        let mut chunker = Utf8ChunkAccumulator::default();
+        assert!(chunker.push_chunk(vec![0xE4]).is_none());
+        assert_eq!(chunker.finish(), Some(vec![0xE4]));
+    }
+
+    #[test]
+    fn utf8_chunk_accumulator_does_not_hold_back_non_utf8_prefixes() {
+        let mut chunker = Utf8ChunkAccumulator::default();
+        assert_eq!(chunker.push_chunk(vec![0xFF, 0xE4]), Some(vec![0xFF, 0xE4]));
+        assert!(chunker.finish().is_none());
+    }
+
+    #[test]
+    fn output_buffer_trim_after_incomplete_merge_does_not_underflow() {
+        let mut buffer = OutputBuffer::new();
+
+        // Create an incomplete line first.
+        buffer.append(b"hello");
+
+        // Merge a large chunk that contains the first newline at the tail.
+        // This exercises the "append to last incomplete line" branch.
+        let mut large = vec![b'a'; 30_000];
+        large.push(b'\n');
+        buffer.append(&large);
+
+        // Exceed MAX_BUFFER_LINES so trim pops the first large merged line.
+        for _ in 0..=MAX_BUFFER_LINES {
+            buffer.append(b"x\n");
+        }
+
+        let actual_size: usize = buffer.lines.iter().map(|line| line.len()).sum();
+        assert_eq!(buffer.total_size, actual_size);
+    }
+}

src/ui_cm_interface.rs

@@ -464,7 +464,7 @@ pub fn has_active_clients() -> bool {
 
 #[inline]
 #[cfg(feature = "flutter")]
-#[cfg(not(any(target_os = "ios")))]
+#[cfg(not(any(target_os = "android", target_os = "ios")))]
 pub fn switch_back(id: i32) {
     if let Some(client) = CLIENTS.read().unwrap().get(&id) {
         allow_err!(client.tx.send(Data::SwitchSidesBack));

src/ui_session_interface.rs

@@ -1464,10 +1464,11 @@ impl<T: InvokeUiSession> Session<T> {
         self.send(Data::ElevateWithLogon(username, password));
     }
 
-    #[cfg(any(target_os = "ios"))]
+    #[cfg(any(target_os = "android", target_os = "ios", not(feature = "flutter")))]
     pub fn switch_sides(&self) {}
 
-    #[cfg(not(any(target_os = "ios")))]
+    #[cfg(feature = "flutter")]
+    #[cfg(not(any(target_os = "android", target_os = "ios")))]
     #[tokio::main(flavor = "current_thread")]
     pub async fn switch_sides(&self) {
         match crate::ipc::connect(1000, "").await {