diff --git a/lib/screens/monthly_view.dart b/lib/screens/monthly_view.dart
index 2eafb82..28421cb 100644
--- a/lib/screens/monthly_view.dart
+++ b/lib/screens/monthly_view.dart
@@ -25,6 +25,9 @@ class _MonthlyViewState extends State<MonthlyView> {
   static const double _wNumber = 76;
   static const double _fontSize = 12;
 
+  // Codes, die Zeiten sperren/ leeren
+  static const Set<String> _lockCodes = {'G', 'K', 'U', 'SU'};
+
   // Edit/Fokus/Controller je Feld
   final Set<String> _invalidCells = <String>{};
   final Map<String, FocusNode> _focusNodes = {};
@@ -156,16 +159,16 @@ class _MonthlyViewState extends State<MonthlyView> {
 
   Color? _rowColorFor(WorkDay d, {required Color? holidayBg, required Color? weekendBg}) {
     switch (d.code) {
-      case 'GZ':
-        return const Color(0xFFBFBFFF); // 0xBFBFFF mit vollem Alpha
+      case 'G':
+        return const Color(0xFFBFBFFF); // Gleitzeit
       case 'U':
-        return const Color(0xFF7F7FFF); // 0x7F7FFF mit vollem Alpha
+        return const Color(0xFF7F7FFF); // Urlaub
       case 'SU':
-        return const Color(0xFF7F7FFF);
+        return const Color(0xFF7F7FFF); // Sonderurlaub
       case 'K':
-        return Colors.yellow;
+        return Colors.yellow;           // Krankenstand
       case 'T':
-        return Colors.red;
+        return Colors.red;              // Training
     }
     final isHoliday = _holidays.containsKey(ymd(d.date));
     final isWeekend = d.date.weekday == DateTime.saturday || d.date.weekday == DateTime.sunday;
@@ -355,7 +358,16 @@ class _MonthlyViewState extends State<MonthlyView> {
     final rightLabel = leftDayLabel(day.date);  // Datum Wochentag
     final hName = _holidays[ymd(day.date)] ?? '';
 
+    // Sperre Zeiten, wenn Code in _lockCodes
+    final bool lockTimes = day.code != null && _lockCodes.contains(day.code);
+
+    // Ist Wochenende/Feiertag => Code nicht änderbar
+    final bool isHoliday = _holidays.containsKey(ymd(day.date));
+    final bool isWeekend = day.date.weekday == DateTime.saturday || day.date.weekday == DateTime.sunday;
+    final bool codeDisabled = isHoliday || isWeekend;
+
     String slotText(int slot, bool isStart) {
+      if (lockTimes) return '';
       if (slot < day.intervals.length) {
         final p = day.intervals[slot];
         return fmtTimeOfDay(isStart ? p.start : p.end);
@@ -385,12 +397,13 @@ class _MonthlyViewState extends State<MonthlyView> {
       ),
     )));
 
-    // 2..11: Zeiten
+    // 2..11: Zeiten (evtl. gesperrt & geleert)
     for (int slot = 0; slot < 5; slot++) {
       // Start
       final keyS = 't_${dayIndex}_${slot}_s';
       final fnS = _nodeFor(keyS);
       final ctrlS = _controllerFor(keyS, slotText(slot, true));
+      if (lockTimes && ctrlS.text.isNotEmpty) ctrlS.text = '';
       cells.add(DataCell(SizedBox(
         width: _wTime,
         child: Align(
@@ -399,8 +412,10 @@ class _MonthlyViewState extends State<MonthlyView> {
             key: ValueKey(keyS),
             controller: ctrlS,
             focusNode: fnS,
+            enabled: !lockTimes,
             invalid: isInvalid(slot, true),
             onChanged: (text) {
+              if (lockTimes) return;
               final k = _cellKey(dayIndex, slot, true);
               final valid = text.isEmpty || _isValidHHMM(text);
               setState(() {
@@ -417,6 +432,7 @@ class _MonthlyViewState extends State<MonthlyView> {
               }
             },
             onSubmitted: (text) {
+              if (lockTimes) return;
               if (text.isEmpty || _isValidHHMM(text)) {
                 _commitTime(dayIndex, slot, true, text);
               }
@@ -429,6 +445,7 @@ class _MonthlyViewState extends State<MonthlyView> {
       final keyE = 't_${dayIndex}_${slot}_e';
       final fnE = _nodeFor(keyE);
       final ctrlE = _controllerFor(keyE, slotText(slot, false));
+      if (lockTimes && ctrlE.text.isNotEmpty) ctrlE.text = '';
       cells.add(DataCell(SizedBox(
         width: _wTime,
         child: Align(
@@ -437,8 +454,10 @@ class _MonthlyViewState extends State<MonthlyView> {
             key: ValueKey(keyE),
             controller: ctrlE,
             focusNode: fnE,
+            enabled: !lockTimes,
             invalid: isInvalid(slot, false),
             onChanged: (text) {
+              if (lockTimes) return;
               final k = _cellKey(dayIndex, slot, false);
               final valid = text.isEmpty || _isValidHHMM(text);
               setState(() {
@@ -455,6 +474,7 @@ class _MonthlyViewState extends State<MonthlyView> {
               }
             },
             onSubmitted: (text) {
+              if (lockTimes) return;
               if (text.isEmpty || _isValidHHMM(text)) {
                 _commitTime(dayIndex, slot, false, text);
               }
@@ -464,10 +484,13 @@ class _MonthlyViewState extends State<MonthlyView> {
       )));
     }
 
-    // 12: Code
+    // 12: Code (Dropdown) — zentriert (disable bei Sa/So/Feiertag)
     cells.add(DataCell(SizedBox(
       width: _wCode,
-      child: Align(alignment: Alignment.center, child: _codeDropdown(dayIndex, day)),
+      child: Align(
+        alignment: Alignment.center,
+        child: _codeDropdown(dayIndex, day, disabled: codeDisabled),
+      ),
     )));
 
     // 13..16: Kennzahlen (mit Override)
@@ -516,8 +539,8 @@ class _MonthlyViewState extends State<MonthlyView> {
         ),
       );
 
-  Widget _codeDropdown(int dayIndex, WorkDay day) {
-    final value = day.code;
+  Widget _codeDropdown(int dayIndex, WorkDay day, {required bool disabled}) {
+    final value = day.code; // null => —
     final values = <String?>[null, ...kAbsenceCodes];
 
     return DropdownButton<String?>(
@@ -536,19 +559,37 @@ class _MonthlyViewState extends State<MonthlyView> {
           return Center(child: Text(shortText, style: const TextStyle(fontSize: _fontSize)));
         }).toList();
       },
-      onChanged: (newCode) {
-        final d = _days[dayIndex];
-        setState(() {
-          final newDays = List<WorkDay>.from(_days);
-          newDays[dayIndex] = WorkDay(
-            date: d.date,
-            intervals: d.intervals,
-            targetMinutes: d.targetMinutes,
-            code: newCode,
-          );
-          _days = newDays;
-        });
-      },
+      onChanged: disabled
+          ? null
+          : (newCode) {
+              final d = _days[dayIndex];
+              // Wenn neuer Code ein Lock-Code ist: Zeiten löschen & sperren
+              final bool willLock = newCode != null && _lockCodes.contains(newCode);
+              setState(() {
+                final newDays = List<WorkDay>.from(_days);
+                newDays[dayIndex] = WorkDay(
+                  date: d.date,
+                  intervals: willLock ? <WorkInterval>[] : d.intervals,
+                  targetMinutes: d.targetMinutes,
+                  code: newCode,
+                );
+                _days = newDays;
+
+                if (willLock) {
+                  // Controller leeren & Invalid-Flags löschen
+                  for (int slot = 0; slot < 5; slot++) {
+                    final sKey = 't_${dayIndex}_${slot}_s';
+                    final eKey = 't_${dayIndex}_${slot}_e';
+                    final cs = _controllers[sKey];
+                    final ce = _controllers[eKey];
+                    if (cs != null && cs.text.isNotEmpty) cs.text = '';
+                    if (ce != null && ce.text.isNotEmpty) ce.text = '';
+                    _invalidCells.remove(_cellKey(dayIndex, slot, true));
+                    _invalidCells.remove(_cellKey(dayIndex, slot, false));
+                  }
+                }
+              });
+            },
     );
   }
 
@@ -567,6 +608,9 @@ class _MonthlyViewState extends State<MonthlyView> {
     final t = text.trim().isEmpty ? null : parseTextHHMM(text);
     final d = _days[dayIndex];
 
+    // Wenn Code sperrt: ignorieren (Sicherheit)
+    if (d.code != null && _lockCodes.contains(d.code)) return;
+
     final starts = List<TimeOfDay?>.filled(5, null);
     final ends = List<TimeOfDay?>.filled(5, null);
 
@@ -602,13 +646,20 @@ class _MonthlyViewState extends State<MonthlyView> {
 
   void _syncControllersWithDays() {
     for (int i = 0; i < _days.length; i++) {
+      final lock = _days[i].code != null && _lockCodes.contains(_days[i].code);
       for (int slot = 0; slot < 5; slot++) {
         final sKey = 't_${i}_${slot}_s';
         final eKey = 't_${i}_${slot}_e';
-        final sText =
-            (slot < _days[i].intervals.length) ? fmtTimeOfDay(_days[i].intervals[slot].start) : '';
-        final eText =
-            (slot < _days[i].intervals.length) ? fmtTimeOfDay(_days[i].intervals[slot].end) : '';
+        final sText = lock
+            ? ''
+            : (slot < _days[i].intervals.length)
+                ? fmtTimeOfDay(_days[i].intervals[slot].start)
+                : '';
+        final eText = lock
+            ? ''
+            : (slot < _days[i].intervals.length)
+                ? fmtTimeOfDay(_days[i].intervals[slot].end)
+                : '';
         final cs = _controllers[sKey];
         final ce = _controllers[eKey];
         if (cs != null && cs.text != sText && !(_focusNodes[sKey]?.hasFocus ?? false)) cs.text = sText;
@@ -618,6 +669,12 @@ class _MonthlyViewState extends State<MonthlyView> {
   }
 
   WorkDay _effectiveDay(int row, WorkDay base) {
+    // Wenn Code sperrt, sind die Intervalle leer (unabhängig von Controller-Text)
+    if (base.code != null && _lockCodes.contains(base.code)) {
+      final target = _dailyPlan[base.date.weekday] ?? base.targetMinutes;
+      return WorkDay(date: base.date, intervals: const [], targetMinutes: target, code: base.code);
+    }
+
     TimeOfDay? baseSlot(WorkDay d, int slot, bool isStart) {
       if (slot >= d.intervals.length) return null;
       final iv = d.intervals[slot];
@@ -656,6 +713,7 @@ class _MonthlyViewState extends State<MonthlyView> {
     required bool invalid,
     required ValueChanged<String> onChanged,
     required ValueChanged<String> onSubmitted,
+    bool enabled = true,
     FocusNode? focusNode,
   }) {
     final theme = Theme.of(context);
@@ -667,6 +725,7 @@ class _MonthlyViewState extends State<MonthlyView> {
         key: key,
         controller: controller,
         focusNode: focusNode,
+        enabled: enabled,
         textAlign: TextAlign.center,
         style: const TextStyle(
           fontFeatures: [FontFeature.tabularFigures()],
@@ -680,6 +739,7 @@ class _MonthlyViewState extends State<MonthlyView> {
           border: InputBorder.none,
           enabledBorder: InputBorder.none,
           focusedBorder: InputBorder.none,
+          disabledBorder: InputBorder.none,
         ).copyWith(
           filled: invalid,
           fillColor: invalid ? errorFill : null,
diff --git a/lib/utils/helpers.dart b/lib/utils/helpers.dart
index 099ee2a..9b2d79c 100644
--- a/lib/utils/helpers.dart
+++ b/lib/utils/helpers.dart
@@ -105,11 +105,11 @@ int? minutesFromHHMMSS(String? s) {
 }
 
 // Abwesenheitscodes und Labels
-const List<String> kAbsenceCodes = ['GZ', 'K', 'U', 'SU', 'T'];
+const List<String> kAbsenceCodes = ['G', 'K', 'U', 'SU', 'T'];
 
 String codeLabel(String? code) {
   switch (code) {
-    case 'GZ': return 'Gleitzeit';
+    case 'G': return 'Gleitzeit';
     case 'K':  return 'Krankenstand';
     case 'U':  return 'Urlaub';
     case 'SU': return 'Sonderurlaub';