diff --git a/src/Models/TextMateHelper.cs b/src/Models/TextMateHelper.cs
index 38c0aaa72..d2d14eec6 100644
--- a/src/Models/TextMateHelper.cs
+++ b/src/Models/TextMateHelper.cs
@@ -84,8 +84,6 @@ private record ExtraGrammar(string Scope, List<string> Extensions, string File)
 
     public class RegistryOptionsWrapper(ThemeName defaultTheme) : IRegistryOptions
     {
-        public string LastScope { get; set; } = string.Empty;
-
         public IRawTheme GetTheme(string scopeName) => _backend.GetTheme(scopeName);
         public IRawTheme GetDefaultTheme() => _backend.GetDefaultTheme();
         public IRawTheme LoadTheme(ThemeName name) => _backend.LoadTheme(name);
@@ -98,11 +96,20 @@ public class RegistryOptionsWrapper(ThemeName defaultTheme) : IRegistryOptions
 
     public static class TextMateHelper
     {
+        private static RegistryOptionsWrapper s_darkRegistry;
+        private static RegistryOptionsWrapper s_lightRegistry;
+
+        private static RegistryOptionsWrapper GetRegistry(bool isDark)
+        {
+            if (isDark)
+                return s_darkRegistry ??= new RegistryOptionsWrapper(ThemeName.DarkPlus);
+            return s_lightRegistry ??= new RegistryOptionsWrapper(ThemeName.LightPlus);
+        }
+
         public static TextMate.Installation CreateForEditor(TextEditor editor)
         {
-            return editor.InstallTextMate(Application.Current?.ActualThemeVariant == ThemeVariant.Dark ?
-                new RegistryOptionsWrapper(ThemeName.DarkPlus) :
-                new RegistryOptionsWrapper(ThemeName.LightPlus));
+            var isDark = Application.Current?.ActualThemeVariant == ThemeVariant.Dark;
+            return editor.InstallTextMate(GetRegistry(isDark == true));
         }
 
         public static void SetThemeByApp(TextMate.Installation installation)
@@ -114,18 +121,29 @@ public static void SetThemeByApp(TextMate.Installation installation)
             }
         }
 
-        public static void SetGrammarByFileName(TextMate.Installation installation, string filePath)
+        public static void SetGrammarByFileName(TextMate.Installation installation, string filePath, ref string lastScope)
         {
             if (installation is { RegistryOptions: RegistryOptionsWrapper reg } && !string.IsNullOrEmpty(filePath))
             {
+                // Registry options are shared across editors, so the last grammar scope must stay editor-local.
                 var scope = reg.GetScope(filePath);
-                if (reg.LastScope != scope)
+                if (lastScope != scope)
                 {
-                    reg.LastScope = scope;
-                    installation.SetGrammar(reg.GetScope(filePath));
+                    lastScope = scope;
+                    installation.SetGrammar(scope);
                     GC.Collect();
                 }
             }
         }
+
+        public static void DisposeInstallation(ref TextMate.Installation installation, ref string lastScope, bool collectGarbage = false)
+        {
+            installation?.Dispose();
+            installation = null;
+            lastScope = string.Empty;
+
+            if (collectGarbage)
+                GC.Collect();
+        }
     }
 }
diff --git a/src/Views/AIAssistant.axaml.cs b/src/Views/AIAssistant.axaml.cs
index c49e407f9..c622f0ab4 100644
--- a/src/Views/AIAssistant.axaml.cs
+++ b/src/Views/AIAssistant.axaml.cs
@@ -63,7 +63,7 @@ protected override void OnLoaded(RoutedEventArgs e)
             if (_textMate == null)
             {
                 _textMate = Models.TextMateHelper.CreateForEditor(this);
-                Models.TextMateHelper.SetGrammarByFileName(_textMate, "README.md");
+                Models.TextMateHelper.SetGrammarByFileName(_textMate, "README.md", ref _lastGrammarScope);
                 TextArea.TextView.LineTransformers.Add(new LineStyleTransformer());
             }
         }
@@ -75,10 +75,7 @@ protected override void OnUnloaded(RoutedEventArgs e)
             TextArea.TextView.ContextRequested -= OnTextViewContextRequested;
 
             if (_textMate != null)
-            {
-                _textMate.Dispose();
-                _textMate = null;
-            }
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope);
 
             GC.Collect();
         }
@@ -125,6 +122,7 @@ private void OnTextViewContextRequested(object sender, ContextRequestedEventArgs
         }
 
         private TextMate.Installation _textMate = null;
+        private string _lastGrammarScope = string.Empty;
     }
 
     public partial class AIAssistant : ChromelessWindow
diff --git a/src/Views/Blame.axaml.cs b/src/Views/Blame.axaml.cs
index 8bc36160c..4137abf6c 100644
--- a/src/Views/Blame.axaml.cs
+++ b/src/Views/Blame.axaml.cs
@@ -375,10 +375,7 @@ protected override void OnUnloaded(RoutedEventArgs e)
             TextArea.TextView.VisualLinesChanged -= OnTextViewVisualLinesChanged;
 
             if (_textMate != null)
-            {
-                _textMate.Dispose();
-                _textMate = null;
-            }
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope);
         }
 
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
@@ -388,7 +385,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             if (change.Property == FileProperty)
             {
                 if (File is { Length: > 0 })
-                    Models.TextMateHelper.SetGrammarByFileName(_textMate, File);
+                    Models.TextMateHelper.SetGrammarByFileName(_textMate, File, ref _lastGrammarScope);
             }
             if (change.Property == BlameDataProperty)
             {
@@ -454,6 +451,7 @@ private void OnTextViewVisualLinesChanged(object sender, EventArgs e)
         }
 
         private TextMate.Installation _textMate = null;
+        private string _lastGrammarScope = string.Empty;
         private string _highlight = string.Empty;
     }
 
diff --git a/src/Views/CommandLogContentPresenter.cs b/src/Views/CommandLogContentPresenter.cs
index 99dc6d13d..64a06eaa3 100644
--- a/src/Views/CommandLogContentPresenter.cs
+++ b/src/Views/CommandLogContentPresenter.cs
@@ -107,7 +107,7 @@ protected override void OnLoaded(RoutedEventArgs e)
             if (_textMate == null)
             {
                 _textMate = Models.TextMateHelper.CreateForEditor(this);
-                Models.TextMateHelper.SetGrammarByFileName(_textMate, "Log.log");
+                Models.TextMateHelper.SetGrammarByFileName(_textMate, "Log.log", ref _lastGrammarScope);
                 TextArea.TextView.LineTransformers.Add(new LineStyleTransformer());
             }
         }
@@ -117,10 +117,7 @@ protected override void OnUnloaded(RoutedEventArgs e)
             base.OnUnloaded(e);
 
             if (_textMate != null)
-            {
-                _textMate.Dispose();
-                _textMate = null;
-            }
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope);
 
             GC.Collect();
         }
@@ -152,5 +149,6 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
         }
 
         private TextMate.Installation _textMate = null;
+        private string _lastGrammarScope = string.Empty;
     }
 }
diff --git a/src/Views/MergeConflictEditor.axaml.cs b/src/Views/MergeConflictEditor.axaml.cs
index 8c7b2621d..1dd565b80 100644
--- a/src/Views/MergeConflictEditor.axaml.cs
+++ b/src/Views/MergeConflictEditor.axaml.cs
@@ -310,7 +310,7 @@ protected override void OnLoaded(RoutedEventArgs e)
 
             _textMate = Models.TextMateHelper.CreateForEditor(this);
             if (!string.IsNullOrEmpty(FileName))
-                Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName);
+                Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName, ref _lastGrammarScope);
 
             TextArea.TextView.ContextRequested += OnTextViewContextRequested;
             TextArea.TextView.PointerEntered += OnTextViewPointerChanged;
@@ -331,10 +331,7 @@ protected override void OnUnloaded(RoutedEventArgs e)
             TextArea.TextView.VisualLinesChanged -= OnTextViewVisualLinesChanged;
 
             if (_textMate != null)
-            {
-                _textMate.Dispose();
-                _textMate = null;
-            }
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope);
 
             base.OnUnloaded(e);
         }
@@ -346,7 +343,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             if (change.Property == LinesProperty)
                 UpdateContent();
             else if (change.Property == FileNameProperty)
-                Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName);
+                Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName, ref _lastGrammarScope);
             else if (change.Property.Name == nameof(ActualThemeVariant) && change.NewValue != null)
                 Models.TextMateHelper.SetThemeByApp(_textMate);
             else if (change.Property == SelectedChunkProperty)
@@ -539,6 +536,7 @@ private void UpdateSelectedChunkPosition(ViewModels.MergeConflictEditor vm, doub
         }
 
         private TextMate.Installation _textMate;
+        private string _lastGrammarScope = string.Empty;
         private ScrollViewer _scrollViewer;
     }
 
diff --git a/src/Views/RevisionFileContentViewer.axaml.cs b/src/Views/RevisionFileContentViewer.axaml.cs
index eddb7b95c..5511eb927 100644
--- a/src/Views/RevisionFileContentViewer.axaml.cs
+++ b/src/Views/RevisionFileContentViewer.axaml.cs
@@ -67,10 +67,7 @@ protected override void OnUnloaded(RoutedEventArgs e)
             TextArea.TextView.ContextRequested -= OnTextViewContextRequested;
 
             if (_textMate != null)
-            {
-                _textMate.Dispose();
-                _textMate = null;
-            }
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope);
 
             GC.Collect();
         }
@@ -82,7 +79,7 @@ protected override void OnDataContextChanged(EventArgs e)
             if (DataContext is Models.RevisionTextFile source)
             {
                 Text = source.Content;
-                Models.TextMateHelper.SetGrammarByFileName(_textMate, source.FileName);
+                Models.TextMateHelper.SetGrammarByFileName(_textMate, source.FileName, ref _lastGrammarScope);
                 ScrollToHome();
             }
             else
@@ -139,19 +136,18 @@ private void UpdateTextMate()
                 _textMate ??= Models.TextMateHelper.CreateForEditor(this);
 
                 if (DataContext is Models.RevisionTextFile file)
-                    Models.TextMateHelper.SetGrammarByFileName(_textMate, file.FileName);
+                    Models.TextMateHelper.SetGrammarByFileName(_textMate, file.FileName, ref _lastGrammarScope);
             }
             else if (_textMate != null)
             {
-                _textMate.Dispose();
-                _textMate = null;
-                GC.Collect();
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope, true);
 
                 TextArea.TextView.Redraw();
             }
         }
 
         private TextMate.Installation _textMate = null;
+        private string _lastGrammarScope = string.Empty;
     }
 
     public partial class RevisionFileContentViewer : UserControl
diff --git a/src/Views/SelfUpdate.axaml.cs b/src/Views/SelfUpdate.axaml.cs
index 97f1bc772..0783c6fae 100644
--- a/src/Views/SelfUpdate.axaml.cs
+++ b/src/Views/SelfUpdate.axaml.cs
@@ -34,7 +34,7 @@ protected override void OnLoaded(RoutedEventArgs e)
             if (_textMate == null)
             {
                 _textMate = Models.TextMateHelper.CreateForEditor(this);
-                Models.TextMateHelper.SetGrammarByFileName(_textMate, "README.md");
+                Models.TextMateHelper.SetGrammarByFileName(_textMate, "README.md", ref _lastGrammarScope);
             }
         }
 
@@ -43,10 +43,7 @@ protected override void OnUnloaded(RoutedEventArgs e)
             base.OnUnloaded(e);
 
             if (_textMate != null)
-            {
-                _textMate.Dispose();
-                _textMate = null;
-            }
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope);
 
             GC.Collect();
         }
@@ -60,6 +57,7 @@ protected override void OnDataContextChanged(EventArgs e)
         }
 
         private TextMate.Installation _textMate = null;
+        private string _lastGrammarScope = string.Empty;
     }
 
     public partial class SelfUpdate : ChromelessWindow
diff --git a/src/Views/TextDiffView.axaml.cs b/src/Views/TextDiffView.axaml.cs
index 94940e743..4addf2d0b 100644
--- a/src/Views/TextDiffView.axaml.cs
+++ b/src/Views/TextDiffView.axaml.cs
@@ -550,10 +550,7 @@ protected override void OnUnloaded(RoutedEventArgs e)
             TextArea.TextView.VisualLinesChanged -= OnTextViewVisualLinesChanged;
 
             if (_textMate != null)
-            {
-                _textMate.Dispose();
-                _textMate = null;
-            }
+                Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope);
         }
 
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
@@ -576,7 +573,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             }
             else if (change.Property == FileNameProperty)
             {
-                Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName);
+                Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName, ref _lastGrammarScope);
             }
             else if (change.Property.Name == nameof(ActualThemeVariant) && change.NewValue != null)
             {
@@ -773,16 +770,14 @@ private void UpdateTextMate()
                     TextArea.TextView.LineTransformers.Remove(_lineStyleTransformer);
                     _textMate = Models.TextMateHelper.CreateForEditor(this);
                     TextArea.TextView.LineTransformers.Add(_lineStyleTransformer);
-                    Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName);
+                    Models.TextMateHelper.SetGrammarByFileName(_textMate, FileName, ref _lastGrammarScope);
                 }
             }
             else
             {
                 if (_textMate != null)
                 {
-                    _textMate.Dispose();
-                    _textMate = null;
-                    GC.Collect();
+                    Models.TextMateHelper.DisposeInstallation(ref _textMate, ref _lastGrammarScope, true);
 
                     TextArea.TextView.Redraw();
                 }
@@ -885,6 +880,7 @@ private async Task CopyWithoutIndicatorsAsync()
 
         private bool _execSizeChanged;
         private TextMate.Installation _textMate;
+        private string _lastGrammarScope = string.Empty;
         private TextLocation _lastSelectStart = TextLocation.Empty;
         private TextLocation _lastSelectEnd = TextLocation.Empty;
         private LineStyleTransformer _lineStyleTransformer;