diff --git a/src/Integrations/Divi/BlockTree/Block.php b/src/Integrations/Divi/BlockTree/Block.php
index 89a1872..9266bf4 100644
--- a/src/Integrations/Divi/BlockTree/Block.php
+++ b/src/Integrations/Divi/BlockTree/Block.php
@@ -141,6 +141,30 @@ final class Block extends Container
         return clone $this;
     }
 
+    /**
+     * A deep copy of this block under another name and attributes: opener and closer are
+     * regenerated, children and the text between them are kept, the void flag too. Opaque exactly
+     * when the Parser would make it so. GlobalInstance uses it to turn a library root into an
+     * instance and back.
+     *
+     * @param array<string, mixed> $attrs
+     */
+    public function copyAs(string $name, array $attrs): self
+    {
+        if (preg_match(self::NAME_PATTERN, $name) !== 1) {
+            throw new InvalidArgumentException(sprintf('"%s" is not a valid block name.', $name));
+        }
+
+        $copy = clone $this;
+        $copy->name = $name;
+        $copy->attrs = self::deepCloneAttrs($attrs);
+        $copy->rawOpen = null;
+        $copy->rawClose = null;
+        $copy->opaque = $name === 'divi/global-layout' || array_key_exists('globalModule', $attrs);
+
+        return $copy;
+    }
+
     public function __clone()
     {
         foreach ($this->parts as $position => $part) {
diff --git a/src/Integrations/Divi/BlockTree/Container.php b/src/Integrations/Divi/BlockTree/Container.php
index 05447ed..5f79f14 100644
--- a/src/Integrations/Divi/BlockTree/Container.php
+++ b/src/Integrations/Divi/BlockTree/Container.php
@@ -93,12 +93,41 @@ abstract class Container
         return $index;
     }
 
+    /** Puts $new where the child $old is; the text around it stays. */
+    public function replaceChild(Block $old, Block $new): void
+    {
+        $this->guardMutable();
+        $this->parts[$this->partPosition($old)] = $new;
+        $this->touched();
+    }
+
+    /**
+     * "\r\n" → "\n" in whitespace-only text between blocks, at every depth. Library entries saved
+     * through Divi's "add to library" form carry CRLF (browsers normalise form fields, fixture
+     * finding 9); the Visual Builder writes "\n". Text inside blocks' own content stays untouched,
+     * and so do opaque blocks (global instances keep Divi's bytes).
+     */
+    public function unifyLineBreaks(): void
+    {
+        if ($this instanceof Block && $this->isOpaque()) {
+            return;
+        }
+
+        foreach ($this->parts as $position => $part) {
+            if ($part instanceof Block) {
+                $part->unifyLineBreaks();
+            } elseif (trim($part) === '' && str_contains($part, "\r\n")) {
+                $this->parts[$position] = str_replace("\r\n", "\n", $part);
+            }
+        }
+    }
+
     /** Called after the list of children changed. */
     protected function touched(): void
     {
     }
 
-    /** insertChild()/removeChild() are the tools' structural edits – never on an opaque block. */
+    /** insertChild()/removeChild()/replaceChild() are the tools' structural edits – never on an opaque block. */
     private function guardMutable(): void
     {
         if ($this instanceof Block && $this->isOpaque()) {
diff --git a/src/Integrations/Divi/BlockTree/GlobalInstance.php b/src/Integrations/Divi/BlockTree/GlobalInstance.php
new file mode 100644
index 0000000..2b56f44
--- /dev/null
+++ b/src/Integrations/Divi/BlockTree/GlobalInstance.php
@@ -0,0 +1,115 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Integrations\Divi\BlockTree;
+
+use InvalidArgumentException;
+
+defined('ABSPATH') || exit;
+
+/**
+ * Global modules the way Divi 5 stores them (F6, F10, fixtures stage3): an instance on a page is a
+ * divi/global-layout block whose content Divi takes from the library entry at render time (F7).
+ * Instances stay opaque for the page tools; edits go to the library entry. Pure PHP.
+ */
+final class GlobalInstance
+{
+    public const BLOCK = 'divi/global-layout';
+
+    /** Block name the node counts as for structure rules: an instance counts as its root type. */
+    public static function effectiveName(Block $block): string
+    {
+        if ($block->name() !== self::BLOCK) {
+            return $block->name();
+        }
+
+        $name = $block->attrs()['blockName'] ?? '';
+
+        return is_string($name) ? $name : '';
+    }
+
+    /**
+     * The instance the Visual Builder writes for library entry $libraryId whose content root is
+     * $root (serialized-post.js, filter divi.serializedPost.parseFlatModuleObjectIntoBlockArray.nested;
+     * fixture page--globale-instanzen.html): divi/global-layout with globalModule, blockName and
+     * localAttrs – the root's attributes, top-level keys sorted like the builder's store, left out
+     * when empty –, the root's children as snapshot with "globalParent": "<id>" appended to every
+     * block below. A void root gives a void instance. $root is not changed.
+     */
+    public static function of(Block $root, int $libraryId): Block
+    {
+        $id = (string) $libraryId;
+        $local = $root->attrs();
+        ksort($local);
+        $attrs = ['globalModule' => $id, 'blockName' => $root->name()];
+        if ($local !== []) {
+            $attrs['localAttrs'] = $local;
+        }
+
+        $instance = $root->copyAs(self::BLOCK, $attrs);
+        foreach ($instance->children() as $child) {
+            self::markParent($child, $id);
+        }
+
+        return $instance;
+    }
+
+    /**
+     * Divi's PortabilityPost::maybe_deglobalize_nested_global_modules() on a tree (Divi 5.2.1
+     * PortabilityPost.php:3518, used by DiviLibraryController::load for global entries): every
+     * divi/global-layout at or below $block becomes its blockName with localAttrs as attributes,
+     * and globalParent disappears from every block. Other opaque blocks stay, and so does an instance
+     * without a usable blockName. Changes $block in place (pass a copy) and returns the result – a
+     * new block when $block itself was an instance.
+     */
+    public static function deglobalize(Block $block): Block
+    {
+        if ($block->name() === self::BLOCK) {
+            $name = self::effectiveName($block);
+            if ($name === '') {
+                return $block;
+            }
+            $local = $block->attrs()['localAttrs'] ?? [];
+            try {
+                $block = $block->copyAs($name, is_array($local) ? $local : []);
+            } catch (InvalidArgumentException) {
+                return $block; // Stored blockName is no block name: the instance stays opaque.
+            }
+        }
+
+        if ($block->isOpaque()) {
+            return $block;
+        }
+
+        if (array_key_exists('globalParent', $block->attrs())) {
+            $attrs = $block->attrs();
+            unset($attrs['globalParent']);
+            $block->setAttrs($attrs);
+        }
+
+        foreach ($block->children() as $child) {
+            $plain = self::deglobalize($child);
+            if ($plain !== $child) {
+                $block->replaceChild($child, $plain);
+            }
+        }
+
+        return $block;
+    }
+
+    private static function markParent(Block $block, string $id): void
+    {
+        if ($block->isOpaque()) {
+            return;
+        }
+
+        $attrs = $block->attrs();
+        unset($attrs['globalParent']);
+        $attrs['globalParent'] = $id;
+        $block->setAttrs($attrs);
+        foreach ($block->children() as $child) {
+            self::markParent($child, $id);
+        }
+    }
+}
diff --git a/src/Integrations/Divi/BlockTree/LibraryContent.php b/src/Integrations/Divi/BlockTree/LibraryContent.php
new file mode 100644
index 0000000..6235a40
--- /dev/null
+++ b/src/Integrations/Divi/BlockTree/LibraryContent.php
@@ -0,0 +1,107 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Integrations\Divi\BlockTree;
+
+defined('ABSPATH') || exit;
+
+/**
+ * post_content of Divi Library entries (F4, fixtures stage3): the nodes sit in a divi/placeholder
+ * frame; a section/row/module entry has exactly one root, a layout entry sections. Pure PHP.
+ */
+final class LibraryContent
+{
+    public const WRAPPER = 'divi/placeholder';
+
+    /**
+     * Parses library content for copying and unifies its line breaks (Container::unifyLineBreaks()).
+     * Never used for the content a tool edits in place – that keeps its bytes.
+     *
+     * @throws MalformedMarkup
+     */
+    public static function load(Parser $parser, string $content): Document
+    {
+        $document = $parser->parse($content);
+        $document->unifyLineBreaks();
+
+        return $document;
+    }
+
+    /** post_content of a library entry holding $node, framed like the builder's "add to library". */
+    public static function wrap(Block $node): string
+    {
+        return '<!-- wp:' . self::WRAPPER . ' -->' . Serializer::block($node) . '<!-- /wp:' . self::WRAPPER . ' -->';
+    }
+
+    /** @return list<Block> Top-level nodes: the children of the first divi/placeholder, else of the document. */
+    public static function roots(Document $document): array
+    {
+        foreach ($document->children() as $block) {
+            if ($block->isPlaceholder()) {
+                return $block->children();
+            }
+        }
+
+        return $document->children();
+    }
+
+    /** Whether $block is or contains a global module. */
+    public static function containsGlobal(Block $block): bool
+    {
+        if ($block->isGlobal()) {
+            return true;
+        }
+
+        foreach ($block->children() as $child) {
+            if (self::containsGlobal($child)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Why the roots $after may not replace $before, or null. Instances on pages expect their
+     * entry's root type (blockName), so a section/row/module entry keeps exactly one root of the
+     * same type; a layout entry (or one with several roots) holds sections only. A global entry
+     * contains no global modules (F10: Divi forbids nesting).
+     *
+     * @param list<Block> $before
+     * @param list<Block> $after
+     */
+    public static function shapeViolation(array $before, array $after, ?string $layoutType, bool $global): ?string
+    {
+        if ($after === []) {
+            return 'Der Bibliothekseintrag darf nicht leer werden.';
+        }
+
+        if ($layoutType === 'layout' || count($before) !== 1) {
+            foreach ($after as $root) {
+                if (GlobalInstance::effectiveName($root) !== 'divi/section') {
+                    return 'Ein Layout-Eintrag der Bibliothek enthält nur Abschnitte.';
+                }
+            }
+        } else {
+            $expected = GlobalInstance::effectiveName($before[0]);
+            if (count($after) !== 1 || GlobalInstance::effectiveName($after[0]) !== $expected) {
+                return sprintf(
+                    'Der Bibliothekseintrag muss genau ein %s bleiben (Instanzen auf den Seiten erwarten diesen Typ).',
+                    $expected
+                );
+            }
+        }
+
+        if ($global) {
+            foreach ($after as $root) {
+                if (self::containsGlobal($root)) {
+                    return 'Ein globaler Bibliothekseintrag darf keine globalen Module enthalten (Divi erlaubt keine '
+                        . 'Verschachtelung).';
+                }
+            }
+        }
+
+        return null;
+    }
+}
diff --git a/src/Integrations/Divi/Compose/TreeEditor.php b/src/Integrations/Divi/Compose/TreeEditor.php
index 4da8a96..dc8bf68 100644
--- a/src/Integrations/Divi/Compose/TreeEditor.php
+++ b/src/Integrations/Divi/Compose/TreeEditor.php
@@ -7,6 +7,7 @@ namespace LIT\MCP\Integrations\Divi\Compose;
 use LIT\MCP\Integrations\Divi\BlockTree\Block;
 use LIT\MCP\Integrations\Divi\BlockTree\Container;
 use LIT\MCP\Integrations\Divi\BlockTree\Document;
+use LIT\MCP\Integrations\Divi\BlockTree\GlobalInstance;
 use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
 
 defined('ABSPATH') || exit;
@@ -14,7 +15,8 @@ defined('ABSPATH') || exit;
 /**
  * Structural changes on a parsed page (spec §5.7): where to insert (parent / before / after,
  * optional index), move, remove, duplicate – always checked against StructureRules. Works on
- * the tree only; saving is DiviWriter's job. Pure PHP.
+ * the tree only; saving is DiviWriter's job. Global instances count as their root type
+ * (blockName, GlobalInstance::effectiveName()). Pure PHP.
  */
 final class TreeEditor
 {
@@ -79,7 +81,7 @@ final class TreeEditor
     public function insert(array $position, array $blocks): ?string
     {
         foreach ($blocks as $block) {
-            $violation = $this->rules->violation($position['parent'], $block->name());
+            $violation = $this->rules->violation($position['parent'], GlobalInstance::effectiveName($block));
             if ($violation !== null) {
                 return $violation;
             }
@@ -104,7 +106,7 @@ final class TreeEditor
             }
         }
 
-        $violation = $this->rules->violation($position['parent'], $node->name());
+        $violation = $this->rules->violation($position['parent'], GlobalInstance::effectiveName($node));
         if ($violation !== null) {
             return $violation;
         }
diff --git a/tests/Fixtures/divi/stage3/README.md b/tests/Fixtures/divi/stage3/README.md
index 7a40732..e81f8f1 100644
--- a/tests/Fixtures/divi/stage3/README.md
+++ b/tests/Fixtures/divi/stage3/README.md
@@ -79,6 +79,7 @@ Im Body-Layout: Überschrift = `post_title`, Text = `post_meta_key` mit manuelle
 6. **TB-Layouts haben keinen `layout_type`-Term**, obwohl `et_theme_builder_insert_layout` ihn setzen will (`theme-builder.php:1663`). In `wp_term_relationships` steht für 1061–1063 nichts; vermutlich ist die Taxonomie im admin-ajax-Aufruf nicht registriert (Registrierung über `ET_Builder_Library`, `builder/feature/Library.php:397`) – die Ursache ist nicht weiter geprüft. Nicht auf Terme bei TB-Layouts verlassen.
 7. **TB-Bedingungen** stehen als mehrfaches Meta `_et_use_on` / `_et_exclude_from` mit IDs wie `singular:post_type:page:id:1053`. Die Vorlagenzuordnung ist `_et_template` (mehrfach) am `et_theme_builder`-Post; Vorlagen-Titel der Standardvorlage ist übersetzt („Standard-Website-Template“).
 8. TB-Layouts heißen nach dem Anlegen alle „Theme Builder Layout“ mit Slug `theme-builder-layout` (in jedem Post-Typ gleich); erst der Titel im Builder benennt sie um. `_et_pb_post_settings_title` spiegelt den Titel.
+9. **Zeilenumbrüche in Bibliothekseinträgen:** Einträge aus dem Dialog „Zur Bibliothek hinzufügen“ haben zwischen den Blöcken `\r\n` (1054–1056, 1058; der Browser normalisiert Formularfelder beim Senden an `divi-library/create-item`), Seiten und TB-Layouts `\n`. Der Builder schreibt globale Instanzen mit `\n`. `LibraryContent::load()` vereinheitlicht deshalb Zeilenumbrüche im Leerraum zwischen Blöcken, bevor Inhalte aus der Bibliothek übernommen werden; damit entstehen Instanzen byte-genau wie in `page--globale-instanzen.html`.
 
 ## Wirkung auf die Live-Site
 
diff --git a/tests/Unit/Integrations/Divi/BlockTree/BlockTest.php b/tests/Unit/Integrations/Divi/BlockTree/BlockTest.php
index ed2fffc..0c1605e 100644
--- a/tests/Unit/Integrations/Divi/BlockTree/BlockTest.php
+++ b/tests/Unit/Integrations/Divi/BlockTree/BlockTest.php
@@ -7,6 +7,7 @@ namespace LIT\MCP\Tests\Unit\Integrations\Divi\BlockTree;
 use InvalidArgumentException;
 use LIT\MCP\Integrations\Divi\BlockTree\Block;
 use LIT\MCP\Integrations\Divi\BlockTree\Parser;
+use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
 use LogicException;
 use PHPUnit\Framework\TestCase;
 use stdClass;
@@ -74,4 +75,31 @@ final class BlockTest extends TestCase
         self::assertEquals($block->attrs()['localAttrs'], $copy->attrs()['localAttrs']);
         self::assertNotSame($block->attrs()['nested']['obj'], $copy->attrs()['nested']['obj']);
     }
+
+    public function testCopyAsRegeneratesTheDelimitersAndKeepsChildrenAndText(): void
+    {
+        $document = (new Parser())->parse("<!-- wp:divi/row {\"a\":1} -->\n<!-- wp:divi/column /-->\n<!-- /wp:divi/row -->");
+        $row = $document->children()[0];
+
+        $copy = $row->copyAs('divi/global-layout', ['globalModule' => '5', 'blockName' => 'divi/row']);
+
+        self::assertSame(
+            "<!-- wp:divi/global-layout {\"globalModule\":\"5\",\"blockName\":\"divi/row\"} -->\n<!-- wp:divi/column /-->\n"
+                . '<!-- /wp:divi/global-layout -->',
+            Serializer::block($copy)
+        );
+        self::assertTrue($copy->isOpaque());
+        self::assertSame(
+            "<!-- wp:divi/row {\"a\":1} -->\n<!-- wp:divi/column /-->\n<!-- /wp:divi/row -->",
+            Serializer::block($row)
+        );
+        self::assertFalse($row->copyAs('divi/row', [])->isOpaque());
+    }
+
+    public function testCopyAsRefusesInvalidNames(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        Block::create('divi/text')->copyAs('Divi Text', []);
+    }
 }
diff --git a/tests/Unit/Integrations/Divi/BlockTree/ContainerTest.php b/tests/Unit/Integrations/Divi/BlockTree/ContainerTest.php
index 8fd85d9..13aecc8 100644
--- a/tests/Unit/Integrations/Divi/BlockTree/ContainerTest.php
+++ b/tests/Unit/Integrations/Divi/BlockTree/ContainerTest.php
@@ -6,6 +6,7 @@ namespace LIT\MCP\Tests\Unit\Integrations\Divi\BlockTree;
 
 use LIT\MCP\Integrations\Divi\BlockTree\Block;
 use LIT\MCP\Integrations\Divi\BlockTree\Parser;
+use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
 use LogicException;
 use PHPUnit\Framework\TestCase;
 
@@ -51,4 +52,52 @@ final class ContainerTest extends TestCase
         $this->expectException(LogicException::class);
         $void->append('text');
     }
+
+    public function testReplaceChildKeepsTheTextAround(): void
+    {
+        $document = (new Parser())->parse("A<!-- wp:divi/text /-->B");
+        $new = Block::create('divi/button');
+
+        $document->replaceChild($document->children()[0], $new);
+
+        self::assertSame('A<!-- wp:divi/button --><!-- /wp:divi/button -->B', Serializer::document($document));
+    }
+
+    public function testUnifyLineBreaksOnlyTouchesWhitespaceBetweenBlocks(): void
+    {
+        $document = (new Parser())->parse(
+            "<!-- wp:divi/section -->\r\n<!-- wp:divi/row -->\r\n<!-- /wp:divi/row -->\r\n<!-- /wp:divi/section -->x\r\ny"
+        );
+
+        $document->unifyLineBreaks();
+
+        self::assertSame(
+            "<!-- wp:divi/section -->\n<!-- wp:divi/row -->\n<!-- /wp:divi/row -->\n<!-- /wp:divi/section -->x\r\ny",
+            Serializer::document($document)
+        );
+    }
+
+    /** Global instances stay opaque: their bytes are Divi's, even the whitespace inside. */
+    public function testUnifyLineBreaksLeavesOpaqueBlocksAlone(): void
+    {
+        $markup = "<!-- wp:divi/global-layout {\"globalModule\":\"5\"} -->\r\n<!-- wp:divi/text /-->\r\n"
+            . "<!-- /wp:divi/global-layout -->\r\n";
+        $document = (new Parser())->parse($markup);
+
+        $document->unifyLineBreaks();
+
+        self::assertSame(substr($markup, 0, -2) . "\n", Serializer::document($document));
+    }
+
+    public function testReplaceChildRefusesOnAnOpaqueBlock(): void
+    {
+        $document = (new Parser())->parse(
+            '<!-- wp:divi/global-layout {"globalModule":"5"} --><!-- wp:divi/text /--><!-- /wp:divi/global-layout -->'
+        );
+        $instance = $document->children()[0];
+
+        $this->expectException(LogicException::class);
+
+        $instance->replaceChild($instance->children()[0], Block::create('divi/button'));
+    }
 }
diff --git a/tests/Unit/Integrations/Divi/BlockTree/GlobalInstanceTest.php b/tests/Unit/Integrations/Divi/BlockTree/GlobalInstanceTest.php
new file mode 100644
index 0000000..5c4676e
--- /dev/null
+++ b/tests/Unit/Integrations/Divi/BlockTree/GlobalInstanceTest.php
@@ -0,0 +1,106 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Tests\Unit\Integrations\Divi\BlockTree;
+
+use LIT\MCP\Integrations\Divi\BlockTree\Block;
+use LIT\MCP\Integrations\Divi\BlockTree\GlobalInstance;
+use LIT\MCP\Integrations\Divi\BlockTree\LibraryContent;
+use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
+use LIT\MCP\Integrations\Divi\BlockTree\Parser;
+use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
+use LIT\MCP\Tests\Support\DiviFixtures;
+use PHPUnit\Framework\TestCase;
+
+final class GlobalInstanceTest extends TestCase
+{
+    private static function libraryRoot(string $file): Block
+    {
+        return LibraryContent::roots(LibraryContent::load(new Parser(), DiviFixtures::markup('stage3/' . $file)))[0];
+    }
+
+    private static function pageIndex(): NodeIndex
+    {
+        return NodeIndex::build((new Parser())->parse(DiviFixtures::markup('stage3/page--globale-instanzen.html')));
+    }
+
+    /** @return array<string, array{string, int, string}> */
+    public static function instances(): array
+    {
+        return [
+            'global section' => ['library-global--globaler-abschnitt.html', 1058, '<!-- /wp:divi/global-layout -->'],
+            'global module (void)' => ['library-global--globales-modul.html', 1059, '/-->'],
+        ];
+    }
+
+    /** @dataProvider instances */
+    public function testInstanceMatchesTheVisualBuilderByteForByte(string $file, int $id, string $end): void
+    {
+        $page = DiviFixtures::markup('stage3/page--globale-instanzen.html');
+        $start = (int) strpos($page, '<!-- wp:divi/global-layout {"globalModule":"' . $id . '"');
+        $expected = substr($page, $start, (int) strpos($page, $end, $start) + strlen($end) - $start);
+
+        $instance = GlobalInstance::of(self::libraryRoot($file), $id);
+
+        self::assertSame($expected, Serializer::block($instance));
+        self::assertTrue($instance->isOpaque());
+        self::assertTrue($instance->isGlobal());
+    }
+
+    public function testOfLeavesTheLibraryRootUnchanged(): void
+    {
+        $root = self::libraryRoot('library-global--globaler-abschnitt.html');
+        $before = Serializer::block($root);
+
+        GlobalInstance::of($root, 1058);
+
+        self::assertSame($before, Serializer::block($root));
+    }
+
+    public function testEffectiveNameOfAnInstanceIsItsRootType(): void
+    {
+        $index = self::pageIndex();
+
+        self::assertSame('divi/section', GlobalInstance::effectiveName($index->find('g0')));
+        self::assertSame('divi/text', GlobalInstance::effectiveName($index->find('s0.r0.c0.g0')));
+        self::assertSame('divi/section', GlobalInstance::effectiveName($index->find('s0')));
+    }
+
+    public function testDeglobalizeRestoresTheLibraryRoot(): void
+    {
+        $root = self::libraryRoot('library-global--globaler-abschnitt.html');
+
+        $plain = GlobalInstance::deglobalize(self::pageIndex()->find('g0')->copy());
+
+        self::assertSame('divi/section', $plain->name());
+        self::assertFalse($plain->isOpaque());
+        self::assertEquals($root->attrs(), $plain->attrs());
+        self::assertSame(
+            array_map([Serializer::class, 'block'], $root->children()),
+            array_map([Serializer::class, 'block'], $plain->children())
+        );
+        self::assertStringNotContainsString('globalParent', Serializer::block($plain));
+    }
+
+    public function testDeglobalizeReachesNestedInstances(): void
+    {
+        $section = GlobalInstance::deglobalize(self::pageIndex()->find('s0')->copy());
+
+        $markup = Serializer::block($section);
+        self::assertStringNotContainsString('global-layout', $markup);
+        self::assertStringContainsString('<!-- wp:divi/text {"builderVersion":"5.2.1","content":', $markup);
+    }
+
+    /** Stored content is not trusted: an instance with an unusable blockName stays an opaque instance. */
+    public function testDeglobalizeKeepsAnInstanceWithAnInvalidBlockName(): void
+    {
+        $markup = '<!-- wp:divi/global-layout {"globalModule":"5","blockName":"Divi Text"} /-->';
+        $instance = (new Parser())->parse($markup)->children()[0];
+
+        $result = GlobalInstance::deglobalize($instance);
+
+        self::assertSame($instance, $result);
+        self::assertSame($markup, Serializer::block($result));
+    }
+}
diff --git a/tests/Unit/Integrations/Divi/BlockTree/LibraryContentTest.php b/tests/Unit/Integrations/Divi/BlockTree/LibraryContentTest.php
new file mode 100644
index 0000000..ccb8996
--- /dev/null
+++ b/tests/Unit/Integrations/Divi/BlockTree/LibraryContentTest.php
@@ -0,0 +1,103 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Tests\Unit\Integrations\Divi\BlockTree;
+
+use LIT\MCP\Integrations\Divi\BlockTree\Block;
+use LIT\MCP\Integrations\Divi\BlockTree\GlobalInstance;
+use LIT\MCP\Integrations\Divi\BlockTree\LibraryContent;
+use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
+use LIT\MCP\Integrations\Divi\BlockTree\Parser;
+use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
+use LIT\MCP\Tests\Support\DiviFixtures;
+use PHPUnit\Framework\TestCase;
+
+final class LibraryContentTest extends TestCase
+{
+    /** @return array<string, array{string, string}> */
+    public static function savedNodes(): array
+    {
+        return [
+            'section' => ['s1', 'library--library-abschnitt.html'],
+            'row' => ['s1.r0', 'library--library-zeile.html'],
+            'module' => ['s1.r0.c0.m0', 'library--library-modul.html'],
+        ];
+    }
+
+    /**
+     * The builder's "add to library" wraps the node in divi/placeholder (F4); the fixtures only
+     * differ by the CRLF of the form upload (finding 9).
+     *
+     * @dataProvider savedNodes
+     */
+    public function testWrapMatchesTheBuilderEntry(string $id, string $file): void
+    {
+        $index = NodeIndex::build((new Parser())->parse(DiviFixtures::markup('stage3/page--globale-instanzen.html')));
+
+        self::assertSame(
+            str_replace("\r\n", "\n", DiviFixtures::markup('stage3/' . $file)),
+            LibraryContent::wrap($index->find($id))
+        );
+    }
+
+    public function testLoadUnifiesLineBreaksAndRootsSkipThePlaceholder(): void
+    {
+        $document = LibraryContent::load(new Parser(), DiviFixtures::markup('stage3/library--layout-ganze-seite.html'));
+
+        self::assertStringNotContainsString("\r", Serializer::document($document));
+        self::assertSame(
+            ['divi/section', 'divi/section', 'divi/section'],
+            array_map(static fn (Block $block): string => $block->name(), LibraryContent::roots($document))
+        );
+        self::assertSame(
+            ['divi/text'],
+            array_map(
+                static fn (Block $block): string => $block->name(),
+                LibraryContent::roots((new Parser())->parse('<!-- wp:divi/text /-->'))
+            )
+        );
+    }
+
+    public function testContainsGlobal(): void
+    {
+        $index = NodeIndex::build((new Parser())->parse(DiviFixtures::markup('stage3/page--globale-instanzen.html')));
+
+        self::assertTrue(LibraryContent::containsGlobal($index->find('s0')));
+        self::assertFalse(LibraryContent::containsGlobal($index->find('s1')));
+    }
+
+    public function testShapeViolations(): void
+    {
+        $section = Block::create('divi/section');
+        $row = Block::create('divi/row');
+        $instance = GlobalInstance::of(Block::create('divi/text'), 9);
+        $withInstance = Block::create('divi/section', [], [Block::create('divi/row', [], [
+            Block::create('divi/column', [], [$instance]),
+        ])]);
+
+        self::assertNull(LibraryContent::shapeViolation([$section], [$section], 'section', false));
+        self::assertStringContainsString(
+            'nicht leer',
+            (string) LibraryContent::shapeViolation([$section], [], 'section', false)
+        );
+        self::assertStringContainsString(
+            'genau ein divi/section',
+            (string) LibraryContent::shapeViolation([$section], [$section, $section], 'section', false)
+        );
+        self::assertStringContainsString(
+            'genau ein divi/section',
+            (string) LibraryContent::shapeViolation([$section], [$row], null, false)
+        );
+        self::assertNull(LibraryContent::shapeViolation([$section, $section], [$section], 'layout', false));
+        self::assertStringContainsString(
+            'nur Abschnitte',
+            (string) LibraryContent::shapeViolation([$section, $section], [$section, $row], 'layout', false)
+        );
+        self::assertNull(LibraryContent::shapeViolation([$section], [$withInstance], 'section', false));
+        self::assertStringContainsString(
+            'keine globalen Module',
+            (string) LibraryContent::shapeViolation([$section], [$withInstance], 'section', true)
+        );
+    }
+}
diff --git a/tests/Unit/Integrations/Divi/Compose/TreeEditorTest.php b/tests/Unit/Integrations/Divi/Compose/TreeEditorTest.php
index c0da09e..ba38032 100644
--- a/tests/Unit/Integrations/Divi/Compose/TreeEditorTest.php
+++ b/tests/Unit/Integrations/Divi/Compose/TreeEditorTest.php
@@ -6,6 +6,7 @@ namespace LIT\MCP\Tests\Unit\Integrations\Divi\Compose;
 
 use LIT\MCP\Integrations\Divi\BlockTree\Block;
 use LIT\MCP\Integrations\Divi\BlockTree\Document;
+use LIT\MCP\Integrations\Divi\BlockTree\GlobalInstance;
 use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
 use LIT\MCP\Integrations\Divi\BlockTree\Parser;
 use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
@@ -201,4 +202,22 @@ final class TreeEditorTest extends TestCase
         self::assertStringContainsString('Spezialabschnitte', (string) $editor->insert($editor->position($index, ['parent' => 's0']), [Block::create('divi/row')]));
         self::assertNull($editor->insert($editor->position($index, ['parent' => 's0.c0']), [$text]));
     }
+
+    /** A global instance counts as its root type: a section instance at the top, a module instance in a column. */
+    public function testGlobalInstancesFollowTheRulesOfTheirRootType(): void
+    {
+        $document = $this->document('stage3/page--globale-instanzen.html');
+        $index = NodeIndex::build($document);
+        $editor = new TreeEditor(ComposeFixture::rules());
+
+        self::assertNull($editor->move($index, $index->find('g0'), $editor->position($index, ['after' => 's1'])));
+
+        $index = NodeIndex::build($document);
+        $module = GlobalInstance::of(Block::create('divi/text'), 1059);
+        self::assertNull($editor->insert($editor->position($index, ['parent' => 's1.r0.c0']), [$module]));
+        self::assertSame(
+            'auf oberster Ebene sind nur Abschnitte (section) erlaubt',
+            $editor->insert($editor->position($index, []), [GlobalInstance::of(Block::create('divi/text'), 1059)])
+        );
+    }
 }