diff --git a/CHANGELOG.md b/CHANGELOG.md
index 724856e5..b8c6c4aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,5 @@
+- Fixed a Warning dialog appearing on NetBeans exit when a diff tab had been opened during the session
+
 # 1.2.8 (2026-05-24)
 
 - Added "Auto Mode" to the edit-mode selector (Claude Code 2.1.83+): file edits in auto mode are auto-approved; when auto mode is selected on an older Claude Code version, the plugin falls back to Bypass Permissions or Accept on Edit
diff --git a/pom.xml b/pom.xml
index 72fe8ecf..951ccbf8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
 
     <groupId>io.github.nbplugins</groupId>
     <artifactId>netbeans-plugin-claude-code-gui</artifactId>
-    <version>1.2.12-SNAPSHOT</version>
+    <version>1.2.14-SNAPSHOT</version>
     <packaging>nbm</packaging>
     <name>Netbeans Plugin Claude Code GUI</name>
     <description>NetBeans plugin that provides a GUI for Claude Code CLI — run claude code sessions directly inside the IDE.</description>
diff --git a/src/main/java/io/github/nbplugins/claudecodegui/ClaudeCodeInstaller.java b/src/main/java/io/github/nbplugins/claudecodegui/ClaudeCodeInstaller.java
index 3246cff3..20ae26b1 100644
--- a/src/main/java/io/github/nbplugins/claudecodegui/ClaudeCodeInstaller.java
+++ b/src/main/java/io/github/nbplugins/claudecodegui/ClaudeCodeInstaller.java
@@ -51,8 +51,12 @@ public void restored() {
         // Migrate window settings files (must run before window system reads them)
         String userDir = System.getProperty("netbeans.user");
         if (userDir != null) {
-            V1MigrationHelper.migrateWindowsSettings(
-                    Paths.get(userDir, "config", "Windows2Local", "Components"));
+            Path componentsDir = Paths.get(userDir, "config", "Windows2Local", "Components");
+            V1MigrationHelper.migrateWindowsSettings(componentsDir);
+            // FileDiffOpener$1 was renamed to FileDiffOpener$DiffTopComponent in 1.2.13;
+            // delete stale .settings files so NetBeans does not warn about the unknown class.
+            V1MigrationHelper.removeStaleComponentSettings(componentsDir,
+                    "FileDiffOpener$1");
         }
 
         // Migrate preferences from old package paths (one-time, after package rename in 1.0)
diff --git a/src/main/java/io/github/nbplugins/claudecodegui/V1MigrationHelper.java b/src/main/java/io/github/nbplugins/claudecodegui/V1MigrationHelper.java
index 42ca90bb..7bc3b87e 100644
--- a/src/main/java/io/github/nbplugins/claudecodegui/V1MigrationHelper.java
+++ b/src/main/java/io/github/nbplugins/claudecodegui/V1MigrationHelper.java
@@ -41,6 +41,34 @@ static void migrateWindowsSettings(Path componentsDir) {
         }
     }
 
+    /**
+     * Deletes stale .settings files in componentsDir that reference class names matching
+     * any of the given substrings. Use this when a TopComponent class is renamed or removed
+     * and its serialized binary data can no longer be deserialized.
+     */
+    static void removeStaleComponentSettings(Path componentsDir, String... classNameSubstrings) {
+        if (!Files.exists(componentsDir)) return;
+        try (var stream = Files.list(componentsDir)) {
+            stream.filter(p -> p.toString().endsWith(".settings"))
+                  .forEach(p -> {
+                      try {
+                          String content = Files.readString(p);
+                          for (String substring : classNameSubstrings) {
+                              if (content.contains(substring)) {
+                                  Files.delete(p);
+                                  LOG.log(Level.FINE, "Removed stale window settings: {0}", p);
+                                  break;
+                              }
+                          }
+                      } catch (IOException e) {
+                          LOG.log(Level.WARNING, "Could not process window settings: " + p, e);
+                      }
+                  });
+        } catch (IOException e) {
+            LOG.log(Level.WARNING, "Stale settings cleanup failed", e);
+        }
+    }
+
     /** Copies keys from oldPath NbPreferences node to newNode, then removes the old node. */
     static void migratePrefsNode(String oldPath, Preferences newNode) {
         migratePrefsNode(NbPreferences.root(), oldPath, newNode);
diff --git a/src/main/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpener.java b/src/main/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpener.java
index 5d37e02f..ca5592be 100644
--- a/src/main/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpener.java
+++ b/src/main/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpener.java
@@ -341,17 +341,7 @@ public static void open(
             }
 
             // --- TOPLEVEL branch ---
-            TopComponent diffTC = new TopComponent() {
-                @Override
-                public void componentClosed() {
-                    super.componentClosed();
-                    removeAwtListener[0].run();
-                    if (!decided.get()) {
-                        onClose.run();
-                        activateSessionForFile(filePath);
-                    }
-                }
-            };
+            TopComponent diffTC = new DiffTopComponent(removeAwtListener, decided, onClose, filePath);
             closeDiffRef[0] = diffTC::close;
             diffTC.setDisplayName(tabName);
             diffTC.setLayout(new java.awt.BorderLayout());
@@ -596,6 +586,36 @@ public static void cancelCurrentPromptForFile(String filePath) {
         }
     }
 
+    static final class DiffTopComponent extends TopComponent {
+        private final Runnable[] removeAwtListener;
+        private final AtomicBoolean decided;
+        private final Runnable onClose;
+        private final String filePath;
+
+        DiffTopComponent(Runnable[] removeAwtListener, AtomicBoolean decided,
+                         Runnable onClose, String filePath) {
+            this.removeAwtListener = removeAwtListener;
+            this.decided = decided;
+            this.onClose = onClose;
+            this.filePath = filePath;
+        }
+
+        @Override
+        public int getPersistenceType() {
+            return TopComponent.PERSISTENCE_NEVER;
+        }
+
+        @Override
+        public void componentClosed() {
+            super.componentClosed();
+            removeAwtListener[0].run();
+            if (!decided.get()) {
+                onClose.run();
+                activateSessionForFile(filePath);
+            }
+        }
+    }
+
     private static StreamSource textSource(String name, String filePath, String content) {
         return new StreamSource() {
             @Override public String getName()     { return name; }
diff --git a/src/test/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpenerTest.java b/src/test/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpenerTest.java
index 1de48093..3ee82542 100644
--- a/src/test/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpenerTest.java
+++ b/src/test/java/io/github/nbplugins/claudecodegui/ui/FileDiffOpenerTest.java
@@ -3,10 +3,12 @@
 import java.awt.Component;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
 import javax.swing.JCheckBoxMenuItem;
 import javax.swing.JMenuItem;
 import javax.swing.JPopupMenu;
 import org.junit.jupiter.api.Test;
+import org.openide.windows.TopComponent;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -283,4 +285,14 @@ private static long countCheckItems(JPopupMenu menu, String text) {
         }
         return count;
     }
+
+    @Test
+    void diffTopComponentPersistenceTypeIsNever() {
+        FileDiffOpener.DiffTopComponent tc = new FileDiffOpener.DiffTopComponent(
+                new Runnable[]{() -> {}},
+                new AtomicBoolean(false),
+                () -> {},
+                "/tmp/test.java");
+        assertEquals(TopComponent.PERSISTENCE_NEVER, tc.getPersistenceType());
+    }
 }