perf: route- and modal-level code splitting (React.lazy)

The whole app shipped in one bundle, so the logged-out landing and every page
pulled all module code. Split into lazy chunks:
- main.tsx: lazy App + the public leaves (WatchPage, Privacy, Terms), so a
  public /watch share link never downloads the authenticated app.
- App.tsx: each module page (Feed, Channels, Playlists, Stats, Scheduler,
  Config, Users, Settings, Notifications, Messages, Downloads, ChannelPage) and
  the About/ReleaseNotes/Onboarding modals load on demand behind <Suspense>.
- Heavy modals lazy in their parents: PlayerModal (Feed, Playlists),
  DownloadDialog (DownloadButton — kept out of the feed chunk), and the
  VideoEditor/ShareDialog/ProfileEditor (DownloadCenter).
- Extracted focusAccessRequestsTab + the tab constants to lib/adminUsersTab so
  callers can pre-select the admin tab without statically importing the now
  lazy-loaded AdminUsers page (which would defeat the split).

Build now emits ~25 chunks. Landing no longer downloads any module code
(~350 KB deferred); dev landing Perf 93->95. Verified in a real browser: every
page + the video editor load with no console errors.

frontend/src/App.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useRef, useState } from "react";
+import { lazy, Suspense, useCallback, useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import {
@@ -40,36 +40,43 @@ import {
 } from "./lib/storage";
 import { useConfirm } from "./components/ConfirmProvider";
 import type { PrefsController } from "./components/SettingsPanel";
+import type { ChannelStatusFilter, ChannelsView } from "./components/Channels";
+// Persistent shell — always mounted, so eagerly imported.
 import Welcome from "./components/Welcome";
 import SetupWizard from "./components/SetupWizard";
 import Header from "./components/Header";
 import NavSidebar from "./components/NavSidebar";
 import Sidebar from "./components/Sidebar";
-import Feed from "./components/Feed";
-import ChannelPage from "./components/ChannelPage";
 import BackToTop from "./components/BackToTop";
-import Channels, { type ChannelStatusFilter, type ChannelsView } from "./components/Channels";
-import Playlists from "./components/Playlists";
-import Stats from "./components/Stats";
-import Scheduler from "./components/Scheduler";
-import ConfigPanel from "./components/ConfigPanel";
-import AdminUsers, { focusAccessRequestsTab } from "./components/AdminUsers";
-import SettingsPanel from "./components/SettingsPanel";
-import NotificationsPanel from "./components/NotificationsPanel";
-import Messages from "./components/Messages";
-import DownloadCenter from "./components/DownloadCenter";
-import { setNavigator } from "./lib/nav";
 import ChatDock from "./components/ChatDock";
-import OnboardingWizard from "./components/OnboardingWizard";
-import { shouldAutoOpenOnboarding } from "./lib/onboarding";
 import Toaster from "./components/Toaster";
 import ErrorDialog from "./components/ErrorDialog";
-import About from "./components/About";
-import ReleaseNotes from "./components/ReleaseNotes";
 import VersionBanner from "./components/VersionBanner";
 import DemoBanner from "./components/DemoBanner";
+import { setNavigator } from "./lib/nav";
+import { focusAccessRequestsTab } from "./lib/adminUsersTab";
+import { shouldAutoOpenOnboarding } from "./lib/onboarding";
 import { CURRENT_VERSION } from "./lib/releaseNotes";
 
+// Route-level code splitting: each module page (and the heavier modals) is its own lazy chunk,
+// so the initial load — and the logged-out landing — pulls only the shell, and admin-only pages
+// never reach non-admins. All are rendered inside a <Suspense> boundary below.
+const Feed = lazy(() => import("./components/Feed"));
+const ChannelPage = lazy(() => import("./components/ChannelPage"));
+const Channels = lazy(() => import("./components/Channels"));
+const Playlists = lazy(() => import("./components/Playlists"));
+const Stats = lazy(() => import("./components/Stats"));
+const Scheduler = lazy(() => import("./components/Scheduler"));
+const ConfigPanel = lazy(() => import("./components/ConfigPanel"));
+const AdminUsers = lazy(() => import("./components/AdminUsers"));
+const SettingsPanel = lazy(() => import("./components/SettingsPanel"));
+const NotificationsPanel = lazy(() => import("./components/NotificationsPanel"));
+const Messages = lazy(() => import("./components/Messages"));
+const DownloadCenter = lazy(() => import("./components/DownloadCenter"));
+const OnboardingWizard = lazy(() => import("./components/OnboardingWizard"));
+const About = lazy(() => import("./components/About"));
+const ReleaseNotes = lazy(() => import("./components/ReleaseNotes"));
+
 const DEFAULT_FILTERS: FeedFilters = {
   tags: [],
   tagMode: "or",
@@ -656,6 +663,11 @@ export default function App() {
     );
   if (!meQuery.data) return <Welcome />;
 
+  // Shown briefly while a lazy page/module chunk loads (first visit to that page only).
+  const pageFallback = (
+    <div className="flex-1 grid place-items-center text-muted">{t("common.loading")}</div>
+  );
+
   return (
     <div className="h-screen flex bg-bg text-fg">
       <NavSidebar
@@ -690,6 +702,7 @@ export default function App() {
       )}
       <div className="relative flex-1 min-w-0 flex flex-col">
         {channelView ? (
+          <Suspense fallback={pageFallback}>
             <ChannelPage
               key={channelView.id}
               channelId={channelView.id}
@@ -699,6 +712,7 @@ export default function App() {
               onBack={closeChannel}
               onOpenChannel={openChannel}
             />
+          </Suspense>
         ) : (
           <>
         <Header
@@ -711,6 +725,7 @@ export default function App() {
         {meQuery.data!.is_demo && <DemoBanner />}
         <VersionBanner onOpen={() => openReleaseNotes(CURRENT_VERSION)} />
           <main className="flex-1 min-w-0 overflow-y-auto">
+          <Suspense fallback={pageFallback}>
           {page === "channels" ? (
             <Channels
               canWrite={meQuery.data!.can_write}
@@ -768,6 +783,7 @@ export default function App() {
               onOpenChannel={openChannel}
             />
           )}
+          </Suspense>
           </main>
           </>
         )}
@@ -777,6 +793,7 @@ export default function App() {
         <Toaster />
       </div>
       {meQuery.data && !meQuery.data.is_demo && <ChatDock meId={meQuery.data.id} />}
+      <Suspense fallback={null}>
         {wizardOpen && meQuery.data && !meQuery.data.is_demo && (
           <OnboardingWizard me={meQuery.data} onClose={() => setWizardOpen(false)} />
         )}
@@ -792,6 +809,7 @@ export default function App() {
         {notesOpen && (
           <ReleaseNotes onClose={() => setNotesOpen(false)} highlight={notesHighlight} />
         )}
+      </Suspense>
       <ErrorDialog />
       {/* Re-binds to the active page's scroll container on navigation (page or channel change). */}
       <BackToTop dep={channelView ? `chan:${channelView.id}` : page} />

frontend/src/components/AdminUsers.tsx

@@ -4,7 +4,7 @@ import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { Ban, Check, RotateCcw, Shield, Trash2, UserPlus, X } from "lucide-react";
 import { api, type AdminUserRow, type Invite, type Me } from "../lib/api";
 import { notify } from "../lib/notifications";
-import { LS, setAccountRaw } from "../lib/storage";
+import { ADMIN_USERS_TAB_KEY } from "../lib/adminUsersTab";
 import Tooltip from "./Tooltip";
 import { Section } from "./ui/form";
 import { useConfirm } from "./ConfirmProvider";
@@ -13,15 +13,8 @@ import Tabs, { usePersistedTab } from "./Tabs";
 // Admin-only user & access management: roles, access requests (the Invite whitelist), and the
 // demo whitelist + reset. Each section is its own tab (persisted across reloads); the Access tab
 // carries a badge with the count of pending requests so it's visible without switching to it.
-// The persisted-tab storage key + the access-requests tab id, exported so a notification's
-// "Review" link can pre-select that tab before navigating here (usePersistedTab reads the key
-// on mount, and this page mounts fresh on navigation).
-export const ADMIN_USERS_TAB_KEY = LS.adminUsersTab;
-export const ADMIN_USERS_ACCESS_TAB = "access";
-
-export function focusAccessRequestsTab(): void {
-  setAccountRaw(ADMIN_USERS_TAB_KEY, ADMIN_USERS_ACCESS_TAB);
-}
+// (The tab key + a "focus the Access tab" helper live in lib/adminUsersTab so callers can
+// pre-select the tab without importing this lazy-loaded page — see that file.)
 
 export default function AdminUsers({ me }: { me: Me }) {
   const { t } = useTranslation();

frontend/src/components/DownloadButton.tsx

@@ -1,9 +1,11 @@
-import { useState } from "react";
+import { lazy, Suspense, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import { Download } from "lucide-react";
 import clsx from "clsx";
-import DownloadDialog from "./DownloadDialog";
+// Lazy: the download dialog (+ its profile editor) loads only when a card's download button is
+// clicked, so it never ships in the feed chunk for the majority who just browse.
+const DownloadDialog = lazy(() => import("./DownloadDialog"));
 import { api, type Me } from "../lib/api";
 
 // Self-contained download affordance for a video card / the player. Hidden for the demo account
@@ -59,7 +61,9 @@ export default function DownloadButton({
         <Download className={clsx("w-4 h-4", inQueue && "animate-pulse")} />
       </button>
       {open && (
+        <Suspense fallback={null}>
           <DownloadDialog source={videoId} title={title} onClose={() => setOpen(false)} />
+        </Suspense>
       )}
     </>
   );

frontend/src/components/DownloadCenter.tsx

@@ -1,4 +1,4 @@
-import { useMemo, useState } from "react";
+import { lazy, Suspense, useMemo, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import {
@@ -16,10 +16,12 @@ import {
 import clsx from "clsx";
 import Tabs, { usePersistedTab } from "./Tabs";
 import Modal from "./Modal";
-import DownloadDialog from "./DownloadDialog";
-import ProfileEditor from "./ProfileEditor";
-import VideoEditor from "./VideoEditor";
-import ShareDialog from "./ShareDialog";
+// Lazy: these dialogs/editors open on demand, so they stay out of the Downloads page chunk until
+// used (the video editor in particular is heavy — filmstrip + scrubber).
+const DownloadDialog = lazy(() => import("./DownloadDialog"));
+const ProfileEditor = lazy(() => import("./ProfileEditor"));
+const VideoEditor = lazy(() => import("./VideoEditor"));
+const ShareDialog = lazy(() => import("./ShareDialog"));
 import { useConfirm } from "./ConfirmProvider";
 import { useLiveQuery } from "../lib/useLiveQuery";
 import { api, type DownloadJob, type Me } from "../lib/api";
@@ -582,6 +584,7 @@ export default function DownloadCenter({ me }: { me: Me }) {
 
       {tab === "system" && me.role === "admin" && <AdminSystem />}
 
+      <Suspense fallback={null}>
         {addSource && (
           <DownloadDialog
             source={addSource}
@@ -595,6 +598,7 @@ export default function DownloadCenter({ me }: { me: Me }) {
         {renameJob && <RenameModal job={renameJob} onClose={() => setRenameJob(null)} />}
         {shareJob && <ShareDialog job={shareJob} onClose={() => setShareJob(null)} />}
         {editJob && <VideoEditor job={editJob} onClose={() => setEditJob(null)} />}
+      </Suspense>
     </div>
   );
 }

frontend/src/components/DownloadDialog.tsx

@@ -1,9 +1,11 @@
-import { useState } from "react";
+import { lazy, Suspense, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import Modal from "./Modal";
-import ProfileEditor from "./ProfileEditor";
 import { api } from "../lib/api";
+
+// Lazy: the full profile editor only opens from the dialog's "manage presets" affordance.
+const ProfileEditor = lazy(() => import("./ProfileEditor"));
 import { notify } from "../lib/notifications";
 import { navigateTo } from "../lib/nav";
 
@@ -105,12 +107,14 @@ export default function DownloadDialog({
       </div>
 
       {manage && (
+        <Suspense fallback={null}>
           <ProfileEditor
             onClose={() => {
               setManage(false);
               profilesQ.refetch();
             }}
           />
+        </Suspense>
       )}
     </Modal>
   );

frontend/src/components/Feed.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useRef, useState } from "react";
+import { lazy, Suspense, useCallback, useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { keepPreviousData, useInfiniteQuery, useQuery, useQueryClient } from "@tanstack/react-query";
 import { ArrowDown, ArrowUp, ArrowLeft, Info, RefreshCw, Trash2, Youtube } from "lucide-react";
@@ -7,7 +7,8 @@ import i18n from "../i18n";
 import { notify, resolveVideo } from "../lib/notifications";
 import { useDebounced } from "../lib/useDebounced";
 import VirtualFeed from "./VirtualFeed";
-import PlayerModal from "./PlayerModal";
+// Lazy: the in-app YouTube player (IFrame API) loads only when a video is first opened.
+const PlayerModal = lazy(() => import("./PlayerModal"));
 
 const PAGE = 60;
 
@@ -441,6 +442,7 @@ export default function Feed({
         )}
 
         {activeVideo && (
+          <Suspense fallback={null}>
             <PlayerModal
               video={activeVideo.video}
               startAt={activeVideo.startAt}
@@ -448,6 +450,7 @@ export default function Feed({
               onState={onState}
               onOpenChannel={onOpenChannel}
             />
+          </Suspense>
         )}
       </div>
     );
@@ -647,6 +650,7 @@ export default function Feed({
         />
       )}
       {activeVideo && (
+        <Suspense fallback={null}>
           <PlayerModal
             video={activeVideo.video}
             startAt={activeVideo.startAt}
@@ -654,6 +658,7 @@ export default function Feed({
             onState={onState}
             onOpenChannel={onOpenChannel}
           />
+        </Suspense>
       )}
       {isFetchingNextPage && (
         <div className="text-center text-muted py-4">{t("feed.loadingMore")}</div>

frontend/src/components/NotificationsPanel.tsx

@@ -4,7 +4,7 @@ import { useMutation, useQueryClient } from "@tanstack/react-query";
 import { Activity, Bell, Check, CheckCheck, ExternalLink, Eye, RotateCcw, Search, Trash2, Tv, UserPlus, X } from "lucide-react";
 import { api, type AppNotification, type FeedFilters } from "../lib/api";
 import { useLiveQuery } from "../lib/useLiveQuery";
-import { focusAccessRequestsTab } from "./AdminUsers";
+import { focusAccessRequestsTab } from "../lib/adminUsersTab";
 import {
   clearAll as clearClient,
   dismiss as dismissClient,

frontend/src/components/Playlists.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useMemo, useRef, useState } from "react";
+import { lazy, Suspense, useEffect, useMemo, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import {
@@ -39,7 +39,7 @@ import { formatDuration } from "../lib/format";
 import { notify } from "../lib/notifications";
 import { getAccountRaw, LS, readAccountMerged, setAccountRaw, writeAccount } from "../lib/storage";
 import { useUndoable } from "../lib/useUndoable";
-import PlayerModal from "./PlayerModal";
+const PlayerModal = lazy(() => import("./PlayerModal"));
 import UndoToolbar from "./UndoToolbar";
 import { useConfirm } from "./ConfirmProvider";
 
@@ -850,6 +850,7 @@ export default function Playlists({ canWrite }: { canWrite: boolean }) {
       </main>
 
       {playingIndex != null && items[playingIndex] && (
+        <Suspense fallback={null}>
           <PlayerModal
             video={items[playingIndex]}
             queue={items}
@@ -858,6 +859,7 @@ export default function Playlists({ canWrite }: { canWrite: boolean }) {
             onClose={() => setPlayingIndex(null)}
             onState={playerState}
           />
+        </Suspense>
       )}
     </div>
   );

frontend/src/lib/adminUsersTab.ts

@@ -0,0 +1,15 @@
+import { LS, setAccountRaw } from "./storage";
+
+// The admin Users page's persisted-tab key + the Access-requests tab id, plus a helper to
+// pre-select that tab before navigating there (a notification's "Review" link uses it —
+// usePersistedTab reads the key on mount, and the page mounts fresh on navigation).
+//
+// Kept out of AdminUsers.tsx so callers (App, NotificationsPanel) can pre-select the tab
+// WITHOUT statically importing the — now lazy-loaded — admin page, which would otherwise pull
+// it back into the main bundle and defeat the code-split.
+export const ADMIN_USERS_TAB_KEY = LS.adminUsersTab;
+export const ADMIN_USERS_ACCESS_TAB = "access";
+
+export function focusAccessRequestsTab(): void {
+  setAccountRaw(ADMIN_USERS_TAB_KEY, ADMIN_USERS_ACCESS_TAB);
+}

frontend/src/main.tsx

@@ -1,22 +1,25 @@
-import React from "react";
+import React, { lazy, Suspense } from "react";
 import { createRoot } from "react-dom/client";
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
-import App from "./App";
 import ErrorBoundary from "./components/ErrorBoundary";
 import { ConfirmProvider } from "./components/ConfirmProvider";
-import PrivacyPolicy from "./components/legal/PrivacyPolicy";
-import Terms from "./components/legal/Terms";
-import WatchPage from "./components/WatchPage";
 import "./i18n";
 import "./index.css";
 
+// Split by top-level route so each entry point is its own chunk: a public /watch share link or a
+// legal page never downloads the authenticated app bundle, and the app never carries them either.
+// The legal pages live outside the App tree (no /api/me) so Google's consent screen and reviewers
+// can fetch them directly; the watch page is a login-free public player. Reached by full-page
+// navigation (plain <a href>), so a simple pathname switch is enough — no router needed.
+const App = lazy(() => import("./App"));
+const PrivacyPolicy = lazy(() => import("./components/legal/PrivacyPolicy"));
+const Terms = lazy(() => import("./components/legal/Terms"));
+const WatchPage = lazy(() => import("./components/WatchPage"));
+
 const queryClient = new QueryClient({
   defaultOptions: { queries: { retry: false, staleTime: 30_000, refetchOnWindowFocus: false } },
 });
 
-// Public, login-free legal pages. They live outside the authenticated App tree (no /api/me)
-// so Google's consent screen and reviewers can fetch them directly. Reached by full-page
-// navigation (plain <a href>), so a simple pathname switch is enough — no router needed.
 const path = window.location.pathname;
 const root =
   path === "/privacy" ? <PrivacyPolicy /> :
@@ -32,5 +35,7 @@ const root =
   );
 
 createRoot(document.getElementById("root")!).render(
-  <React.StrictMode>{root}</React.StrictMode>
+  <React.StrictMode>
+    <Suspense fallback={<div style={{ minHeight: "100vh" }} />}>{root}</Suspense>
+  </React.StrictMode>
 );