diff --git a/LehrerApp.Desktop.Tests/ParticipationSessionEditingTests.cs b/LehrerApp.Desktop.Tests/ParticipationSessionEditingTests.cs
new file mode 100644
index 0000000..5950e7c
--- /dev/null
+++ b/LehrerApp.Desktop.Tests/ParticipationSessionEditingTests.cs
@@ -0,0 +1,62 @@
+using LehrerApp.Core.Models;
+using LehrerApp.Desktop.ViewModels.Groups;
+using Xunit;
+
+namespace LehrerApp.Desktop.Tests;
+
+public sealed class ParticipationSessionEditingTests
+{
+    [Fact]
+    public void Bearbeitungsdialog_AendertBestehendeSessionOhneVerknuepfungenZuErsetzen()
+    {
+        var session = new ParticipationSession
+        {
+            GroupId = Guid.NewGuid(),
+            Date = new DateOnly(2026, 8, 19),
+            Comment = "Sitzplan",
+            LessonId = Guid.NewGuid(),
+            CompetencyCodes = ["K1"],
+        };
+        var vm = new AddSessionDialogViewModel(session)
+        {
+            DateText = "20.08.2026",
+            Comment = "Elektrische Stromkreise",
+        };
+
+        vm.SaveCommand.Execute(null);
+
+        Assert.Same(session, vm.Result);
+        Assert.Equal(new DateOnly(2026, 8, 20), session.Date);
+        Assert.Equal("Elektrische Stromkreise", session.Comment);
+        Assert.NotNull(session.LessonId);
+        Assert.Equal(["K1"], session.CompetencyCodes);
+    }
+
+    [Fact]
+    public async Task BearbeitenBefehl_SpeichertSessionUndAktualisiertAnzeige()
+    {
+        var group = new LearningGroup { Name = "8a", SchoolYear = "2026/27" };
+        var session = new ParticipationSession
+        {
+            GroupId = group.Id,
+            Date = new DateOnly(2026, 8, 19),
+            Comment = "Sitzplan",
+        };
+        var sessions = new FakeSessions([session]);
+        var vm = new ParticipationTabViewModel(
+            sessions, new FakeEntries(), new FakeAspects(), new FakeStudents([]),
+            new FakeMemberships([]), new FakeGroups([group]), new FakeCompetencyDomains());
+        vm.OnEditSession = existing =>
+        {
+            existing.Comment = "Nachbesprechung Elektrizität";
+            return Task.FromResult<ParticipationSession?>(existing);
+        };
+        vm.Initialize(group.Id, group.SchoolYear);
+
+        await vm.EditSessionCommand.ExecuteAsync(null);
+
+        Assert.Equal(session.Id, vm.SelectedSession?.Id);
+        Assert.Equal("Nachbesprechung Elektrizität", sessions.GetById(session.Id)?.Comment);
+        Assert.Contains("Nachbesprechung Elektrizität", vm.SelectedSessionDisplay);
+    }
+}
diff --git a/LehrerApp.Desktop/ViewModels/Groups/ParticipationViewModels.cs b/LehrerApp.Desktop/ViewModels/Groups/ParticipationViewModels.cs
index 0606b7f..ea6ef03 100644
--- a/LehrerApp.Desktop/ViewModels/Groups/ParticipationViewModels.cs
+++ b/LehrerApp.Desktop/ViewModels/Groups/ParticipationViewModels.cs
@@ -48,6 +48,7 @@ public partial class ParticipationTabViewModel : ObservableObject
     public ObservableCollection<CompetencyTagGroup>        CompetencyTagGroups { get; } = [];
 
     public Func<Task<ParticipationSession?>>? OnAddSession   { get; set; }
+    public Func<ParticipationSession, Task<ParticipationSession?>>? OnEditSession { get; set; }
     public Func<ParticipationTabViewModel, Task>? OnQuickInput { get; set; }
     public Func<ParticipationTabViewModel, Task>? OnStatusQuickInput { get; set; }
     public Func<ParticipationTabViewModel, Task>? OnComputeGrade { get; set; }
@@ -118,6 +119,7 @@ public partial class ParticipationTabViewModel : ObservableObject
     partial void OnSelectedSessionChanged(ParticipationSessionItem? value)
     {
         OnPropertyChanged(nameof(SelectedSessionDisplay));
+        EditSessionCommand.NotifyCanExecuteChanged();
         if (value is null)
         {
             StudentRows.Clear();
@@ -265,6 +267,23 @@ public partial class ParticipationTabViewModel : ObservableObject
         SelectedSession = Sessions.FirstOrDefault(s => s.Id == session.Id);
     }
 
+    [RelayCommand(CanExecute = nameof(CanEditSession))]
+    private async Task EditSession()
+    {
+        if (SelectedSession is null || OnEditSession is null) return;
+        var session = _sessions.GetById(SelectedSession.Id);
+        if (session is null) return;
+        var edited = await OnEditSession(session);
+        if (edited is null) return;
+        edited.GroupId = _groupId;
+        _sessions.Save(edited);
+        LoadSessions();
+    }
+
+    private bool CanEditSession() => !IsReadOnly && SelectedSession is not null;
+
+    partial void OnIsReadOnlyChanged(bool value) => EditSessionCommand.NotifyCanExecuteChanged();
+
     [RelayCommand(CanExecute = nameof(CanQuickInput))]
     private async Task QuickInput()
     {
@@ -716,12 +735,26 @@ public class ParticipationSessionItem
 
 public partial class AddSessionDialogViewModel : ObservableObject
 {
+    private readonly ParticipationSession? _editingSession;
+
     [ObservableProperty] private DateOnly _date = DateOnly.FromDateTime(DateTime.Today);
     [ObservableProperty] private string   _comment = "";
     [ObservableProperty] private string   _dateText = DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy");
     [ObservableProperty] private string   _dateTextError = "";
 
     public ParticipationSession? Result { get; private set; }
+    public bool IsEditing => _editingSession is not null;
+    public string DialogTitle => IsEditing ? "Bewertungszeitpunkt bearbeiten" : "Bewertungszeitpunkt anlegen";
+    public string SaveButtonText => IsEditing ? "Speichern" : "Anlegen";
+
+    public AddSessionDialogViewModel(ParticipationSession? editingSession = null)
+    {
+        _editingSession = editingSession;
+        if (editingSession is null) return;
+        Date = editingSession.Date;
+        DateText = editingSession.Date.ToString("dd.MM.yyyy");
+        Comment = editingSession.Comment ?? "";
+    }
 
     [RelayCommand]
     private void Save()
@@ -733,7 +766,10 @@ public partial class AddSessionDialogViewModel : ObservableObject
             return;
         }
         DateTextError = "";
-        Result = new ParticipationSession { Date = date, Comment = Comment.Trim() };
+        var session = _editingSession ?? new ParticipationSession();
+        session.Date = date;
+        session.Comment = Comment.Trim();
+        Result = session;
     }
 }
 
diff --git a/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml b/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml
index 9475110..5089d98 100644
--- a/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml
+++ b/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml
@@ -3,13 +3,13 @@
         xmlns:vm="clr-namespace:LehrerApp.Desktop.ViewModels.Groups"
         x:Class="LehrerApp.Desktop.Views.Groups.AddSessionDialog"
         x:DataType="vm:AddSessionDialogViewModel"
-        Title="Bewertungszeitpunkt anlegen"
+        Title="{Binding DialogTitle}"
         Width="380" SizeToContent="Height"
         CanResize="False" WindowStartupLocation="CenterOwner">
 
   <Grid RowDefinitions="*,Auto" Margin="24">
     <StackPanel Grid.Row="0" Spacing="14">
-      <TextBlock Text="Neuer Bewertungszeitpunkt" Classes="dialogtitle"/>
+      <TextBlock Text="{Binding DialogTitle}" Classes="dialogtitle"/>
 
       <StackPanel Spacing="4">
         <TextBlock Text="Datum *" FontSize="12" Opacity="0.7"/>
@@ -20,13 +20,14 @@
 
       <StackPanel Spacing="4">
         <TextBlock Text="Kommentar (optional)" FontSize="12" Opacity="0.7"/>
-        <TextBox Text="{Binding Comment}" PlaceholderText="z. B. Stunde 12 – Säure-Base-Reaktion"/>
+        <TextBox Text="{Binding Comment}" PlaceholderText="z. B. Stunde 12 – Säure-Base-Reaktion"
+                 x:Name="CommentBox"/>
       </StackPanel>
     </StackPanel>
 
     <Grid Grid.Row="1" ColumnDefinitions="*,8,*" Margin="0,20,0,0">
       <Button Grid.Column="0" Content="Abbrechen"  HorizontalAlignment="Stretch" Click="OnCancel"/>
-      <Button Grid.Column="2" Content="Anlegen"    HorizontalAlignment="Stretch" Click="OnSave"/>
+      <Button Grid.Column="2" Content="{Binding SaveButtonText}" HorizontalAlignment="Stretch" Click="OnSave"/>
     </Grid>
   </Grid>
 </Window>
diff --git a/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml.cs b/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml.cs
index 7f96032..feb871e 100644
--- a/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml.cs
+++ b/LehrerApp.Desktop/Views/Groups/AddSessionDialog.axaml.cs
@@ -11,7 +11,16 @@ public partial class AddSessionDialog : Window
     protected override void OnOpened(EventArgs e)
     {
         base.OnOpened(e);
-        this.FindControl<TextBox>("DateBox")?.Focus();
+        if (DataContext is AddSessionDialogViewModel { IsEditing: true })
+        {
+            var commentBox = this.FindControl<TextBox>("CommentBox");
+            commentBox?.Focus();
+            commentBox?.SelectAll();
+        }
+        else
+        {
+            this.FindControl<TextBox>("DateBox")?.Focus();
+        }
     }
 
     private void OnSave(object? s, RoutedEventArgs e)
diff --git a/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml b/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml
index 5dead17..2b41fb5 100644
--- a/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml
+++ b/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml
@@ -53,13 +53,16 @@
                    Text="{Binding SelectedSessionDisplay}"
                    FontSize="13" FontWeight="SemiBold"
                    VerticalAlignment="Center"/>
-        <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="6"
-                    IsVisible="{Binding HasCompetencyCatalog}">
+        <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="6">
+          <Button Content="✎ Sitzung bearbeiten" Command="{Binding EditSessionCommand}"
+                  IsVisible="{Binding !IsReadOnly}" FontSize="11" Padding="8,3"/>
           <ToggleButton Content="◇ Kompetenzen"
                         IsChecked="{Binding CompetencyTagsVisible}"
+                        IsVisible="{Binding HasCompetencyCatalog}"
                         FontSize="11" Padding="8,3"/>
           <ToggleButton Content="◈ Schüler-Bewertungen"
                         IsChecked="{Binding StudentCompetencyRatingsVisible}"
+                        IsVisible="{Binding HasCompetencyCatalog}"
                         FontSize="11" Padding="8,3"/>
         </StackPanel>
       </Grid>
diff --git a/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml.cs b/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml.cs
index 02fd4c9..a45325f 100644
--- a/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml.cs
+++ b/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml.cs
@@ -23,6 +23,7 @@ public partial class ParticipationTabView : UserControl
         {
             _vm = vm;
             vm.OnAddSession = ShowAddSessionDialog;
+            vm.OnEditSession = ShowEditSessionDialog;
             vm.OnQuickInput = ShowQuickInputDialog;
             vm.OnStatusQuickInput = ShowStatusQuickInputDialog;
             vm.OnComputeGrade = ShowComputeGradeDialog;
@@ -283,6 +284,17 @@ public partial class ParticipationTabView : UserControl
         return ok ? vm.Result : null;
     }
 
+    private async Task<LehrerApp.Core.Models.ParticipationSession?> ShowEditSessionDialog(
+        LehrerApp.Core.Models.ParticipationSession session)
+    {
+        var vm = new AddSessionDialogViewModel(session);
+        var dialog = new AddSessionDialog { DataContext = vm };
+        var owner = TopLevel.GetTopLevel(this) as Window;
+        if (owner is null) return null;
+        var ok = await dialog.ShowDialog<bool>(owner);
+        return ok ? vm.Result : null;
+    }
+
     private async Task ShowQuickInputDialog(ParticipationTabViewModel tabVm)
     {
         if (tabVm.StudentRows.Count == 0) return;