diff --git a/docs/guides/theme-builder.md b/docs/guides/theme-builder.md
index 4ac7eb0..4e86c6e 100644
--- a/docs/guides/theme-builder.md
+++ b/docs/guides/theme-builder.md
@@ -76,7 +76,8 @@ bleiben die Felder ungeprüft (die Antwort sagt das). Kopf- und Fußzeile werden
 - Speichert jemand in einem Theme-Builder-Fenster, das vor dem Anlegen einer Vorlage geöffnet wurde, entfernt
   Divi die neue Vorlage wieder aus der Liste und löscht sie 7 Tage später. `lit/tb-list` zeigt sie dann unter
   `detached` (mit `marked_unused`). Nur auf ausdrücklichen Wunsch: `lit/tb-assign` mit `reattach: true` ordnet
-  sie wieder zu – immer deaktiviert, und nur, wenn ihre Layouts noch aktiv sind.
+  sie wieder zu – immer deaktiviert, nur Vorlagen unter `detached` (keine, die eine Theme-Builder-Vorlage der
+  Divi-Bibliothek nutzt) und nur, wenn ihre Layouts noch aktiv sind.
 
 ## Rechte
 
diff --git a/src/Integrations/Divi/ThemeBuilder/DiviThemeBuilder.php b/src/Integrations/Divi/ThemeBuilder/DiviThemeBuilder.php
index 0457fa2..aa9eede 100644
--- a/src/Integrations/Divi/ThemeBuilder/DiviThemeBuilder.php
+++ b/src/Integrations/Divi/ThemeBuilder/DiviThemeBuilder.php
@@ -177,6 +177,23 @@ class DiviThemeBuilder
         return array_values(array_map('intval', is_array($ids) ? $ids : []));
     }
 
+    /**
+     * Whether any Theme Builder post (live, draft or a Theme Builder library item) lists template $templateId –
+     * the criterion detachedIds() uses; lit/tb-assign reattaches only templates none lists (audit L4).
+     */
+    public function isListedAnywhere(int $templateId): bool
+    {
+        global $wpdb;
+        // phpcs:ignore WordPress.DB.DirectDatabaseQuery -- the _et_template rows of every Theme Builder post.
+        $found = $wpdb->get_var($wpdb->prepare(
+            "SELECT 1 FROM {$wpdb->postmeta} WHERE meta_key = %s AND meta_value = %s LIMIT 1",
+            self::TEMPLATE_LIST,
+            (string) $templateId
+        ));
+
+        return $found !== null;
+    }
+
     /** @throws RuntimeException */
     public function insertLayout(string $area, string $title): int
     {
diff --git a/src/Integrations/Divi/ThemeBuilder/TbAssignAbility.php b/src/Integrations/Divi/ThemeBuilder/TbAssignAbility.php
index d595d34..b4f57bf 100644
--- a/src/Integrations/Divi/ThemeBuilder/TbAssignAbility.php
+++ b/src/Integrations/Divi/ThemeBuilder/TbAssignAbility.php
@@ -23,7 +23,8 @@ defined('ABSPATH') || exit;
  * (ruling Q3/B3). A live template changes the website at once, so it is a dry run first and needs confirm: true
  * (ruling Q9/B22), listing both lists before/after and overlaps (identical and possible, B9) with other live
  * templates for the resulting lists. reattach: true puts a template a stale Theme Builder save removed back on the
- * live list (only on the user's request, B19) – always disabled, Divi's "unused" marks removed from it and its
+ * live list (only on the user's request, B19; only one no Theme Builder post lists – tb-list's detached, audit L4)
+ * – always disabled, Divi's "unused" marks removed from it and its
  * layouts, which must still be published (B10). Templates have no revisions: the previous conditions are in the
  * answer and the change log; a failed write restores them (and undoes the reattach).
  */
@@ -144,13 +145,30 @@ final class TbAssignAbility implements Ability
         return $this->write($template, $useOn['ids'], $excludeFrom['ids'], $reattach);
     }
 
-    /** A detached template needs reattach: true, a live Theme Builder post and published layouts (B10). */
+    /**
+     * A detached template needs reattach: true, a live Theme Builder post and published layouts (B10). Detached
+     * means what tb-list shows as detached: no Theme Builder post lists it – a template of a Theme Builder library
+     * item or draft is none (audit L4).
+     */
     private function reattachRefusal(Template $template, bool $reattach): ?WP_Error
     {
         if ($template->attached) {
             return null;
         }
 
+        if ($this->access->store()->isListedAnywhere($template->id)) {
+            return Errors::invalidInput(
+                sprintf(
+                    'Vorlage %d ist keine entfernte Vorlage (siehe detached in lit/tb-list); nichts wurde gespeichert.',
+                    $template->id
+                ),
+                [
+                    'template_id' => 'nur Vorlagen der Website (templates) oder entfernte Vorlagen (detached) aus '
+                        . 'lit/tb-list',
+                ]
+            );
+        }
+
         if (! $reattach) {
             $marked = $template->markedUnused === null
                 ? ''
diff --git a/tests/Support/ThemeBuilderFixtures.php b/tests/Support/ThemeBuilderFixtures.php
index 774c65b..1bd9e72 100644
--- a/tests/Support/ThemeBuilderFixtures.php
+++ b/tests/Support/ThemeBuilderFixtures.php
@@ -128,6 +128,9 @@ final class ThemeBuilderFixtures
         $store->allows('templateIds')->andReturn(array_map(static fn (Template $t): int => $t->id, $templates));
         $store->allows('template')->andReturnUsing(static fn (int $id): ?Template => $byId[$id] ?? null)->byDefault();
         $store->allows('detachedIds')->andReturn(array_map(static fn (Template $t): int => $t->id, $detached));
+        $store->allows('isListedAnywhere')->andReturnUsing(
+            static fn (int $id): bool => in_array($id, array_map(static fn (Template $t): int => $t->id, $templates), true)
+        )->byDefault();
         $store->allows('flatConditions')->andReturn(self::conditions());
 
         return $store;
diff --git a/tests/Unit/Integrations/Divi/ThemeBuilder/DiviThemeBuilderTest.php b/tests/Unit/Integrations/Divi/ThemeBuilder/DiviThemeBuilderTest.php
index 9be6ea8..6c2048e 100644
--- a/tests/Unit/Integrations/Divi/ThemeBuilder/DiviThemeBuilderTest.php
+++ b/tests/Unit/Integrations/Divi/ThemeBuilder/DiviThemeBuilderTest.php
@@ -26,6 +26,38 @@ final class DiviThemeBuilderTest extends TestCase
         self::assertNull(DiviThemeBuilder::areaOf('page'));
     }
 
+    /** Review M-3: one list of every Theme Builder post type. */
+    public function testPostTypesNameEveryThemeBuilderType(): void
+    {
+        self::assertSame(
+            ['et_theme_builder', 'et_template', 'et_header_layout', 'et_body_layout', 'et_footer_layout'],
+            DiviThemeBuilder::postTypes()
+        );
+    }
+
+    /** Audit L4: a template is listed when any Theme Builder post's _et_template row names it. */
+    public function testIsListedAnywhereAsksEveryThemeBuilderPost(): void
+    {
+        $db = Mockery::mock(\wpdb::class)->makePartial();
+        $db->postmeta = 'wp_postmeta';
+        $sql = [];
+        $db->allows('get_var')->andReturnUsing(static function (string $query) use (&$sql): ?string {
+            $sql[] = $query;
+
+            return str_contains($query, "'1066'") ? '1' : null;
+        });
+        $GLOBALS['wpdb'] = $db;
+
+        try {
+            self::assertTrue((new DiviThemeBuilder())->isListedAnywhere(1066));
+            self::assertFalse((new DiviThemeBuilder())->isListedAnywhere(2394));
+        } finally {
+            unset($GLOBALS['wpdb']);
+        }
+        self::assertStringContainsString("meta_key = '_et_template'", $sql[0]);
+        self::assertStringContainsString('LIMIT 1', $sql[0]);
+    }
+
     /** F17/F18: Divi wp_die()s without edit_others_posts – the adapter never gets there. */
     public function testWithoutEditOthersPostsDiviIsNeverCalled(): void
     {
diff --git a/tests/Unit/Integrations/Divi/ThemeBuilder/TbAssignAbilityTest.php b/tests/Unit/Integrations/Divi/ThemeBuilder/TbAssignAbilityTest.php
index 9cdab43..e77e23b 100644
--- a/tests/Unit/Integrations/Divi/ThemeBuilder/TbAssignAbilityTest.php
+++ b/tests/Unit/Integrations/Divi/ThemeBuilder/TbAssignAbilityTest.php
@@ -180,6 +180,27 @@ final class TbAssignAbilityTest extends TestCase
         self::assertTrue($result['previous']['enabled']);
     }
 
+    /**
+     * Audit L4: reattach takes only templates no Theme Builder post lists (tb-list's detached) – not one that a
+     * Theme Builder library item or draft lists; nothing is written.
+     */
+    public function testReattachRefusesATemplateAnotherThemeBuilderPostLists(): void
+    {
+        $listedElsewhere = ThemeBuilderFixtures::template(1066, ['attached' => false]);
+        $store = ThemeBuilderFixtures::store([], 0, [], [$listedElsewhere]);
+        $store->allows('isListedAnywhere')->with(1066)->andReturn(true);
+        foreach (['setEnabled', 'attach', 'unmarkUnused', 'setConditions'] as $method) {
+            $store->shouldReceive($method)->never();
+        }
+
+        foreach ([['reattach' => true], []] as $extra) {
+            $refused = self::ability($store, FakeChangeLog::forbidden())->execute(self::input($listedElsewhere, $extra));
+            self::assertToolError($refused, 'validation_failed');
+            self::assertStringContainsString('keine entfernte Vorlage', self::clientError($refused)['message']);
+            self::assertArrayHasKey('template_id', self::errorFields($refused));
+        }
+    }
+
     /** Ruling Q8/B10: a layout Divi trashed meanwhile blocks the reattach; nothing is written. */
     public function testReattachNeedsPublishedLayouts(): void
     {