diff --git a/app/MindWork AI Studio/Layout/MainLayout.razor b/app/MindWork AI Studio/Layout/MainLayout.razor
index 7ed77410..f73bfb3b 100644
--- a/app/MindWork AI Studio/Layout/MainLayout.razor	
+++ b/app/MindWork AI Studio/Layout/MainLayout.razor	
@@ -102,4 +102,4 @@
     </MudLayout>
 </MudPaper>
 
-<MudThemeProvider @ref="@this.themeProvider" Theme="@this.ColorTheme" IsDarkMode="@this.useDarkMode" />
\ No newline at end of file
+<MudThemeProvider @ref="@this.themeProvider" Theme="@this.ColorTheme" IsDarkMode="@this.useDarkMode" ObserveSystemThemeChange="@this.FollowSystemTheme" />
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Layout/MainLayout.razor.cs b/app/MindWork AI Studio/Layout/MainLayout.razor.cs
index a4d0c324..ca77acc7 100644
--- a/app/MindWork AI Studio/Layout/MainLayout.razor.cs	
+++ b/app/MindWork AI Studio/Layout/MainLayout.razor.cs	
@@ -144,7 +144,7 @@ public partial class MainLayout : LayoutComponentBase, IMessageBusReceiver, ILan
         // Send a message to start the plugin system:
         await this.MessageBus.SendMessage<bool>(this, Event.STARTUP_PLUGIN_SYSTEM);
         
-        await this.themeProvider.WatchSystemDarkModeAsync(this.SystemeThemeChanged);
+        await this.themeProvider.WatchSystemDarkModeAsync(this.SystemThemeChanged);
         await this.UpdateThemeConfiguration();
         this.LoadNavItems();
         this.LoadEmbeddingItem();
@@ -564,19 +564,28 @@ public partial class MainLayout : LayoutComponentBase, IMessageBusReceiver, ILan
         }
     }
     
-    private async Task SystemeThemeChanged(bool isDark)
+    /// <summary>
+    /// True, when the user wants AI Studio to follow the light or dark mode of the operating system.
+    /// </summary>
+    /// <remarks>
+    /// This also decides whether the MudThemeProvider watches the operating system at all. On a system
+    /// change, the provider takes the new mode into its own state first and calls our handler only
+    /// afterward, so the handler cannot prevent it. Nor can a new render of this layout undo it: the
+    /// provider takes over its IsDarkMode parameter only when that value changes, and with a fixed theme,
+    /// it never does. Were the provider watching while the user chose a fixed theme, MudBlazor would show
+    /// the colors of the system from the next render on, while the rest of the app kept the chosen ones.
+    /// </remarks>
+    private bool FollowSystemTheme => this.SettingsManager.ConfigurationData.App.PreferredTheme is Themes.SYSTEM;
+
+    private async Task SystemThemeChanged(bool isDark)
     {
         this.Logger.LogInformation($"The system theme changed to {(isDark ? "dark" : "light")}.");
-
-        if (this.SettingsManager.ConfigurationData.App.PreferredTheme is not Themes.SYSTEM)
-            return;
-
         await this.UpdateThemeConfiguration();
     }
 
     private async Task UpdateThemeConfiguration()
     {
-        if (this.SettingsManager.ConfigurationData.App.PreferredTheme is Themes.SYSTEM)
+        if (this.FollowSystemTheme)
             this.useDarkMode = await this.themeProvider.GetSystemDarkModeAsync();
         else
             this.useDarkMode = this.SettingsManager.ConfigurationData.App.PreferredTheme == Themes.DARK;
diff --git a/app/MindWork AI Studio/wwwroot/changelog/v26.9.1.md b/app/MindWork AI Studio/wwwroot/changelog/v26.9.1.md
index f707ca40..da3085df 100644
--- a/app/MindWork AI Studio/wwwroot/changelog/v26.9.1.md	
+++ b/app/MindWork AI Studio/wwwroot/changelog/v26.9.1.md	
@@ -87,5 +87,6 @@
 - Fixed AI Studio trying for minutes when a provider turns a request down for good. Such an answer does not change by asking a second time, so AI Studio now stops at the first one and tells you what the provider said about it.
 - Fixed errors about a provider arriving as two messages at once, the second of which spoke of several attempts that were never made. You now get the single message which names the cause.
 - Fixed the button in the chat toolbar that deletes the current chat and starts a new one doing so without asking. It now asks for your confirmation first, just like the chat list does, because a deleted chat cannot be brought back. The button shows a delete icon in red now, instead of one that looked like a reload.
+- Fixed AI Studio following your system into light or dark mode even though you had chosen a fixed color theme in the app settings.
 - Upgraded the Visual Briefing assistant (in preview) from the prototype to the beta state. The assistant is now completely implemented and is undergoing a deeper testing phase in preparation for release. To try it, open the app settings, allow preview features down to beta, and then enable the Visual Briefing assistant there.
 - Upgraded the vector database behind local RAG (Qdrant Edge) to version 0.8.0.