diff --git a/packages/editor/src/extensions/global-content.spec.ts b/packages/editor/src/extensions/global-content.spec.ts
new file mode 100644
index 0000000000..7d4c258e10
--- /dev/null
+++ b/packages/editor/src/extensions/global-content.spec.ts
@@ -0,0 +1,237 @@
+import type { JSONContent } from '@tiptap/core';
+import { Editor } from '@tiptap/core';
+import { TextSelection } from '@tiptap/pm/state';
+import { afterEach, describe, expect, it } from 'vitest';
+import { StarterKit } from './index';
+
+vi.mock('@/actions/ai', () => ({
+  uploadImageViaAI: vi.fn(),
+}));
+
+describe('GlobalContent Node', () => {
+  let editor: Editor | null = null;
+
+  afterEach(() => {
+    editor?.destroy();
+    editor = null;
+  });
+
+  function createEditor(content: JSONContent) {
+    editor = new Editor({
+      content,
+      extensions: [StarterKit],
+    });
+    editor.view.dispatch(editor.state.tr);
+    return editor;
+  }
+
+  it('preserves globalContent when selecting all and deleting', () => {
+    const themeData = { theme: 'basic', css: 'body { color: red; }' };
+
+    const ed = createEditor({
+      type: 'doc',
+      content: [
+        {
+          type: 'globalContent',
+          attrs: { data: themeData },
+        },
+        {
+          type: 'paragraph',
+          content: [{ type: 'text', text: 'Hello world' }],
+        },
+      ],
+    });
+
+    const { state } = ed;
+    const allSelection = TextSelection.create(
+      state.doc,
+      0,
+      state.doc.content.size,
+    );
+    ed.view.dispatch(state.tr.setSelection(allSelection).deleteSelection());
+
+    const json = ed.getJSON();
+    const globalContentNodes = json.content!.filter(
+      (n) => n.type === 'globalContent',
+    );
+
+    expect(globalContentNodes).toHaveLength(1);
+    expect(globalContentNodes[0].attrs!.data).toEqual(themeData);
+  });
+
+  it('preserves globalContent data after multiple select-all + delete cycles', () => {
+    const themeData = { theme: 'minimal', styles: [{ id: 'test' }] };
+
+    const ed = createEditor({
+      type: 'doc',
+      content: [
+        {
+          type: 'globalContent',
+          attrs: { data: themeData },
+        },
+        {
+          type: 'paragraph',
+          content: [{ type: 'text', text: 'First content' }],
+        },
+      ],
+    });
+
+    for (let i = 0; i < 3; i++) {
+      const { state } = ed;
+      const allSelection = TextSelection.create(
+        state.doc,
+        0,
+        state.doc.content.size,
+      );
+      ed.view.dispatch(state.tr.setSelection(allSelection).deleteSelection());
+    }
+
+    const json = ed.getJSON();
+    const globalContentNodes = json.content!.filter(
+      (n) => n.type === 'globalContent',
+    );
+
+    expect(globalContentNodes).toHaveLength(1);
+    expect(globalContentNodes[0].attrs!.data).toEqual(themeData);
+  });
+
+  it('does not duplicate globalContent when it already exists', () => {
+    const ed = createEditor({
+      type: 'doc',
+      content: [
+        {
+          type: 'globalContent',
+          attrs: { data: { theme: 'basic' } },
+        },
+        {
+          type: 'paragraph',
+          content: [{ type: 'text', text: 'Hello' }],
+        },
+      ],
+    });
+
+    ed.commands.insertContent({
+      type: 'paragraph',
+      content: [{ type: 'text', text: 'New paragraph' }],
+    });
+
+    const json = ed.getJSON();
+    const globalContentNodes = json.content!.filter(
+      (n) => n.type === 'globalContent',
+    );
+
+    expect(globalContentNodes).toHaveLength(1);
+  });
+
+  it('restores globalContent at position 0 when deleted via replaceWith', () => {
+    const themeData = { theme: 'basic', css: '.test {}' };
+
+    const ed = createEditor({
+      type: 'doc',
+      content: [
+        {
+          type: 'globalContent',
+          attrs: { data: themeData },
+        },
+        {
+          type: 'container',
+          content: [
+            {
+              type: 'paragraph',
+              content: [{ type: 'text', text: 'Content' }],
+            },
+          ],
+        },
+      ],
+    });
+
+    const { state } = ed;
+    const { schema } = state;
+    const newParagraph = schema.nodes.paragraph.create(
+      null,
+      schema.text('Replaced content'),
+    );
+    const tr = state.tr.replaceWith(0, state.doc.content.size, newParagraph);
+    ed.view.dispatch(tr);
+
+    const json = ed.getJSON();
+    const globalContentNodes = json.content!.filter(
+      (n) => n.type === 'globalContent',
+    );
+
+    expect(globalContentNodes).toHaveLength(1);
+    expect(globalContentNodes[0].attrs!.data).toEqual(themeData);
+  });
+
+  it('does not restore globalContent if it was never present', () => {
+    const ed = createEditor({
+      type: 'doc',
+      content: [
+        {
+          type: 'paragraph',
+          content: [{ type: 'text', text: 'No global content here' }],
+        },
+      ],
+    });
+
+    ed.commands.clearContent();
+
+    const json = ed.getJSON();
+    const globalContentNodes = (json.content ?? []).filter(
+      (n) => n.type === 'globalContent',
+    );
+
+    expect(globalContentNodes).toHaveLength(0);
+  });
+
+  it('setGlobalContent command creates globalContent if not present', () => {
+    const ed = createEditor({
+      type: 'doc',
+      content: [
+        {
+          type: 'paragraph',
+          content: [{ type: 'text', text: 'Hello' }],
+        },
+      ],
+    });
+
+    ed.commands.setGlobalContent('theme', 'basic');
+
+    const json = ed.getJSON();
+    const globalContentNodes = json.content!.filter(
+      (n) => n.type === 'globalContent',
+    );
+
+    expect(globalContentNodes).toHaveLength(1);
+    expect(globalContentNodes[0].attrs!.data.theme).toBe('basic');
+  });
+
+  it('setGlobalContent command updates existing globalContent data', () => {
+    const ed = createEditor({
+      type: 'doc',
+      content: [
+        {
+          type: 'globalContent',
+          attrs: { data: { theme: 'basic' } },
+        },
+        {
+          type: 'paragraph',
+          content: [{ type: 'text', text: 'Hello' }],
+        },
+      ],
+    });
+
+    ed.commands.setGlobalContent('css', 'body { color: blue; }');
+
+    const json = ed.getJSON();
+    const globalContentNodes = json.content!.filter(
+      (n) => n.type === 'globalContent',
+    );
+
+    expect(globalContentNodes).toHaveLength(1);
+    expect(globalContentNodes[0].attrs!.data).toEqual({
+      theme: 'basic',
+      css: 'body { color: blue; }',
+    });
+  });
+});
diff --git a/packages/editor/src/extensions/global-content.ts b/packages/editor/src/extensions/global-content.ts
index a6781e10a2..23ab797b55 100644
--- a/packages/editor/src/extensions/global-content.ts
+++ b/packages/editor/src/extensions/global-content.ts
@@ -1,4 +1,7 @@
 import { type Editor, mergeAttributes, Node } from '@tiptap/core';
+import type { Node as PmNode } from '@tiptap/pm/model';
+import { Plugin, PluginKey } from '@tiptap/pm/state';
+import { hasCollaborationExtension } from '../utils/is-collaboration';
 
 const GLOBAL_CONTENT_NODE_TYPE = 'globalContent' as const;
 
@@ -136,4 +139,91 @@ export const GlobalContent = Node.create<GlobalContentOptions>({
         },
     };
   },
+
+  addProseMirrorPlugins() {
+    const nodeType = this.type;
+    const isCollaborative = hasCollaborationExtension(
+      this.editor.extensionManager.extensions,
+    );
+
+    return [
+      new Plugin({
+        key: new PluginKey('globalContentProtector'),
+
+        view: isCollaborative
+          ? undefined
+          : (editorView) => {
+              let lastGlobalContentNode: PmNode | null = null;
+
+              const findAndCache = (doc: PmNode) => {
+                let found: PmNode | null = null;
+                doc.descendants((node) => {
+                  if (node.type.name === GLOBAL_CONTENT_NODE_TYPE) {
+                    found = node;
+                    return false;
+                  }
+                });
+                if (found) {
+                  lastGlobalContentNode = found;
+                }
+                return found;
+              };
+
+              findAndCache(editorView.state.doc);
+
+              return {
+                update(view) {
+                  const doc = view.state.doc;
+                  const current = findAndCache(doc);
+
+                  if (!current && lastGlobalContentNode) {
+                    const restoredNode = nodeType.create(
+                      lastGlobalContentNode.attrs,
+                    );
+                    const tr = view.state.tr;
+                    tr.insert(0, restoredNode);
+                    tr.setMeta('addToHistory', false);
+                    cachedGlobalPosition = 0;
+                    view.dispatch(tr);
+                  }
+                },
+              };
+            },
+
+        appendTransaction(_transactions, oldState, newState) {
+          if (findGlobalContentPositions(newState.doc).length > 0) {
+            return null;
+          }
+
+          // Skip no-op transactions from collaboration extensions (e.g.
+          // Liveblocks stabilisation rounds) to avoid restoring the node
+          // before the real document content arrives — same guard used by
+          // the containerEnforcer plugin.
+          if (newState.doc.eq(oldState.doc)) {
+            return null;
+          }
+
+          let previousNode: PmNode | null = null;
+          oldState.doc.descendants((node) => {
+            if (node.type.name === GLOBAL_CONTENT_NODE_TYPE) {
+              previousNode = node;
+              return false;
+            }
+          });
+
+          if (!previousNode) {
+            return null;
+          }
+
+          const restoredNode = nodeType.create((previousNode as PmNode).attrs);
+          const tr = newState.tr;
+          tr.insert(0, restoredNode);
+          tr.setMeta('addToHistory', false);
+          cachedGlobalPosition = 0;
+
+          return tr;
+        },
+      }),
+    ];
+  },
 });