--- a/gin_toolbar.module
+++ b/gin_toolbar.module
@@ -179,29 +179,54 @@
  * Attach libraries.
  */
 function gin_toolbar_library_info_alter(&$libraries, $extension) {
+  // Gin's own .info.yml already adds these same 'gin/...' dependencies via
+  // libraries-extend whenever Gin is actually the active theme, which is
+  // cache-safe because Drupal's library cache is keyed by active theme
+  // (see LibraryDiscoveryCollector::getCid() and AssetResolver's css/js
+  // cache keys). The additions below are only meaningful, then, for
+  // bridging Gin's dialog/ckeditor/media_library styling into contexts
+  // where Gin ISN'T the active theme (e.g. the frontend theme, or a theme
+  // negotiator forcing something else on admin routes) — but that decision
+  // can't safely depend on anything other than the active theme name
+  // (e.g. the current user), since nothing besides active theme partitions
+  // those caches. So, unlike gin_toolbar's other cross-theme bridging (see
+  // _gin_toolbar_gin_is_active(), used by gin_toolbar_preprocess_html() and
+  // gin_toolbar_page_attachments_alter()), skip adding the 'gin/...'
+  // dependencies here entirely and let Gin's own libraries-extend be the
+  // only source of them.
+  $active_theme_is_gin = \Drupal::theme()->getActiveTheme()->getName() === 'gin';
+
   if ($extension == 'core' && isset($libraries['drupal.dialog'])) {
     $libraries['drupal.dialog']['dependencies'][] = 'claro/claro.drupal.dialog';
-    $libraries['drupal.dialog']['dependencies'][] = 'gin/dialog';
+    if ($active_theme_is_gin) {
+      $libraries['drupal.dialog']['dependencies'][] = 'gin/dialog';
+    }
   }

-  if ($extension == 'core' && isset($libraries['ckeditor'])) {
+  if ($extension == 'core' && isset($libraries['ckeditor']) && $active_theme_is_gin) {
     $libraries['ckeditor']['dependencies'][] = 'gin/gin_ckeditor';
     $libraries['ckeditor']['dependencies'][] = 'gin/ckeditor';
   }

   if ($extension == 'core' && isset($libraries['drupal.ajax'])) {
     $libraries['drupal.ajax']['dependencies'][] = 'claro/ajax';
-    $libraries['drupal.ajax']['dependencies'][] = 'gin/ajax';
+    if ($active_theme_is_gin) {
+      $libraries['drupal.ajax']['dependencies'][] = 'gin/ajax';
+    }
   }

   if ($extension == 'media_library' && isset($libraries['widget'])) {
     $libraries['widget']['dependencies'][] = 'claro/media_library.theme';
-    $libraries['widget']['dependencies'][] = 'gin/media_library';
+    if ($active_theme_is_gin) {
+      $libraries['widget']['dependencies'][] = 'gin/media_library';
+    }
   }

   if ($extension == 'media_library' && isset($libraries['view'])) {
     $libraries['view']['dependencies'][] = 'claro/media_library.theme';
-    $libraries['view']['dependencies'][] = 'gin/media_library';
+    if ($active_theme_is_gin) {
+      $libraries['view']['dependencies'][] = 'gin/media_library';
+    }
   }

   if ($extension == 'workbench' && isset($libraries['workbench.toolbar'])) {