diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index b8a2108..d121896 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -4,6 +4,8 @@ import { ThemeProvider } from "@mui/material/styles";
 import CssBaseline from "@mui/material/CssBaseline";
 import Box from "@mui/material/Box";
 import { BrowserRouter, Navigate, Route, Routes, useNavigate } from "react-router-dom";
+import Snackbar from "@mui/material/Snackbar";
+import Alert from "@mui/material/Alert";
 import AppLayout from "./components/Layout/AppLayout";
 import DashboardPage from "./pages/DashboardPage";
 import ModelsPage from "./pages/ModelsPage";
@@ -83,6 +85,7 @@ function AppShell({
       themeSelection={settings.theme.selected}
       apiUp={apiUp}
       folderId={folderId}
+      onSelectFolder={setFolderId}
       onPrintsChanged={handlePrintsChanged}
       onUnauthorized={onUnauthorized}
       isAdmin={isAdmin}
@@ -178,7 +181,11 @@ export default function App() {
   const [user, setUser] = React.useState<AuthUser | null>(() => readUser());
   const [health, setHealth] = React.useState<HealthInfo | null>(null);
   const [tokenTtl, setTokenTtl] = React.useState<number | null>(null);
-  const [sessionExpired, setSessionExpired] = React.useState(false);
+  const [showExpiredToast, setShowExpiredToast] = React.useState(false);
+  // A ref (not state) so concurrent 401s from several in-flight requests all see the guard
+  // synchronously -- state's setSessionExpired(true) wouldn't be visible to the others until
+  // the next render, letting each of them past the check and onto its own alert().
+  const sessionExpiredRef = React.useRef(false);
   const [settings, setSettings] = React.useState<AppSettings>(() => loadSettings());
   const [previewMode, setPreviewMode] = React.useState<PreviewMode>("automatic");
   const resolvedTheme = useResolvedTheme(settings.theme.selected);
@@ -207,17 +214,17 @@ export default function App() {
     setToken(tok);
     setUser(loggedInUser);
     setTokenTtl(ttl);
-    setSessionExpired(false);
+    sessionExpiredRef.current = false;
   };
 
   const handleUnauthorized = React.useCallback(() => {
-    if (sessionExpired) return;
+    if (sessionExpiredRef.current) return;
+    sessionExpiredRef.current = true;
     clearToken();
     setToken(null);
     setTokenTtl(null);
-    setSessionExpired(true);
-    alert(t("shell.sessionExpired"));
-  }, [sessionExpired, t]);
+    setShowExpiredToast(true);
+  }, []);
 
   const handleLogout = () => {
     // Fire-and-forget: the audit-log entry is recorded server-side before the token that
@@ -257,6 +264,21 @@ export default function App() {
     return () => window.clearTimeout(timer);
   }, [token, tokenTtl, handleUnauthorized]);
 
+  // Shared between both branches below so the toast survives the AppShell -> AuthPage swap that
+  // handleUnauthorized triggers (clearing the token unmounts AppShell and mounts this instead).
+  const sessionExpiredToast = (
+    <Snackbar
+      open={showExpiredToast}
+      autoHideDuration={5000}
+      onClose={() => setShowExpiredToast(false)}
+      anchorOrigin={{ vertical: "bottom", horizontal: "center" }}
+    >
+      <Alert onClose={() => setShowExpiredToast(false)} severity="error" variant="filled" sx={{ width: "100%" }}>
+        {t("shell.sessionExpired")}
+      </Alert>
+    </Snackbar>
+  );
+
   if (authRequired && !token) {
     // No BrowserRouter wraps this branch (see AppShell's comment), so /verify-email -- reached
     // pre-login from the link in the verification email -- is checked directly against
@@ -285,26 +307,30 @@ export default function App() {
             />
           )}
         </Box>
+        {sessionExpiredToast}
       </ThemeProvider>
     );
   }
 
   return (
-    <BrowserRouter>
-      <AppShell
-        isAdmin={isAdmin}
-        user={user}
-        apiUp={apiUp}
-        settings={settings}
-        setSettings={setSettings}
-        previewMode={previewMode}
-        setPreviewMode={setPreviewMode}
-        resolvedTheme={resolvedTheme}
-        muiTheme={muiTheme}
-        onUnauthorized={handleUnauthorized}
-        onLogout={handleLogout}
-        onUserUpdated={handleUserUpdated}
-      />
-    </BrowserRouter>
+    <>
+      <BrowserRouter>
+        <AppShell
+          isAdmin={isAdmin}
+          user={user}
+          apiUp={apiUp}
+          settings={settings}
+          setSettings={setSettings}
+          previewMode={previewMode}
+          setPreviewMode={setPreviewMode}
+          resolvedTheme={resolvedTheme}
+          muiTheme={muiTheme}
+          onUnauthorized={handleUnauthorized}
+          onLogout={handleLogout}
+          onUserUpdated={handleUserUpdated}
+        />
+      </BrowserRouter>
+      <ThemeProvider theme={muiTheme}>{sessionExpiredToast}</ThemeProvider>
+    </>
   );
 }
diff --git a/frontend/src/assets/under-maintenance.png b/frontend/src/assets/under-maintenance.png
new file mode 100644
index 0000000..08412b6
Binary files /dev/null and b/frontend/src/assets/under-maintenance.png differ
diff --git a/frontend/src/components/Layout/AppLayout.tsx b/frontend/src/components/Layout/AppLayout.tsx
index 2ce2bc3..7d734dd 100644
--- a/frontend/src/components/Layout/AppLayout.tsx
+++ b/frontend/src/components/Layout/AppLayout.tsx
@@ -24,6 +24,7 @@ type AppLayoutProps = {
   themeSelection: ThemeSelection;
   apiUp: boolean | null;
   folderId: string | null;
+  onSelectFolder: (id: string | null) => void;
   onPrintsChanged: () => void;
   onUnauthorized: () => void;
   isAdmin: boolean;
@@ -111,6 +112,7 @@ function AppLayoutShell({
   themeSelection,
   apiUp,
   folderId,
+  onSelectFolder,
   onPrintsChanged,
   onUnauthorized,
   isAdmin,
@@ -140,7 +142,7 @@ function AppLayoutShell({
           display: "flex",
         }}
       >
-        <Sidebar isAdmin={isAdmin} />
+        <Sidebar isAdmin={isAdmin} onSelectFolder={onSelectFolder} />
         <Box component="main" sx={{ flex: 1, p: 2, overflow: "auto" }}>
           {apiUp === false && (
             <Alert severity="error" sx={{ mb: 1.5 }}>
diff --git a/frontend/src/components/Layout/Sidebar/index.tsx b/frontend/src/components/Layout/Sidebar/index.tsx
index c1e434c..ea23ecf 100644
--- a/frontend/src/components/Layout/Sidebar/index.tsx
+++ b/frontend/src/components/Layout/Sidebar/index.tsx
@@ -57,11 +57,12 @@ function CollapsedNavIcon({ icon, label, selected, onClick }: {
 
 type Props = {
   isAdmin: boolean;
+  onSelectFolder: (id: string | null) => void;
 };
 
 /** The persistent app-wide navigation rail: Dashboard, Models, Collections, Downloads, and
  *  (for admins) Administration. Folder browsing lives inside the Models page itself, not here. */
-export default function Sidebar({ isAdmin }: Props) {
+export default function Sidebar({ isAdmin, onSelectFolder }: Props) {
   const { t } = useTranslation(["app", "common"]);
   const location = useLocation();
   const navigate = useNavigate();
@@ -97,6 +98,13 @@ export default function Sidebar({ isAdmin }: Props) {
 
   const currentWidth = collapsed ? SIDEBAR_COLLAPSED_WIDTH : SIDEBAR_WIDTH;
 
+  // Always lands on the unfiltered grid, even if a category was selected the last time Models
+  // was open -- unlike the in-page back button, which keeps the filter (see useRouteChrome).
+  const goToModelsRoot = () => {
+    onSelectFolder(null);
+    navigate("/models");
+  };
+
   return (
     <Box
       component="aside"
@@ -161,12 +169,12 @@ export default function Sidebar({ isAdmin }: Props) {
               icon={<ViewInArIcon fontSize="small" />}
               label={t("sidebar.models")}
               selected={onModels}
-              onClick={() => navigate("/models")}
+              onClick={goToModelsRoot}
             />
           ) : (
             <ListItemButton
               selected={onModels}
-              onClick={() => navigate("/models")}
+              onClick={goToModelsRoot}
               sx={{ borderRadius: 1, mb: 0.5 }}
             >
               <ListItemIcon sx={{ minWidth: 30 }}>
diff --git a/frontend/src/i18n/locales/en.json b/frontend/src/i18n/locales/en.json
index 92ed682..1e362f6 100644
--- a/frontend/src/i18n/locales/en.json
+++ b/frontend/src/i18n/locales/en.json
@@ -1080,6 +1080,7 @@
       "removeFromFavorites": "Remove from Favourites",
       "favoriteFailed": "Failed to update favourites. Please try again.",
       "category": "Category",
+      "author": "Author",
       "downloadModelFiles": "Download model files",
       "imported": "Imported {{date}}"
     },
diff --git a/frontend/src/i18n/locales/lt.json b/frontend/src/i18n/locales/lt.json
index 058cea8..7cc5178 100644
--- a/frontend/src/i18n/locales/lt.json
+++ b/frontend/src/i18n/locales/lt.json
@@ -1081,6 +1081,7 @@
       "removeFromFavorites": "Pašalinti iš mėgstamų",
       "favoriteFailed": "Nepavyko atnaujinti mėgstamų. Bandykite dar kartą.",
       "category": "Kategorija",
+      "author": "Autorius",
       "downloadModelFiles": "Atsisiųsti modelio failus",
       "imported": "Importuota {{date}}"
     },
diff --git a/frontend/src/pages/ModelDetailPage/ModelSidePanel.tsx b/frontend/src/pages/ModelDetailPage/ModelSidePanel.tsx
index de85e4c..a2989cd 100644
--- a/frontend/src/pages/ModelDetailPage/ModelSidePanel.tsx
+++ b/frontend/src/pages/ModelDetailPage/ModelSidePanel.tsx
@@ -4,6 +4,7 @@ import Paper from "@mui/material/Paper";
 import Stack from "@mui/material/Stack";
 import Box from "@mui/material/Box";
 import Typography from "@mui/material/Typography";
+import Avatar from "@mui/material/Avatar";
 import Button from "@mui/material/Button";
 import ButtonBase from "@mui/material/ButtonBase";
 import FolderIcon from "@mui/icons-material/Folder";
@@ -25,12 +26,13 @@ type Props = {
   onUnauthorized?: () => void;
 };
 
-/** The model detail page's right-hand summary card: category (jumps back to the Models grid
- *  filtered to it), "Open in {Slicer}" (only when both a preference is set and this print has a
- *  slicer_url -- same condition ModelActionsMenu's menu item uses), "Download model files" (the
- *  same picker-or-direct-download flow as ModelActionsMenu's Download, via useDownloadPrint so
- *  the two can't drift), view/print counts, and -- only for an actually-imported print, per
- *  source_provider -- when it was imported. */
+/** The model detail page's right-hand summary card, sticky so it stays in view while the
+ *  description/tags column scrolls: author (jumps to their author page), category (jumps back
+ *  to the Models grid filtered to it), "Open in {Slicer}" (only when both a preference is set
+ *  and this print has a slicer_url -- same condition ModelActionsMenu's menu item uses),
+ *  "Download model files" (the same picker-or-direct-download flow as ModelActionsMenu's
+ *  Download, via useDownloadPrint so the two can't drift), view/print counts, and -- only for an
+ *  actually-imported print, per source_provider -- when it was imported. */
 export default function ModelSidePanel({ print, onSelectFolder, onUnauthorized }: Props) {
   const { t } = useTranslation(["models", "common"]);
   const navigate = useNavigate();
@@ -54,9 +56,35 @@ export default function ModelSidePanel({ print, onSelectFolder, onUnauthorized }
     ? new Date(print.created_at).toLocaleDateString(undefined, { year: "numeric", month: "long", day: "numeric" })
     : null;
 
+  const authorName = print.author?.name || print.author?.handle || print.creator || null;
+
   return (
-    <Paper variant="outlined" sx={{ p: 2.5, borderRadius: "12px" }}>
+    <Paper variant="outlined" sx={{ p: 2.5, borderRadius: "12px", position: "sticky", top: 16 }}>
       <Stack spacing={2}>
+        <Box>
+          <Typography variant="caption" color="text.secondary" sx={{ display: "block", mb: 0.5 }}>
+            {t("models:detail.author")}
+          </Typography>
+          <Stack
+            direction="row"
+            alignItems="center"
+            spacing={1}
+            sx={{
+              width: "fit-content",
+              cursor: print.author ? "pointer" : "default",
+              ...(print.author ? { "&:hover": { color: "primary.main" } } : undefined),
+            }}
+            onClick={() => print.author && navigate(`/authors/${print.author.id}`)}
+          >
+            <Avatar src={print.author?.avatar_url || undefined} sx={{ width: 28, height: 28, fontSize: 13, color: "inherit !important" }}>
+              {(authorName || "?").slice(0, 1).toUpperCase()}
+            </Avatar>
+            <Typography variant="body2" sx={{ color: "inherit" }}>
+              {authorName || t("models:card.unknownAuthor")}
+            </Typography>
+          </Stack>
+        </Box>
+
         {print.folder_id && print.folder_name && (
           <Box>
             <Typography variant="caption" color="text.secondary" sx={{ display: "block", mb: 0.5 }}>
diff --git a/frontend/src/pages/ModelDetailPage/index.tsx b/frontend/src/pages/ModelDetailPage/index.tsx
index b500183..f7ce1aa 100644
--- a/frontend/src/pages/ModelDetailPage/index.tsx
+++ b/frontend/src/pages/ModelDetailPage/index.tsx
@@ -5,7 +5,6 @@ import Box from "@mui/material/Box";
 import Stack from "@mui/material/Stack";
 import Paper from "@mui/material/Paper";
 import Typography from "@mui/material/Typography";
-import Avatar from "@mui/material/Avatar";
 import Button from "@mui/material/Button";
 import ButtonBase from "@mui/material/ButtonBase";
 import IconButton from "@mui/material/IconButton";
@@ -103,7 +102,6 @@ export default function ModelDetailPage({ theme, onSelectFolder, onUnauthorized
   const images = print.preview_images.toSorted((a, b) => a.position - b.position);
   const hasImages = images.length > 0;
   const activeImage = images[activeImageIndex] || images[0];
-  const authorName = print.author?.name || print.author?.handle || print.creator || null;
   const firstPlate = print.plates[0];
   const canPreview3d = Boolean(firstPlate) && MODEL_EXTS.has(extOf(firstPlate?.filename || ""));
   // Every model should end up with at least one preview image -- an import brings its own cover
@@ -127,26 +125,6 @@ export default function ModelDetailPage({ theme, onSelectFolder, onUnauthorized
         }}
       >
         <Box>
-          <Stack
-            direction="row"
-            alignItems="center"
-            spacing={1}
-            sx={{
-              mb: 2,
-              width: "fit-content",
-              cursor: print.author ? "pointer" : "default",
-              ...(print.author ? { "&:hover": { color: "primary.main" } } : undefined),
-            }}
-            onClick={() => print.author && navigate(`/authors/${print.author.id}`)}
-          >
-            <Avatar src={print.author?.avatar_url || undefined} sx={{ width: 28, height: 28, fontSize: 13, color: "inherit !important" }}>
-              {(authorName || "?").slice(0, 1).toUpperCase()}
-            </Avatar>
-            <Typography variant="body2" sx={{ color: "inherit" }}>
-              {authorName || t("models:card.unknownAuthor")}
-            </Typography>
-          </Stack>
-
           <Box sx={{ position: "relative", width: "100%", aspectRatio: "16 / 10", borderRadius: "12px", overflow: "hidden", bgcolor: "action.hover" }}>
             {hasImages ? (
               <Box