diff --git a/apps/client/src/features/editor/components/html-embed/html-embed-view.module.css b/apps/client/src/features/editor/components/html-embed/html-embed-view.module.css
new file mode 100644
index 00000000..75304685
--- /dev/null
+++ b/apps/client/src/features/editor/components/html-embed/html-embed-view.module.css
@@ -0,0 +1,43 @@
+.htmlEmbedNodeView {
+  position: relative;
+}
+
+/* The container the raw source is injected into. */
+.htmlEmbedContent {
+  width: 100%;
+}
+
+/* Edit affordance overlay, only shown while editing the document. */
+.htmlEmbedToolbar {
+  position: absolute;
+  top: 4px;
+  right: 4px;
+  z-index: 2;
+  opacity: 0;
+  transition: opacity 0.15s ease;
+}
+
+.htmlEmbedNodeView:hover .htmlEmbedToolbar {
+  opacity: 1;
+}
+
+/* Placeholder card shown when the source is empty (edit mode only). */
+.htmlEmbedPlaceholder {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 8px;
+  padding: 16px;
+  border: 1px dashed var(--mantine-color-gray-4);
+  border-radius: 8px;
+  color: var(--mantine-color-dimmed);
+
+  @mixin dark {
+    border-color: var(--mantine-color-dark-3);
+  }
+}
+
+.htmlEmbedSelected {
+  outline: 2px solid var(--mantine-color-blue-5);
+  border-radius: 8px;
+}
diff --git a/apps/client/src/features/editor/components/html-embed/html-embed-view.tsx b/apps/client/src/features/editor/components/html-embed/html-embed-view.tsx
new file mode 100644
index 00000000..a46b383a
--- /dev/null
+++ b/apps/client/src/features/editor/components/html-embed/html-embed-view.tsx
@@ -0,0 +1,185 @@
+import { NodeViewProps, NodeViewWrapper } from "@tiptap/react";
+import React, { useCallback, useEffect, useRef, useState } from "react";
+import clsx from "clsx";
+import {
+  ActionIcon,
+  Button,
+  Group,
+  Modal,
+  Text,
+  Textarea,
+} from "@mantine/core";
+import { IconCode, IconEdit } from "@tabler/icons-react";
+import { useTranslation } from "react-i18next";
+import { useAtomValue } from "jotai";
+import useUserRole from "@/hooks/use-user-role.tsx";
+import { workspaceAtom } from "@/features/user/atoms/current-user-atom.ts";
+import classes from "./html-embed-view.module.css";
+
+/**
+ * Inject raw HTML (including <script> tags) into `container`, executing any
+ * scripts.
+ *
+ * Setting `innerHTML` does NOT run inline or external <script> tags the browser
+ * parses that way: the HTML spec marks scripts inserted via innerHTML as
+ * "already started" so they never execute. To get the tracker/analytics
+ * use-case working we walk the freshly-parsed scripts and replace each with a
+ * brand-new <script> element copying its attributes and inline code. A
+ * programmatically created+inserted <script> DOES execute, so this restores
+ * normal script behaviour in the wiki origin (Variant C).
+ */
+function renderRawHtml(container: HTMLElement, source: string) {
+  // Clear any previous render (re-render on source change).
+  container.innerHTML = "";
+  if (!source) return;
+
+  container.innerHTML = source;
+
+  const scripts = Array.from(container.querySelectorAll("script"));
+  for (const oldScript of scripts) {
+    const newScript = document.createElement("script");
+    // Copy every attribute (src, type, async, defer, data-*, etc.).
+    for (const attr of Array.from(oldScript.attributes)) {
+      newScript.setAttribute(attr.name, attr.value);
+    }
+    // Copy inline code.
+    newScript.text = oldScript.textContent ?? "";
+    // Replacing the node in place triggers execution.
+    oldScript.parentNode?.replaceChild(newScript, oldScript);
+  }
+}
+
+export default function HtmlEmbedView(props: NodeViewProps) {
+  const { t } = useTranslation();
+  const { node, selected, updateAttributes, editor } = props;
+  const { source } = node.attrs as { source: string };
+  const { isAdmin } = useUserRole();
+
+  // Defense in depth: only execute the raw HTML/JS when the workspace HTML embed
+  // feature toggle is ON. When OFF (the default), we render a neutral disabled
+  // placeholder and inject nothing — so turning the feature off neutralizes
+  // existing embeds at render time as well as on the next server-side save.
+  const workspace = useAtomValue(workspaceAtom);
+  const htmlEmbedEnabled = workspace?.settings?.htmlEmbed === true;
+
+  // Execution policy split by editor mode:
+  //  - READ-ONLY / public-share view: the SERVER already decided whether to
+  //    include the embed (it strips htmlEmbed from shared content when the
+  //    workspace toggle is OFF). An anonymous viewer has no workspace and thus
+  //    reads `htmlEmbedEnabled` as false, so we must NOT gate execution on it
+  //    here — we execute exactly the `source` the server chose to serve.
+  //  - EDITABLE editor (admin authoring): keep gating on the per-workspace
+  //    toggle so an admin sees the inert placeholder when the feature is OFF.
+  const shouldExecute = !editor.isEditable || htmlEmbedEnabled;
+
+  const contentRef = useRef<HTMLDivElement | null>(null);
+  const [modalOpen, setModalOpen] = useState(false);
+  const [draft, setDraft] = useState<string>(source || "");
+
+  // (Re)render the raw source whenever it changes. This runs in BOTH the
+  // editable editor and the read-only / public-share editor (same NodeView),
+  // so trackers fire for readers too — that is the intended behaviour. When the
+  // feature toggle is OFF we clear the container and inject/execute nothing.
+  useEffect(() => {
+    if (!contentRef.current) return;
+    if (shouldExecute) {
+      renderRawHtml(contentRef.current, source || "");
+    } else {
+      contentRef.current.innerHTML = "";
+    }
+  }, [source, shouldExecute]);
+
+  const openEditor = useCallback(() => {
+    setDraft(source || "");
+    setModalOpen(true);
+  }, [source]);
+
+  const onSave = useCallback(() => {
+    if (editor.isEditable) {
+      updateAttributes({ source: draft });
+    }
+    setModalOpen(false);
+  }, [draft, editor.isEditable, updateAttributes]);
+
+  // The edit affordance is only meaningful in edit mode, is restricted to admins
+  // (the server strips the node for non-admins anyway), and is offered only when
+  // the workspace feature toggle is ON.
+  const canEdit = editor.isEditable && isAdmin && htmlEmbedEnabled;
+
+  return (
+    <NodeViewWrapper
+      data-drag-handle
+      className={clsx(classes.htmlEmbedNodeView, {
+        [classes.htmlEmbedSelected]: selected,
+      })}
+    >
+      {canEdit && (
+        <div className={classes.htmlEmbedToolbar}>
+          <ActionIcon
+            variant="default"
+            size="sm"
+            aria-label={t("Edit HTML embed")}
+            onClick={openEditor}
+          >
+            <IconEdit size={16} />
+          </ActionIcon>
+        </div>
+      )}
+
+      {!shouldExecute ? (
+        // Feature disabled for this workspace AND we're in the editable editor:
+        // never inject/execute the source. Show a neutral placeholder so an
+        // existing embed is visibly inert for the authoring admin. Read-only /
+        // share viewers never hit this branch (`shouldExecute` is always true
+        // there) — they execute exactly the source the server chose to serve.
+        <div className={classes.htmlEmbedPlaceholder}>
+          <IconCode size={18} />
+          <Text size="sm">
+            {t("HTML embed is disabled in this workspace")}
+          </Text>
+        </div>
+      ) : source ? (
+        // Raw HTML/CSS/JS rendered into the wiki origin. Scripts are re-created
+        // in renderRawHtml so they execute.
+        <div ref={contentRef} className={classes.htmlEmbedContent} />
+      ) : canEdit ? (
+        <div className={classes.htmlEmbedPlaceholder} onClick={openEditor}>
+          <IconCode size={18} />
+          <Text size="sm">{t("Click to add HTML / CSS / JS")}</Text>
+        </div>
+      ) : (
+        // Empty source, non-editor: render nothing visible.
+        <div ref={contentRef} className={classes.htmlEmbedContent} />
+      )}
+
+      <Modal
+        opened={modalOpen}
+        onClose={() => setModalOpen(false)}
+        title={t("Edit HTML embed")}
+        size="lg"
+      >
+        <Text size="xs" c="dimmed" mb="xs">
+          {t(
+            "This HTML/CSS/JS runs in the page origin for everyone who views it. Admins only.",
+          )}
+        </Text>
+        <Textarea
+          autosize
+          minRows={10}
+          maxRows={24}
+          value={draft}
+          onChange={(e) => setDraft(e.currentTarget.value)}
+          placeholder={t("<script>...</script>")}
+          styles={{ input: { fontFamily: "monospace" } }}
+          data-autofocus
+        />
+        <Group justify="flex-end" mt="md">
+          <Button variant="default" onClick={() => setModalOpen(false)}>
+            {t("Cancel")}
+          </Button>
+          <Button onClick={onSave}>{t("Save")}</Button>
+        </Group>
+      </Modal>
+    </NodeViewWrapper>
+  );
+}
diff --git a/apps/client/src/features/editor/components/slash-menu/menu-items.ts b/apps/client/src/features/editor/components/slash-menu/menu-items.ts
index 7f856755..bb52fbca 100644
--- a/apps/client/src/features/editor/components/slash-menu/menu-items.ts
+++ b/apps/client/src/features/editor/components/slash-menu/menu-items.ts
@@ -587,6 +587,22 @@ const CommandGroups: SlashMenuGroupedItemsType = {
           .insertColumns({ layout: "five_equal" })
           .run(),
     },
+    {
+      title: "HTML embed",
+      description: "Embed raw HTML, CSS and JavaScript (admins only).",
+      searchTerms: ["html", "css", "js", "javascript", "script", "tracker", "analytics", "raw", "embed"],
+      icon: IconCode,
+      adminOnly: true,
+      requiresHtmlEmbedFeature: true,
+      command: ({ editor, range }: CommandProps) => {
+        editor
+          .chain()
+          .focus()
+          .deleteRange(range)
+          .setHtmlEmbed({ source: "" })
+          .run();
+      },
+    },
     {
       title: "Iframe embed",
       description: "Embed any Iframe",
@@ -744,6 +760,43 @@ const CommandGroups: SlashMenuGroupedItemsType = {
   ],
 };
 
+/**
+ * Read whether the current user is a workspace admin/owner from the persisted
+ * `currentUser` (the same payload `currentUserAtom` stores via localStorage).
+ * Used to hide admin-only slash items (e.g. raw HTML embed). This is a UI gate
+ * only; the server independently strips admin-only nodes from non-admin writes.
+ */
+function isCurrentUserAdmin(): boolean {
+  try {
+    const raw = localStorage.getItem("currentUser");
+    if (!raw) return false;
+    const parsed = JSON.parse(raw);
+    const role = parsed?.user?.role;
+    return role === "owner" || role === "admin";
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Read the workspace-level HTML embed feature toggle from the persisted
+ * `currentUser` payload (the same localStorage entry `currentUserAtom` writes,
+ * carrying `workspace.settings`). ABSENT/false => OFF (the default). The slash
+ * `getSuggestionItems` is a plain function (no React/atom context), so we read
+ * the persisted state the same way `isCurrentUserAdmin()` does. UI gate only;
+ * the server independently strips htmlEmbed from every non-allowed write.
+ */
+function isHtmlEmbedFeatureEnabled(): boolean {
+  try {
+    const raw = localStorage.getItem("currentUser");
+    if (!raw) return false;
+    const parsed = JSON.parse(raw);
+    return parsed?.workspace?.settings?.htmlEmbed === true;
+  } catch {
+    return false;
+  }
+}
+
 export const getSuggestionItems = ({
   query,
   excludeItems,
@@ -753,6 +806,8 @@ export const getSuggestionItems = ({
 }): SlashMenuGroupedItemsType => {
   const search = query.toLowerCase();
   const filteredGroups: SlashMenuGroupedItemsType = {};
+  const isAdmin = isCurrentUserAdmin();
+  const htmlEmbedFeatureEnabled = isHtmlEmbedFeatureEnabled();
 
   const fuzzyMatch = (query: string, target: string) => {
     let queryIndex = 0;
@@ -767,6 +822,11 @@ export const getSuggestionItems = ({
   for (const [group, items] of Object.entries(CommandGroups)) {
     const filteredItems = items.filter((item) => {
       if (excludeItems?.has(item.title)) return false;
+      // Hide admin-only items (raw HTML embed) from non-admins.
+      if (item.adminOnly && !isAdmin) return false;
+      // Hide HTML-embed-gated items unless the workspace feature toggle is ON.
+      if (item.requiresHtmlEmbedFeature && !htmlEmbedFeatureEnabled)
+        return false;
       return (
         fuzzyMatch(search, item.title) ||
         item.description.toLowerCase().includes(search) ||
diff --git a/apps/client/src/features/editor/components/slash-menu/types.ts b/apps/client/src/features/editor/components/slash-menu/types.ts
index cf5bd3e4..c650b605 100644
--- a/apps/client/src/features/editor/components/slash-menu/types.ts
+++ b/apps/client/src/features/editor/components/slash-menu/types.ts
@@ -21,6 +21,14 @@ export type SlashMenuItemType = {
   searchTerms: string[];
   command: (props: CommandProps) => void;
   disable?: (editor: ReturnType<typeof useEditor>) => boolean;
+  // When true, the item is only offered to workspace admins/owners. This is a
+  // UI convenience only — the real authoring gate is enforced server-side.
+  adminOnly?: boolean;
+  // When true, the item is hidden unless the workspace HTML embed feature toggle
+  // is ON. Combined with adminOnly, the item shows only for admins in workspaces
+  // where the feature is enabled. UI gate only — the server strips htmlEmbed on
+  // every write where the toggle is OFF or the user is not an admin.
+  requiresHtmlEmbedFeature?: boolean;
 };
 
 export type SlashMenuGroupedItemsType = {
diff --git a/apps/client/src/features/editor/extensions/extensions.ts b/apps/client/src/features/editor/extensions/extensions.ts
index 87c7b9e5..edac4b26 100644
--- a/apps/client/src/features/editor/extensions/extensions.ts
+++ b/apps/client/src/features/editor/extensions/extensions.ts
@@ -41,6 +41,7 @@ import {
   Drawio,
   Excalidraw,
   Embed,
+  HtmlEmbed,
   TiptapPdf,
   PageBreak,
   SearchAndReplace,
@@ -87,6 +88,7 @@ import CodeBlockView from "@/features/editor/components/code-block/code-block-vi
 import DrawioView from "../components/drawio/drawio-view";
 import ExcalidrawView from "@/features/editor/components/excalidraw/excalidraw-view-lazy.tsx";
 import EmbedView from "@/features/editor/components/embed/embed-view.tsx";
+import HtmlEmbedView from "@/features/editor/components/html-embed/html-embed-view.tsx";
 import PdfView from "@/features/editor/components/pdf/pdf-view.tsx";
 import SubpagesView from "@/features/editor/components/subpages/subpages-view.tsx";
 import TransclusionView from "@/features/editor/components/transclusion/transclusion-view.tsx";
@@ -365,6 +367,13 @@ export const mainExtensions = [
   Embed.configure({
     view: EmbedView,
   }),
+  // Raw HTML/CSS/JS node (Variant C). The node is registered for ALL users so
+  // documents authored by admins render correctly for everyone; INSERTION is
+  // gated to admins in the slash menu, and the server strips the node from any
+  // non-admin write so a non-admin cannot persist it.
+  HtmlEmbed.configure({
+    view: HtmlEmbedView,
+  }),
   TiptapPdf.configure({
     view: PdfView,
   }),
diff --git a/apps/client/src/features/workspace/components/settings/components/html-embed-settings.tsx b/apps/client/src/features/workspace/components/settings/components/html-embed-settings.tsx
new file mode 100644
index 00000000..27a21a8e
--- /dev/null
+++ b/apps/client/src/features/workspace/components/settings/components/html-embed-settings.tsx
@@ -0,0 +1,99 @@
+import { workspaceAtom } from "@/features/user/atoms/current-user-atom.ts";
+import { useAtom } from "jotai";
+import { useState } from "react";
+import { updateWorkspace } from "@/features/workspace/services/workspace-service.ts";
+import { Switch, Stack, Paper, Group, Text, List } from "@mantine/core";
+import { notifications } from "@mantine/notifications";
+import useUserRole from "@/hooks/use-user-role.tsx";
+import { useTranslation } from "react-i18next";
+
+/**
+ * Admin toggle for the workspace HTML embed feature.
+ *
+ * SECURITY: when ON, workspace admins/owners can embed raw HTML/CSS/JS that
+ * EXECUTES in the wiki page origin for every reader (a deliberate stored-XSS
+ * surface, e.g. for analytics trackers). OFF by default. The server strips
+ * htmlEmbed nodes on every write where the toggle is OFF or the saver is not an
+ * admin, so this switch fully enables/disables the feature workspace-wide.
+ */
+export default function HtmlEmbedSettings() {
+  const { t } = useTranslation();
+  const [workspace, setWorkspace] = useAtom(workspaceAtom);
+  const { isAdmin } = useUserRole();
+
+  const [checked, setChecked] = useState<boolean>(
+    workspace?.settings?.htmlEmbed ?? false,
+  );
+  const [isLoading, setIsLoading] = useState(false);
+
+  async function handleToggle(value: boolean) {
+    setIsLoading(true);
+    const previous = checked;
+    setChecked(value); // optimistic update
+    try {
+      const updated = await updateWorkspace({ htmlEmbed: value });
+      // Force settings.htmlEmbed to the new value so the atom is consistent even
+      // if the response shape omits it.
+      setWorkspace({
+        ...updated,
+        settings: {
+          ...updated.settings,
+          htmlEmbed: value,
+        },
+      });
+      notifications.show({ message: t("Updated successfully") });
+    } catch (err) {
+      console.log(err);
+      setChecked(previous); // revert on failure
+      notifications.show({
+        message: t("Failed to update data"),
+        color: "red",
+      });
+    } finally {
+      setIsLoading(false);
+    }
+  }
+
+  return (
+    <Stack mt="sm">
+      <Group justify="space-between" align="center">
+        <Text fw={700} size="lg">
+          {t("HTML embed")}
+        </Text>
+        <Text size="xs" c="dimmed" tt="uppercase" fw={600}>
+          {t("advanced")}
+        </Text>
+      </Group>
+
+      <Paper withBorder radius="md" p="lg">
+        <Switch
+          label={t("Enable HTML embed")}
+          description={t(
+            "Allow workspace admins to insert raw HTML/CSS/JavaScript that EXECUTES in the wiki page origin for everyone who views the page (a deliberate stored-XSS surface, e.g. for analytics trackers). Off by default.",
+          )}
+          checked={checked}
+          disabled={!isAdmin || isLoading}
+          onChange={(event) => handleToggle(event.currentTarget.checked)}
+        />
+
+        <List size="xs" c="dimmed" mt="md" spacing={4}>
+          <List.Item>
+            {t(
+              "Only workspace admins/owners can insert HTML embeds. Members never can: the editor option is hidden for them and the server strips the embed on save at every write path.",
+            )}
+          </List.Item>
+          <List.Item>
+            {t(
+              "If a non-admin edits and saves a page that contains an admin's embed, that save strips the embed (fail-closed). An admin must re-add it.",
+            )}
+          </List.Item>
+          <List.Item>
+            {t(
+              "Turning this off strips existing embeds on their next save and immediately disables execution (existing embeds render as a disabled placeholder).",
+            )}
+          </List.Item>
+        </List>
+      </Paper>
+    </Stack>
+  );
+}
diff --git a/apps/client/src/features/workspace/types/workspace.types.ts b/apps/client/src/features/workspace/types/workspace.types.ts
index 53d1d5ce..4447821c 100644
--- a/apps/client/src/features/workspace/types/workspace.types.ts
+++ b/apps/client/src/features/workspace/types/workspace.types.ts
@@ -30,6 +30,9 @@ export interface IWorkspace {
   restrictApiToAdmins?: boolean;
   allowMemberTemplates?: boolean;
   isScimEnabled?: boolean;
+  // Write-only field for updateWorkspace({ htmlEmbed }). Read state lives at
+  // settings.htmlEmbed.
+  htmlEmbed?: boolean;
 }
 
 export interface IWorkspaceSettings {
@@ -37,6 +40,8 @@ export interface IWorkspaceSettings {
   sharing?: IWorkspaceSharingSettings;
   api?: IWorkspaceApiSettings;
   templates?: IWorkspaceTemplateSettings;
+  // Admin-only HTML embed feature toggle. ABSENT/false => OFF (default).
+  htmlEmbed?: boolean;
 }
 
 export interface IWorkspaceApiSettings {
diff --git a/apps/client/src/pages/settings/workspace/workspace-settings.tsx b/apps/client/src/pages/settings/workspace/workspace-settings.tsx
index bb759a9b..484ad860 100644
--- a/apps/client/src/pages/settings/workspace/workspace-settings.tsx
+++ b/apps/client/src/pages/settings/workspace/workspace-settings.tsx
@@ -1,6 +1,7 @@
 import SettingsTitle from "@/components/settings/settings-title.tsx";
 import WorkspaceNameForm from "@/features/workspace/components/settings/components/workspace-name-form";
 import WorkspaceIcon from "@/features/workspace/components/settings/components/workspace-icon.tsx";
+import HtmlEmbedSettings from "@/features/workspace/components/settings/components/html-embed-settings.tsx";
 import { useTranslation } from "react-i18next";
 import { getAppName } from "@/lib/config.ts";
 import { Helmet } from "react-helmet-async";
@@ -15,6 +16,7 @@ export default function WorkspaceSettings() {
       <SettingsTitle title={t("General")} />
       <WorkspaceIcon />
       <WorkspaceNameForm />
+      <HtmlEmbedSettings />
     </>
   );
 }
diff --git a/apps/server/src/collaboration/collaboration.handler.html-embed.spec.ts b/apps/server/src/collaboration/collaboration.handler.html-embed.spec.ts
new file mode 100644
index 00000000..23b11ba9
--- /dev/null
+++ b/apps/server/src/collaboration/collaboration.handler.html-embed.spec.ts
@@ -0,0 +1,120 @@
+import * as Y from 'yjs';
+import { TiptapTransformer } from '@hocuspocus/transformer';
+import { CollaborationHandler } from './collaboration.handler';
+import { hasHtmlEmbedNode } from '../common/helpers/prosemirror/html-embed.util';
+
+// Exercises the REAL CollaborationHandler.updatePageContent admin gate (the
+// REST/MCP/AI content-update entrypoint, used by the page update endpoint and
+// the MCP/AI agent). updatePageContent reads `user?.role` and strips htmlEmbed
+// BEFORE handing the json to withYdocConnection. We stub only
+// withYdocConnection (which would otherwise open a real hocuspocus connection):
+// the role-extraction (`user?.role`) + strip that run upstream of it are REAL
+// production code. The 'replace' branch then runs the production
+// TiptapTransformer.toYdoc on the gated json against a real Y.Doc, which we
+// decode back to JSON and assert on. This replaces the re-implemented
+// `applyAdminGate` stand-in for this entrypoint.
+
+const docWithEmbed = () => ({
+  type: 'doc',
+  content: [
+    { type: 'paragraph', content: [{ type: 'text', text: 'keep' }] },
+    {
+      type: 'columns',
+      content: [
+        {
+          type: 'column',
+          attrs: { position: 'left' },
+          content: [
+            { type: 'htmlEmbed', attrs: { source: '<script>nested</script>' } },
+            { type: 'paragraph', content: [{ type: 'text', text: 'inner' }] },
+          ],
+        },
+        {
+          type: 'column',
+          attrs: { position: 'right' },
+          content: [
+            { type: 'paragraph', content: [{ type: 'text', text: 'r' }] },
+          ],
+        },
+      ],
+    },
+    { type: 'htmlEmbed', attrs: { source: '<script>top</script>' } },
+  ],
+});
+
+/**
+ * Run the REAL updatePageContent('replace') with a stubbed withYdocConnection.
+ * The stub provides a real Y.Doc + recording fragment; the production fn calls
+ * TiptapTransformer.toYdoc(<gated json>) and applies it to the doc, so decoding
+ * the doc afterward yields exactly the gated content.
+ */
+async function gatedContentFor(
+  role: string | null | undefined,
+  featureEnabled = true,
+) {
+  // Workspace settings read used by the toggle-AND-admin gate.
+  const workspaceRepo = {
+    findById: jest.fn(async () => ({
+      id: 'ws-1',
+      settings: { htmlEmbed: featureEnabled },
+    })),
+  };
+  const handler = new CollaborationHandler(workspaceRepo as any);
+  const captureDoc = new Y.Doc();
+
+  jest
+    .spyOn(handler, 'withYdocConnection')
+    .mockImplementation(async (_hp, _name, _ctx, fn: any) => {
+      const fragment = captureDoc.getXmlFragment('default');
+      // Mirror the real Document surface the fn touches.
+      const docLike: any = {
+        getXmlFragment: () => fragment,
+      };
+      // The fn does: fragment.delete(0,len) then
+      // Y.applyUpdate(doc, encodeStateAsUpdate(toYdoc(gatedJson))). It calls
+      // Y.applyUpdate(doc, ...) — so docLike must be a real Y.Doc target.
+      fn(captureDoc);
+    });
+
+  const handlers = handler.getHandlers({} as any);
+  await handlers.updatePageContent('page-1', {
+    prosemirrorJson: docWithEmbed(),
+    operation: 'replace',
+    user: { id: 'u1', role, workspaceId: 'ws-1' } as any,
+  });
+
+  return TiptapTransformer.fromYdoc(captureDoc, 'default');
+}
+
+describe('CollaborationHandler.updatePageContent htmlEmbed admin gate (real code)', () => {
+  it('non-admin (member): every htmlEmbed (top-level + nested) stripped before the ydoc', async () => {
+    const gated = await gatedContentFor('member');
+    expect(hasHtmlEmbedNode(gated)).toBe(false);
+    // Non-embed siblings survive.
+    const json = JSON.stringify(gated);
+    expect(json).toContain('keep');
+    expect(json).toContain('inner');
+  });
+
+  it('unknown/empty role: fails closed (stripped)', async () => {
+    for (const role of [undefined, null, 'viewer'] as const) {
+      expect(hasHtmlEmbedNode(await gatedContentFor(role))).toBe(false);
+    }
+  });
+
+  it('toggle ON + admin: htmlEmbed preserved', async () => {
+    expect(hasHtmlEmbedNode(await gatedContentFor('admin', true))).toBe(true);
+  });
+
+  it('toggle ON + owner: htmlEmbed preserved', async () => {
+    expect(hasHtmlEmbedNode(await gatedContentFor('owner', true))).toBe(true);
+  });
+
+  it('toggle OFF + admin: stripped (feature disabled for everyone)', async () => {
+    expect(hasHtmlEmbedNode(await gatedContentFor('admin', false))).toBe(false);
+  });
+
+  it('toggle OFF + member: stripped', async () => {
+    expect(hasHtmlEmbedNode(await gatedContentFor('member', false))).toBe(false);
+  });
+});
diff --git a/apps/server/src/collaboration/collaboration.handler.ts b/apps/server/src/collaboration/collaboration.handler.ts
index 992f9b74..debfde60 100644
--- a/apps/server/src/collaboration/collaboration.handler.ts
+++ b/apps/server/src/collaboration/collaboration.handler.ts
@@ -8,6 +8,13 @@ import {
 import { setYjsMark, updateYjsMarkAttribute, YjsSelection } from './yjs.util';
 import * as Y from 'yjs';
 import { User } from '@docmost/db/types/entity.types';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from '../common/helpers/prosemirror/html-embed.util';
+import { WorkspaceRepo } from '@docmost/db/repos/workspace/workspace.repo';
 
 export type CollabEventHandlers = ReturnType<
   CollaborationHandler['getHandlers']
@@ -17,7 +24,7 @@ export type CollabEventHandlers = ReturnType<
 export class CollaborationHandler {
   private readonly logger = new Logger(CollaborationHandler.name);
 
-  constructor() {}
+  constructor(private readonly workspaceRepo: WorkspaceRepo) {}
 
   getHandlers(hocuspocus: Hocuspocus) {
     return {
@@ -83,8 +90,31 @@ export class CollaborationHandler {
           user: User;
         },
       ) => {
-        const { prosemirrorJson, operation, user } = payload;
+        const { operation, user } = payload;
+        let { prosemirrorJson } = payload;
         this.logger.debug('Updating page content via yjs', documentName);
+
+        // SECURITY (Variant C admin gate, REST/MCP/AI write path):
+        // updatePageContent is the server-side entrypoint used by the REST page
+        // update endpoint and by the MCP/AI agent. Raw `htmlEmbed` nodes execute
+        // arbitrary JS in every reader's browser, so a NON-admin caller must not
+        // be able to persist them here. If the editing user is not a workspace
+        // admin/owner, strip every htmlEmbed node before it reaches the ydoc.
+        // Toggle-AND-admin gate: htmlEmbed survives only when the workspace
+        // feature toggle is ON and the editing user is an admin/owner. OFF
+        // (default) => stripped for everyone.
+        const htmlEmbedEnabled = isHtmlEmbedFeatureEnabled(
+          (await this.workspaceRepo.findById(user?.workspaceId))?.settings,
+        );
+        if (!htmlEmbedAllowed(htmlEmbedEnabled, user?.role)) {
+          if (hasHtmlEmbedNode(prosemirrorJson)) {
+            this.logger.warn(
+              `Stripping htmlEmbed node(s) from update by user ${user?.id} on ${documentName}`,
+            );
+            prosemirrorJson = stripHtmlEmbedNodes(prosemirrorJson);
+          }
+        }
+
         await this.withYdocConnection(
           hocuspocus,
           documentName,
diff --git a/apps/server/src/collaboration/collaboration.util.ts b/apps/server/src/collaboration/collaboration.util.ts
index 554aa43b..d99636db 100644
--- a/apps/server/src/collaboration/collaboration.util.ts
+++ b/apps/server/src/collaboration/collaboration.util.ts
@@ -32,6 +32,7 @@ import {
   Drawio,
   Excalidraw,
   Embed,
+  HtmlEmbed,
   Mention,
   Subpages,
   Highlight,
@@ -102,6 +103,10 @@ export const tiptapExtensions = [
   Drawio,
   Excalidraw,
   Embed,
+  // Registered server-side so the node survives schema parsing/serialization.
+  // Authoring is gated to admins at the document WRITE paths (see
+  // stripHtmlEmbedNodes usage in persistence/page services), NOT here.
+  HtmlEmbed,
   Mention,
   Subpages,
   Columns,
diff --git a/apps/server/src/collaboration/extensions/persistence.extension.html-embed.spec.ts b/apps/server/src/collaboration/extensions/persistence.extension.html-embed.spec.ts
new file mode 100644
index 00000000..a78173a6
--- /dev/null
+++ b/apps/server/src/collaboration/extensions/persistence.extension.html-embed.spec.ts
@@ -0,0 +1,280 @@
+import * as Y from 'yjs';
+import { TiptapTransformer } from '@hocuspocus/transformer';
+import { PersistenceExtension } from './persistence.extension';
+import { tiptapExtensions } from '../collaboration.util';
+import {
+  hasHtmlEmbedNode,
+  HTML_EMBED_NODE_NAME,
+} from '../../common/helpers/prosemirror/html-embed.util';
+
+// Exercises the REAL PersistenceExtension.onStoreDocument (the primary collab
+// WebSocket write path) against a REAL ydoc, with thin repo/db/queue mocks.
+// This replaces the prior re-implemented `applyAdminGate` stand-in for this
+// entrypoint: if the role-extraction expression (`context?.user?.role`), the
+// strip call, or the ydoc-rebuild branch is deleted/changed, these tests fail.
+
+const RICH_DOC = {
+  type: 'doc',
+  content: [
+    {
+      type: 'paragraph',
+      content: [{ type: 'text', text: 'intro paragraph' }],
+    },
+    {
+      type: 'columns',
+      content: [
+        {
+          type: 'column',
+          attrs: { position: 'left' },
+          content: [
+            {
+              type: 'paragraph',
+              content: [
+                { type: 'text', text: 'left col, mentioning ' },
+                {
+                  type: 'mention',
+                  attrs: {
+                    id: 'mention-1',
+                    label: 'Alice',
+                    entityType: 'user',
+                    entityId: 'user-123',
+                    creatorId: 'creator-1',
+                  },
+                },
+              ],
+            },
+            // Nested embed inside a column — must be stripped recursively.
+            {
+              type: HTML_EMBED_NODE_NAME,
+              attrs: { source: '<script>nested()</script>' },
+            },
+          ],
+        },
+        {
+          type: 'column',
+          attrs: { position: 'right' },
+          content: [
+            {
+              type: 'table',
+              content: [
+                {
+                  type: 'tableRow',
+                  content: [
+                    {
+                      type: 'tableHeader',
+                      attrs: { colspan: 1, rowspan: 1 },
+                      content: [
+                        { type: 'paragraph', content: [{ type: 'text', text: 'H' }] },
+                      ],
+                    },
+                  ],
+                },
+                {
+                  type: 'tableRow',
+                  content: [
+                    {
+                      type: 'tableCell',
+                      attrs: { colspan: 1, rowspan: 1 },
+                      content: [
+                        { type: 'paragraph', content: [{ type: 'text', text: 'cell' }] },
+                      ],
+                    },
+                  ],
+                },
+              ],
+            },
+          ],
+        },
+      ],
+    },
+    // Top-level embed — must be stripped.
+    {
+      type: HTML_EMBED_NODE_NAME,
+      attrs: { source: '<script>top()</script>' },
+    },
+    {
+      type: 'paragraph',
+      content: [{ type: 'text', text: 'outro paragraph' }],
+    },
+  ],
+};
+
+function buildYdoc(json: any): Y.Doc {
+  return TiptapTransformer.toYdoc(json, 'default', tiptapExtensions);
+}
+
+// Count nodes by type across the whole tree (excludes htmlEmbed by listing it
+// separately) so we can assert every OTHER node type survived the strip.
+function nodeTypeCounts(json: any): Record<string, number> {
+  const counts: Record<string, number> = {};
+  const walk = (n: any) => {
+    if (!n || typeof n !== 'object') return;
+    if (n.type) counts[n.type] = (counts[n.type] ?? 0) + 1;
+    if (Array.isArray(n.content)) n.content.forEach(walk);
+  };
+  walk(json);
+  return counts;
+}
+
+/**
+ * Construct a real PersistenceExtension with the minimum mocks needed for
+ * onStoreDocument to reach the strip + persist branch, and capture the content
+ * that would be written to the page row.
+ */
+function buildExtension(featureEnabled = true) {
+  const captured: { content?: any } = {};
+
+  const existingPage = {
+    id: 'page-1',
+    slugId: 'slug-1',
+    spaceId: 'space-1',
+    workspaceId: 'ws-1',
+    creatorId: 'creator-1',
+    contributorIds: [],
+    content: { type: 'doc', content: [] }, // differs from new content -> persist runs
+    createdAt: new Date(),
+    lastUpdatedSource: 'user',
+  };
+
+  const pageRepo = {
+    findById: jest.fn(async () => ({ ...existingPage })),
+    updatePage: jest.fn(async (values: any) => {
+      captured.content = values.content;
+    }),
+  };
+  const pageHistoryRepo = {
+    findPageLastHistory: jest.fn(async () => null),
+    saveHistory: jest.fn(async () => undefined),
+  };
+  // db.transaction().execute(cb) just runs the callback (no real DB).
+  const db = {
+    transaction: () => ({
+      execute: (cb: any) => cb({} as any),
+    }),
+  };
+  const noopQueue = { add: jest.fn(async () => undefined) } as any;
+  const collabHistory = { addContributors: jest.fn(async () => undefined) } as any;
+  const transclusionService = {
+    syncPageTransclusions: jest.fn(async () => undefined),
+    syncPageReferences: jest.fn(async () => undefined),
+  } as any;
+
+  // Workspace settings read used by the toggle-AND-admin gate.
+  const workspaceRepo = {
+    findById: jest.fn(async () => ({
+      id: 'ws-1',
+      settings: { htmlEmbed: featureEnabled },
+    })),
+  };
+
+  const ext = new PersistenceExtension(
+    pageRepo as any,
+    pageHistoryRepo as any,
+    db as any,
+    noopQueue,
+    noopQueue,
+    noopQueue,
+    collabHistory,
+    transclusionService,
+    workspaceRepo as any,
+  );
+
+  return { ext, captured, pageRepo };
+}
+
+async function runStore(
+  role: string | null | undefined,
+  doc: Y.Doc,
+  featureEnabled = true,
+) {
+  const { ext, captured } = buildExtension(featureEnabled);
+  // hocuspocus augments the Y.Doc with broadcastStateless; a bare Y.Doc has
+  // none, so stub it (the post-persist broadcast is not under test here).
+  (doc as any).broadcastStateless = () => undefined;
+  await ext.onStoreDocument({
+    documentName: 'page-1',
+    document: doc,
+    context: { user: { id: 'u1', role } },
+  } as any);
+  return captured;
+}
+
+describe('PersistenceExtension.onStoreDocument htmlEmbed admin gate (real code)', () => {
+  it('non-admin store: strips EVERY htmlEmbed but preserves every other node', async () => {
+    const doc = buildYdoc(RICH_DOC);
+    const before = TiptapTransformer.fromYdoc(doc, 'default');
+    expect(hasHtmlEmbedNode(before)).toBe(true);
+    const beforeCounts = nodeTypeCounts(before);
+
+    const captured = await runStore('member', doc);
+
+    expect(captured.content).toBeDefined();
+    // htmlEmbed gone from the persisted content.
+    expect(hasHtmlEmbedNode(captured.content)).toBe(false);
+
+    // Every non-embed node type is preserved with the SAME count (guards against
+    // data loss if a node were missing from tiptapExtensions and dropped on the
+    // toYdoc rebuild).
+    const afterCounts = nodeTypeCounts(captured.content);
+    for (const [type, count] of Object.entries(beforeCounts)) {
+      if (type === HTML_EMBED_NODE_NAME) continue;
+      expect(afterCounts[type]).toBe(count);
+    }
+    // The two embeds are gone.
+    expect(beforeCounts[HTML_EMBED_NODE_NAME]).toBe(2);
+    expect(afterCounts[HTML_EMBED_NODE_NAME]).toBeUndefined();
+
+    // The shared ydoc fragment was also rewritten clean (re-decode it).
+    const reDecoded = TiptapTransformer.fromYdoc(doc, 'default');
+    expect(hasHtmlEmbedNode(reDecoded)).toBe(false);
+  });
+
+  it('toggle ON + admin store: htmlEmbed preserved in persisted content', async () => {
+    const captured = await runStore('admin', buildYdoc(RICH_DOC), true);
+    expect(captured.content).toBeDefined();
+    expect(hasHtmlEmbedNode(captured.content)).toBe(true);
+    expect(nodeTypeCounts(captured.content)[HTML_EMBED_NODE_NAME]).toBe(2);
+  });
+
+  it('toggle ON + owner store: htmlEmbed preserved', async () => {
+    const captured = await runStore('owner', buildYdoc(RICH_DOC), true);
+    expect(hasHtmlEmbedNode(captured.content)).toBe(true);
+  });
+
+  it('toggle OFF + admin store: stripped (feature disabled for everyone)', async () => {
+    const captured = await runStore('admin', buildYdoc(RICH_DOC), false);
+    expect(hasHtmlEmbedNode(captured.content)).toBe(false);
+  });
+
+  it('toggle OFF + owner store: stripped', async () => {
+    const captured = await runStore('owner', buildYdoc(RICH_DOC), false);
+    expect(hasHtmlEmbedNode(captured.content)).toBe(false);
+  });
+
+  it('toggle OFF + member store: stripped', async () => {
+    const captured = await runStore('member', buildYdoc(RICH_DOC), false);
+    expect(hasHtmlEmbedNode(captured.content)).toBe(false);
+  });
+
+  it('unknown/empty role: fails closed (stripped)', async () => {
+    expect(
+      hasHtmlEmbedNode((await runStore(undefined, buildYdoc(RICH_DOC))).content),
+    ).toBe(false);
+    expect(
+      hasHtmlEmbedNode((await runStore(null, buildYdoc(RICH_DOC))).content),
+    ).toBe(false);
+    expect(
+      hasHtmlEmbedNode((await runStore('viewer', buildYdoc(RICH_DOC))).content),
+    ).toBe(false);
+  });
+
+  it('empty-fragment ydoc (no content) does not throw and persists no embed', async () => {
+    const emptyDoc = buildYdoc({
+      type: 'doc',
+      content: [{ type: 'paragraph' }],
+    });
+    // Non-admin path with an empty/embed-free fragment must be a no-op strip,
+    // not throw.
+    await expect(runStore('member', emptyDoc)).resolves.toBeDefined();
+  });
+});
diff --git a/apps/server/src/collaboration/extensions/persistence.extension.ts b/apps/server/src/collaboration/extensions/persistence.extension.ts
index af4137d6..91331dec 100644
--- a/apps/server/src/collaboration/extensions/persistence.extension.ts
+++ b/apps/server/src/collaboration/extensions/persistence.extension.ts
@@ -39,6 +39,13 @@ import {
   HISTORY_INTERVAL,
 } from '../constants';
 import { TransclusionService } from '../../core/page/transclusion/transclusion.service';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from '../../common/helpers/prosemirror/html-embed.util';
+import { WorkspaceRepo } from '@docmost/db/repos/workspace/workspace.repo';
 
 @Injectable()
 export class PersistenceExtension implements Extension {
@@ -59,6 +66,7 @@ export class PersistenceExtension implements Extension {
     @InjectQueue(QueueName.NOTIFICATION_QUEUE) private notificationQueue: Queue,
     private readonly collabHistory: CollabHistoryService,
     private readonly transclusionService: TransclusionService,
+    private readonly workspaceRepo: WorkspaceRepo,
   ) {}
 
   async onLoadDocument(data: onLoadDocumentPayload) {
@@ -112,7 +120,62 @@ export class PersistenceExtension implements Extension {
 
     const pageId = getPageId(documentName);
 
-    const tiptapJson = TiptapTransformer.fromYdoc(document, 'default');
+    let tiptapJson = TiptapTransformer.fromYdoc(document, 'default');
+
+    // SECURITY (Variant C admin gate, collab WebSocket write path):
+    // The persisted snapshot is the merged ydoc, which may contain an htmlEmbed
+    // node inserted by ANY connected editor. htmlEmbed renders raw, unsanitized
+    // JS in every reader's browser, so only workspace admins/owners may author
+    // it. When the user whose store triggers this persist is not an admin, strip
+    // every htmlEmbed node before it is written to the page row AND before the
+    // ydoc state is re-encoded, so the node cannot be reintroduced by a
+    // non-admin via the collab socket.
+    // NOTE (residual risk): the gate is keyed to the storing connection's user.
+    // If an admin already authored an htmlEmbed and a non-admin's later store
+    // does not touch it, this strip would remove the admin's embed on that
+    // non-admin store. This is intentionally conservative (fail closed): the
+    // admin re-adds/keeps the node on their own next edit. A future refinement
+    // could diff against the previously persisted admin-authored embeds.
+    //
+    // ACCEPTED RESIDUAL RISK (pre-persist broadcast window): this strip runs in
+    // the debounced onStoreDocument, but hocuspocus broadcasts each inbound Yjs
+    // update to connected clients immediately, so a non-admin's transient
+    // htmlEmbed can execute in OTHER open editors' browsers in the brief window
+    // before this persist strips it. The exposure is limited to concurrent
+    // AUTHENTICATED space members who have the doc open with Edit rights
+    // (semi-trusted) — anonymous public-share/readonly viewers do NOT open a
+    // collab socket (ReadonlyPageEditor renders fetched, already-stripped
+    // content; HocuspocusProvider is only used by the authenticated editable
+    // page-editor), and the PERSISTED page row plus every share/readonly read
+    // path are protected by this strip. The window is therefore accepted rather
+    // than mitigated with an inbound beforeBroadcast strip.
+    // Toggle-AND-admin gate: htmlEmbed survives only when the workspace feature
+    // toggle is ON and the storing user is an admin/owner. OFF (default) =>
+    // stripped for everyone (existing embeds get cleaned up on next save).
+    const htmlEmbedEnabled = isHtmlEmbedFeatureEnabled(
+      (await this.workspaceRepo.findById(context?.user?.workspaceId))?.settings,
+    );
+    if (!htmlEmbedAllowed(htmlEmbedEnabled, context?.user?.role)) {
+      if (hasHtmlEmbedNode(tiptapJson)) {
+        this.logger.warn(
+          `Stripping htmlEmbed node(s) from collab store by user ${context?.user?.id} on ${documentName}`,
+        );
+        tiptapJson = stripHtmlEmbedNodes(tiptapJson);
+        // Reflect the stripped content back into the shared ydoc so the node is
+        // removed for all connected clients, not just the persisted row.
+        const fragment = document.getXmlFragment('default');
+        if (fragment.length > 0) {
+          fragment.delete(0, fragment.length);
+        }
+        const cleanDoc = TiptapTransformer.toYdoc(
+          tiptapJson,
+          'default',
+          tiptapExtensions,
+        );
+        Y.applyUpdate(document, Y.encodeStateAsUpdate(cleanDoc));
+      }
+    }
+
     const ydocState = Buffer.from(Y.encodeStateAsUpdate(document));
 
     let textContent = null;
diff --git a/apps/server/src/common/helpers/prosemirror/html-embed.spec.ts b/apps/server/src/common/helpers/prosemirror/html-embed.spec.ts
new file mode 100644
index 00000000..6b07ec0b
--- /dev/null
+++ b/apps/server/src/common/helpers/prosemirror/html-embed.spec.ts
@@ -0,0 +1,214 @@
+import {
+  canAuthorHtmlEmbed,
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from './html-embed.util';
+import { htmlToJson, jsonToHtml } from '../../../collaboration/collaboration.util';
+import {
+  decodeHtmlEmbedSource,
+  encodeHtmlEmbedSource,
+} from '@docmost/editor-ext';
+
+const findFirstChild = (json: any, type: string): any | undefined => {
+  if (!json || typeof json !== 'object') return undefined;
+  if (json.type === type) return json;
+  if (Array.isArray(json.content)) {
+    for (const child of json.content) {
+      const found = findFirstChild(child, type);
+      if (found) return found;
+    }
+  }
+  return undefined;
+};
+
+describe('stripHtmlEmbedNodes', () => {
+  it('removes a top-level htmlEmbed node', () => {
+    const doc = {
+      type: 'doc',
+      content: [
+        { type: 'paragraph', content: [{ type: 'text', text: 'before' }] },
+        { type: 'htmlEmbed', attrs: { source: '<script>alert(1)</script>' } },
+        { type: 'paragraph', content: [{ type: 'text', text: 'after' }] },
+      ],
+    };
+
+    const result = stripHtmlEmbedNodes(doc);
+    expect(hasHtmlEmbedNode(result)).toBe(false);
+    // Other nodes are preserved.
+    expect(result.content).toHaveLength(2);
+    expect(result.content[0].content[0].text).toBe('before');
+    expect(result.content[1].content[0].text).toBe('after');
+  });
+
+  it('removes nested htmlEmbed nodes (e.g. inside columns)', () => {
+    const doc = {
+      type: 'doc',
+      content: [
+        {
+          type: 'columns',
+          content: [
+            {
+              type: 'column',
+              content: [
+                { type: 'htmlEmbed', attrs: { source: '<b>x</b>' } },
+                {
+                  type: 'paragraph',
+                  content: [{ type: 'text', text: 'keep' }],
+                },
+              ],
+            },
+          ],
+        },
+      ],
+    };
+
+    const result = stripHtmlEmbedNodes(doc);
+    expect(hasHtmlEmbedNode(result)).toBe(false);
+    const col = findFirstChild(result, 'column');
+    expect(col.content).toHaveLength(1);
+    expect(col.content[0].type).toBe('paragraph');
+  });
+
+  it('does not mutate the input document', () => {
+    const doc = {
+      type: 'doc',
+      content: [{ type: 'htmlEmbed', attrs: { source: 'x' } }],
+    };
+    stripHtmlEmbedNodes(doc);
+    expect(doc.content).toHaveLength(1);
+    expect(doc.content[0].type).toBe('htmlEmbed');
+  });
+
+  it('leaves documents without htmlEmbed untouched', () => {
+    const doc = {
+      type: 'doc',
+      content: [
+        { type: 'paragraph', content: [{ type: 'text', text: 'hi' }] },
+      ],
+    };
+    expect(hasHtmlEmbedNode(doc)).toBe(false);
+    const result = stripHtmlEmbedNodes(doc);
+    expect(result).toEqual(doc);
+  });
+});
+
+describe('canAuthorHtmlEmbed', () => {
+  it('allows owner and admin', () => {
+    expect(canAuthorHtmlEmbed('owner')).toBe(true);
+    expect(canAuthorHtmlEmbed('admin')).toBe(true);
+  });
+  it('denies member and unknown/empty roles', () => {
+    expect(canAuthorHtmlEmbed('member')).toBe(false);
+    expect(canAuthorHtmlEmbed(null)).toBe(false);
+    expect(canAuthorHtmlEmbed(undefined)).toBe(false);
+    expect(canAuthorHtmlEmbed('viewer')).toBe(false);
+  });
+});
+
+describe('isHtmlEmbedFeatureEnabled', () => {
+  it('is true only when settings.htmlEmbed === true', () => {
+    expect(isHtmlEmbedFeatureEnabled({ htmlEmbed: true })).toBe(true);
+  });
+  it('defaults to false (absent / false / non-object)', () => {
+    expect(isHtmlEmbedFeatureEnabled({})).toBe(false);
+    expect(isHtmlEmbedFeatureEnabled({ htmlEmbed: false })).toBe(false);
+    expect(isHtmlEmbedFeatureEnabled(null)).toBe(false);
+    expect(isHtmlEmbedFeatureEnabled(undefined)).toBe(false);
+    // Truthy-but-not-true values must NOT enable the feature.
+    expect(isHtmlEmbedFeatureEnabled({ htmlEmbed: 'true' as any })).toBe(false);
+  });
+});
+
+describe('htmlEmbedAllowed (toggle AND admin)', () => {
+  it('toggle OFF + admin/owner => not allowed (feature disabled for everyone)', () => {
+    expect(htmlEmbedAllowed(false, 'admin')).toBe(false);
+    expect(htmlEmbedAllowed(false, 'owner')).toBe(false);
+  });
+  it('toggle OFF + member => not allowed', () => {
+    expect(htmlEmbedAllowed(false, 'member')).toBe(false);
+  });
+  it('toggle ON + admin/owner => allowed', () => {
+    expect(htmlEmbedAllowed(true, 'admin')).toBe(true);
+    expect(htmlEmbedAllowed(true, 'owner')).toBe(true);
+  });
+  it('toggle ON + member/unknown => not allowed', () => {
+    expect(htmlEmbedAllowed(true, 'member')).toBe(false);
+    expect(htmlEmbedAllowed(true, null)).toBe(false);
+    expect(htmlEmbedAllowed(true, undefined)).toBe(false);
+    expect(htmlEmbedAllowed(true, 'viewer')).toBe(false);
+  });
+});
+
+// NOTE: a previous revision of this file re-implemented the write-path admin
+// gate as a local `applyAdminGate` stand-in and asserted against THAT. A
+// deleted/misplaced real guard would have kept those green. The stand-in is
+// removed. The collab store, REST/MCP update, and transclusion-unsync paths are
+// now tested against their REAL code in:
+//   - collaboration/extensions/persistence.extension.html-embed.spec.ts
+//   - collaboration/collaboration.handler.html-embed.spec.ts
+//   - core/page/transclusion/spec/transclusion-unsync-html-embed.spec.ts
+//   - core/page/services/page-service-html-embed-identity.spec.ts (create/dup)
+//   - integrations/import/services/import-html-embed-identity.spec.ts (import)
+//
+// The case below stays here because it asserts a REAL parse path
+// (htmlToJson, the markdown/html create format) feeding the REAL helpers — not a
+// re-implemented gate.
+describe('htmlEmbed smuggled via the markdown/html <!--html-embed--> form (real parse + real helpers)', () => {
+  it('the parsed node is detected and stripped by the real helpers', () => {
+    // The markdown/html create formats decode to the same htmlEmbed node, so the
+    // gate (run on the parsed JSON) covers them identically.
+    const source = '<script>steal()</script>';
+    const encoded = encodeHtmlEmbedSource(source);
+    const html = `<div data-type="htmlEmbed" data-source="${encoded}"></div>`;
+    const parsed = htmlToJson(html);
+    expect(hasHtmlEmbedNode(parsed)).toBe(true);
+
+    // A non-admin role gates to strip via the real helpers.
+    expect(canAuthorHtmlEmbed('member')).toBe(false);
+    const stripped = stripHtmlEmbedNodes(parsed);
+    expect(hasHtmlEmbedNode(stripped)).toBe(false);
+  });
+});
+
+describe('htmlEmbed source base64 codec', () => {
+  it('round-trips arbitrary source including UTF-8', () => {
+    const source = '<script>console.log("héllo → 世界")</script>';
+    const encoded = encodeHtmlEmbedSource(source);
+    expect(encoded).not.toContain('<');
+    expect(decodeHtmlEmbedSource(encoded)).toBe(source);
+  });
+});
+
+describe('htmlEmbed node HTML <-> JSON round-trip', () => {
+  it('preserves the raw source through HTML -> JSON', () => {
+    const source = '<script>track("page")</script><style>.a{color:red}</style>';
+    const encoded = encodeHtmlEmbedSource(source);
+    const html = `<div data-type="htmlEmbed" data-source="${encoded}"></div>`;
+
+    const json = htmlToJson(html);
+    const node = findFirstChild(json, 'htmlEmbed');
+    expect(node).toBeDefined();
+    expect(node.attrs.source).toBe(source);
+  });
+
+  it('round-trips JSON -> HTML -> JSON keeping the source', () => {
+    const source = '<div onclick="x()">raw &amp; markup</div>';
+    const json = {
+      type: 'doc',
+      content: [{ type: 'htmlEmbed', attrs: { source } }],
+    };
+
+    const html = jsonToHtml(json);
+    // The static HTML carries the encoded source but does NOT inline the raw
+    // markup (it must not be an injection vector by itself).
+    expect(html).toContain('data-type="htmlEmbed"');
+    expect(html).not.toContain('onclick');
+
+    const back = htmlToJson(html);
+    const node = findFirstChild(back, 'htmlEmbed');
+    expect(node).toBeDefined();
+    expect(node.attrs.source).toBe(source);
+  });
+});
diff --git a/apps/server/src/common/helpers/prosemirror/html-embed.util.ts b/apps/server/src/common/helpers/prosemirror/html-embed.util.ts
new file mode 100644
index 00000000..f1d0b6e5
--- /dev/null
+++ b/apps/server/src/common/helpers/prosemirror/html-embed.util.ts
@@ -0,0 +1,102 @@
+import { JSONContent } from '@tiptap/core';
+
+export const HTML_EMBED_NODE_NAME = 'htmlEmbed';
+
+/**
+ * Recursively remove every `htmlEmbed` node from a ProseMirror JSON document.
+ *
+ * SECURITY: `htmlEmbed` renders raw, unsanitized HTML/CSS/JS in the wiki origin
+ * (stored-XSS by design, Variant C). Only workspace admins/owners are allowed to
+ * author it. This helper is the server-side enforcement primitive: every WRITE
+ * path that may persist content from a NON-admin caller must run the incoming
+ * document through this function so a non-admin cannot smuggle the node in via
+ * the collab socket, the REST/MCP/AI content-update path, paste, or import.
+ *
+ * Returns a NEW document; the input is not mutated. If the input is not a valid
+ * doc object it is returned unchanged (callers persist what they were given).
+ */
+export function stripHtmlEmbedNodes<T = JSONContent>(pmJson: T): T {
+  if (!pmJson || typeof pmJson !== 'object') {
+    return pmJson;
+  }
+
+  const node = pmJson as unknown as JSONContent;
+
+  if (Array.isArray(node.content)) {
+    const filtered: JSONContent[] = [];
+    for (const child of node.content) {
+      // Drop any htmlEmbed child outright.
+      if (child && child.type === HTML_EMBED_NODE_NAME) {
+        continue;
+      }
+      // Recurse so nested htmlEmbed nodes (e.g. inside columns/callouts) are
+      // also removed.
+      filtered.push(stripHtmlEmbedNodes(child));
+    }
+    return { ...node, content: filtered } as unknown as T;
+  }
+
+  return { ...node } as unknown as T;
+}
+
+/**
+ * Returns true if the document contains at least one `htmlEmbed` node anywhere
+ * in its tree. Useful to decide whether a strip pass actually changed anything
+ * (e.g. for logging a rejected non-admin embed attempt).
+ */
+export function hasHtmlEmbedNode(pmJson: unknown): boolean {
+  if (!pmJson || typeof pmJson !== 'object') {
+    return false;
+  }
+  const node = pmJson as JSONContent;
+  if (node.type === HTML_EMBED_NODE_NAME) {
+    return true;
+  }
+  if (Array.isArray(node.content)) {
+    return node.content.some((child) => hasHtmlEmbedNode(child));
+  }
+  return false;
+}
+
+/**
+ * Map the workspace user role to whether it may author `htmlEmbed` nodes.
+ * Owners and admins are trusted; everyone else (member, and any unknown role)
+ * is not. Kept here so every write path shares one definition of "trusted".
+ */
+export function canAuthorHtmlEmbed(role: string | null | undefined): boolean {
+  return role === 'owner' || role === 'admin';
+}
+
+/**
+ * Combined write-path gate for the htmlEmbed feature.
+ *
+ * htmlEmbed is allowed in a document only when the workspace feature toggle is
+ * ON and the authoring/saving user is a workspace admin/owner. OFF (default) =>
+ * stripped for EVERYONE, including admins (the feature is disabled).
+ *
+ * `featureEnabled` is read from the workspace settings for the relevant write
+ * (`workspace.settings?.htmlEmbed === true`). Every WRITE path that may persist
+ * htmlEmbed content must gate on this combined predicate, so that turning the
+ * toggle OFF strips existing embeds on the next save and prevents new ones from
+ * being persisted regardless of role.
+ */
+export function htmlEmbedAllowed(
+  featureEnabled: boolean,
+  role: string | null | undefined,
+): boolean {
+  return featureEnabled === true && canAuthorHtmlEmbed(role);
+}
+
+/**
+ * Read the workspace-level htmlEmbed feature toggle from a workspace's settings
+ * jsonb. ABSENT/non-true => OFF (the default). Kept here so every server write
+ * path resolves the toggle the same way.
+ */
+export function isHtmlEmbedFeatureEnabled(
+  settings: unknown | null | undefined,
+): boolean {
+  if (!settings || typeof settings !== 'object') {
+    return false;
+  }
+  return (settings as Record<string, unknown>).htmlEmbed === true;
+}
diff --git a/apps/server/src/core/page/page.controller.ts b/apps/server/src/core/page/page.controller.ts
index fd5c866e..968480c9 100644
--- a/apps/server/src/core/page/page.controller.ts
+++ b/apps/server/src/core/page/page.controller.ts
@@ -237,6 +237,9 @@ export class PageController {
       user.id,
       workspace.id,
       createPageDto,
+      // Pass the caller's workspace role so create() can enforce the htmlEmbed
+      // admin gate (non-admins cannot author raw-JS embeds).
+      user.role,
       provenance,
     );
 
diff --git a/apps/server/src/core/page/services/page-service-html-embed-identity.spec.ts b/apps/server/src/core/page/services/page-service-html-embed-identity.spec.ts
new file mode 100644
index 00000000..f23d565a
--- /dev/null
+++ b/apps/server/src/core/page/services/page-service-html-embed-identity.spec.ts
@@ -0,0 +1,102 @@
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  stripHtmlEmbedNodes,
+} from '../../../common/helpers/prosemirror/html-embed.util';
+
+// PageService.create() and duplicatePage() guards.
+//
+// page.service.ts cannot be unit-LOADED under the server's jest config (a
+// transitive ESM dep, @sindresorhus/slugify, is not in transformIgnorePatterns),
+// so we cover the two load-bearing properties at the strongest feasible layer:
+//
+//  (1) BEHAVIOR — using the REAL html-embed helpers, replay the exact predicate
+//      each path applies: non-admin/unknown role -> strip, admin/owner -> keep.
+//
+//  (2) IDENTITY — source-pin which role each path reads (create: the `callerRole`
+//      param threaded from the request; duplicate: `authUser.role`), so a
+//      refactor that drops the guard or reads the wrong role trips the test.
+//      This is what replaces the removed `applyAdminGate` stand-in for these
+//      two entrypoints.
+
+const docWithEmbed = () => ({
+  type: 'doc',
+  content: [
+    { type: 'paragraph', content: [{ type: 'text', text: 'body' }] },
+    { type: 'htmlEmbed', attrs: { source: '<script>alert(1)</script>' } },
+  ],
+});
+
+// The real predicate both paths apply (see SECURITY blocks in page.service.ts):
+// toggle AND admin.
+function applyGate(
+  json: any,
+  featureEnabled: boolean,
+  role: string | null | undefined,
+) {
+  if (!htmlEmbedAllowed(featureEnabled, role) && hasHtmlEmbedNode(json)) {
+    return stripHtmlEmbedNodes(json);
+  }
+  return json;
+}
+
+describe('page create/duplicate gate decision (real helpers)', () => {
+  it('toggle ON + non-admin (member) strips', () => {
+    const result = applyGate(docWithEmbed(), true, 'member');
+    expect(hasHtmlEmbedNode(result)).toBe(false);
+    expect(result.content).toHaveLength(1);
+    expect(result.content[0].content[0].text).toBe('body');
+  });
+
+  it('toggle ON + unknown/empty role fails closed (strips)', () => {
+    for (const role of [null, undefined, 'viewer'] as const) {
+      expect(hasHtmlEmbedNode(applyGate(docWithEmbed(), true, role))).toBe(
+        false,
+      );
+    }
+  });
+
+  it('toggle ON + admin/owner keep', () => {
+    expect(hasHtmlEmbedNode(applyGate(docWithEmbed(), true, 'admin'))).toBe(
+      true,
+    );
+    expect(hasHtmlEmbedNode(applyGate(docWithEmbed(), true, 'owner'))).toBe(
+      true,
+    );
+  });
+
+  it('toggle OFF strips for everyone (admin/owner/member)', () => {
+    for (const role of ['admin', 'owner', 'member'] as const) {
+      expect(hasHtmlEmbedNode(applyGate(docWithEmbed(), false, role))).toBe(
+        false,
+      );
+    }
+  });
+});
+
+const SRC = readFileSync(join(__dirname, 'page.service.ts'), 'utf-8');
+
+describe('page create/duplicate gate identity is pinned (source contract)', () => {
+  it('create() gates on toggle AND the caller role param before deriving content/ydoc', () => {
+    // create() receives the caller's workspace role as `callerRole` and gates on
+    // the combined toggle-AND-admin predicate; the embed must be stripped BEFORE
+    // insertPage.
+    expect(SRC).toMatch(
+      /!htmlEmbedAllowed\(\s*htmlEmbedEnabled\s*,\s*callerRole\s*\)\s*&&\s*hasHtmlEmbedNode\(\s*prosemirrorJson\s*\)/,
+    );
+    expect(SRC).toContain('prosemirrorJson = stripHtmlEmbedNodes(prosemirrorJson)');
+  });
+
+  it('duplicatePage() gates on toggle AND the duplicating user role (authUser.role)', () => {
+    expect(SRC).toMatch(
+      /!htmlEmbedAllowed\(\s*htmlEmbedEnabled\s*,\s*authUser\.role\s*\)\s*&&\s*hasHtmlEmbedNode\(\s*prosemirrorJson\s*\)/,
+    );
+  });
+
+  it('both paths resolve the toggle from the workspace settings', () => {
+    expect(SRC).toContain('isHtmlEmbedFeatureEnabled(');
+    expect(SRC).toContain('this.workspaceRepo.findById(');
+  });
+});
diff --git a/apps/server/src/core/page/services/page.service.ts b/apps/server/src/core/page/services/page.service.ts
index 27b394e7..0dc2276f 100644
--- a/apps/server/src/core/page/services/page.service.ts
+++ b/apps/server/src/core/page/services/page.service.ts
@@ -30,6 +30,13 @@ import {
   isAttachmentNode,
   removeMarkTypeFromDoc,
 } from '../../../common/helpers/prosemirror/utils';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from '../../../common/helpers/prosemirror/html-embed.util';
+import { WorkspaceRepo } from '@docmost/db/repos/workspace/workspace.repo';
 import {
   htmlToJson,
   jsonToNode,
@@ -74,6 +81,7 @@ export class PageService {
     private collaborationGateway: CollaborationGateway,
     private readonly watcherService: WatcherService,
     private readonly transclusionService: TransclusionService,
+    private readonly workspaceRepo: WorkspaceRepo,
   ) {}
 
   async findById(
@@ -93,6 +101,10 @@ export class PageService {
     userId: string,
     workspaceId: string,
     createPageDto: CreatePageDto,
+    // Workspace role of the caller. Used to enforce the htmlEmbed admin gate on
+    // the create write path (see below). Optional/typed loosely so unknown or
+    // missing roles fall through to the non-admin (strip) branch by default.
+    callerRole?: string | null,
     // Optional agent-edit provenance (from the signed access claim). When the
     // actor is 'agent', stamp the page's source marker so a freshly created page
     // shows it was created by the AI agent (§14 N2) — create goes through REST,
@@ -123,11 +135,36 @@ export class PageService {
     let ydoc = undefined;
 
     if (createPageDto?.content && createPageDto?.format) {
-      const prosemirrorJson = await this.parseProsemirrorContent(
+      let prosemirrorJson = await this.parseProsemirrorContent(
         createPageDto.content,
         createPageDto.format,
       );
 
+      // SECURITY (Variant C admin gate, plain page-create write path):
+      // create() builds content/textContent/ydoc directly and persists them via
+      // insertPage, bypassing the collab onStoreDocument strip. htmlEmbed renders
+      // raw, unsanitized JS in readers' browsers, so only workspace admins/owners
+      // may author it. The create controller requires only space Edit, so a
+      // regular member could otherwise POST a doc (json, or the markdown/html
+      // <!--html-embed:BASE64--> forms that parse to the same node) containing an
+      // htmlEmbed and store XSS for every reader. Strip every htmlEmbed node when
+      // the caller is not an admin, BEFORE deriving textContent/ydoc/insert.
+      // The gate is toggle-AND-admin: htmlEmbed survives only when the workspace
+      // feature toggle is ON and the caller is an admin/owner. OFF (default) =>
+      // stripped for everyone. Cheap settings read keyed to the workspace.
+      const htmlEmbedEnabled = isHtmlEmbedFeatureEnabled(
+        (await this.workspaceRepo.findById(workspaceId))?.settings,
+      );
+      if (
+        !htmlEmbedAllowed(htmlEmbedEnabled, callerRole) &&
+        hasHtmlEmbedNode(prosemirrorJson)
+      ) {
+        this.logger.warn(
+          `Stripping htmlEmbed node(s) from page creation by user ${userId} (space ${createPageDto.spaceId})`,
+        );
+        prosemirrorJson = stripHtmlEmbedNodes(prosemirrorJson);
+      }
+
       content = prosemirrorJson;
       textContent = jsonToText(prosemirrorJson);
       ydoc = createYdocFromJson(prosemirrorJson);
@@ -589,6 +626,12 @@ export class PageService {
 
     const attachmentMap = new Map<string, ICopyPageAttachment>();
 
+    // Resolve the htmlEmbed toggle ONCE for the workspace; the per-page gate
+    // below is toggle-AND-admin (OFF default => stripped for everyone).
+    const htmlEmbedEnabled = isHtmlEmbedFeatureEnabled(
+      (await this.workspaceRepo.findById(rootPage.workspaceId))?.settings,
+    );
+
     const insertablePages: InsertablePage[] = await Promise.all(
       pages.map(async (page) => {
         const pageContent = getProsemirrorContent(page.content);
@@ -688,7 +731,25 @@ export class PageService {
           }
         });
 
-        const prosemirrorJson = prosemirrorDoc.toJSON();
+        let prosemirrorJson = prosemirrorDoc.toJSON();
+
+        // SECURITY (Variant C admin gate, duplication write path):
+        // Duplication builds the ydoc directly and bypasses the collab
+        // onStoreDocument strip. htmlEmbed renders raw, unsanitized JS in
+        // readers' browsers, so only workspace admins/owners may author it. A
+        // non-admin with space Edit could otherwise duplicate an admin page
+        // that contains an embed into a new page authored by them. Strip every
+        // htmlEmbed node from each duplicated page when the duplicating user is
+        // not an admin, BEFORE computing textContent/ydoc/insert.
+        if (
+          !htmlEmbedAllowed(htmlEmbedEnabled, authUser.role) &&
+          hasHtmlEmbedNode(prosemirrorJson)
+        ) {
+          this.logger.warn(
+            `Stripping htmlEmbed node(s) from page duplication by user ${authUser.id} (source page ${page.id})`,
+          );
+          prosemirrorJson = stripHtmlEmbedNodes(prosemirrorJson);
+        }
 
         // Add "Copy of " prefix to the root page title only for duplicates in same space
         let title = page.title;
diff --git a/apps/server/src/core/page/transclusion/spec/transclusion-unsync-html-embed.spec.ts b/apps/server/src/core/page/transclusion/spec/transclusion-unsync-html-embed.spec.ts
new file mode 100644
index 00000000..8ad13121
--- /dev/null
+++ b/apps/server/src/core/page/transclusion/spec/transclusion-unsync-html-embed.spec.ts
@@ -0,0 +1,144 @@
+import { TransclusionService } from '../transclusion.service';
+import { hasHtmlEmbedNode } from '../../../../common/helpers/prosemirror/html-embed.util';
+
+// Exercises the REAL TransclusionService.unsyncReference htmlEmbed admin gate.
+// unsync returns a source snapshot the client materializes into the reference
+// page; a non-admin must never receive an embed payload to re-persist. The gate
+// reads `user.role` and strips before returning. All repos / access checks are
+// mocked so the REAL gate logic runs end-to-end. Complements the existing
+// transclusion specs (rewriteAttachmentsForUnsync, controller).
+
+const WS = 'ws-1';
+const REF_PAGE = 'ref-1';
+const SRC_PAGE = 'src-1';
+const TX_ID = 'tx-1';
+
+const sourceContentWithEmbed = () => ({
+  type: 'doc',
+  content: [
+    { type: 'paragraph', content: [{ type: 'text', text: 'snapshot body' }] },
+    { type: 'htmlEmbed', attrs: { source: '<script>steal()</script>' } },
+  ],
+});
+
+function buildService(featureEnabled = true) {
+  const pageRepo = {
+    findById: jest.fn(async (id: string) => ({
+      id,
+      workspaceId: WS,
+      spaceId: 'space-1',
+      deletedAt: null,
+    })),
+  };
+  const pageTransclusionsRepo = {
+    findByPageAndTransclusion: jest.fn(async () => ({
+      content: sourceContentWithEmbed(),
+    })),
+  };
+  const pageTransclusionReferencesRepo = {
+    deleteOne: jest.fn(async () => undefined),
+  };
+  const attachmentRepo = { findByIds: jest.fn(async () => []) };
+  const storageService = { copy: jest.fn(async () => undefined) };
+  const pageAccessService = {
+    validateCanEdit: jest.fn(async () => undefined),
+    validateCanView: jest.fn(async () => undefined),
+  };
+  // Workspace settings read used by the toggle-AND-admin gate.
+  const workspaceRepo = {
+    findById: jest.fn(async () => ({
+      id: WS,
+      settings: { htmlEmbed: featureEnabled },
+    })),
+  };
+
+  const service = new TransclusionService(
+    {} as any, // db (unused on this path)
+    pageTransclusionsRepo as any,
+    pageTransclusionReferencesRepo as any,
+    pageRepo as any,
+    {} as any, // pagePermissionRepo (unused)
+    {} as any, // spaceMemberRepo (unused)
+    attachmentRepo as any,
+    storageService as any,
+    pageAccessService as any,
+    workspaceRepo as any,
+  );
+  return service;
+}
+
+function userWithRole(role: string | null | undefined) {
+  return { id: 'u1', workspaceId: WS, role } as any;
+}
+
+describe('TransclusionService.unsyncReference htmlEmbed admin gate (real code)', () => {
+  it('non-admin (member): returned content has htmlEmbed stripped', async () => {
+    const service = buildService();
+    const { content } = await service.unsyncReference(
+      REF_PAGE,
+      SRC_PAGE,
+      TX_ID,
+      userWithRole('member'),
+    );
+    expect(hasHtmlEmbedNode(content)).toBe(false);
+    // Non-embed content is preserved.
+    expect(JSON.stringify(content)).toContain('snapshot body');
+  });
+
+  it('unknown/empty role: fails closed (stripped)', async () => {
+    for (const role of [undefined, null, 'viewer'] as const) {
+      const service = buildService();
+      const { content } = await service.unsyncReference(
+        REF_PAGE,
+        SRC_PAGE,
+        TX_ID,
+        userWithRole(role),
+      );
+      expect(hasHtmlEmbedNode(content)).toBe(false);
+    }
+  });
+
+  it('toggle ON + admin: returned content keeps the htmlEmbed', async () => {
+    const service = buildService(true);
+    const { content } = await service.unsyncReference(
+      REF_PAGE,
+      SRC_PAGE,
+      TX_ID,
+      userWithRole('admin'),
+    );
+    expect(hasHtmlEmbedNode(content)).toBe(true);
+  });
+
+  it('toggle ON + owner: returned content keeps the htmlEmbed', async () => {
+    const service = buildService(true);
+    const { content } = await service.unsyncReference(
+      REF_PAGE,
+      SRC_PAGE,
+      TX_ID,
+      userWithRole('owner'),
+    );
+    expect(hasHtmlEmbedNode(content)).toBe(true);
+  });
+
+  it('toggle OFF + admin: stripped (feature disabled for everyone)', async () => {
+    const service = buildService(false);
+    const { content } = await service.unsyncReference(
+      REF_PAGE,
+      SRC_PAGE,
+      TX_ID,
+      userWithRole('admin'),
+    );
+    expect(hasHtmlEmbedNode(content)).toBe(false);
+  });
+
+  it('toggle OFF + member: stripped', async () => {
+    const service = buildService(false);
+    const { content } = await service.unsyncReference(
+      REF_PAGE,
+      SRC_PAGE,
+      TX_ID,
+      userWithRole('member'),
+    );
+    expect(hasHtmlEmbedNode(content)).toBe(false);
+  });
+});
diff --git a/apps/server/src/core/page/transclusion/transclusion.service.ts b/apps/server/src/core/page/transclusion/transclusion.service.ts
index e208707c..2fd92402 100644
--- a/apps/server/src/core/page/transclusion/transclusion.service.ts
+++ b/apps/server/src/core/page/transclusion/transclusion.service.ts
@@ -23,6 +23,13 @@ import { rewriteAttachmentsForUnsync } from './utils/transclusion-unsync.util';
 import { TransclusionLookup } from './transclusion.types';
 import { Page, User } from '@docmost/db/types/entity.types';
 import { PageAccessService } from '../page-access/page-access.service';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from '../../../common/helpers/prosemirror/html-embed.util';
+import { WorkspaceRepo } from '@docmost/db/repos/workspace/workspace.repo';
 
 type ReferencingPageInfo = {
   id: string;
@@ -47,6 +54,7 @@ export class TransclusionService {
     private readonly attachmentRepo: AttachmentRepo,
     private readonly storageService: StorageService,
     private readonly pageAccessService: PageAccessService,
+    private readonly workspaceRepo: WorkspaceRepo,
   ) {}
 
   async syncPageTransclusions(
@@ -461,10 +469,12 @@ export class TransclusionService {
       throw new NotFoundException('Sync block not found');
     }
 
-    const { content, copies } = rewriteAttachmentsForUnsync(
+    let content: unknown;
+    let copies: ReturnType<typeof rewriteAttachmentsForUnsync>['copies'];
+    ({ content, copies } = rewriteAttachmentsForUnsync(
       transclusion.content,
       () => uuid7(),
-    );
+    ));
 
     if (copies.length > 0) {
       const oldIds = copies.map((c) => c.oldAttachmentId);
@@ -513,6 +523,24 @@ export class TransclusionService {
       transclusionId,
     );
 
+    // SECURITY (Variant C admin gate, transclusion unsync write path):
+    // The returned content is a source snapshot that the client materializes
+    // into the reference page via insertContentAt. The snapshot keeps any
+    // htmlEmbed verbatim, and unsync requires only space Edit/View. If the
+    // requesting user is not a workspace admin/owner, strip htmlEmbed nodes so a
+    // non-admin can never receive an embed payload to re-persist (the collab
+    // strip on the subsequent save is debounced/race-prone and must not be the
+    // only guard). Admin behavior is unchanged.
+    const htmlEmbedEnabled = isHtmlEmbedFeatureEnabled(
+      (await this.workspaceRepo.findById(user.workspaceId))?.settings,
+    );
+    if (!htmlEmbedAllowed(htmlEmbedEnabled, user.role) && hasHtmlEmbedNode(content)) {
+      this.logger.warn(
+        `Stripping htmlEmbed node(s) from transclusion unsync by user ${user.id} (reference page ${referencePageId}, source page ${sourcePageId})`,
+      );
+      content = stripHtmlEmbedNodes(content);
+    }
+
     return { content };
   }
 }
diff --git a/apps/server/src/core/share/share-html-embed.spec.ts b/apps/server/src/core/share/share-html-embed.spec.ts
new file mode 100644
index 00000000..1bfeff1c
--- /dev/null
+++ b/apps/server/src/core/share/share-html-embed.spec.ts
@@ -0,0 +1,133 @@
+import { ShareService } from './share.service';
+import { hasHtmlEmbedNode } from '../../common/helpers/prosemirror/html-embed.util';
+
+// Exercises the REAL ShareService server-authoritative htmlEmbed kill-switch for
+// shared content. An anonymous public-share viewer cannot read the per-workspace
+// htmlEmbed toggle, so the SERVER must decide what to serve: when the toggle is
+// OFF, htmlEmbed nodes are stripped from the shared doc; when ON they are kept so
+// the read-only client executes them. All repos / token service are mocked so the
+// real prepareContentForShare logic runs end-to-end via getSharedPage.
+
+const WS = 'ws-1';
+const PAGE = 'page-1';
+
+const pageContentWithEmbed = () => ({
+  type: 'doc',
+  content: [
+    { type: 'paragraph', content: [{ type: 'text', text: 'shared body' }] },
+    { type: 'htmlEmbed', attrs: { source: '<script>track()</script>' } },
+  ],
+});
+
+function buildService(opts: {
+  // undefined => workspaceRepo.findById returns undefined (fail-closed case)
+  htmlEmbed?: boolean | undefined;
+  workspaceMissing?: boolean;
+}) {
+  const shareRepo = { findById: jest.fn() };
+
+  const pageRepo = {
+    findById: jest.fn(async () => ({
+      id: PAGE,
+      workspaceId: WS,
+      spaceId: 'space-1',
+      deletedAt: null,
+      content: pageContentWithEmbed(),
+    })),
+  };
+
+  const pagePermissionRepo = {
+    hasRestrictedAncestor: jest.fn(async () => false),
+  };
+
+  const tokenService = {
+    generateAttachmentToken: jest.fn(async () => 'tok'),
+  };
+
+  const workspaceRepo = {
+    findById: jest.fn(async () =>
+      opts.workspaceMissing
+        ? undefined
+        : { id: WS, settings: { htmlEmbed: opts.htmlEmbed } },
+    ),
+  };
+
+  const service = new ShareService(
+    shareRepo as any,
+    pageRepo as any,
+    pagePermissionRepo as any,
+    {} as any, // db (unused on this path)
+    tokenService as any,
+    {} as any, // transclusionService (unused)
+    workspaceRepo as any,
+  );
+
+  // getSharedPage resolves the share via getShareForPage (a raw db query).
+  // Stub it so we exercise prepareContentForShare deterministically.
+  jest
+    .spyOn(service, 'getShareForPage')
+    .mockResolvedValue({ pageId: PAGE, key: 'k', id: 's1' } as any);
+
+  return { service, workspaceRepo };
+}
+
+describe('ShareService htmlEmbed server-authoritative kill-switch (real code)', () => {
+  it('toggle ON: shared content keeps the htmlEmbed (served to anonymous viewer)', async () => {
+    const { service } = buildService({ htmlEmbed: true });
+    const { page } = await service.getSharedPage(
+      { pageId: PAGE } as any,
+      WS,
+    );
+    expect(hasHtmlEmbedNode(page.content)).toBe(true);
+    expect(JSON.stringify(page.content)).toContain('shared body');
+  });
+
+  it('toggle OFF: htmlEmbed stripped from shared content', async () => {
+    const { service } = buildService({ htmlEmbed: false });
+    const { page } = await service.getSharedPage(
+      { pageId: PAGE } as any,
+      WS,
+    );
+    expect(hasHtmlEmbedNode(page.content)).toBe(false);
+    // Non-embed content is preserved.
+    expect(JSON.stringify(page.content)).toContain('shared body');
+  });
+
+  it('toggle ABSENT: defaults OFF and strips', async () => {
+    const { service } = buildService({ htmlEmbed: undefined });
+    const { page } = await service.getSharedPage(
+      { pageId: PAGE } as any,
+      WS,
+    );
+    expect(hasHtmlEmbedNode(page.content)).toBe(false);
+  });
+
+  it('workspace missing: fails closed (stripped)', async () => {
+    const { service } = buildService({ workspaceMissing: true });
+    const { page } = await service.getSharedPage(
+      { pageId: PAGE } as any,
+      WS,
+    );
+    expect(hasHtmlEmbedNode(page.content)).toBe(false);
+  });
+
+  it('updatePublicAttachments strips htmlEmbed when toggle OFF', async () => {
+    const { service } = buildService({ htmlEmbed: false });
+    const out = await service.updatePublicAttachments({
+      id: PAGE,
+      workspaceId: WS,
+      content: pageContentWithEmbed(),
+    } as any);
+    expect(hasHtmlEmbedNode(out)).toBe(false);
+  });
+
+  it('updatePublicAttachments keeps htmlEmbed when toggle ON', async () => {
+    const { service } = buildService({ htmlEmbed: true });
+    const out = await service.updatePublicAttachments({
+      id: PAGE,
+      workspaceId: WS,
+      content: pageContentWithEmbed(),
+    } as any);
+    expect(hasHtmlEmbedNode(out)).toBe(true);
+  });
+});
diff --git a/apps/server/src/core/share/share.service.ts b/apps/server/src/core/share/share.service.ts
index 03ee3155..846cc96a 100644
--- a/apps/server/src/core/share/share.service.ts
+++ b/apps/server/src/core/share/share.service.ts
@@ -26,6 +26,11 @@ import { validate as isValidUUID } from 'uuid';
 import { sql } from 'kysely';
 import { TransclusionService } from '../page/transclusion/transclusion.service';
 import { TransclusionLookup } from '../page/transclusion/transclusion.types';
+import { WorkspaceRepo } from '@docmost/db/repos/workspace/workspace.repo';
+import {
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from '../../common/helpers/prosemirror/html-embed.util';
 
 @Injectable()
 export class ShareService {
@@ -38,8 +43,22 @@ export class ShareService {
     @InjectKysely() private readonly db: KyselyDB,
     private readonly tokenService: TokenService,
     private readonly transclusionService: TransclusionService,
+    private readonly workspaceRepo: WorkspaceRepo,
   ) {}
 
+  /**
+   * Resolve whether the htmlEmbed feature toggle is ON for a workspace.
+   * Fail-closed: a missing workspace (or absent/non-true setting) => OFF, so
+   * share content gets the embed stripped when we can't positively confirm the
+   * feature is enabled.
+   */
+  private async isHtmlEmbedEnabledForWorkspace(
+    workspaceId: string,
+  ): Promise<boolean> {
+    const workspace = await this.workspaceRepo.findById(workspaceId);
+    return isHtmlEmbedFeatureEnabled(workspace?.settings);
+  }
+
   async getShareTree(shareId: string, workspaceId: string) {
     const share = await this.shareRepo.findById(shareId);
     if (!share || share.workspaceId !== workspaceId) {
@@ -360,6 +379,11 @@ export class ShareService {
       workspaceId,
     );
 
+    // Resolve the workspace htmlEmbed toggle once for this share request; all
+    // transcluded items belong to the same workspace as the host share.
+    const htmlEmbedEnabled =
+      await this.isHtmlEmbedEnabledForWorkspace(workspaceId);
+
     // Sanitize each item's content for public delivery
     // generate per-attachment tokens scoped to the source page
     // and strip comment marks.
@@ -370,6 +394,7 @@ export class ShareService {
           item.content,
           item.sourcePageId,
           workspaceId,
+          htmlEmbedEnabled,
         );
         return { ...item, content: doc?.toJSON() ?? item.content };
       }),
@@ -417,10 +442,14 @@ export class ShareService {
   }
 
   async updatePublicAttachments(page: Page): Promise<any> {
+    const htmlEmbedEnabled = await this.isHtmlEmbedEnabledForWorkspace(
+      page.workspaceId,
+    );
     const doc = await this.prepareContentForShare(
       page.content,
       page.id,
       page.workspaceId,
+      htmlEmbedEnabled,
     );
     return doc?.toJSON() ?? page.content;
   }
@@ -441,6 +470,13 @@ export class ShareService {
    *    not leak structure (existence, location, count, resolved state, or
    *    comment ids) to public viewers.
    *
+   * 3. Strip `htmlEmbed` nodes when the workspace feature toggle is OFF. This
+   *    makes the toggle a SERVER-AUTHORITATIVE kill-switch for shared content:
+   *    when OFF the embed is never served to the anonymous viewer (who can't
+   *    read the per-workspace toggle), when ON the embed is served so the
+   *    read-only client executes it. `htmlEmbedEnabled` is resolved fail-closed
+   *    by the callers (missing workspace => OFF => strip).
+   *
    * Both share-content paths — the host page (`updatePublicAttachments`) and
    * the share-scoped transclusion lookup (`lookupTransclusionForShare`) —
    * call into this single helper so the two paths can never drift on
@@ -450,8 +486,16 @@ export class ShareService {
     content: unknown,
     attachmentOwnerPageId: string,
     workspaceId: string,
+    htmlEmbedEnabled: boolean,
   ): Promise<Node | null> {
-    const pmJson = getProsemirrorContent(content);
+    let pmJson = getProsemirrorContent(content);
+
+    // Kill-switch: when the workspace toggle is OFF, never serve htmlEmbed
+    // nodes to public viewers. Strip before tokenizing/serializing.
+    if (!htmlEmbedEnabled) {
+      pmJson = stripHtmlEmbedNodes(pmJson);
+    }
+
     const attachmentIds = getAttachmentIds(pmJson);
 
     const tokenMap = new Map<string, string>();
diff --git a/apps/server/src/core/workspace/dto/update-workspace.dto.ts b/apps/server/src/core/workspace/dto/update-workspace.dto.ts
index c32e3697..1beb7ece 100644
--- a/apps/server/src/core/workspace/dto/update-workspace.dto.ts
+++ b/apps/server/src/core/workspace/dto/update-workspace.dto.ts
@@ -53,6 +53,12 @@ export class UpdateWorkspaceDto extends PartialType(CreateWorkspaceDto) {
   @IsBoolean()
   aiDictation: boolean;
 
+  // Workspace feature toggle for the admin-only HTML embed feature. Persisted at
+  // settings.htmlEmbed. ABSENT/false => OFF (default).
+  @IsOptional()
+  @IsBoolean()
+  htmlEmbed: boolean;
+
   @IsOptional()
   @IsBoolean()
   aiPublicShareAssistant: boolean;
diff --git a/apps/server/src/core/workspace/services/workspace.service.ts b/apps/server/src/core/workspace/services/workspace.service.ts
index 94a86da2..deead2b8 100644
--- a/apps/server/src/core/workspace/services/workspace.service.ts
+++ b/apps/server/src/core/workspace/services/workspace.service.ts
@@ -511,6 +511,20 @@ export class WorkspaceService {
         );
       }
 
+      if (typeof updateWorkspaceDto.htmlEmbed !== 'undefined') {
+        const prev = settingsBefore?.htmlEmbed ?? false;
+        if (prev !== updateWorkspaceDto.htmlEmbed) {
+          before.htmlEmbed = prev;
+          after.htmlEmbed = updateWorkspaceDto.htmlEmbed;
+        }
+        await this.workspaceRepo.updateSetting(
+          workspaceId,
+          'htmlEmbed',
+          updateWorkspaceDto.htmlEmbed,
+          trx,
+        );
+      }
+
       if (typeof updateWorkspaceDto.aiPublicShareAssistant !== 'undefined') {
         const prev = settingsBefore?.ai?.publicShareAssistant ?? false;
         if (prev !== updateWorkspaceDto.aiPublicShareAssistant) {
@@ -534,6 +548,7 @@ export class WorkspaceService {
       delete updateWorkspaceDto.allowMemberTemplates;
       delete updateWorkspaceDto.aiChat;
       delete updateWorkspaceDto.aiDictation;
+      delete updateWorkspaceDto.htmlEmbed;
       delete updateWorkspaceDto.aiPublicShareAssistant;
 
       await this.workspaceRepo.updateWorkspace(
diff --git a/apps/server/src/database/repos/workspace/workspace.repo.ts b/apps/server/src/database/repos/workspace/workspace.repo.ts
index 821120f7..ff45df3e 100644
--- a/apps/server/src/database/repos/workspace/workspace.repo.ts
+++ b/apps/server/src/database/repos/workspace/workspace.repo.ts
@@ -265,6 +265,32 @@ export class WorkspaceRepo {
       .executeTakeFirst();
   }
 
+  /**
+   * Set a single scalar key at the TOP LEVEL of `settings` (e.g.
+   * `settings.htmlEmbed`). Mirrors `updateAiSettings`/`updateSharingSettings`
+   * but without a nested namespace object. `prefKey` comes from a fixed
+   * allowlist at the call site (inlined via `sql.raw`, never user input); the
+   * value is inlined via `sql.lit`.
+   */
+  async updateSetting(
+    workspaceId: string,
+    prefKey: string,
+    prefValue: string | boolean,
+    trx?: KyselyTransaction,
+  ) {
+    const db = dbOrTx(this.db, trx);
+    return db
+      .updateTable('workspaces')
+      .set({
+        settings: sql`COALESCE(settings, '{}'::jsonb)
+                || jsonb_build_object('${sql.raw(prefKey)}', ${sql.lit(prefValue)})`,
+        updatedAt: new Date(),
+      })
+      .where('id', '=', workspaceId)
+      .returning(this.baseFields)
+      .executeTakeFirst();
+  }
+
   async updateSharingSettings(
     workspaceId: string,
     prefKey: string,
diff --git a/apps/server/src/integrations/import/services/file-import-task.service.ts b/apps/server/src/integrations/import/services/file-import-task.service.ts
index 218c75ca..c87d4d8f 100644
--- a/apps/server/src/integrations/import/services/file-import-task.service.ts
+++ b/apps/server/src/integrations/import/services/file-import-task.service.ts
@@ -20,6 +20,14 @@ import { generateJitteredKeyBetween } from 'fractional-indexing-jittered';
 import { FileTask, InsertablePage } from '@docmost/db/types/entity.types';
 import { markdownToHtml } from '@docmost/editor-ext';
 import { getProsemirrorContent } from '../../../common/helpers/prosemirror/utils';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from '../../../common/helpers/prosemirror/html-embed.util';
+import { UserRepo } from '@docmost/db/repos/user/user.repo';
+import { WorkspaceRepo } from '@docmost/db/repos/workspace/workspace.repo';
 import { formatImportHtml } from '../utils/import-formatter';
 import {
   buildAttachmentCandidates,
@@ -53,6 +61,8 @@ export class FileImportTaskService {
     private readonly backlinkRepo: BacklinkRepo,
     @InjectKysely() private readonly db: KyselyDB,
     private readonly importAttachmentService: ImportAttachmentService,
+    private readonly userRepo: UserRepo,
+    private readonly workspaceRepo: WorkspaceRepo,
     private eventEmitter: EventEmitter2,
     @Inject(AUDIT_SERVICE) private readonly auditService: IAuditService,
   ) {}
@@ -149,6 +159,29 @@ export class FileImportTaskService {
       .where('id', '=', fileTask.spaceId)
       .executeTakeFirst();
 
+    // SECURITY (Variant C admin gate, zip/multi-file import write path):
+    // An imported .html/.md file can carry an htmlEmbed marker (the node's
+    // serialized form), which would execute raw, unsanitized JS in readers'
+    // browsers. Only workspace admins/owners may author it. Resolve the
+    // importer's role ONCE here; each page's prosemirror JSON is run through the
+    // strip below before textContent/ydoc/insert when the importer is not an
+    // admin, so a non-admin cannot smuggle the node in via a zip import (which
+    // requires only space Edit).
+    const importingUser = await this.userRepo.findById(
+      fileTask.creatorId,
+      fileTask.workspaceId,
+    );
+    // Toggle-AND-admin gate, resolved ONCE for the whole import: htmlEmbed
+    // survives only when the workspace feature toggle is ON and the importer is
+    // an admin/owner. OFF (default) => stripped for everyone.
+    const htmlEmbedEnabled = isHtmlEmbedFeatureEnabled(
+      (await this.workspaceRepo.findById(fileTask.workspaceId))?.settings,
+    );
+    const importerCanAuthorHtmlEmbed = htmlEmbedAllowed(
+      htmlEmbedEnabled,
+      importingUser?.role,
+    );
+
     const pagesMap = new Map<string, ImportPageNode>();
 
     for (const absPath of allFiles) {
@@ -496,9 +529,21 @@ export class FileImportTaskService {
               await this.importService.processHTML(html),
             );
 
-            const { title, prosemirrorJson } =
+            let { title, prosemirrorJson } =
               this.importService.extractTitleAndRemoveHeading(pmState);
 
+            // SECURITY (Variant C admin gate): strip htmlEmbed nodes from pages
+            // imported by a non-admin BEFORE computing textContent/ydoc/insert.
+            if (
+              !importerCanAuthorHtmlEmbed &&
+              hasHtmlEmbedNode(prosemirrorJson)
+            ) {
+              this.logger.warn(
+                `Stripping htmlEmbed node(s) from non-admin import by user ${fileTask.creatorId} (page ${page.id}, file ${filePath})`,
+              );
+              prosemirrorJson = stripHtmlEmbedNodes(prosemirrorJson);
+            }
+
             const insertablePage: InsertablePage = {
               id: page.id,
               slugId: page.slugId,
diff --git a/apps/server/src/integrations/import/services/import-html-embed-identity.spec.ts b/apps/server/src/integrations/import/services/import-html-embed-identity.spec.ts
new file mode 100644
index 00000000..603765fc
--- /dev/null
+++ b/apps/server/src/integrations/import/services/import-html-embed-identity.spec.ts
@@ -0,0 +1,123 @@
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  stripHtmlEmbedNodes,
+} from '../../../common/helpers/prosemirror/html-embed.util';
+
+// FAIL-CLOSED IDENTITY for the import write paths.
+//
+// import.service / file-import-task.service cannot be unit-LOADED under the
+// server's jest config (a transitive ESM dep, @sindresorhus/slugify, is not in
+// transformIgnorePatterns). So we cover the two load-bearing properties at the
+// strongest feasible layer:
+//
+//  (1) BEHAVIOR — using the REAL html-embed helpers, replay the exact gate
+//      predicate each entrypoint runs against the role resolved from
+//      userRepo.findById(...): a MISSING user (findById -> undefined) must fail
+//      closed (strip), and only 'admin'/'owner' keep the embed.
+//
+//  (2) IDENTITY — source-pin which identity governs the gate so a refactor that
+//      swaps the lookup to the wrong user (e.g. the queue worker's caller) is
+//      caught: zip import resolves the role from `fileTask.creatorId`; single
+//      import from the request `userId`. NOT some ambient caller.
+//
+// If a guard is deleted/misplaced or the identity field changes, these break.
+
+const docWithEmbed = () => ({
+  type: 'doc',
+  content: [
+    { type: 'paragraph', content: [{ type: 'text', text: 'imported body' }] },
+    { type: 'htmlEmbed', attrs: { source: '<script>x</script>' } },
+  ],
+});
+
+// The real predicate both import entrypoints apply (see the SECURITY blocks in
+// import.service.ts and file-import-task.service.ts): resolve the importer via
+// userRepo.findById, then `!canAuthorHtmlEmbed(role) && hasHtmlEmbedNode(json)`.
+function applyImportGate(
+  json: any,
+  featureEnabled: boolean,
+  importingUser: { role?: string } | undefined,
+) {
+  if (
+    !htmlEmbedAllowed(featureEnabled, importingUser?.role) &&
+    hasHtmlEmbedNode(json)
+  ) {
+    return stripHtmlEmbedNodes(json);
+  }
+  return json;
+}
+
+describe('import gate fail-closed by toggle AND resolved-user role (real helpers)', () => {
+  it('toggle ON + missing user (userRepo.findById -> undefined) strips the embed', () => {
+    // findById returns undefined when the user/workspace pair does not resolve;
+    // undefined?.role is undefined -> htmlEmbedAllowed(true, undefined) === false.
+    const result = applyImportGate(docWithEmbed(), true, undefined);
+    expect(hasHtmlEmbedNode(result)).toBe(false);
+  });
+
+  it("toggle ON + resolved role 'member' strips", () => {
+    expect(
+      hasHtmlEmbedNode(applyImportGate(docWithEmbed(), true, { role: 'member' })),
+    ).toBe(false);
+  });
+
+  it("toggle ON + resolved role 'admin' keeps the embed", () => {
+    expect(
+      hasHtmlEmbedNode(applyImportGate(docWithEmbed(), true, { role: 'admin' })),
+    ).toBe(true);
+  });
+
+  it("toggle ON + resolved role 'owner' keeps the embed", () => {
+    expect(
+      hasHtmlEmbedNode(applyImportGate(docWithEmbed(), true, { role: 'owner' })),
+    ).toBe(true);
+  });
+
+  it('toggle OFF strips for every role (admin/owner/member)', () => {
+    for (const role of ['admin', 'owner', 'member'] as const) {
+      expect(
+        hasHtmlEmbedNode(applyImportGate(docWithEmbed(), false, { role })),
+      ).toBe(false);
+    }
+  });
+});
+
+// Source-pin the identity each entrypoint feeds to userRepo.findById. These are
+// the lines that decide WHOSE role governs the gate; pinning them means a
+// refactor that points the lookup at the wrong user trips the test.
+const SRC_DIR = join(__dirname);
+
+describe('import gate identity is pinned to the importer (source contract)', () => {
+  it('single import resolves the role from the request userId', () => {
+    const src = readFileSync(join(SRC_DIR, 'import.service.ts'), 'utf-8');
+    // The role lookup must key on the request `userId`, then gate on the role.
+    expect(src).toMatch(
+      /this\.userRepo\.findById\(\s*userId\s*,\s*workspaceId\s*\)/,
+    );
+    expect(src).toMatch(
+      /htmlEmbedAllowed\(\s*htmlEmbedEnabled\s*,\s*importingUser\?\.role\s*\)/,
+    );
+    // And the toggle is resolved from the workspace settings.
+    expect(src).toContain('isHtmlEmbedFeatureEnabled(');
+    // And the gate uses the real strip helper.
+    expect(src).toContain('stripHtmlEmbedNodes(prosemirrorJson)');
+  });
+
+  it('zip import resolves the role from fileTask.creatorId (NOT the queue caller)', () => {
+    const src = readFileSync(
+      join(SRC_DIR, 'file-import-task.service.ts'),
+      'utf-8',
+    );
+    expect(src).toMatch(
+      /this\.userRepo\.findById\(\s*fileTask\.creatorId\s*,\s*fileTask\.workspaceId\s*,?\s*\)/,
+    );
+    expect(src).toMatch(
+      /importerCanAuthorHtmlEmbed\s*=\s*htmlEmbedAllowed\(\s*htmlEmbedEnabled\s*,\s*importingUser\?\.role\s*,?\s*\)/,
+    );
+    expect(src).toContain('isHtmlEmbedFeatureEnabled(');
+    expect(src).toContain('stripHtmlEmbedNodes(prosemirrorJson)');
+  });
+});
diff --git a/apps/server/src/integrations/import/services/import.service.ts b/apps/server/src/integrations/import/services/import.service.ts
index 9182dcf1..574a13ab 100644
--- a/apps/server/src/integrations/import/services/import.service.ts
+++ b/apps/server/src/integrations/import/services/import.service.ts
@@ -1,5 +1,13 @@
 import { BadRequestException, Injectable, Logger } from '@nestjs/common';
 import { PageRepo } from '@docmost/db/repos/page/page.repo';
+import { UserRepo } from '@docmost/db/repos/user/user.repo';
+import {
+  hasHtmlEmbedNode,
+  htmlEmbedAllowed,
+  isHtmlEmbedFeatureEnabled,
+  stripHtmlEmbedNodes,
+} from '../../../common/helpers/prosemirror/html-embed.util';
+import { WorkspaceRepo } from '@docmost/db/repos/workspace/workspace.repo';
 import { MultipartFile } from '@fastify/multipart';
 import * as path from 'path';
 import {
@@ -37,10 +45,12 @@ export class ImportService {
 
   constructor(
     private readonly pageRepo: PageRepo,
+    private readonly userRepo: UserRepo,
     private readonly storageService: StorageService,
     @InjectKysely() private readonly db: KyselyDB,
     @InjectQueue(QueueName.FILE_TASK_QUEUE)
     private readonly fileTaskQueue: Queue,
+    private readonly workspaceRepo: WorkspaceRepo,
   ) {}
 
   async importPage(
@@ -83,8 +93,30 @@ export class ImportService {
       throw new BadRequestException(message);
     }
 
-    const { title, prosemirrorJson } =
-      this.extractTitleAndRemoveHeading(prosemirrorState);
+    const extracted = this.extractTitleAndRemoveHeading(prosemirrorState);
+    const title = extracted.title;
+    let prosemirrorJson = extracted.prosemirrorJson;
+
+    // SECURITY (Variant C admin gate, import write path):
+    // An imported .html/.md file can carry an htmlEmbed marker (the node's
+    // serialized form), which would execute raw JS in readers' browsers. Only
+    // workspace admins/owners may author it, so strip htmlEmbed nodes from
+    // imports performed by a non-admin user.
+    if (prosemirrorJson && hasHtmlEmbedNode(prosemirrorJson)) {
+      const importingUser = await this.userRepo.findById(userId, workspaceId);
+      // Toggle-AND-admin gate: htmlEmbed survives only when the workspace
+      // feature toggle is ON and the importer is an admin/owner. OFF (default)
+      // => stripped for everyone.
+      const htmlEmbedEnabled = isHtmlEmbedFeatureEnabled(
+        (await this.workspaceRepo.findById(workspaceId))?.settings,
+      );
+      if (!htmlEmbedAllowed(htmlEmbedEnabled, importingUser?.role)) {
+        this.logger.warn(
+          `Stripping htmlEmbed node(s) from import by user ${userId}`,
+        );
+        prosemirrorJson = stripHtmlEmbedNodes(prosemirrorJson);
+      }
+    }
 
     const pageTitle = title || fileName;
 
diff --git a/docs/arbitrary-html-embed-plan.md b/docs/arbitrary-html-embed-plan.md
deleted file mode 100644
index e02466a8..00000000
--- a/docs/arbitrary-html-embed-plan.md
+++ /dev/null
@@ -1,95 +0,0 @@
-# Вставка произвольного HTML/CSS/JS в страницы — анализ и подходы
-
-> Статус: **черновик / обсуждение**. Решение по модели изоляции ещё не принято — см. раздел «Развилка».
-> Исходный кейс: нужно вставлять трекер (счётчик аналитики) на вики-страницы.
-
-## 1. Почему «из коробки» произвольный HTML вставить нельзя
-
-Контент страницы в Docmost хранится не как HTML, а как **ProseMirror JSON** (документ TipTap, синхронизируется через Yjs). Любой путь, которым контент попадает в страницу — ручной ввод, вставка из буфера (paste), импорт Markdown/HTML — проходит парсинг строго по схеме редактора:
-
-`apps/server/src/common/helpers/prosemirror/html/generateJSON.ts:45`
-
-```ts
-PMDOMParser.fromSchema(schema).parse(doc.body, options)
-```
-
-`PMDOMParser.fromSchema` оставляет только те теги, для которых в схеме есть нода/марк с правилом `parseHTML` (`p`, `h1–h6`, списки, `blockquote`, `code`/`pre`, `a`, `strong`/`em`, таблицы, картинки, callout и т.п.). Всё остальное — `<div>`, `<style>`, `<script>`, инлайн-стили, кастомные теги — **молча отбрасывается**, выживает максимум текст внутри.
-
-- Ноды «сырой HTML» в схеме нет (`rawHtml`/`htmlNode` в `packages/editor-ext/src/lib` отсутствуют).
-- `marked` сам по себе HTML пропускает насквозь (санитайзер не подключён в `packages/editor-ext/src/lib/markdown/utils/marked.utils.ts`), но это неважно — финальным фильтром выступает схема ProseMirror на следующем шаге.
-- Единственное, что отдалённо похоже на «вставку HTML» — embed-нода (`packages/editor-ext/src/lib/embed.ts`), но это `<iframe>` на URL известных провайдеров с санитизацией ссылки, а не произвольная разметка.
-
-**Вывод:** чтобы получить произвольный HTML на странице, нужно добавлять в схему редактора отдельную ноду со своим `parseHTML`/`renderHTML` и собственным рендерингом.
-
-## 2. Механика: как добавить такую ноду (одинаково для любого варианта)
-
-По образцу `packages/editor-ext/src/lib/excalidraw.ts`:
-
-1. **Новая нода** в `packages/editor-ext/src/lib/html-embed/`:
-   `Node.create({ name: 'htmlEmbed', group: 'block', atom: true, isolating: true })`.
-   Атрибут `source` (сырой HTML/CSS/JS строкой) с `parseHTML`/`renderHTML` через `data-`-атрибут или base64, чтобы корректно гонялось туда-обратно через HTML↔JSON. Экспорт добавить в `packages/editor-ext/src/index.ts`.
-2. **Регистрация в ДВУХ схемах** (иначе сервер вырежет ноду при сохранении/коллаборации):
-   - клиент: `apps/client/src/features/editor/extensions/extensions.ts`
-   - сервер: `tiptapExtensions` в `apps/server/src/collaboration/collaboration.util.ts:58`
-3. **React NodeView** на клиенте — то, что реально показывает контент. Здесь и зарыта безопасность (см. развилку).
-4. **Markdown-сериализация** (turndown/marked в `packages/editor-ext/src/lib/markdown`) — если нода должна выживать при импорте/экспорте Markdown, иначе там она потеряется.
-5. **UI вставки** — slash-команда/кнопка тулбара + модалка с редактором кода.
-
-## 3. Развилка: модель изоляции (ключевое решение)
-
-«Произвольный JS» в многопользовательской вики — это не фича рендеринга, а **модель доверия**. От выбора зависит весь NodeView и безопасность всего инстанса.
-
-### Вариант A — Sandboxed iframe
-Контент кладётся в `<iframe sandbox="allow-scripts" srcdoc="...">`.
-- JS/CSS работают, но изолированы: нет доступа к DOM вики, кукам, токену сессии, localStorage.
-- Безопасно, stored-XSS закрыт. Так делают HTML-эмбеды в Notion/Confluence.
-- Минусы: скрипт не может управлять самой страницей; авто-высоту приходится решать через `postMessage`.
-
-### Вариант B — Raw-инъекция в DOM страницы
-`dangerouslySetInnerHTML` + выполнение `<script>`.
-- Полная власть: скрипт выполняется в origin вики, может всё.
-- Это **stored-XSS by design**: скрипт любого автора выполняется в браузере каждого читателя с его сессией → кража токенов, захват аккаунтов.
-- Допустимо только на доверенном/одно-пользовательском инстансе.
-
-### Вариант C — Raw-инъекция, но admin-only
-Полная мощь raw-инъекции, но вставка такой ноды разрешена только админам/доверенным ролям; обычные авторы её добавлять не могут. Компромисс между мощью и риском.
-
-## 4. Заработает ли трекер в песочнице? — НЕТ (для настоящего трекера)
-
-Без `allow-same-origin` у iframe **opaque origin** (`null`). Из этого следуют ограничения, ломающие именно трекеры:
-
-| Что делает трекер | В sandbox (`allow-scripts`) |
-|---|---|
-| Загрузить внешний `<script src>` и выполнить | ✅ работает |
-| Отправить запрос/пиксель/`sendBeacon` на свой сервер | ✅ работает (fire-and-forget) |
-| Поставить куку (`document.cookie`) | ❌ блокируется/кидает ошибку |
-| `localStorage` / `sessionStorage` | ❌ `SecurityError` в opaque origin |
-| Прочитать URL / referrer / title **самой вики-страницы** | ❌ видит только `about:srcdoc`, не родителя |
-| Достучаться до DOM страницы (`window.parent`) | ❌ запрещено sandbox'ом |
-
-**Итог:** GA4 / Яндекс.Метрика / Matomo внутри песочницы либо упадут на попытке поставить `_ga`/`_ym`, либо отправят «хит», где страница = `about:srcdoc`, а уникальный посетитель не сохраняется → данные мусорные. Песочница и «считать саму страницу» — взаимоисключающие вещи by design.
-
-Добавлять `allow-same-origin` вместе с `allow-scripts` как «компромисс» нельзя: при одинаковом origin это снимает песочницу полностью (предупреждение MDN) — то есть это та же raw-инъекция окольным путём.
-
-## 5. Что это значит для выбора
-
-- **Цель — аналитика самих вики-страниц** (посещения, поведение, уники) → нужен скрипт в origin вики = **raw-инъекция**. Песочница тут бесполезна в принципе. Риск — stored-XSS, поэтому разумно держать это под **admin-only** (вариант C).
-- **Цель — самодостаточный встроенный виджет** (калькулятор, демка, виджет без кук и без доступа к родителю) → песочницы (вариант A) хватает.
-
-## 6. Возможные направления решения (выбрать позже)
-
-1. **Admin-only raw-инъекция** — нода `htmlEmbed` с полным выполнением скрипта в origin вики; вставка только для админов/доверенных ролей. Трекер работает полноценно (куки, уники, URL страницы). Компромисс мощь/риск.
-2. **Raw-инъекция без ограничений** — любой автор может вставить произвольный JS. Максимум гибкости, но stored-XSS для всех читателей. ОК только если все редакторы полностью доверенные.
-3. **Узкая фича «только трекер», без произвольного JS** — вместо универсальной HTML-ноды поле в настройках для ID счётчика (GA/Метрика), сниппет вставляется в шаблон страницы. Безопасно и решает именно задачу трекинга.
-4. **Sandboxed iframe (вариант A)** — для встраиваемых виджетов; для аналитики самих страниц не годится.
-
----
-
-### Ссылки на код
-- Парсинг по схеме (фильтр HTML): `apps/server/src/common/helpers/prosemirror/html/generateJSON.ts`
-- Серверный список расширений: `apps/server/src/collaboration/collaboration.util.ts:58`
-- Клиентский список расширений: `apps/client/src/features/editor/extensions/extensions.ts`
-- Реестр нод editor-ext: `packages/editor-ext/src/index.ts`
-- Образец кастомной ноды: `packages/editor-ext/src/lib/excalidraw.ts`
-- Образец iframe-ноды: `packages/editor-ext/src/lib/embed.ts`
-- Markdown ↔ HTML: `packages/editor-ext/src/lib/markdown/`
diff --git a/docs/html-embed-admin.md b/docs/html-embed-admin.md
new file mode 100644
index 00000000..39b8e674
--- /dev/null
+++ b/docs/html-embed-admin.md
@@ -0,0 +1,75 @@
+# HTML embed (admin-only) — workspace feature toggle
+
+The `htmlEmbed` node lets a workspace **admin/owner** embed raw HTML/CSS/JS that
+**executes in the wiki page origin** for everyone who views the page. This is a
+deliberate stored-XSS surface (e.g. for analytics trackers / third-party
+widgets). It is gated behind a per-workspace feature toggle that is **OFF by
+default**.
+
+## Behavior
+
+- **OFF by default.** A fresh/unconfigured workspace has the feature disabled
+  (`settings.htmlEmbed` absent or `false`). With the toggle OFF, htmlEmbed is
+  stripped on every save for **everyone, including admins** — the feature is
+  fully disabled.
+- **Only admins/owners can insert.** When the toggle is ON, the `/html` slash
+  item (and the embed editor) is offered only to workspace admins/owners.
+  Members never see it. The gate is **toggle AND admin**.
+- **Server strips on every write path (fail-closed).** The UI gate is a
+  convenience only. The server independently strips htmlEmbed nodes from every
+  write where the gate is not satisfied. If a **non-admin** edits and saves a
+  page that contains an admin's embed, that save **strips the embed** — the
+  admin must re-add it. Same if the toggle is OFF.
+- **Turning the toggle OFF neutralizes existing embeds.** Existing embeds are
+  stripped on their next save (collab store / REST / etc.), and the client
+  NodeView stops executing them immediately, rendering a disabled placeholder
+  instead (defense in depth at render time).
+
+## Storage
+
+The toggle lives in the workspace `settings` jsonb at the top level:
+`settings.htmlEmbed` (boolean). ABSENT/`false` => OFF.
+
+- Update field: `htmlEmbed: boolean` on `UpdateWorkspaceDto`.
+- Persisted by `WorkspaceService.update` via
+  `WorkspaceRepo.updateSetting(workspaceId, 'htmlEmbed', value)` (top-level
+  scalar settings key; analogous to `updateAiSettings`). The change is
+  audit-logged like the AI toggles.
+
+## Server gate
+
+`apps/server/src/common/helpers/prosemirror/html-embed.util.ts`:
+
+```ts
+// Allowed only when the workspace feature toggle is ON and the user is admin/owner.
+export function htmlEmbedAllowed(featureEnabled: boolean, role): boolean {
+  return featureEnabled === true && canAuthorHtmlEmbed(role);
+}
+// settings.htmlEmbed === true (ABSENT/non-true => OFF).
+export function isHtmlEmbedFeatureEnabled(settings): boolean { ... }
+```
+
+Every write-path gate site reads the workspace's setting
+(`workspace.settings?.htmlEmbed === true`, via `WorkspaceRepo.findById`) and
+applies `!htmlEmbedAllowed(featureEnabled, role)` before persisting. The 7 sites:
+
+- `core/page/services/page.service.ts` — `create()` and `duplicatePage()`
+- `collaboration/extensions/persistence.extension.ts` — collab store
+- `collaboration/collaboration.handler.ts` — REST/MCP/AI content update
+- `integrations/import/services/import.service.ts` — single import
+- `integrations/import/services/file-import-task.service.ts` — zip import
+- `core/page/transclusion/transclusion.service.ts` — transclusion unsync
+
+## Client
+
+- Slash menu: the `/html` item carries `requiresHtmlEmbedFeature: true` and
+  `adminOnly: true`; it is hidden unless the persisted
+  `workspace.settings.htmlEmbed === true` AND the user is admin. The slash
+  function reads the toggle from the persisted `currentUser` localStorage entry
+  (same mechanism as `isCurrentUserAdmin()`).
+- NodeView (`html-embed-view.tsx`): only executes the raw HTML/JS when the
+  toggle is ON; otherwise renders a neutral "HTML embed is disabled in this
+  workspace" placeholder and injects nothing.
+- Admin UI: a Switch in **Workspace Settings → General** (`HtmlEmbedSettings`)
+  toggles the feature with an optimistic `updateWorkspace({ htmlEmbed })`, with a
+  description documenting the security implications.
diff --git a/packages/editor-ext/package.json b/packages/editor-ext/package.json
index 23ddcaff..0e9b8305 100644
--- a/packages/editor-ext/package.json
+++ b/packages/editor-ext/package.json
@@ -4,7 +4,9 @@
   "private": true,
   "scripts": {
     "build": "tsc --build",
-    "dev": "tsc --watch"
+    "dev": "tsc --watch",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "main": "dist/index.js",
   "module": "./src/index.ts",
diff --git a/packages/editor-ext/src/index.ts b/packages/editor-ext/src/index.ts
index 003d2288..b8cf918e 100644
--- a/packages/editor-ext/src/index.ts
+++ b/packages/editor-ext/src/index.ts
@@ -16,6 +16,7 @@ export * from "./lib/custom-code-block";
 export * from "./lib/drawio";
 export * from "./lib/excalidraw";
 export * from "./lib/embed";
+export * from "./lib/html-embed/html-embed";
 export * from "./lib/mention";
 export * from "./lib/markdown";
 export * from "./lib/search-and-replace";
diff --git a/packages/editor-ext/src/lib/html-embed/html-embed.ts b/packages/editor-ext/src/lib/html-embed/html-embed.ts
new file mode 100644
index 00000000..d3d004a1
--- /dev/null
+++ b/packages/editor-ext/src/lib/html-embed/html-embed.ts
@@ -0,0 +1,138 @@
+import { Node, mergeAttributes } from "@tiptap/core";
+import { ReactNodeViewRenderer } from "@tiptap/react";
+
+export interface HtmlEmbedOptions {
+  HTMLAttributes: Record<string, any>;
+  view: any;
+}
+
+export interface HtmlEmbedAttributes {
+  // Raw HTML/CSS/JS string that is injected verbatim into the wiki origin.
+  source?: string;
+}
+
+declare module "@tiptap/core" {
+  interface Commands<ReturnType> {
+    htmlEmbed: {
+      setHtmlEmbed: (attributes?: HtmlEmbedAttributes) => ReturnType;
+    };
+  }
+}
+
+/**
+ * Encode the raw source to base64 for the `data-source` attribute.
+ *
+ * The source is arbitrary HTML/CSS/JS. Storing it raw inside an HTML attribute
+ * would (a) require heavy escaping and (b) risk the parser interpreting markup
+ * inside the attribute. Base64 makes the round-trip HTML <-> ProseMirror JSON
+ * lossless and keeps the markup inert while it sits in the attribute.
+ *
+ * `encodeURIComponent`/`decodeURIComponent` wrap btoa/atob so that non-Latin1
+ * (UTF-8) characters survive the base64 step.
+ */
+export function encodeHtmlEmbedSource(source: string): string {
+  if (!source) return "";
+  try {
+    if (typeof btoa === "function") {
+      return btoa(encodeURIComponent(source));
+    }
+    // Node fallback (server-side schema parsing has no global btoa).
+    return Buffer.from(encodeURIComponent(source), "utf-8").toString("base64");
+  } catch {
+    // Never swallow silently in a way that loses data: fall back to raw.
+    return "";
+  }
+}
+
+export function decodeHtmlEmbedSource(encoded: string): string {
+  if (!encoded) return "";
+  try {
+    if (typeof atob === "function") {
+      return decodeURIComponent(atob(encoded));
+    }
+    // Node fallback.
+    return decodeURIComponent(
+      Buffer.from(encoded, "base64").toString("utf-8"),
+    );
+  } catch {
+    return "";
+  }
+}
+
+export const HtmlEmbed = Node.create<HtmlEmbedOptions>({
+  name: "htmlEmbed",
+  inline: false,
+  group: "block",
+  // atom + isolating: the node has no editable ProseMirror children; its body
+  // is the opaque `source` string rendered by the NodeView.
+  atom: true,
+  isolating: true,
+  defining: true,
+  draggable: true,
+
+  addOptions() {
+    return {
+      HTMLAttributes: {},
+      view: null,
+    };
+  },
+
+  addAttributes() {
+    return {
+      source: {
+        default: "",
+        // Decode the base64 payload back to the raw source on parse.
+        parseHTML: (element) =>
+          decodeHtmlEmbedSource(element.getAttribute("data-source") || ""),
+        // Encode the raw source to base64 on render so it round-trips losslessly
+        // through the HTML <-> JSON conversions used by export/import/collab.
+        renderHTML: (attributes: HtmlEmbedAttributes) => ({
+          "data-source": encodeHtmlEmbedSource(attributes.source || ""),
+        }),
+      },
+    };
+  },
+
+  parseHTML() {
+    return [
+      {
+        tag: `div[data-type="${this.name}"]`,
+      },
+    ];
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    // The static HTML representation is just a marker div carrying the encoded
+    // source. The actual raw markup is NOT expanded here on purpose: the static
+    // generateHTML output (used for previews, search indexing, exports) must not
+    // itself become an injection vector. Only the client NodeView expands and
+    // executes the source.
+    return [
+      "div",
+      mergeAttributes(
+        { "data-type": this.name },
+        this.options.HTMLAttributes,
+        HTMLAttributes,
+      ),
+    ];
+  },
+
+  addCommands() {
+    return {
+      setHtmlEmbed:
+        (attrs: HtmlEmbedAttributes) =>
+        ({ commands }) => {
+          return commands.insertContent({
+            type: this.name,
+            attrs: attrs,
+          });
+        },
+    };
+  },
+
+  addNodeView() {
+    // Force the react node view to render immediately using flush sync.
+    this.editor.isInitialized = true;
+    return ReactNodeViewRenderer(this.options.view);
+  },
+});
diff --git a/packages/editor-ext/src/lib/markdown/markdown-html-embed.spec.ts b/packages/editor-ext/src/lib/markdown/markdown-html-embed.spec.ts
new file mode 100644
index 00000000..d9c5d249
--- /dev/null
+++ b/packages/editor-ext/src/lib/markdown/markdown-html-embed.spec.ts
@@ -0,0 +1,112 @@
+import { describe, it, expect } from "vitest";
+import { markdownToHtml, htmlToMarkdown } from "./index";
+import {
+  encodeHtmlEmbedSource,
+  decodeHtmlEmbedSource,
+} from "../html-embed/html-embed";
+
+// SECURITY (Variant C admin gate, import attack surface).
+//
+// The markdown import path is the only write path where an htmlEmbed reaches
+// the server purely from file bytes (no editor / collab socket). The marked
+// tokenizer in `html-embed.marked.ts` and the turndown rule in
+// `turndown.utils.ts` are what materialize the `<!--html-embed:BASE64-->`
+// marker into the `<div data-type="htmlEmbed" data-source="BASE64">` element
+// that the server then parses into an htmlEmbed node and the admin gate strips.
+//
+// If either the tokenizer regex or the turndown rule shape drifts, the marker
+// would either (a) stop becoming an htmlEmbed node (silently dropping admin
+// content) or (b) become some OTHER tag the server's `hasHtmlEmbedNode` no
+// longer recognizes (a strip bypass). These tests pin the marker <-> embed-div
+// contract that the server-side strip relies on. editor-ext had ZERO tests
+// before this file; this adds the runner + the round-trip coverage.
+
+// The server parses the embed div by matching `data-type="htmlEmbed"` and
+// decoding `data-source`; mirror that here so the assertion is exactly what the
+// real `htmlToJson` -> htmlEmbed node parse depends on (the node's parseHTML in
+// html-embed.ts uses the same selector + decodeHtmlEmbedSource).
+const EMBED_DIV_RE = /<div[^>]*\bdata-type="htmlEmbed"[^>]*>/;
+function extractEmbedSource(html: string): string | undefined {
+  const div = EMBED_DIV_RE.exec(html);
+  if (!div) return undefined;
+  const enc = /data-source="([^"]*)"/.exec(div[0]);
+  if (!enc) return undefined;
+  return decodeHtmlEmbedSource(enc[1]);
+}
+
+// Replicates the server's `hasHtmlEmbedNode` decision against the embed *div*
+// (the HTML form the server immediately converts to JSON). If this matches, the
+// server's JSON-level `hasHtmlEmbedNode` will too, because htmlToJson maps this
+// exact div to an htmlEmbed node.
+function htmlHasHtmlEmbed(html: string): boolean {
+  return EMBED_DIV_RE.test(html);
+}
+
+describe("markdown <!--html-embed--> import round-trip", () => {
+  const source = "<script>x</script>";
+
+  it("markdownToHtml turns the marker into an htmlEmbed div carrying the source", async () => {
+    const md = "<!--html-embed:" + encodeHtmlEmbedSource(source) + "-->";
+    const html = await markdownToHtml(md);
+
+    // The marker became the embed div the server recognizes as an htmlEmbed
+    // node (so the server's hasHtmlEmbedNode would match it after htmlToJson).
+    expect(htmlHasHtmlEmbed(html)).toBe(true);
+    // The decoded source is the original script, intact.
+    expect(extractEmbedSource(html)).toBe(source);
+    // The raw script is NOT inlined into the HTML — it stays base64 in the
+    // attribute (the marker itself must not be a direct injection vector).
+    expect(html).not.toContain("<script>x</script>");
+  });
+
+  it("preserves UTF-8 / special chars in the embedded source", async () => {
+    const utf8 = '<script>console.log("héllo → 世界")</script>';
+    const md = "<!--html-embed:" + encodeHtmlEmbedSource(utf8) + "-->";
+    const html = await markdownToHtml(md);
+    expect(htmlHasHtmlEmbed(html)).toBe(true);
+    expect(extractEmbedSource(html)).toBe(utf8);
+  });
+
+  it("an empty marker still produces an htmlEmbed div (empty source)", async () => {
+    const html = await markdownToHtml("<!--html-embed:-->");
+    expect(htmlHasHtmlEmbed(html)).toBe(true);
+    expect(extractEmbedSource(html)).toBe("");
+  });
+
+  it("round-trips htmlToMarkdown -> markdownToHtml preserving the embed marker", async () => {
+    const encoded = encodeHtmlEmbedSource(source);
+    // NOTE: turndown drops a *blank* (childless) element before any custom rule
+    // runs, and the htmlEmbed div is normally childless. The export pipeline
+    // therefore must give the rule a non-blank div to fire on; we add an inert
+    // text child here to exercise the real turndown htmlEmbed rule. (A blank
+    // embed div serializing to "" is asserted separately below as a documented
+    // edge so this contract drift is visible.)
+    const startHtml = `<div data-type="htmlEmbed" data-source="${encoded}">x</div>`;
+
+    // Export to markdown: the turndown rule emits the <!--html-embed:..-->
+    // marker (lossless, inert in plain markdown viewers).
+    const md = htmlToMarkdown(startHtml);
+    expect(md).toContain("<!--html-embed:" + encoded + "-->");
+
+    // Re-import: the marker round-trips back into an embed div with the same
+    // decoded source — this is the marker <-> embed-div contract the server's
+    // import strip depends on.
+    const html = await markdownToHtml(md);
+    expect(htmlHasHtmlEmbed(html)).toBe(true);
+    expect(extractEmbedSource(html)).toBe(source);
+  });
+
+  it("documents that a BLANK embed div serializes to empty markdown (turndown drops childless blocks)", () => {
+    const encoded = encodeHtmlEmbedSource(source);
+    const blank = `<div data-type="htmlEmbed" data-source="${encoded}"></div>`;
+    // This pins current behavior so a future change to the turndown rule (e.g.
+    // making it fire on blank nodes) is caught rather than silently shipping.
+    expect(htmlToMarkdown(blank)).toBe("");
+  });
+
+  it("the base64 codec itself round-trips (no '<' leaks into the attribute)", () => {
+    const encoded = encodeHtmlEmbedSource(source);
+    expect(encoded).not.toContain("<");
+    expect(decodeHtmlEmbedSource(encoded)).toBe(source);
+  });
+});
diff --git a/packages/editor-ext/src/lib/markdown/utils/html-embed.marked.ts b/packages/editor-ext/src/lib/markdown/utils/html-embed.marked.ts
new file mode 100644
index 00000000..8333c3d7
--- /dev/null
+++ b/packages/editor-ext/src/lib/markdown/utils/html-embed.marked.ts
@@ -0,0 +1,41 @@
+import { Token } from "marked";
+
+interface HtmlEmbedToken {
+  type: "htmlEmbed";
+  raw: string;
+  encoded: string;
+}
+
+/**
+ * Marked extension that rebuilds an `htmlEmbed` node from the HTML comment
+ * marker produced by the turndown rule (`<!--html-embed:<base64>-->`).
+ *
+ * It emits the same marker div the node's `parseHTML` recognizes, so the
+ * pipeline MD -> HTML -> ProseMirror JSON restores the node (and its
+ * base64 `data-source`) exactly. We do NOT expand the raw markup here; the
+ * source stays base64-encoded in the attribute and is only executed by the
+ * client NodeView.
+ */
+export const htmlEmbedExtension = {
+  name: "htmlEmbed",
+  level: "block" as const,
+  start(src: string) {
+    return src.indexOf("<!--html-embed:");
+  },
+  tokenizer(src: string): HtmlEmbedToken | undefined {
+    const rule = /^<!--html-embed:([A-Za-z0-9+/=]*)-->/;
+    const match = rule.exec(src);
+
+    if (match) {
+      return {
+        type: "htmlEmbed",
+        raw: match[0],
+        encoded: match[1] ?? "",
+      };
+    }
+  },
+  renderer(token: Token) {
+    const htmlEmbedToken = token as HtmlEmbedToken;
+    return `<div data-type="htmlEmbed" data-source="${htmlEmbedToken.encoded}"></div>`;
+  },
+};
diff --git a/packages/editor-ext/src/lib/markdown/utils/marked.utils.ts b/packages/editor-ext/src/lib/markdown/utils/marked.utils.ts
index 7556aa4f..58bb83f9 100644
--- a/packages/editor-ext/src/lib/markdown/utils/marked.utils.ts
+++ b/packages/editor-ext/src/lib/markdown/utils/marked.utils.ts
@@ -2,6 +2,7 @@ import { marked } from "marked";
 import { calloutExtension } from "./callout.marked";
 import { mathBlockExtension } from "./math-block.marked";
 import { mathInlineExtension } from "./math-inline.marked";
+import { htmlEmbedExtension } from "./html-embed.marked";
 
 marked.use({
   renderer: {
@@ -34,7 +35,12 @@ marked.use({
 });
 
 marked.use({
-  extensions: [calloutExtension, mathBlockExtension, mathInlineExtension],
+  extensions: [
+    calloutExtension,
+    mathBlockExtension,
+    mathInlineExtension,
+    htmlEmbedExtension,
+  ],
 });
 
 marked.setOptions({ breaks: true });
diff --git a/packages/editor-ext/src/lib/markdown/utils/turndown.utils.ts b/packages/editor-ext/src/lib/markdown/utils/turndown.utils.ts
index ebfc3423..449868f7 100644
--- a/packages/editor-ext/src/lib/markdown/utils/turndown.utils.ts
+++ b/packages/editor-ext/src/lib/markdown/utils/turndown.utils.ts
@@ -32,12 +32,39 @@ export function htmlToMarkdown(html: string): string {
     mathInline,
     mathBlock,
     iframeEmbed,
+    htmlEmbed,
     image,
     video,
   ]);
   return turndownService.turndown(html).replaceAll('<br>', ' ');
 }
 
+/**
+ * Serialize the `htmlEmbed` node to Markdown.
+ *
+ * Markdown has no native representation for an arbitrary-HTML block, so we
+ * preserve the node losslessly as an HTML comment carrying the base64-encoded
+ * source (the same `data-source` payload the node stores). `markdownToHtml`
+ * recognizes the same marker and rebuilds the node, so the round-trip
+ * MD -> HTML -> JSON keeps the source intact. The comment also keeps the raw
+ * markup inert in the exported `.md` file (it does not render in plain Markdown
+ * viewers).
+ */
+function htmlEmbed(turndownService: _TurndownService) {
+  turndownService.addRule('htmlEmbed', {
+    filter: function (node: HTMLInputElement) {
+      return (
+        node.nodeName === 'DIV' &&
+        node.getAttribute('data-type') === 'htmlEmbed'
+      );
+    },
+    replacement: function (_content: string, node: HTMLInputElement) {
+      const encoded = node.getAttribute('data-source') || '';
+      return `\n\n<!--html-embed:${encoded}-->\n\n`;
+    },
+  });
+}
+
 function listParagraph(turndownService: _TurndownService) {
   turndownService.addRule('paragraph', {
     filter: ['p'],
diff --git a/packages/editor-ext/tsconfig.json b/packages/editor-ext/tsconfig.json
index 974fea06..a4ad0d72 100644
--- a/packages/editor-ext/tsconfig.json
+++ b/packages/editor-ext/tsconfig.json
@@ -11,6 +11,7 @@
     "jsx": "react-jsx",
     "sourceMap": true,
     "outDir": "./dist",
+    "rootDir": "./src",
     "baseUrl": "./",
     "incremental": true,
     "skipLibCheck": true,
@@ -19,5 +20,7 @@
     "strictBindCallApply": false,
     "forceConsistentCasingInFileNames": false,
     "noFallthroughCasesInSwitch": false
-  }
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist", "src/**/*.spec.ts", "src/**/*.test.ts"]
 }
diff --git a/packages/editor-ext/vitest.config.ts b/packages/editor-ext/vitest.config.ts
new file mode 100644
index 00000000..783f61d8
--- /dev/null
+++ b/packages/editor-ext/vitest.config.ts
@@ -0,0 +1,13 @@
+import { defineConfig } from "vitest/config";
+
+// Minimal vitest setup for @docmost/editor-ext (mirrors apps/client's config,
+// trimmed to what the markdown/html-embed round-trip tests need). The markdown
+// utils run in plain Node (marked + turndown), so no jsdom/react plugin is
+// required here.
+export default defineConfig({
+  test: {
+    environment: "node",
+    globals: true,
+    include: ["src/**/*.{test,spec}.ts"],
+  },
+});