feat(offline): PWA shell, Yjs-backed titles, and offline read cache (M0–M2)

Implements docs/offline-sync-plan.md milestones M0–M2.

M0 (PWA shell):
- Add vite-plugin-pwa (generateSW, registerType: 'prompt', manifest:false);
  NetworkOnly for /api,/collab,/socket.io, NetworkFirst for GET /api,
  navigateFallback to index.html.
- Register SW via useRegisterSW with a Mantine update prompt; skip
  registration inside Capacitor native WebView (is-capacitor guard).

M1 (harden CRDT body + title into Yjs):
- Lift the per-page Y.Doc/Hocuspocus providers into a shared hook+context so
  body and title editors share one doc.
- Move the page title into a dedicated 'title' Yjs fragment (CRDT, offline-
  tolerant); drop the REST title save. Server persists the title fragment to
  page.title and seeds it for legacy pages (empty-fragment guard); a collab
  rename emits a treeUpdate so other users' tree/breadcrumbs refresh.
- Persist the rebuilt ydoc on the content->ydoc path to neutralize the Yjs
  duplication trap. Add a 3-state sync indicator.

M2 (offline read/navigation):
- Persist React Query to IndexedDB (idb-keyval persister, version buster,
  selected roots only).
- "Make available offline" action warms page, space, tree (root+ancestors+
  children) and comments under exact hook keys, plus the page ydoc.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/package.json

@@ -32,7 +32,9 @@
     "@slidoapp/emoji-mart-data": "1.2.4",
     "@slidoapp/emoji-mart-react": "1.1.5",
     "@tabler/icons-react": "3.40.0",
+    "@tanstack/query-async-storage-persister": "5.90.17",
     "@tanstack/react-query": "5.90.17",
+    "@tanstack/react-query-persist-client": "5.90.17",
     "@tanstack/react-virtual": "3.13.24",
     "ai": "6.0.207",
     "alfaaz": "1.1.0",
@@ -44,6 +46,7 @@
     "highlightjs-sap-abap": "0.3.0",
     "i18next": "25.10.1",
     "i18next-http-backend": "3.0.6",
+    "idb-keyval": "6.2.5",
     "jotai": "2.18.1",
     "jotai-optics": "0.4.0",
     "js-cookie": "3.0.7",
@@ -93,6 +96,7 @@
     "typescript": "5.9.3",
     "typescript-eslint": "8.57.1",
     "vite": "8.0.5",
+    "vite-plugin-pwa": "1.3.0",
     "vitest": "4.1.6"
   }
 }

apps/client/public/locales/en-US/translation.json

@@ -459,6 +459,15 @@
   "Move page": "Move page",
   "Move page to a different space.": "Move page to a different space.",
   "Real-time editor connection lost. Retrying...": "Real-time editor connection lost. Retrying...",
+  "Offline — changes are saved locally and will sync when you reconnect": "Offline — changes are saved locally and will sync when you reconnect",
+  "Syncing changes…": "Syncing changes…",
+  "All changes synced": "All changes synced",
+  "Update available": "Update available",
+  "Reload": "Reload",
+  "Make available offline": "Make available offline",
+  "Saving page for offline use...": "Saving page for offline use...",
+  "Page is now available offline": "Page is now available offline",
+  "Failed to make page available offline": "Failed to make page available offline",
   "Table of contents": "Table of contents",
   "Add headings (H1, H2, H3) to generate a table of contents.": "Add headings (H1, H2, H3) to generate a table of contents.",
   "Share": "Share",

apps/client/public/locales/ru-RU/translation.json

@@ -464,6 +464,15 @@
   "Move page": "Переместить страницу",
   "Move page to a different space.": "Переместите страницу в другое пространство.",
   "Real-time editor connection lost. Retrying...": "Соединение с редактором в реальном времени потеряно. Повторная попытка...",
+  "Offline — changes are saved locally and will sync when you reconnect": "Нет сети — изменения сохраняются локально и синхронизируются при восстановлении соединения",
+  "Syncing changes…": "Синхронизация изменений…",
+  "All changes synced": "Все изменения синхронизированы",
+  "Update available": "Доступно обновление",
+  "Reload": "Перезагрузить",
+  "Make available offline": "Сделать доступным офлайн",
+  "Saving page for offline use...": "Сохраняем страницу для офлайн-доступа…",
+  "Page is now available offline": "Страница доступна офлайн",
+  "Failed to make page available offline": "Не удалось сделать страницу доступной офлайн",
   "Table of contents": "Оглавление",
   "Add headings (H1, H2, H3) to generate a table of contents.": "Добавьте заголовки (H1, H2, H3), чтобы создать оглавление.",
   "Share": "Поделиться",

apps/client/src/features/editor/atoms/editor-atoms.ts

@@ -10,6 +10,12 @@ export const readOnlyEditorAtom = atom<Editor | null>(null);
 
 export const yjsConnectionStatusAtom = atom<string>("");
 
+// Local (IndexedDB) persistence sync state for the current page's Y.Doc.
+export const isLocalSyncedAtom = atom<boolean>(false);
+
+// Remote (Hocuspocus) sync state for the current page's Y.Doc.
+export const isRemoteSyncedAtom = atom<boolean>(false);
+
 export const showAiMenuAtom = atom(false);
 
 export const showLinkMenuAtom = atom(false);

apps/client/src/features/editor/contexts/editor-providers-context.tsx

@@ -0,0 +1,21 @@
+import { createContext, useContext } from "react";
+import type { HocuspocusProvider } from "@hocuspocus/provider";
+import type * as Y from "yjs";
+
+// Shared collaboration providers lifted above the title/body editors so that
+// both siblings bind to the SAME Y.Doc and HocuspocusProvider. The title lives
+// in a dedicated 'title' fragment of the same doc as the body.
+export interface EditorProvidersContextValue {
+  ydoc: Y.Doc;
+  remote: HocuspocusProvider;
+  providersReady: boolean;
+}
+
+export const EditorProvidersContext =
+  createContext<EditorProvidersContextValue | null>(null);
+
+// Returns the shared providers, or null when rendered outside of a provider.
+// Consumers must be null-safe (the body editor falls back to a non-collab mode).
+export function useEditorProviders(): EditorProvidersContextValue | null {
+  return useContext(EditorProvidersContext);
+}

apps/client/src/features/editor/full-editor.tsx

@@ -25,6 +25,8 @@ import { useAsideTriggerProps } from "@/hooks/use-toggle-aside.tsx";
 import { DeletedPageBanner } from "@/features/page/trash/components/deleted-page-banner.tsx";
 import clsx from "clsx";
 import { currentPageEditModeAtom } from "@/features/editor/atoms/editor-atoms.ts";
+import { usePageCollabProviders } from "@/features/editor/hooks/use-page-collab-providers";
+import { EditorProvidersContext } from "@/features/editor/contexts/editor-providers-context";
 
 const MemoizedTitleEditor = React.memo(TitleEditor);
 const MemoizedPageEditor = React.memo(PageEditor);
@@ -75,6 +77,10 @@ export function FullEditor({
     user.settings?.preferences?.pageEditMode ?? PageEditMode.Edit;
   const isEditMode = currentPageEditMode === PageEditMode.Edit;
 
+  // Single shared Y.Doc + HocuspocusProvider for both the title and body
+  // editors (title lives in the 'title' fragment of the same doc).
+  const { ydoc, remote, providersReady } = usePageCollabProviders(pageId);
+
   // Apply the user's saved preference only once on initial load, not on every
   // page navigation — so the mode sticks across navigations within a session.
   useEffect(() => {
@@ -94,6 +100,11 @@ export function FullEditor({
         <MemoizedFixedToolbar />
       )}
       <MemoizedDeletedPageBanner slugId={slugId} />
+      <EditorProvidersContext.Provider
+        value={
+          ydoc && remote ? { ydoc, remote, providersReady } : null
+        }
+      >
         <MemoizedTitleEditor
           pageId={pageId}
           slugId={slugId}
@@ -101,16 +112,14 @@ export function FullEditor({
           spaceSlug={spaceSlug}
           editable={editable}
         />
-      <PageByline
-        creator={creator}
-        contributors={contributors}
-      />
+        <PageByline creator={creator} contributors={contributors} />
         <MemoizedPageEditor
           pageId={pageId}
           editable={editable}
           content={content}
           canComment={canComment}
         />
+      </EditorProvidersContext.Provider>
     </Container>
   );
 }

apps/client/src/features/editor/hooks/use-page-collab-providers.ts

@@ -0,0 +1,194 @@
+import { useEffect, useRef, useState } from "react";
+import { IndexeddbPersistence } from "y-indexeddb";
+import * as Y from "yjs";
+import {
+  HocuspocusProvider,
+  onStatusParameters,
+  WebSocketStatus,
+  HocuspocusProviderWebsocket,
+  onSyncedParameters,
+  onStatelessParameters,
+} from "@hocuspocus/provider";
+import { useAtom, useSetAtom } from "jotai";
+import useCollaborationUrl from "@/features/editor/hooks/use-collaboration-url";
+import {
+  isLocalSyncedAtom,
+  isRemoteSyncedAtom,
+  yjsConnectionStatusAtom,
+} from "@/features/editor/atoms/editor-atoms";
+import { useCollabToken } from "@/features/auth/queries/auth-query.tsx";
+import { useDocumentVisibility } from "@mantine/hooks";
+import { useIdle } from "@/hooks/use-idle.ts";
+import { queryClient } from "@/main.tsx";
+import { IPage } from "@/features/page/types/page.types.ts";
+import { useParams } from "react-router-dom";
+import { extractPageSlugId } from "@/lib";
+import { FIVE_MINUTES } from "@/lib/constants.ts";
+import { jwtDecode } from "jwt-decode";
+
+export interface PageCollabProviders {
+  ydoc: Y.Doc | null;
+  remote: HocuspocusProvider | null;
+  socket: HocuspocusProviderWebsocket | null;
+  providersReady: boolean;
+  isLocalSynced: boolean;
+  isRemoteSynced: boolean;
+}
+
+/**
+ * Owns the full collaboration provider lifecycle for a page so that the title
+ * and body editors can share a single Y.Doc + HocuspocusProvider. The behavior
+ * is relocated verbatim from page-editor.tsx: it creates the providers once per
+ * pageId, connects/disconnects on idle/visibility, attaches each render,
+ * destroys on unmount, refreshes the collab token on auth failure, and applies
+ * the onStateless 'page.updated' cache update.
+ */
+export function usePageCollabProviders(pageId: string): PageCollabProviders {
+  const collaborationURL = useCollaborationUrl();
+  const [isLocalSynced, setIsLocalSynced] = useState(false);
+  const [isRemoteSynced, setIsRemoteSynced] = useState(false);
+  const [yjsConnectionStatus, setYjsConnectionStatus] = useAtom(
+    yjsConnectionStatusAtom,
+  );
+  const setIsLocalSyncedAtom = useSetAtom(isLocalSyncedAtom);
+  const setIsRemoteSyncedAtom = useSetAtom(isRemoteSyncedAtom);
+  const { data: collabQuery, refetch: refetchCollabToken } = useCollabToken();
+  const { isIdle, resetIdle } = useIdle(FIVE_MINUTES, { initialState: false });
+  const documentState = useDocumentVisibility();
+  const { pageSlug } = useParams();
+  const slugId = extractPageSlugId(pageSlug);
+
+  // Providers only created once per pageId
+  const providersRef = useRef<{
+    ydoc: Y.Doc;
+    local: IndexeddbPersistence;
+    remote: HocuspocusProvider;
+    socket: HocuspocusProviderWebsocket;
+  } | null>(null);
+  const [providersReady, setProvidersReady] = useState(false);
+
+  // Mirror the local/remote sync flags into shared atoms so the header
+  // indicator can read them, and keep the local component state in sync too.
+  const setLocalSynced = (value: boolean) => {
+    setIsLocalSynced(value);
+    setIsLocalSyncedAtom(value);
+  };
+  const setRemoteSynced = (value: boolean) => {
+    setIsRemoteSynced(value);
+    setIsRemoteSyncedAtom(value);
+  };
+
+  useEffect(() => {
+    if (!providersRef.current) {
+      const documentName = `page.${pageId}`;
+      const ydoc = new Y.Doc();
+      const local = new IndexeddbPersistence(documentName, ydoc);
+      const socket = new HocuspocusProviderWebsocket({
+        url: collaborationURL,
+      });
+      const onLocalSyncedHandler = () => {
+        setLocalSynced(true);
+      };
+      const onStatusHandler = (event: onStatusParameters) => {
+        setYjsConnectionStatus(event.status);
+      };
+      const onSyncedHandler = (event: onSyncedParameters) => {
+        setRemoteSynced(event.state);
+      };
+      const onStatelessHandler = ({ payload }: onStatelessParameters) => {
+        try {
+          const message = JSON.parse(payload);
+          if (message?.type !== "page.updated" || !message.updatedAt) return;
+          const pageData = queryClient.getQueryData<IPage>(["pages", slugId]);
+          if (pageData) {
+            queryClient.setQueryData(["pages", slugId], {
+              ...pageData,
+              updatedAt: message.updatedAt,
+              ...(message.lastUpdatedBy && {
+                lastUpdatedBy: message.lastUpdatedBy,
+              }),
+            });
+          }
+        } catch {
+          // ignore unrelated stateless messages
+        }
+      };
+      const onAuthenticationFailedHandler = () => {
+        const payload = jwtDecode(collabQuery?.token);
+        const now = Date.now().valueOf() / 1000;
+        const isTokenExpired = now >= payload.exp;
+        if (isTokenExpired) {
+          refetchCollabToken().then((result) => {
+            if (result.data?.token) {
+              socket.disconnect();
+              setTimeout(() => {
+                remote.configuration.token = result.data.token;
+                socket.connect();
+              }, 100);
+            }
+          });
+        }
+      };
+      const remote = new HocuspocusProvider({
+        websocketProvider: socket,
+        name: documentName,
+        document: ydoc,
+        token: collabQuery?.token,
+        onAuthenticationFailed: onAuthenticationFailedHandler,
+        onStatus: onStatusHandler,
+        onSynced: onSyncedHandler,
+        onStateless: onStatelessHandler,
+      });
+
+      local.on("synced", onLocalSyncedHandler);
+      providersRef.current = { ydoc, socket, local, remote };
+      setProvidersReady(true);
+    } else {
+      setProvidersReady(true);
+    }
+    // Only destroy on final unmount
+    return () => {
+      providersRef.current?.socket.destroy();
+      providersRef.current?.remote.destroy();
+      providersRef.current?.local.destroy();
+      providersRef.current = null;
+      // Reset shared sync state on page change/unmount.
+      setLocalSynced(false);
+      setRemoteSynced(false);
+    };
+  }, [pageId]);
+
+  // Only connect/disconnect on tab/idle, not destroy
+  useEffect(() => {
+    if (!providersReady || !providersRef.current) return;
+    const socket = providersRef.current.socket;
+
+    if (
+      isIdle &&
+      documentState === "hidden" &&
+      yjsConnectionStatus === WebSocketStatus.Connected
+    ) {
+      socket.disconnect();
+      return;
+    }
+    if (
+      documentState === "visible" &&
+      yjsConnectionStatus === WebSocketStatus.Disconnected
+    ) {
+      resetIdle();
+      socket.connect();
+    }
+  }, [isIdle, documentState, providersReady, resetIdle]);
+
+  // Attach here, to make sure the connection gets properly established
+  providersRef.current?.remote.attach();
+
+  return {
+    ydoc: providersRef.current?.ydoc ?? null,
+    remote: providersRef.current?.remote ?? null,
+    socket: providersRef.current?.socket ?? null,
+    providersReady,
+    isLocalSynced,
+    isRemoteSynced,
+  };
+}

apps/client/src/features/editor/page-editor.tsx

@@ -6,16 +6,7 @@ import React, {
   useRef,
   useState,
 } from "react";
-import { IndexeddbPersistence } from "y-indexeddb";
-import * as Y from "yjs";
-import {
-  HocuspocusProvider,
-  onStatusParameters,
-  WebSocketStatus,
-  HocuspocusProviderWebsocket,
-  onSyncedParameters,
-  onStatelessParameters,
-} from "@hocuspocus/provider";
+import { WebSocketStatus } from "@hocuspocus/provider";
 import {
   Editor,
   EditorContent,
@@ -28,13 +19,15 @@ import {
   mainExtensions,
 } from "@/features/editor/extensions/extensions";
 import { useAtom, useAtomValue } from "jotai";
-import useCollaborationUrl from "@/features/editor/hooks/use-collaboration-url";
 import { currentUserAtom } from "@/features/user/atoms/current-user-atom";
 import {
   currentPageEditModeAtom,
+  isLocalSyncedAtom,
+  isRemoteSyncedAtom,
   pageEditorAtom,
   yjsConnectionStatusAtom,
 } from "@/features/editor/atoms/editor-atoms";
+import { useEditorProviders } from "@/features/editor/contexts/editor-providers-context";
 import { asideStateAtom } from "@/components/layouts/global/hooks/atoms/sidebar-atom";
 import {
   activeCommentIdAtom,
@@ -57,17 +50,13 @@ import {
 } from "@/features/editor/components/common/editor-paste-handler.tsx";
 import ExcalidrawMenu from "./components/excalidraw/excalidraw-menu-lazy";
 import DrawioMenu from "./components/drawio/drawio-menu";
-import { useCollabToken } from "@/features/auth/queries/auth-query.tsx";
 import SearchAndReplaceDialog from "@/features/editor/components/search-and-replace/search-and-replace-dialog.tsx";
-import { useDebouncedCallback, useDocumentVisibility } from "@mantine/hooks";
-import { useIdle } from "@/hooks/use-idle.ts";
+import { useDebouncedCallback } from "@mantine/hooks";
 import { queryClient } from "@/main.tsx";
 import { IPage } from "@/features/page/types/page.types.ts";
 import { useParams } from "react-router-dom";
 import { extractPageSlugId, platformModifierKey } from "@/lib";
-import { FIVE_MINUTES } from "@/lib/constants.ts";
 import { PageEditMode } from "@/features/user/types/user.types.ts";
-import { jwtDecode } from "jwt-decode";
 import { searchSpotlight } from "@/features/search/constants.ts";
 import { useEditorScroll } from "./hooks/use-editor-scroll";
 import { EditorLinkMenu } from "@/features/editor/components/link/link-menu";
@@ -92,7 +81,6 @@ export default function PageEditor({
   canComment,
 }: PageEditorProps) {
   const { t } = useTranslation();
-  const collaborationURL = useCollaborationUrl();
   const isComponentMounted = useRef(false);
   const editorRef = useRef<Editor | null>(null);
 
@@ -106,15 +94,10 @@ export default function PageEditor({
   const [, setActiveCommentId] = useAtom(activeCommentIdAtom);
   const [showCommentPopup, setShowCommentPopup] = useAtom(showCommentPopupAtom);
   const [showReadOnlyCommentPopup] = useAtom(showReadOnlyCommentPopupAtom);
-  const [isLocalSynced, setIsLocalSynced] = useState(false);
-  const [isRemoteSynced, setIsRemoteSynced] = useState(false);
   const [yjsConnectionStatus, setYjsConnectionStatus] = useAtom(
     yjsConnectionStatusAtom,
   );
   const menuContainerRef = useRef(null);
-  const { data: collabQuery, refetch: refetchCollabToken } = useCollabToken();
-  const { isIdle, resetIdle } = useIdle(FIVE_MINUTES, { initialState: false });
-  const documentState = useDocumentVisibility();
   const { pageSlug } = useParams();
   const slugId = extractPageSlugId(pageSlug);
   const currentPageEditMode = useAtomValue(currentPageEditModeAtom);
@@ -123,128 +106,27 @@ export default function PageEditor({
     [isComponentMounted],
   );
   const { handleScrollTo } = useEditorScroll({ canScroll });
-  // Providers only created once per pageId
-  const providersRef = useRef<{
-    local: IndexeddbPersistence;
-    remote: HocuspocusProvider;
-    socket: HocuspocusProviderWebsocket;
-  } | null>(null);
-  const [providersReady, setProvidersReady] = useState(false);
 
-  useEffect(() => {
-    if (!providersRef.current) {
-      const documentName = `page.${pageId}`;
-      const ydoc = new Y.Doc();
-      const local = new IndexeddbPersistence(documentName, ydoc);
-      const socket = new HocuspocusProviderWebsocket({
-        url: collaborationURL,
-      });
-      const onLocalSyncedHandler = () => {
-        setIsLocalSynced(true);
-      };
-      const onStatusHandler = (event: onStatusParameters) => {
-        setYjsConnectionStatus(event.status);
-      };
-      const onSyncedHandler = (event: onSyncedParameters) => {
-        setIsRemoteSynced(event.state);
-      };
-      const onStatelessHandler = ({ payload }: onStatelessParameters) => {
-        try {
-          const message = JSON.parse(payload);
-          if (message?.type !== "page.updated" || !message.updatedAt) return;
-          const pageData = queryClient.getQueryData<IPage>(["pages", slugId]);
-          if (pageData) {
-            queryClient.setQueryData(["pages", slugId], {
-              ...pageData,
-              updatedAt: message.updatedAt,
-              ...(message.lastUpdatedBy && {
-                lastUpdatedBy: message.lastUpdatedBy,
-              }),
-            });
-          }
-        } catch {
-          // ignore unrelated stateless messages
-        }
-      };
-      const onAuthenticationFailedHandler = () => {
-        const payload = jwtDecode(collabQuery?.token);
-        const now = Date.now().valueOf() / 1000;
-        const isTokenExpired = now >= payload.exp;
-        if (isTokenExpired) {
-          refetchCollabToken().then((result) => {
-            if (result.data?.token) {
-              socket.disconnect();
-              setTimeout(() => {
-                remote.configuration.token = result.data.token;
-                socket.connect();
-              }, 100);
-            }
-          });
-        }
-      };
-      const remote = new HocuspocusProvider({
-        websocketProvider: socket,
-        name: documentName,
-        document: ydoc,
-        token: collabQuery?.token,
-        onAuthenticationFailed: onAuthenticationFailedHandler,
-        onStatus: onStatusHandler,
-        onSynced: onSyncedHandler,
-        onStateless: onStatelessHandler,
-      });
-
-      local.on("synced", onLocalSyncedHandler);
-      providersRef.current = { socket, local, remote };
-      setProvidersReady(true);
-    } else {
-      setProvidersReady(true);
-    }
-    // Only destroy on final unmount
-    return () => {
-      providersRef.current?.socket.destroy();
-      providersRef.current?.remote.destroy();
-      providersRef.current?.local.destroy();
-      providersRef.current = null;
-    };
-  }, [pageId]);
-
-  // Only connect/disconnect on tab/idle, not destroy
-  useEffect(() => {
-    if (!providersReady || !providersRef.current) return;
-    const socket = providersRef.current.socket;
-
-    if (
-      isIdle &&
-      documentState === "hidden" &&
-      yjsConnectionStatus === WebSocketStatus.Connected
-    ) {
-      socket.disconnect();
-      return;
-    }
-    if (
-      documentState === "visible" &&
-      yjsConnectionStatus === WebSocketStatus.Disconnected
-    ) {
-      resetIdle();
-      socket.connect();
-    }
-  }, [isIdle, documentState, providersReady, resetIdle]);
-
-  // Attach here, to make sure the connection gets properly established
-  providersRef.current?.remote.attach();
+  // Shared providers + Y.Doc lifted into full-editor via context. The provider
+  // lifecycle (creation, idle/visibility connect, attach, destroy, token
+  // refresh) lives in usePageCollabProviders. Null-safe when rendered without
+  // the context (defensive) — in practice full-editor always provides it.
+  const editorProviders = useEditorProviders();
+  const remote = editorProviders?.remote ?? null;
+  const providersReady = editorProviders?.providersReady ?? false;
+  const isLocalSynced = useAtomValue(isLocalSyncedAtom);
+  const isRemoteSynced = useAtomValue(isRemoteSyncedAtom);
 
   const extensions = useMemo(() => {
-    if (!providersReady || !providersRef.current || !currentUser?.user) {
+    if (!providersReady || !remote || !currentUser?.user) {
       return mainExtensions;
     }
 
-    const remoteProvider = providersRef.current.remote;
-
     return [
       ...mainExtensions,
-      ...collabExtensions(remoteProvider, currentUser?.user),
+      ...collabExtensions(remote, currentUser?.user),
     ];
-  }, [providersReady, currentUser?.user]);
+  }, [providersReady, remote, currentUser?.user]);
 
   const editor = useEditor(
     {
@@ -452,7 +334,7 @@ export default function PageEditor({
             {editor &&
               !editorIsEditable &&
               (editable || canComment) &&
-              providersRef.current && <ReadonlyBubbleMenu editor={editor} />}
+              remote && <ReadonlyBubbleMenu editor={editor} />}
             {showCommentPopup && (
               <CommentDialog editor={editor} pageId={pageId} />
             )}

apps/client/src/features/editor/title-editor.tsx

@@ -1,5 +1,5 @@
 import "@/features/editor/styles/index.css";
-import React, { useCallback, useEffect, useState } from "react";
+import { useEffect } from "react";
 import { EditorContent, useEditor } from "@tiptap/react";
 import { Document } from "@tiptap/extension-document";
 import { Heading } from "@tiptap/extension-heading";
@@ -11,14 +11,14 @@ import {
   pageEditorAtom,
   titleEditorAtom,
 } from "@/features/editor/atoms/editor-atoms";
-import {
-  updatePageData,
-  useUpdateTitlePageMutation,
-} from "@/features/page/queries/page-query";
+import { updatePageData } from "@/features/page/queries/page-query";
 import { useDebouncedCallback, getHotkeyHandler } from "@mantine/hooks";
 import { useAtom } from "jotai";
 import { useQueryEmit } from "@/features/websocket/use-query-emit.ts";
-import { History } from "@tiptap/extension-history";
+import {
+  Collaboration,
+  isChangeOrigin,
+} from "@tiptap/extension-collaboration";
 import { buildPageUrl } from "@/features/page/page.utils.ts";
 import { useNavigate } from "react-router-dom";
 import { useTranslation } from "react-i18next";
@@ -28,6 +28,9 @@ import localEmitter from "@/lib/local-emitter.ts";
 import { PageEditMode } from "@/features/user/types/user.types.ts";
 import { searchSpotlight } from "@/features/search/constants.ts";
 import { platformModifierKey } from "@/lib";
+import { useEditorProviders } from "@/features/editor/contexts/editor-providers-context";
+import { queryClient } from "@/main.tsx";
+import { IPage } from "@/features/page/types/page.types.ts";
 
 export interface TitleEditorProps {
   pageId: string;
@@ -45,16 +48,27 @@ export function TitleEditor({
   editable,
 }: TitleEditorProps) {
   const { t } = useTranslation();
-  const { mutateAsync: updateTitlePageMutationAsync } =
-    useUpdateTitlePageMutation();
   const pageEditor = useAtomValue(pageEditorAtom);
   const [, setTitleEditor] = useAtom(titleEditorAtom);
   const emit = useQueryEmit();
   const navigate = useNavigate();
-  const [activePageId, setActivePageId] = useState(pageId);
   const currentPageEditMode = useAtomValue(currentPageEditModeAtom);
 
-  const titleEditor = useEditor({
+  // Shared Y.Doc (title lives in its own 'title' fragment of the same doc as
+  // the body). Yjs is the source of truth for the title content.
+  const editorProviders = useEditorProviders();
+  const ydoc = editorProviders?.ydoc ?? null;
+  const providersReady = editorProviders?.providersReady ?? false;
+
+  // Until the shared doc is ready, the collaborative editor binds nothing and
+  // would render an empty heading until the Yjs 'title' fragment hydrates. Show
+  // a non-editable static <h1> with the `title` prop in the meantime. The prop
+  // is NEVER fed into the collaborative editor (Yjs stays the single source of
+  // truth — seeding it would duplicate the title).
+  const titleReady = providersReady && !!ydoc;
+
+  const titleEditor = useEditor(
+    {
       extensions: [
         Document.extend({
           content: "heading",
@@ -67,23 +81,28 @@ export function TitleEditor({
           placeholder: t("Untitled"),
           showOnlyWhenEditable: false,
         }),
-      History.configure({
-        depth: 20,
-      }),
+        // Bind the title to the dedicated 'title' fragment of the shared doc.
+        // Collaboration also manages undo/redo, so the History extension is
+        // intentionally omitted (it would conflict with Yjs). When the doc is
+        // not ready yet the editor renders empty until the doc arrives.
+        ...(ydoc
+          ? [Collaboration.configure({ document: ydoc, field: "title" })]
+          : []),
         EmojiCommand,
       ],
       onCreate({ editor }) {
         if (editor) {
           // @ts-ignore
           setTitleEditor(editor);
-        setActivePageId(pageId);
         }
       },
-    onUpdate({ editor }) {
-      debounceUpdate();
+      onUpdate({ editor, transaction }) {
+        // Drive URL + tree propagation only on genuine local edits; skip
+        // remote/collab-origin Yjs updates to avoid feedback loops.
+        if (transaction && isChangeOrigin(transaction)) return;
+        debouncedPropagateTitle(editor.getText());
       },
       editable: editable,
-    content: title,
       immediatelyRender: true,
       shouldRerenderOnTransaction: false,
       editorProps: {
@@ -103,7 +122,9 @@ export function TitleEditor({
           },
         },
       },
-  });
+    },
+    [pageId, ydoc],
+  );
 
   useEffect(() => {
     const anchorId = window.location.hash
@@ -113,49 +134,42 @@ export function TitleEditor({
     navigate(pageSlug, { replace: true });
   }, [title]);
 
-  const saveTitle = useCallback(() => {
-    if (!titleEditor || activePageId !== pageId) return;
+  // On a local title change: update the URL slug and propagate the change to
+  // the live tree/breadcrumbs for online users. No REST round-trip — the title
+  // itself is persisted through Yjs. Offline this simply no-ops the socket
+  // emit and the title syncs on reconnect.
+  const debouncedPropagateTitle = useDebouncedCallback((titleText: string) => {
+    const anchorId = window.location.hash
+      ? window.location.hash.substring(1)
+      : undefined;
+    navigate(buildPageUrl(spaceSlug, slugId, titleText, anchorId), {
+      replace: true,
+    });
 
-    if (
-      titleEditor.getText() === title ||
-      (titleEditor.getText() === "" && title === null)
-    ) {
-      return;
-    }
+    const page =
+      queryClient.getQueryData<IPage>(["pages", slugId]) ??
+      queryClient.getQueryData<IPage>(["pages", pageId]);
+    if (!page) return;
+
+    const updatedPage: IPage = { ...page, title: titleText };
 
-    updateTitlePageMutationAsync({
-      pageId: pageId,
-      title: titleEditor.getText(),
-    }).then((page) => {
     const event: UpdateEvent = {
       operation: "updateOne",
       spaceId: page.spaceId,
       entity: ["pages"],
       id: page.id,
       payload: {
-          title: page.title,
+        title: titleText,
         slugId: page.slugId,
         parentPageId: page.parentPageId,
         icon: page.icon,
       },
     };
 
-      if (page.title !== titleEditor.getText()) return;
-
-      updatePageData(page);
-
+    updatePageData(updatedPage);
     localEmitter.emit("message", event);
     emit(event);
-    });
-  }, [pageId, title, titleEditor]);
-
-  const debounceUpdate = useDebouncedCallback(saveTitle, 500);
-
-  useEffect(() => {
-    if (titleEditor && title !== titleEditor.getText()) {
-      titleEditor.commands.setContent(title);
-    }
-  }, [pageId, title, titleEditor]);
+  }, 500);
 
   useEffect(() => {
     setTimeout(() => {
@@ -165,13 +179,6 @@ export function TitleEditor({
     }, 300);
   }, [titleEditor]);
 
-  useEffect(() => {
-    return () => {
-      // force-save title on navigation
-      saveTitle();
-    };
-  }, [pageId]);
-
   useEffect(() => {
     if (!titleEditor) return;
     titleEditor.setEditable(editable && currentPageEditMode === PageEditMode.Edit);
@@ -238,6 +245,7 @@ export function TitleEditor({
 
   return (
     <div className="page-title">
+      {titleReady ? (
         <EditorContent
           editor={titleEditor}
           onKeyDown={(event) => {
@@ -248,6 +256,11 @@ export function TitleEditor({
             handleTitleKeyDown(event);
           }}
         />
+      ) : (
+        // Static, non-editable fallback so the title is visible before Yjs
+        // hydrates the 'title' fragment. Not wired into the collaborative editor.
+        <h1>{title}</h1>
+      )}
     </div>
   );
 }

apps/client/src/features/offline/make-offline.ts

@@ -0,0 +1,231 @@
+import * as Y from "yjs";
+import { IndexeddbPersistence } from "y-indexeddb";
+import { HocuspocusProvider } from "@hocuspocus/provider";
+
+import { queryClient } from "@/main.tsx";
+import {
+  getPageById,
+  getPageBreadcrumbs,
+  getSidebarPages,
+  getAllSidebarPages,
+} from "@/features/page/services/page-service";
+import { getSpaceById } from "@/features/space/services/space-service.ts";
+import { getPageComments } from "@/features/comment/services/comment-service";
+import { IPage } from "@/features/page/types/page.types";
+import { IPagination } from "@/lib/types.ts";
+
+/**
+ * Fully paginate an infinite query and write the @tanstack InfiniteData cache
+ * shape ({ pages, pageParams }) that the matching useInfiniteQuery hook reads.
+ *
+ * The default prefetchInfiniteQuery only warms the FIRST page, which leaves
+ * hooks that treat hasNextPage as still-loading (e.g. the comments panel)
+ * spinning forever offline, and silently truncates large lists. This walks the
+ * cursor chain until it runs out (or hits maxPages) so the whole list is cached.
+ *
+ * Best-effort: any failure is swallowed so a partial/failed warm never throws.
+ */
+async function warmInfiniteAll<T>(
+  queryKey: unknown[],
+  fetchPage: (cursor: string | undefined) => Promise<IPagination<T>>,
+  maxPages = 50,
+): Promise<void> {
+  try {
+    const pages: IPagination<T>[] = [];
+    const pageParams: (string | undefined)[] = [];
+    let cursor: string | undefined = undefined;
+
+    for (let i = 0; i < maxPages; i++) {
+      const res = await fetchPage(cursor);
+      pages.push(res);
+      pageParams.push(cursor);
+      cursor = res?.meta?.nextCursor ?? undefined;
+      if (!cursor) break;
+    }
+
+    queryClient.setQueryData(queryKey, { pages, pageParams });
+  } catch {
+    // best-effort
+  }
+}
+
+export interface MakePageAvailableOfflineParams {
+  pageId: string;
+  slugId?: string;
+  spaceId?: string;
+  parentPageId?: string;
+}
+
+/**
+ * Best-effort prefetch of a page's read queries so they get persisted to
+ * IndexedDB and become readable offline.
+ *
+ * Each prefetch is isolated in try/catch — this function NEVER throws to its
+ * caller. Only meaningful while online (the underlying requests must succeed).
+ */
+export async function makePageAvailableOffline({
+  pageId,
+  spaceId,
+}: MakePageAvailableOfflineParams): Promise<void> {
+  // Fetch the page document ONCE and write it under BOTH cache keys, exactly
+  // like usePageQuery's onData effect. Every page consumer reads ["pages",
+  // <slugId>] (usePageQuery keys on the slugId for routed reads), so warming
+  // only ["pages", <uuid>] would leave the offline page blank.
+  let page: IPage | undefined;
+  try {
+    page = await getPageById({ pageId });
+    queryClient.setQueryData(["pages", page.slugId], page);
+    queryClient.setQueryData(["pages", page.id], page);
+  } catch {
+    // best-effort
+  }
+
+  // Warm the space — page.tsx renders nothing until the space query resolves
+  // (useGetSpaceBySlugQuery → ["space", <spaceSlug>]). Awaited (not the
+  // fire-and-forget prefetchSpace) so the space is actually persisted before
+  // the caller fires its success toast. Matches the hook's key/fn exactly.
+  try {
+    const spaceSlug = page?.space?.slug;
+    if (spaceSlug) {
+      await queryClient.prefetchQuery({
+        queryKey: ["space", spaceSlug],
+        queryFn: () => getSpaceById(spaceSlug),
+      });
+    }
+  } catch {
+    // best-effort
+  }
+
+  // Warm the sidebar tree root so the WHOLE root level renders offline (matches
+  // useGetRootSidebarPagesQuery's ["root-sidebar-pages", spaceId] infinite
+  // key/fn). Fully paginated so large root levels are not truncated at 100.
+  if (spaceId) {
+    await warmInfiniteAll(["root-sidebar-pages", spaceId], (cursor) =>
+      getSidebarPages({ spaceId, cursor, limit: 100 }),
+    );
+  }
+
+  // Warm the children of the page and of every ancestor so the path to this
+  // page is expandable offline. We MIRROR fetchAllAncestorChildren exactly —
+  // same regular ["sidebar-pages", { pageId, spaceId }] key, same
+  // getAllSidebarPages fn (which aggregates ALL children pages, so nothing is
+  // truncated at 100), same 30min staleTime — otherwise the warmed cache would
+  // never be read by the offline tree.
+  const warmSidebarChildren = async (id: string) => {
+    try {
+      // Keep EXACTLY { pageId, spaceId } so the key hashes identically to
+      // fetchAllAncestorChildren's (no parentPageId, no extra fields).
+      const params = { pageId: id, spaceId };
+      await queryClient.prefetchQuery({
+        queryKey: ["sidebar-pages", params],
+        queryFn: () => getAllSidebarPages(params),
+        staleTime: 30 * 60 * 1000,
+      });
+    } catch {
+      // best-effort per node
+    }
+  };
+
+  // The page's own children.
+  await warmSidebarChildren(pageId);
+
+  // Each ancestor's children. Use the breadcrumbs endpoint ONLY to discover the
+  // ancestor ids — we intentionally do NOT cache the breadcrumbs themselves
+  // (the UI derives the path from the tree).
+  try {
+    const ancestors = (await getPageBreadcrumbs(pageId)) as
+      | Array<{ id?: string }>
+      | undefined;
+    for (const ancestor of ancestors ?? []) {
+      const ancestorId = ancestor?.id;
+      if (!ancestorId || ancestorId === pageId) continue;
+      await warmSidebarChildren(ancestorId);
+    }
+  } catch {
+    // best-effort
+  }
+
+  // Comments (matches useCommentsQuery's ["comments", pageId] infinite cache).
+  // useCommentsQuery reports isLoading while hasNextPage is true, so warming
+  // only the first page leaves the offline comments panel spinning forever on
+  // pages with >100 comments. Fully paginate so the last cached page has no
+  // nextCursor and the panel settles offline.
+  await warmInfiniteAll(["comments", pageId], (cursor) =>
+    getPageComments({ pageId, cursor, limit: 100 }),
+  );
+}
+
+/**
+ * Best-effort warm-up of the page's Yjs document into IndexedDB so the editor
+ * can open offline.
+ *
+ * Opens a local IndexeddbPersistence plus a transient HocuspocusProvider to
+ * pull the server state into IndexedDB, then tears both down once synced (or
+ * after a timeout). Entirely wrapped in try/catch — NEVER throws.
+ *
+ * Only meaningful when online at warm time; offline it is a no-op that resolves.
+ */
+export async function warmPageYdoc(
+  pageId: string,
+  collabUrl: string,
+  token?: string,
+): Promise<void> {
+  let ydoc: Y.Doc | null = null;
+  let local: IndexeddbPersistence | null = null;
+  let remote: HocuspocusProvider | null = null;
+
+  try {
+    const documentName = `page.${pageId}`;
+    ydoc = new Y.Doc();
+    local = new IndexeddbPersistence(documentName, ydoc);
+    remote = new HocuspocusProvider({
+      url: collabUrl,
+      name: documentName,
+      document: ydoc,
+      token,
+    });
+
+    const provider = remote;
+
+    await new Promise<void>((resolve) => {
+      let settled = false;
+      let timeoutId: ReturnType<typeof setTimeout> | undefined;
+      const finish = () => {
+        if (settled) return;
+        settled = true;
+        // Clear the pending timeout and detach the listener so neither leaks
+        // after we resolve.
+        if (timeoutId !== undefined) clearTimeout(timeoutId);
+        try {
+          provider.off("synced", finish);
+        } catch {
+          // best-effort
+        }
+        resolve();
+      };
+
+      // Resolve once the server state has synced into the local doc...
+      provider.on("synced", finish);
+      // ...or give up after a short timeout so we never hang.
+      timeoutId = setTimeout(finish, 8000);
+    });
+  } catch {
+    // best-effort
+  } finally {
+    try {
+      remote?.destroy();
+    } catch {
+      // best-effort
+    }
+    try {
+      local?.destroy();
+    } catch {
+      // best-effort
+    }
+    try {
+      ydoc?.destroy();
+    } catch {
+      // best-effort
+    }
+  }
+}

apps/client/src/features/offline/query-persister.ts

@@ -0,0 +1,45 @@
+import { get, set, del } from "idb-keyval";
+import { createAsyncStoragePersister } from "@tanstack/query-async-storage-persister";
+
+// Structural subset of a TanStack Query we read when deciding what to persist.
+// We avoid importing the branded `Query` class because the persist-client and
+// react-query may resolve to different `@tanstack/query-core` copies, whose
+// `Query` types are nominally incompatible (private brand). This structural
+// shape stays assignable to whichever copy the persister expects.
+type DehydratableQuery = {
+  state: { status: string };
+  queryKey: readonly unknown[];
+};
+
+// IndexedDB-backed storage adapter for TanStack Query's async persister.
+const idbStorage = {
+  getItem: (key: string) => get<string>(key).then((v) => v ?? null),
+  setItem: (key: string, value: string) => set(key, value),
+  removeItem: (key: string) => del(key),
+};
+
+export const queryPersister = createAsyncStoragePersister({
+  storage: idbStorage,
+  key: "gitmost-rq-cache",
+  throttleTime: 1000,
+});
+
+// Only navigation/read query roots are persisted for offline reading.
+// Volatile/auth queries (collab tokens, trash lists) are intentionally excluded.
+export const OFFLINE_PERSIST_ROOTS = new Set<string>([
+  "pages",
+  "sidebar-pages",
+  "root-sidebar-pages",
+  "breadcrumbs",
+  "comments",
+  "space",
+  "spaces",
+  "recent-changes",
+]);
+
+export function shouldDehydrateOfflineQuery(query: DehydratableQuery): boolean {
+  return (
+    query.state.status === "success" &&
+    OFFLINE_PERSIST_ROOTS.has(String(query.queryKey?.[0]))
+  );
+}

apps/client/src/features/page/components/header/page-header-menu.tsx

@@ -12,6 +12,8 @@ import {
   IconMarkdown,
   IconMessage,
   IconPrinter,
+  IconCloud,
+  IconCloudCheck,
   IconStar,
   IconStarFilled,
   IconTrash,
@@ -36,6 +38,8 @@ import { Trans, useTranslation } from "react-i18next";
 import ExportModal from "@/components/common/export-modal";
 import { htmlToMarkdown } from "@docmost/editor-ext";
 import {
+  isLocalSyncedAtom,
+  isRemoteSyncedAtom,
   pageEditorAtom,
   yjsConnectionStatusAtom,
 } from "@/features/editor/atoms/editor-atoms.ts";
@@ -377,14 +381,16 @@ function PageActionMenu({ readOnly }: PageActionMenuProps) {
 function ConnectionWarning() {
   const { t } = useTranslation();
   const yjsConnectionStatus = useAtomValue(yjsConnectionStatusAtom);
+  const isLocalSynced = useAtomValue(isLocalSyncedAtom);
+  const isRemoteSynced = useAtomValue(isRemoteSyncedAtom);
   const [showWarning, setShowWarning] = useState(false);
   const timeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
 
-  useEffect(() => {
   const isDisconnected = ["disconnected", "connecting"].includes(
     yjsConnectionStatus,
   );
 
+  useEffect(() => {
     if (isDisconnected) {
       if (!timeoutRef.current) {
         timeoutRef.current = setTimeout(() => setShowWarning(true), 5000);
@@ -396,7 +402,7 @@ function ConnectionWarning() {
       }
       setShowWarning(false);
     }
-  }, [yjsConnectionStatus]);
+  }, [isDisconnected]);
 
   // Cleanup only on unmount
   useEffect(() => {
@@ -407,19 +413,21 @@ function ConnectionWarning() {
     };
   }, []);
 
+  // State (1): offline/disconnected — changes are kept locally. Preserve the
+  // existing >5s debounce before surfacing this state.
+  if (isDisconnected) {
     if (!showWarning) return null;
 
+    const offlineLabel = t(
+      "Offline — changes are saved locally and will sync when you reconnect",
+    );
     return (
-    <Tooltip
-      label={t("Real-time editor connection lost. Retrying...")}
-      openDelay={250}
-      withArrow
-    >
+      <Tooltip label={offlineLabel} openDelay={250} withArrow>
         <ThemeIcon
           variant="default"
           c="red"
           role="status"
-        aria-label={t("Real-time editor connection lost. Retrying...")}
+          aria-label={offlineLabel}
           style={{ border: "none" }}
         >
           <IconWifiOff size={20} stroke={2} />
@@ -427,3 +435,38 @@ function ConnectionWarning() {
       </Tooltip>
     );
   }
+
+  // State (2): connected but the remote replica is not fully caught up yet.
+  if (!isRemoteSynced || !isLocalSynced) {
+    const syncingLabel = t("Syncing changes…");
+    return (
+      <Tooltip label={syncingLabel} openDelay={250} withArrow>
+        <ThemeIcon
+          variant="default"
+          c="dimmed"
+          role="status"
+          aria-label={syncingLabel}
+          style={{ border: "none" }}
+        >
+          <IconCloud size={20} stroke={2} />
+        </ThemeIcon>
+      </Tooltip>
+    );
+  }
+
+  // State (3): fully synced — subtle confirmation indicator.
+  const syncedLabel = t("All changes synced");
+  return (
+    <Tooltip label={syncedLabel} openDelay={250} withArrow>
+      <ThemeIcon
+        variant="default"
+        c="dimmed"
+        role="status"
+        aria-label={syncedLabel}
+        style={{ border: "none" }}
+      >
+        <IconCloudCheck size={20} stroke={2} />
+      </ThemeIcon>
+    </Tooltip>
+  );
+}

apps/client/src/features/page/queries/page-query.ts

@@ -101,12 +101,6 @@ export function updatePageData(data: IPage) {
   );
 }
 
-export function useUpdateTitlePageMutation() {
-  return useMutation<IPage, Error, Partial<IPageInput>>({
-    mutationFn: (data) => updatePage(data),
-  });
-}
-
 export function useUpdatePageMutation() {
   return useMutation<IPage, Error, Partial<IPageInput>>({
     mutationFn: (data) => updatePage(data),

apps/client/src/features/page/tree/components/space-tree-node-menu.tsx

@@ -6,6 +6,7 @@ import { useDisclosure } from "@mantine/hooks";
 import { notifications } from "@mantine/notifications";
 import {
   IconArrowRight,
+  IconCloudDownload,
   IconCopy,
   IconDotsVertical,
   IconFileExport,
@@ -32,6 +33,12 @@ import {
 } from "@/features/favorite/queries/favorite-query";
 
 import { useToggleTemplateMutation } from "@/features/page-embed/queries/page-embed-query";
+import { useCollabToken } from "@/features/auth/queries/auth-query.tsx";
+import { getCollaborationUrl } from "@/lib/config.ts";
+import {
+  makePageAvailableOffline,
+  warmPageYdoc,
+} from "@/features/offline/make-offline";
 import { treeDataAtom } from "@/features/page/tree/atoms/tree-data-atom.ts";
 import { treeModel } from "@/features/page/tree/model/tree-model";
 import { useTreeMutation } from "@/features/page/tree/hooks/use-tree-mutation.ts";
@@ -67,6 +74,29 @@ export function NodeMenu({ node, canEdit }: NodeMenuProps) {
   const isFavorited = favoriteIds.has(node.id);
   const toggleTemplate = useToggleTemplateMutation();
   const isTemplate = !!node.isTemplate;
+  const { data: collabQuery } = useCollabToken();
+
+  const handleMakeAvailableOffline = async () => {
+    notifications.show({ message: t("Saving page for offline use...") });
+    try {
+      // Prefetch read queries so they get persisted to IndexedDB.
+      await makePageAvailableOffline({
+        pageId: node.id,
+        slugId: node.slugId,
+        spaceId: node.spaceId,
+        parentPageId: node.parentPageId,
+      });
+      // Best-effort: warm the page's Yjs document into IndexedDB.
+      await warmPageYdoc(node.id, getCollaborationUrl(), collabQuery?.token);
+      notifications.show({ message: t("Page is now available offline") });
+    } catch {
+      // makePageAvailableOffline / warmPageYdoc never throw, but stay safe.
+      notifications.show({
+        message: t("Failed to make page available offline"),
+        color: "red",
+      });
+    }
+  };
 
   const handleToggleTemplate = async () => {
     const next = !isTemplate;
@@ -204,6 +234,17 @@ export function NodeMenu({ node, canEdit }: NodeMenuProps) {
             {t("Export page")}
           </Menu.Item>
 
+          <Menu.Item
+            leftSection={<IconCloudDownload size={16} />}
+            onClick={(e) => {
+              e.preventDefault();
+              e.stopPropagation();
+              handleMakeAvailableOffline();
+            }}
+          >
+            {t("Make available offline")}
+          </Menu.Item>
+
           {canEdit && (
             <>
               <Menu.Item

apps/client/src/main.tsx

@@ -11,7 +11,8 @@ import { MantineProvider } from "@mantine/core";
 import { BrowserRouter } from "react-router-dom";
 import { ModalsProvider } from "@mantine/modals";
 import { Notifications } from "@mantine/notifications";
-import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { QueryClient } from "@tanstack/react-query";
+import { PersistQueryClientProvider } from "@tanstack/react-query-persist-client";
 import { HelmetProvider } from "react-helmet-async";
 import "./i18n";
 import { PostHogProvider } from "posthog-js/react";
@@ -21,6 +22,12 @@ import {
   isCloud,
   isPostHogEnabled,
 } from "@/lib/config.ts";
+import {
+  queryPersister,
+  shouldDehydrateOfflineQuery,
+} from "@/features/offline/query-persister";
+import { PwaUpdatePrompt } from "@/pwa/pwa-update-prompt";
+import { isCapacitorNativePlatform } from "@/pwa/is-capacitor";
 import posthog from "posthog-js";
 
 export const queryClient = new QueryClient({
@@ -30,6 +37,8 @@ export const queryClient = new QueryClient({
       refetchOnWindowFocus: false,
       retry: false,
       staleTime: 5 * 60 * 1000,
+      // Keep cached read data around long enough to be persisted/restored for offline use.
+      gcTime: 1000 * 60 * 60 * 24,
     },
   },
 });
@@ -50,14 +59,27 @@ root.render(
   <BrowserRouter>
     <MantineProvider theme={theme} cssVariablesResolver={mantineCssResolver}>
       <ModalsProvider>
-        <QueryClientProvider client={queryClient}>
+        <PersistQueryClientProvider
+          client={queryClient}
+          persistOptions={{
+            persister: queryPersister,
+            maxAge: 1000 * 60 * 60 * 24,
+            buster: APP_VERSION,
+            dehydrateOptions: {
+              shouldDehydrateQuery: shouldDehydrateOfflineQuery,
+            },
+          }}
+        >
           <Notifications position="bottom-center" limit={3} zIndex={10000} />
+          {/* Skip SW registration inside the Capacitor native WebView — the
+              native shell serves assets itself; a browser SW would conflict. */}
+          {!isCapacitorNativePlatform() && <PwaUpdatePrompt />}
           <HelmetProvider>
             <PostHogProvider client={posthog}>
               <App />
             </PostHogProvider>
           </HelmetProvider>
-        </QueryClientProvider>
+        </PersistQueryClientProvider>
       </ModalsProvider>
     </MantineProvider>
   </BrowserRouter>,

apps/client/src/pwa/is-capacitor.ts

@@ -0,0 +1,23 @@
+/**
+ * Detects whether the client is running inside a Capacitor native WebView
+ * (native iOS/Android shell from the feature/mobile-app-bootstrap branch).
+ *
+ * This is a pure runtime check against the global `Capacitor` object that the
+ * native bridge injects — no `@capacitor/*` dependency is added. On the plain
+ * browser / installed-PWA path `window.Capacitor` is undefined, so this returns
+ * false and the Workbox service worker registers normally.
+ *
+ * Inside the native WebView the SW must NOT register: it would layer a redundant
+ * (and conflicting) cache over Capacitor's own asset serving and interfere with
+ * the native auth/CORS flow.
+ */
+export function isCapacitorNativePlatform(): boolean {
+  try {
+    const cap = (globalThis as any)?.Capacitor;
+    return !!(cap && typeof cap.isNativePlatform === "function"
+      ? cap.isNativePlatform()
+      : cap?.isNativePlatform);
+  } catch {
+    return false;
+  }
+}

apps/client/src/pwa/pwa-update-prompt.tsx

@@ -0,0 +1,59 @@
+import { useEffect } from "react";
+import { Button } from "@mantine/core";
+import { notifications } from "@mantine/notifications";
+import { useTranslation } from "react-i18next";
+import { useRegisterSW } from "virtual:pwa-register/react";
+
+// Stable notification id so we can show/hide a single update prompt.
+const UPDATE_NOTIFICATION_ID = "pwa-update-available";
+
+/**
+ * Listens for a waiting service worker and surfaces a Mantine notification
+ * prompting the user to reload into the new version.
+ *
+ * Must be mounted inside the Mantine provider subtree (Notifications must be
+ * available). Renders nothing itself.
+ */
+export function PwaUpdatePrompt() {
+  const { t } = useTranslation();
+
+  const {
+    needRefresh: [needRefresh],
+    updateServiceWorker,
+  } = useRegisterSW({
+    onRegisterError(error) {
+      // Best-effort: a failed registration must not break the app.
+      console.error("Service worker registration error:", error);
+    },
+  });
+
+  useEffect(() => {
+    if (!needRefresh) return;
+
+    notifications.show({
+      id: UPDATE_NOTIFICATION_ID,
+      title: t("Update available"),
+      message: (
+        <Button
+          size="xs"
+          variant="light"
+          mt="xs"
+          onClick={() => updateServiceWorker(true)}
+        >
+          {t("Reload")}
+        </Button>
+      ),
+      autoClose: false,
+      withCloseButton: true,
+    });
+
+    // Hide the notification when the prompt is no longer needed / on cleanup.
+    return () => {
+      notifications.hide(UPDATE_NOTIFICATION_ID);
+    };
+  }, [needRefresh, t, updateServiceWorker]);
+
+  return null;
+}
+
+export default PwaUpdatePrompt;

apps/client/src/vite-env.d.ts

@@ -1,2 +1,4 @@
 /// <reference types="vite/client" />
+/// <reference types="vite-plugin-pwa/react" />
+/// <reference types="vite-plugin-pwa/info" />
 declare const APP_VERSION: string

apps/client/vite.config.ts

@@ -1,5 +1,6 @@
 import { defineConfig, loadEnv } from "vite";
 import react from "@vitejs/plugin-react";
+import { VitePWA } from "vite-plugin-pwa";
 import * as path from "path";
 import { execSync } from "node:child_process";
 
@@ -53,7 +54,41 @@ export default defineConfig(({ mode }) => {
       },
       APP_VERSION: JSON.stringify(resolveAppVersion(envPath)),
     },
-    plugins: [react()],
+    plugins: [
+      react(),
+      VitePWA({
+        registerType: "prompt",
+        injectRegister: null,
+        strategies: "generateSW",
+        manifest: false,
+        workbox: {
+          globPatterns: ["**/*.{js,css,html,svg,png,ico,woff2,json}"],
+          navigateFallback: "index.html",
+          navigateFallbackDenylist: [/^\/api\//, /^\/collab\//, /^\/socket\.io\//],
+          cleanupOutdatedCaches: true,
+          clientsClaim: true,
+          runtimeCaching: [
+            { urlPattern: ({ url }) => url.pathname.startsWith("/collab"), handler: "NetworkOnly" },
+            { urlPattern: ({ url }) => url.pathname.startsWith("/socket.io"), handler: "NetworkOnly" },
+            // M2 read-path: GET navigation API responses fall back to cache when offline.
+            // Only GET is cached; mutations always hit the network (Workbox caching handlers
+            // only match GET by default, but scope explicitly for clarity/safety).
+            {
+              urlPattern: ({ url, request }) => url.pathname.startsWith("/api") && request.method === "GET",
+              handler: "NetworkFirst",
+              options: {
+                cacheName: "api-get-cache",
+                networkTimeoutSeconds: 5,
+                expiration: { maxEntries: 200, maxAgeSeconds: 60 * 60 * 24 },
+              },
+            },
+            // Any non-GET /api stays network-only (never served stale).
+            { urlPattern: ({ url }) => url.pathname.startsWith("/api"), handler: "NetworkOnly" },
+          ],
+        },
+        devOptions: { enabled: false },
+      }),
+    ],
     build: {
       rolldownOptions: {
         output: {

apps/server/src/collaboration/collaboration.util.ts

@@ -59,6 +59,7 @@ import { generateHTML, generateJSON } from '../common/helpers/prosemirror/html';
 import { Node, Schema } from '@tiptap/pm/model';
 import * as Y from 'yjs';
 import { Logger } from '@nestjs/common';
+import { TiptapTransformer } from '@hocuspocus/transformer';
 
 export const tiptapExtensions = [
   StarterKit.configure({
@@ -143,6 +144,34 @@ export function jsonToText(tiptapJson: JSONContent) {
   return generateText(tiptapJson, tiptapExtensions);
 }
 
+/**
+ * Build a standalone Y.Doc that holds ONLY the page title, in a dedicated Yjs
+ * fragment named exactly 'title' (the collaborative title-editor contract with
+ * the client). The ProseMirror shape is a doc with a single level-1 heading
+ * whose text is the title (empty title => heading with no text child).
+ *
+ * The encoded state of the returned doc can be merged into a body doc via
+ * `Y.applyUpdate(doc, Y.encodeStateAsUpdate(titleSeed))` to seed the title
+ * fragment for legacy pages. Seeding MUST be guarded by an emptiness check on
+ * the existing 'title' fragment to avoid the Yjs duplication trap.
+ */
+export function buildTitleSeedYdoc(title: string): Y.Doc {
+  return TiptapTransformer.toYdoc(
+    {
+      type: 'doc',
+      content: [
+        {
+          type: 'heading',
+          attrs: { level: 1 },
+          content: title ? [{ type: 'text', text: title }] : [],
+        },
+      ],
+    },
+    'title',
+    tiptapExtensions,
+  );
+}
+
 export function jsonToNode(tiptapJson: JSONContent) {
   const schema = getSchema(tiptapExtensions);
   try {

apps/server/src/collaboration/extensions/persistence.extension.ts

@@ -9,6 +9,7 @@ import * as Y from 'yjs';
 import { Injectable, Logger } from '@nestjs/common';
 import { TiptapTransformer } from '@hocuspocus/transformer';
 import {
+  buildTitleSeedYdoc,
   getPageId,
   isEmptyParagraphDoc,
   jsonToText,
@@ -86,10 +87,30 @@ export class PersistenceExtension implements Extension {
       const dbState = new Uint8Array(page.ydoc);
 
       Y.applyUpdate(doc, dbState);
+
+      // Legacy pages persisted their title only in the `page.title` column; the
+      // ydoc has no 'title' fragment. Seed it once so the client's
+      // collaborative title editor can show/edit the title. This runs inside the
+      // ydoc branch (NOT gated by the top-level 'default' body guard) because a
+      // body that loaded from page.ydoc can still lack a title fragment. The
+      // seed persists back to the DB so it is one-shot per page.
+      const seeded = this.seedTitleFragment(doc, page.title);
+      if (seeded) {
+        await this.persistYdoc(doc, pageId);
+      }
+
       return doc;
     }
 
-    // if no ydoc state in db convert json in page.content to Ydoc.
+    // NOTE (offline-sync M1, Goal 2): this per-load self-heal converts +
+    // title-seeds + persists every legacy page (content set, ydoc null) on its
+    // first open, which neutralizes the duplication trap incrementally. A
+    // proactive one-shot BATCH migration over all such pages could be added
+    // later, but it requires the tiptap schema + TiptapTransformer (Node/Yjs),
+    // which a Kysely SQL migration cannot run; no runnable-task/CLI convention
+    // exists in this repo yet, so we deliberately avoid a fragile migration.
+    //
+    // If no ydoc state in db, convert the JSON in page.content to a Y.Doc.
     if (page.content) {
       this.logger.debug(`converting json to ydoc: ${pageId}`);
 
@@ -99,7 +120,20 @@ export class PersistenceExtension implements Extension {
         tiptapExtensions,
       );
 
-      Y.encodeStateAsUpdate(ydoc);
+      // Seed the title fragment for legacy pages here too, so the freshly built
+      // ydoc carries the title from the page.title column.
+      this.seedTitleFragment(ydoc, page.title);
+
+      // DUPLICATION TRAP (classic Yjs): this rebuild produces a ydoc with FRESH
+      // Yjs client-ids each time it runs. If we returned it WITHOUT persisting,
+      // a later load would rebuild again with different client-ids, and a
+      // long-offline client holding a ydoc derived from an EARLIER rebuild could
+      // merge its update and DUPLICATE all the content (the two states share no
+      // common ancestor). Persist the built ydoc to page.ydoc immediately so
+      // every subsequent load takes the page.ydoc branch above and this rebuild
+      // never runs again for this page (one-shot per page).
+      await this.persistYdoc(ydoc, pageId);
+
       return ydoc;
     }
 
@@ -107,6 +141,56 @@ export class PersistenceExtension implements Extension {
     return new Y.Doc();
   }
 
+  /**
+   * Seed the 'title' fragment of `doc` from the `page.title` column for legacy
+   * pages whose persisted ydoc has no title fragment yet.
+   *
+   * Guarded STRICTLY by emptiness: we only seed when the existing 'title'
+   * fragment is empty AND there is a non-empty column title. Seeding a non-empty
+   * fragment would re-introduce the Yjs duplication trap, so we never do it.
+   * Returns true when a seed was applied (so the caller can persist).
+   * Defensive: a malformed title must not break document loading.
+   */
+  private seedTitleFragment(doc: Y.Doc, title: string | null): boolean {
+    const trimmed = (title ?? '').trim();
+    if (!trimmed) return false;
+
+    try {
+      const titleFrag = doc.get('title', Y.XmlFragment);
+      if (titleFrag.length !== 0) return false;
+
+      const titleSeed = buildTitleSeedYdoc(title);
+      Y.applyUpdate(doc, Y.encodeStateAsUpdate(titleSeed));
+      this.logger.debug('seeded title fragment from page.title column');
+      return true;
+    } catch (err) {
+      this.logger.warn(`failed to seed title fragment: ${err?.['message']}`);
+      return false;
+    }
+  }
+
+  /**
+   * Persist the current state of `doc` into page.ydoc. Used by the one-shot
+   * rebuild/seed self-heal in onLoadDocument so the conversion is durable and
+   * never repeats. Defensive (try/catch + log): a persistence failure here must
+   * NOT break document loading — the in-memory doc is still returned and the
+   * next store will persist it anyway.
+   */
+  private async persistYdoc(doc: Y.Doc, pageId: string): Promise<void> {
+    try {
+      await this.pageRepo.updatePage(
+        { ydoc: Buffer.from(Y.encodeStateAsUpdate(doc)) },
+        pageId,
+      );
+      this.logger.debug(`persisted rebuilt/seeded ydoc: ${pageId}`);
+    } catch (err) {
+      this.logger.error(
+        `Failed to persist rebuilt/seeded ydoc for page ${pageId}`,
+        err,
+      );
+    }
+  }
+
   async onStoreDocument(data: onStoreDocumentPayload) {
     const { documentName, document, context } = data;
 
@@ -124,7 +208,34 @@ export class PersistenceExtension implements Extension {
       this.logger.warn('jsonToText' + err?.['message']);
     }
 
+    // Title lives in the SAME Y.Doc as the body, in a dedicated 'title' fragment
+    // (the collaborative title-editor contract with the client). Extract it
+    // defensively: a malformed title fragment must NOT crash the document store.
+    // `hasTitleFragment` distinguishes "the doc actually carries a title
+    // fragment" from "legacy doc with no title fragment" — only the former may
+    // write page.title, so a legacy doc never clobbers the column with ''.
+    let titleText = '';
+    let hasTitleFragment = false;
+    try {
+      const titleFrag = document.get('title', Y.XmlFragment);
+      hasTitleFragment = !!titleFrag && titleFrag.length > 0;
+      if (hasTitleFragment) {
+        const titleJson = TiptapTransformer.fromYdoc(document, 'title');
+        titleText = titleJson ? jsonToText(titleJson).trim() : '';
+      }
+    } catch (err) {
+      this.logger.warn('title extraction: ' + err?.['message']);
+      hasTitleFragment = false;
+    }
+
     let page: Page = null;
+    // Tracks whether the BODY ('default') changed in this store. The heavy
+    // body-only side-effects (transclusion sync, mentions, RAG, history) stay
+    // gated on this so a title-only change does not trigger them.
+    let bodyChanged = false;
+    // Tracks a successful title-only persist so the post-tx contributor folding
+    // (collabHistory.addContributors) runs for the title-only case too.
+    let titleOnlyPersisted = false;
     const editingUserIds = this.consumeContributors(documentName);
     // Sticky agent marker: 'agent' if any agent edit landed in this window, OR
     // if the current writer is the agent (covers a store with no prior onChange
@@ -146,11 +257,62 @@ export class PersistenceExtension implements Extension {
           return;
         }
 
-        if (isDeepStrictEqual(tiptapJson, page.content)) {
+        bodyChanged = !isDeepStrictEqual(tiptapJson, page.content);
+        // Only a populated 'title' fragment may update page.title; compare
+        // against the current column value (treat null as '').
+        const titleChanged =
+          hasTitleFragment && titleText !== (page.title ?? '');
+
+        // No-op fast path: neither body nor title changed.
+        if (!bodyChanged && !titleChanged) {
           page = null;
           return;
         }
 
+        // Title-only change: the body is unchanged, so skip the heavy body
+        // history/contributor logic and persist just the new title and the
+        // ydoc (the title fragment edit lives in the same ydoc). The early-skip
+        // used to drop this case entirely, losing the title change.
+        if (!bodyChanged) {
+          // Fold the window's editing users into contributors the same way the
+          // body branch does, so a user who edited ONLY the title is not dropped
+          // from page.contributorIds.
+          const contributorIds = Array.from(
+            new Set([
+              ...(page.contributorIds || []),
+              ...editingUserIds,
+              page.creatorId,
+            ]),
+          );
+          await this.pageRepo.updatePage(
+            {
+              title: titleText,
+              ydoc: ydocState,
+              lastUpdatedById: context.user.id,
+              contributorIds,
+              // A title-only change is not a body-authorship transition; leave
+              // lastUpdatedSource/aiChatId untouched so the user->agent history
+              // boundary in the body branch is not bypassed.
+            },
+            pageId,
+            trx,
+            // Mirror PageService.update's tree snapshot so a collaborative rename
+            // propagates to other users' sidebar/breadcrumbs like the REST rename.
+            {
+              treeUpdate: {
+                id: pageId,
+                slugId: page.slugId,
+                spaceId: page.spaceId,
+                parentPageId: page.parentPageId ?? null,
+                title: titleText,
+              },
+            },
+          );
+          this.logger.debug(`Page title updated: ${pageId} - SlugId: ${page.slugId}`);
+          titleOnlyPersisted = true;
+          return;
+        }
+
         let contributorIds = undefined;
         try {
           const existingContributors = page.contributorIds || [];
@@ -201,9 +363,27 @@ export class PersistenceExtension implements Extension {
             lastUpdatedSource,
             lastUpdatedAiChatId: context?.aiChatId ?? null,
             contributorIds: contributorIds,
+            // Persist the title in the SAME transaction when the title fragment
+            // changed alongside the body.
+            ...(titleChanged ? { title: titleText } : {}),
           },
           pageId,
           trx,
+          // Mirror PageService.update's tree snapshot so a collaborative rename
+          // propagates to other users' sidebar/breadcrumbs like the REST rename.
+          // Only attach when the title actually changed; a body-only save must
+          // not trigger a tree broadcast.
+          titleChanged
+            ? {
+                treeUpdate: {
+                  id: pageId,
+                  slugId: page.slugId,
+                  spaceId: page.spaceId,
+                  parentPageId: page.parentPageId ?? null,
+                  title: titleText,
+                },
+              }
+            : undefined,
         );
 
         this.logger.debug(`Page updated: ${pageId} - SlugId: ${page.slugId}`);
@@ -212,6 +392,8 @@ export class PersistenceExtension implements Extension {
       this.logger.error(`Failed to update page ${pageId}`, err);
     }
 
+    // `page` is truthy whenever anything was persisted (body OR title-only), so
+    // the page.updated broadcast fires for a title-only change too.
     if (page) {
       document.broadcastStateless(
         JSON.stringify({
@@ -229,11 +411,20 @@ export class PersistenceExtension implements Extension {
             : undefined,
         }),
       );
+    }
 
+    // Record the window's editing users in collab history for a title-only
+    // change too (the body branch does this below, gated on bodyChanged).
+    if (page && titleOnlyPersisted) {
+      await this.collabHistory.addContributors(pageId, editingUserIds);
+    }
+
+    // Body-only side-effects: skip them for a title-only change (body unchanged).
+    if (page && bodyChanged) {
       await this.syncTransclusion(pageId, page.workspaceId, tiptapJson);
     }
 
-    if (page) {
+    if (page && bodyChanged) {
       await this.collabHistory.addContributors(pageId, editingUserIds);
 
       const mentions = extractMentions(tiptapJson);