diff --git a/src/components/layout/SectionNav.tsx b/src/components/layout/SectionNav.tsx
new file mode 100644
index 0000000..2ce02ed
--- /dev/null
+++ b/src/components/layout/SectionNav.tsx
@@ -0,0 +1,336 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Coffey Labs
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+/**
+ * INBUXA: tier two of the modern shell. Tier one is the layout switcher in the
+ * top bar (Management / Settings / Account, straight from `schema.layouts`);
+ * this bar carries the active layout's own top-level items, each container
+ * opening its children in a menu. No sidebar, so a list or a form gets the
+ * whole window width.
+ *
+ * The item count comes from the server's schema, so it is never known ahead of
+ * time: the bar measures its items once, then keeps whatever fits and folds the
+ * rest into "More". A layout too deep for a menu bar at all keeps the sidebar —
+ * AdminPanel decides that, not this component.
+ */
+
+import { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react';
+import { useLocation, useNavigate } from 'react-router-dom';
+import { useTranslation } from 'react-i18next';
+import * as LucideIcons from 'lucide-react';
+const { ChevronDown, Lock, MoreHorizontal } = LucideIcons;
+import { cn } from '@/lib/utils';
+import { EnterpriseUpsell } from '@/components/common/EnterpriseUpsell';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuGroup,
+  DropdownMenuItem,
+  DropdownMenuLabel,
+  DropdownMenuSeparator,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
+import { useAccountStore } from '@/stores/accountStore';
+import {
+  checkIsEnterprise,
+  checkLinkVisible,
+  pathMatchesView,
+  resolveViewPath,
+  subtreeContainsActive,
+  subtreeHasVisibleLink,
+  topItemKey,
+  topItemVisible,
+  visibleLinks,
+} from '@/lib/navTree';
+import type { Layout, LayoutItem, LayoutSubItem } from '@/types/schema';
+
+/** Room kept for the "More" trigger when not everything fits. */
+const MORE_WIDTH = 92;
+
+function howManyFit(widths: number[], available: number): number {
+  let total = 0;
+  for (const w of widths) {
+    total += w;
+    if (total > available) {
+      let withMore = 0;
+      for (let j = 0; j < widths.length; j++) {
+        withMore += widths[j];
+        if (withMore + MORE_WIDTH > available) return j;
+      }
+      return widths.length;
+    }
+  }
+  return widths.length;
+}
+
+const TRIGGER_CLASS =
+  'relative flex h-12 shrink-0 items-center gap-1.5 whitespace-nowrap px-3 text-[13px] font-normal text-muted-foreground transition-colors hover:text-foreground';
+const TRIGGER_ACTIVE =
+  "font-medium text-foreground after:absolute after:inset-x-3 after:bottom-0 after:h-0.5 after:rounded-full after:bg-primary after:content-['']";
+
+interface MenuBodyProps {
+  items: LayoutSubItem[];
+  sectionName: string;
+  currentPath: string;
+  edition: string;
+  onPick: (viewName: string, locked: boolean) => void;
+}
+
+/**
+ * A container's children. Direct links stay as items; a nested group becomes a
+ * label over its own links, so "Emails" reads Queued / History: Inbound,
+ * Outbound / Delivery tests rather than one flat list.
+ */
+function MenuBody({ items, sectionName, currentPath, edition, onPick }: MenuBodyProps) {
+  return (
+    <>
+      {items.map((sub, i) => {
+        if (sub.type === 'link') {
+          if (!checkLinkVisible(sub.viewName)) return null;
+          const enterprise = checkIsEnterprise(sub.viewName);
+          if (enterprise && edition === 'oss') return null;
+          const locked = enterprise && edition === 'community';
+          return (
+            <DropdownMenuItem
+              key={sub.viewName}
+              className={cn(
+                pathMatchesView(currentPath, sectionName, sub.viewName) && 'bg-accent text-accent-foreground',
+              )}
+              onClick={() => onPick(sub.viewName, locked)}
+            >
+              <span className="truncate">{sub.name || 'Overview'}</span>
+              {locked && <Lock className="ml-auto h-3 w-3 text-muted-foreground" />}
+            </DropdownMenuItem>
+          );
+        }
+
+        if (!subtreeHasVisibleLink(sub.items, edition)) return null;
+        const links = visibleLinks(sub.items, edition);
+        return (
+          <DropdownMenuGroup key={`${sub.name}-${i}`}>
+            <DropdownMenuLabel className="pt-2 text-[11px] font-semibold uppercase tracking-wider text-muted-foreground">
+              {sub.name}
+            </DropdownMenuLabel>
+            {links.map((l) => (
+              <DropdownMenuItem
+                key={l.viewName}
+                className={cn(
+                  pathMatchesView(currentPath, sectionName, l.viewName) && 'bg-accent text-accent-foreground',
+                )}
+                onClick={() => onPick(l.viewName, checkIsEnterprise(l.viewName) && edition === 'community')}
+              >
+                <span className="truncate">{l.name}</span>
+              </DropdownMenuItem>
+            ))}
+          </DropdownMenuGroup>
+        );
+      })}
+    </>
+  );
+}
+
+interface ItemProps {
+  item: LayoutItem;
+  sectionName: string;
+  currentPath: string;
+  edition: string;
+  onPick: (viewName: string, locked: boolean) => void;
+  measureRef?: (el: HTMLElement | null) => void;
+}
+
+function SectionNavItem({ item, sectionName, currentPath, edition, onPick, measureRef }: ItemProps) {
+  if ('link' in item) {
+    const { name, viewName } = item.link;
+    const enterprise = checkIsEnterprise(viewName);
+    const locked = enterprise && edition === 'community';
+    const isActive = pathMatchesView(currentPath, sectionName, viewName);
+    return (
+      <button
+        type="button"
+        ref={measureRef}
+        aria-current={isActive ? 'page' : undefined}
+        className={cn(TRIGGER_CLASS, isActive && TRIGGER_ACTIVE)}
+        onClick={() => onPick(viewName, locked)}
+      >
+        {name}
+        {locked && <Lock className="h-3 w-3" />}
+      </button>
+    );
+  }
+
+  const { name, items } = item.container;
+  const containsActive = subtreeContainsActive(items, currentPath, sectionName);
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <button
+          type="button"
+          ref={measureRef}
+          className={cn(TRIGGER_CLASS, 'data-[state=open]:text-foreground', containsActive && TRIGGER_ACTIVE)}
+        >
+          {name}
+          <ChevronDown className="h-3.5 w-3.5 shrink-0 opacity-70 transition-transform duration-200 data-[state=open]:rotate-180" />
+        </button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="start" sideOffset={0} className="w-60">
+        <MenuBody items={items} sectionName={sectionName} currentPath={currentPath} edition={edition} onPick={onPick} />
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+}
+
+export function SectionNav({ layout }: { layout: Layout }) {
+  const { t } = useTranslation();
+  const navigate = useNavigate();
+  const location = useLocation();
+  const edition = useAccountStore((s) => s.edition);
+  const [upsellOpen, setUpsellOpen] = useState(false);
+
+  const items = useMemo(() => layout.items.filter((item) => topItemVisible(item, edition)), [layout, edition]);
+
+  const scrollerRef = useRef<HTMLDivElement>(null);
+  const measured = useRef<number[]>([]);
+  const [available, setAvailable] = useState(0);
+
+  /**
+   * A different layout means different labels, so a measurement is only good
+   * for the layout it was taken on: keeping the key beside the widths retires
+   * the old ones without a reset pass.
+   */
+  const measureKey = `${layout.name}|${edition}`;
+  const [measurement, setMeasurement] = useState<{ key: string; widths: number[] } | null>(null);
+  const widths = measurement?.key === measureKey ? measurement.widths : null;
+
+  /**
+   * Attached only while a measurement is wanted. A ref closure is new on every
+   * render, so React would re-run it — and force a reflow reading offsetWidth —
+   * on each one; leaving it off once the widths are known keeps the bar free of
+   * that on ordinary navigation.
+   */
+  const measureRefFor = useCallback(
+    (index: number) => (el: HTMLElement | null) => {
+      if (el) measured.current[index] = el.offsetWidth;
+    },
+    [],
+  );
+
+  useLayoutEffect(() => {
+    if (widths !== null) return;
+    const seen = measured.current.slice(0, items.length);
+    if (seen.length !== items.length || seen.some((w) => !w)) return;
+    setMeasurement({ key: measureKey, widths: seen });
+  }, [widths, items.length, measureKey, location.pathname]);
+
+  useEffect(() => {
+    const el = scrollerRef.current;
+    if (!el) return;
+    setAvailable(el.clientWidth);
+    if (typeof ResizeObserver === 'undefined') return;
+    const ro = new ResizeObserver(() => setAvailable(el.clientWidth));
+    ro.observe(el);
+    return () => ro.disconnect();
+  }, []);
+
+  const onPick = useCallback(
+    (viewName: string, locked: boolean) => {
+      if (locked) {
+        setUpsellOpen(true);
+        return;
+      }
+      navigate(resolveViewPath(layout.name, viewName));
+    },
+    [navigate, layout.name],
+  );
+
+  // Before the first measurement every item renders, clipped by the scroller.
+  const shown = widths === null || available === 0 ? items.length : howManyFit(widths, available);
+  const overflowed = items.slice(shown);
+
+  return (
+    <nav
+      aria-label={layout.name}
+      className="sticky top-14 z-30 hidden h-12 items-stretch border-b bg-background px-4 md:flex"
+    >
+      <div ref={scrollerRef} className="flex min-w-0 flex-1 items-stretch overflow-hidden">
+        {items.slice(0, shown).map((item, i) => (
+          <SectionNavItem
+            key={topItemKey(item)}
+            item={item}
+            sectionName={layout.name}
+            currentPath={location.pathname}
+            edition={edition}
+            onPick={onPick}
+            measureRef={widths === null ? measureRefFor(i) : undefined}
+          />
+        ))}
+      </div>
+
+      {overflowed.length > 0 && (
+        <DropdownMenu>
+          <DropdownMenuTrigger asChild>
+            <button
+              type="button"
+              className={cn(
+                TRIGGER_CLASS,
+                'data-[state=open]:text-foreground',
+                overflowed.some((item) =>
+                  'link' in item
+                    ? pathMatchesView(location.pathname, layout.name, item.link.viewName)
+                    : subtreeContainsActive(item.container.items, location.pathname, layout.name),
+                ) && TRIGGER_ACTIVE,
+              )}
+            >
+              <MoreHorizontal className="h-4 w-4" />
+              {t('nav.more', 'More')}
+            </button>
+          </DropdownMenuTrigger>
+          <DropdownMenuContent align="end" sideOffset={0} className="w-60">
+            {overflowed.map((item, i) => {
+              if ('link' in item) {
+                const { name, viewName } = item.link;
+                const enterprise = checkIsEnterprise(viewName);
+                return (
+                  <DropdownMenuItem
+                    key={viewName}
+                    className={cn(
+                      pathMatchesView(location.pathname, layout.name, viewName) && 'bg-accent text-accent-foreground',
+                    )}
+                    onClick={() => onPick(viewName, enterprise && edition === 'community')}
+                  >
+                    <span className="truncate">{name}</span>
+                  </DropdownMenuItem>
+                );
+              }
+              const { name, items: subItems } = item.container;
+              return (
+                <DropdownMenuGroup key={name}>
+                  {i > 0 && <DropdownMenuSeparator />}
+                  <DropdownMenuLabel className="text-[11px] font-semibold uppercase tracking-wider text-muted-foreground">
+                    {name}
+                  </DropdownMenuLabel>
+                  {visibleLinks(subItems, edition).map((l) => (
+                    <DropdownMenuItem
+                      key={l.viewName}
+                      className={cn(
+                        pathMatchesView(location.pathname, layout.name, l.viewName) &&
+                          'bg-accent text-accent-foreground',
+                      )}
+                      onClick={() => onPick(l.viewName, checkIsEnterprise(l.viewName) && edition === 'community')}
+                    >
+                      <span className="truncate">{l.name}</span>
+                    </DropdownMenuItem>
+                  ))}
+                </DropdownMenuGroup>
+              );
+            })}
+          </DropdownMenuContent>
+        </DropdownMenu>
+      )}
+
+      <EnterpriseUpsell open={upsellOpen} onClose={() => setUpsellOpen(false)} />
+    </nav>
+  );
+}
diff --git a/src/components/layout/Sidebar.tsx b/src/components/layout/Sidebar.tsx
index 4346dbc..3ff25fe 100644
--- a/src/components/layout/Sidebar.tsx
+++ b/src/components/layout/Sidebar.tsx
@@ -25,48 +25,18 @@ import { Collapsible, CollapsibleContent, CollapsibleTrigger } from '@/component
 import { useUIStore } from '@/stores/uiStore';
 import { useAccountStore } from '@/stores/accountStore';
 import { useSchemaStore } from '@/stores/schemaStore';
-import { visibleLayouts, isLinkEnterprise, isLinkVisible } from '@/lib/layout';
+import { visibleLayouts } from '@/lib/layout';
+import {
+  checkIsEnterprise,
+  checkLinkVisible,
+  pathMatchesView,
+  resolveViewPath,
+  subtreeContainsActive,
+  subtreeHasVisibleLink,
+  visibleLinks,
+} from '@/lib/navTree';
 import type { Layout, LayoutItem, LayoutSubItem } from '@/types/schema';
 
-function resolveViewPath(sectionName: string, viewName: string): string {
-  return `/${sectionName}/${viewName}`;
-}
-
-function pathMatchesView(currentPath: string, sectionName: string, viewName: string): boolean {
-  const base = `/${sectionName}/${viewName}`;
-  if (currentPath === base || currentPath.startsWith(`${base}/`)) return true;
-  if (viewName === 'CustomComponent/Dashboard') {
-    const dashBase = `/${sectionName}/Dashboard/`;
-    return currentPath.startsWith(dashBase);
-  }
-  return false;
-}
-
-function subtreeContainsActive(items: LayoutSubItem[], currentPath: string, sectionName: string): boolean {
-  for (const item of items) {
-    if (item.type === 'link') {
-      if (pathMatchesView(currentPath, sectionName, item.viewName)) return true;
-    } else if (item.type === 'container') {
-      if (subtreeContainsActive(item.items, currentPath, sectionName)) return true;
-    }
-  }
-  return false;
-}
-
-function subtreeHasVisibleLink(items: LayoutSubItem[], edition: string): boolean {
-  for (const item of items) {
-    if (item.type === 'link') {
-      if (!checkLinkVisible(item.viewName)) continue;
-      const enterprise = checkIsEnterprise(item.viewName);
-      if (enterprise && edition === 'oss') continue;
-      return true;
-    } else if (item.type === 'container') {
-      if (subtreeHasVisibleLink(item.items, edition)) return true;
-    }
-  }
-  return false;
-}
-
 interface AutoOpenCollapsibleProps {
   containsActive: boolean;
   children: React.ReactNode;
@@ -86,27 +56,6 @@ function AutoOpenCollapsible({ containsActive, children }: AutoOpenCollapsiblePr
   );
 }
 
-function checkLinkVisible(viewName: string): boolean {
-  const schema = useSchemaStore.getState().schema;
-  if (!schema) return true;
-
-  const accountStore = useAccountStore.getState();
-  return isLinkVisible(
-    schema,
-    viewName,
-    accountStore.edition,
-    (prefix: string) => accountStore.hasObjectPermission(prefix, 'Get'),
-    (perm: string) => accountStore.hasPermission(perm),
-  );
-}
-
-function checkIsEnterprise(viewName: string): boolean {
-  const schema = useSchemaStore.getState().schema;
-  if (!schema) return false;
-  const edition = useAccountStore.getState().edition;
-  return isLinkEnterprise(schema, viewName, edition);
-}
-
 type ActiveItemRef = (el: HTMLButtonElement | null) => void;
 
 interface SidebarSubItemProps {
@@ -300,22 +249,6 @@ function SidebarTopItem({
   return null;
 }
 
-/** INBUXA: every visible link under a container, flattened, for the rail's pop-out menu. */
-function visibleLinks(items: LayoutSubItem[], edition: string, prefix = ''): { name: string; viewName: string }[] {
-  const out: { name: string; viewName: string }[] = [];
-  for (const it of items) {
-    if (it.type === 'link') {
-      if (!checkLinkVisible(it.viewName)) continue;
-      const enterprise = checkIsEnterprise(it.viewName);
-      if (enterprise && edition === 'oss') continue;
-      out.push({ name: `${prefix}${it.name || 'Overview'}`, viewName: it.viewName });
-    } else if (subtreeHasVisibleLink(it.items, edition)) {
-      out.push(...visibleLinks(it.items, edition, `${prefix}${it.name} › `));
-    }
-  }
-  return out;
-}
-
 /** INBUXA: one entry of the collapsed sidebar: its tile, a label on hover, a menu for a group. */
 function RailItem({
   item,
@@ -387,7 +320,16 @@ function RailItem({
   );
 }
 
-export function Sidebar() {
+interface SidebarProps {
+  /**
+   * INBUXA: in the modern shell the section bar does the navigating on a wide
+   * screen, but a phone has no room for it — the sidebar stays as the
+   * slide-over behind the hamburger, and nothing else.
+   */
+  mobileOnly?: boolean;
+}
+
+export function Sidebar({ mobileOnly = false }: SidebarProps = {}) {
   const navigate = useNavigate();
   const location = useLocation();
   const activeSection = useUIStore((s) => s.activeSection);
@@ -427,9 +369,10 @@ export function Sidebar() {
   const layout: Layout | undefined = layouts.find((l) => l.name === activeSection);
   if (!layout) return null;
 
-  // Folding to a rail is for wide screens; a phone keeps the slide-over.
+  // Folding to a rail is for wide screens; a phone keeps the slide-over, and so
+  // does the modern shell, where the rail would sit under the section bar.
   const collapsed =
-    sidebarCollapsed && typeof window !== 'undefined' && window.matchMedia('(min-width: 768px)').matches;
+    !mobileOnly && sidebarCollapsed && typeof window !== 'undefined' && window.matchMedia('(min-width: 768px)').matches;
 
   if (collapsed) {
     return (
@@ -474,7 +417,12 @@ export function Sidebar() {
         className="fixed inset-0 top-14 z-20 bg-black/40 md:hidden"
         onClick={() => setSidebarOpen(false)}
       />
-      <aside className="fixed top-14 left-0 bottom-0 z-30 flex w-64 flex-col border-r bg-background">
+      <aside
+        className={cn(
+          'fixed top-14 left-0 bottom-0 z-30 flex w-64 flex-col border-r bg-background',
+          mobileOnly && 'md:hidden',
+        )}
+      >
         <div className="flex items-center justify-between px-4 pt-3 pb-1">
           <span className="text-[11px] font-semibold uppercase tracking-wider text-muted-foreground">
             {layout.name}
@@ -484,7 +432,10 @@ export function Sidebar() {
             aria-label="Collapse sidebar"
             title="Collapse sidebar"
             onClick={toggleSidebarCollapsed}
-            className="hidden h-7 w-7 items-center justify-center rounded-lg text-muted-foreground hover:bg-muted hover:text-foreground md:flex"
+            className={cn(
+              'hidden h-7 w-7 items-center justify-center rounded-lg text-muted-foreground hover:bg-muted hover:text-foreground md:flex',
+              mobileOnly && 'md:hidden',
+            )}
           >
             <PanelLeftClose className="h-4 w-4" />
           </button>
diff --git a/src/components/layout/TopBar.tsx b/src/components/layout/TopBar.tsx
index 510fb54..4df1876 100644
--- a/src/components/layout/TopBar.tsx
+++ b/src/components/layout/TopBar.tsx
@@ -8,7 +8,7 @@
 import { Link, useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
 import * as LucideIcons from 'lucide-react';
-const { Sun, Moon, User, LogOut, Check, Menu, Search, FileCode, Palette } = LucideIcons;
+const { Sun, Moon, User, LogOut, Check, Menu, Search, FileCode, Palette, LayoutTemplate } = LucideIcons;
 import { Button } from '@/components/ui/button';
 import { CommandPalette } from '@/components/common/CommandPalette';
 import {
@@ -33,7 +33,7 @@ import { sourceDownloadUrl } from '@/lib/sourceDownload';
 import { visibleLayouts } from '@/lib/layout';
 import { sectionLandingLink } from '@/lib/lastVisited';
 import { cn } from '@/lib/utils';
-import { useUIStore } from '@/stores/uiStore';
+import { isAdminLayout, useUIStore } from '@/stores/uiStore';
 import { useAuthStore } from '@/stores/authStore';
 import { buildEndSessionUrl, getPostLogoutRedirectUri } from '@/services/auth/oauth';
 import { createElement, useEffect, useState } from 'react';
@@ -57,6 +57,8 @@ export function TopBar() {
   const toggleTheme = useUIStore((s) => s.toggleTheme);
   const palette = useUIStore((s) => s.palette);
   const setPalette = useUIStore((s) => s.setPalette);
+  const adminLayout = useUIStore((s) => s.adminLayout);
+  const setAdminLayout = useUIStore((s) => s.setAdminLayout);
   const toggleSidebar = useUIStore((s) => s.toggleSidebar);
   const setActiveSection = useUIStore((s) => s.setActiveSection);
   const activeSection = useUIStore((s) => s.activeSection);
@@ -159,11 +161,12 @@ export function TopBar() {
                           if (firstLink) navigate(`/${layout.name}/${firstLink}`);
                         }}
                         className={cn(
-                          'flex h-8 w-9 items-center justify-center rounded-lg text-muted-foreground transition-colors hover:text-foreground',
+                          'flex h-8 items-center justify-center gap-1.5 rounded-lg px-2.5 text-[13px] font-medium text-muted-foreground transition-colors hover:text-foreground lg:px-3',
                           isActive && 'bg-card text-primary shadow-soft',
                         )}
                       >
-                        {createElement(getIcon(layout.icon), { className: 'h-4 w-4' })}
+                        {createElement(getIcon(layout.icon), { className: 'h-4 w-4 shrink-0' })}
+                        <span className="hidden lg:inline">{layout.name}</span>
                       </button>
                     </TooltipTrigger>
                     <TooltipContent side="bottom">{layout.name}</TooltipContent>
@@ -228,6 +231,33 @@ export function TopBar() {
               </>
             )}
 
+            {/* INBUXA: the shell is the reader's choice, the way the palette is. */}
+            <DropdownMenuSub>
+              <DropdownMenuSubTrigger>
+                <LayoutTemplate className="mr-2 h-4 w-4" />
+                {t('nav.layoutMenu', 'Layout')}
+              </DropdownMenuSubTrigger>
+              <DropdownMenuSubContent className="w-56">
+                <DropdownMenuRadioGroup
+                  value={adminLayout}
+                  onValueChange={(v) => isAdminLayout(v) && setAdminLayout(v)}
+                >
+                  <DropdownMenuRadioItem value="modern" className="gap-2">
+                    {t('nav.layoutModern', 'Modern')}
+                  </DropdownMenuRadioItem>
+                  <DropdownMenuRadioItem value="legacy" className="gap-2">
+                    {t('nav.layoutLegacy', 'Legacy')}
+                  </DropdownMenuRadioItem>
+                </DropdownMenuRadioGroup>
+                <DropdownMenuSeparator />
+                <p className="px-2 py-1.5 text-[11px] leading-snug text-muted-foreground">
+                  {adminLayout === 'modern'
+                    ? t('nav.layoutModernHint', 'Sections across the top; the page gets the full width.')
+                    : t('nav.layoutLegacyHint', 'The sidebar, as the old web UI had it.')}
+                </p>
+              </DropdownMenuSubContent>
+            </DropdownMenuSub>
+
             {/* INBUXA: the same palettes as INBUXA webmail. */}
             <DropdownMenuSub>
               <DropdownMenuSubTrigger>
diff --git a/src/i18n/en.json b/src/i18n/en.json
index dda7fcf..2013e35 100644
--- a/src/i18n/en.json
+++ b/src/i18n/en.json
@@ -301,6 +301,14 @@
   "version": {
     "label": "INBUXA Admin {{version}}"
   },
+  "nav": {
+    "layoutLegacy": "Legacy",
+    "layoutLegacyHint": "The sidebar, as the old web UI had it.",
+    "layoutMenu": "Layout",
+    "layoutModern": "Modern",
+    "layoutModernHint": "Sections across the top; the page gets the full width.",
+    "more": "More"
+  },
   "oauth": {
     "backToLogin": "Back to login",
     "discoveryFailed": "Discovery failed for \"{{username}}\": {{status}} {{statusText}}",
diff --git a/src/lib/navTree.ts b/src/lib/navTree.ts
new file mode 100644
index 0000000..3b3da89
--- /dev/null
+++ b/src/lib/navTree.ts
@@ -0,0 +1,125 @@
+/*
+ * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <hello@stalw.art>
+ * SPDX-FileCopyrightText: 2026 Coffey Labs
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
+ */
+
+/**
+ * INBUXA: walking the server's menu tree, shared by the two shells that draw it
+ * — the sidebar (legacy) and the section bar (modern). The tree itself is the
+ * schema's `layouts`, so neither shell may assume a depth or a fan-out.
+ */
+
+import { useAccountStore } from '@/stores/accountStore';
+import { useSchemaStore } from '@/stores/schemaStore';
+import { isLinkEnterprise, isLinkVisible } from '@/lib/layout';
+import type { Layout, LayoutItem, LayoutSubItem } from '@/types/schema';
+
+/**
+ * Past this many top-level entries a layout is a configuration browser rather
+ * than a set of destinations, and a menu bar stops helping however wide the
+ * window: on the stock schema that is Settings, with its nineteen groups, which
+ * keeps the sidebar under either shell. Management (nine) and Account (eleven)
+ * fit, and anything left over folds into the section bar's "More".
+ */
+export const SECTION_NAV_MAX_ITEMS = 12;
+
+export function resolveViewPath(sectionName: string, viewName: string): string {
+  return `/${sectionName}/${viewName}`;
+}
+
+export function pathMatchesView(currentPath: string, sectionName: string, viewName: string): boolean {
+  const base = `/${sectionName}/${viewName}`;
+  if (currentPath === base || currentPath.startsWith(`${base}/`)) return true;
+  if (viewName === 'CustomComponent/Dashboard') {
+    const dashBase = `/${sectionName}/Dashboard/`;
+    return currentPath.startsWith(dashBase);
+  }
+  return false;
+}
+
+export function checkLinkVisible(viewName: string): boolean {
+  const schema = useSchemaStore.getState().schema;
+  if (!schema) return true;
+
+  const accountStore = useAccountStore.getState();
+  return isLinkVisible(
+    schema,
+    viewName,
+    accountStore.edition,
+    (prefix: string) => accountStore.hasObjectPermission(prefix, 'Get'),
+    (perm: string) => accountStore.hasPermission(perm),
+  );
+}
+
+export function checkIsEnterprise(viewName: string): boolean {
+  const schema = useSchemaStore.getState().schema;
+  if (!schema) return false;
+  const edition = useAccountStore.getState().edition;
+  return isLinkEnterprise(schema, viewName, edition);
+}
+
+export function subtreeContainsActive(items: LayoutSubItem[], currentPath: string, sectionName: string): boolean {
+  for (const item of items) {
+    if (item.type === 'link') {
+      if (pathMatchesView(currentPath, sectionName, item.viewName)) return true;
+    } else if (item.type === 'container') {
+      if (subtreeContainsActive(item.items, currentPath, sectionName)) return true;
+    }
+  }
+  return false;
+}
+
+export function subtreeHasVisibleLink(items: LayoutSubItem[], edition: string): boolean {
+  for (const item of items) {
+    if (item.type === 'link') {
+      if (!checkLinkVisible(item.viewName)) continue;
+      const enterprise = checkIsEnterprise(item.viewName);
+      if (enterprise && edition === 'oss') continue;
+      return true;
+    } else if (item.type === 'container') {
+      if (subtreeHasVisibleLink(item.items, edition)) return true;
+    }
+  }
+  return false;
+}
+
+/** Every visible link under a container, flattened, deeper names prefixed with their group. */
+export function visibleLinks(
+  items: LayoutSubItem[],
+  edition: string,
+  prefix = '',
+): { name: string; viewName: string }[] {
+  const out: { name: string; viewName: string }[] = [];
+  for (const it of items) {
+    if (it.type === 'link') {
+      if (!checkLinkVisible(it.viewName)) continue;
+      const enterprise = checkIsEnterprise(it.viewName);
+      if (enterprise && edition === 'oss') continue;
+      out.push({ name: `${prefix}${it.name || 'Overview'}`, viewName: it.viewName });
+    } else if (subtreeHasVisibleLink(it.items, edition)) {
+      out.push(...visibleLinks(it.items, edition, `${prefix}${it.name} › `));
+    }
+  }
+  return out;
+}
+
+/** Whether a top-level entry has anything left to show once edition and permissions are applied. */
+export function topItemVisible(item: LayoutItem, edition: string): boolean {
+  if ('link' in item) {
+    if (!checkLinkVisible(item.link.viewName)) return false;
+    return !(checkIsEnterprise(item.link.viewName) && edition === 'oss');
+  }
+  return subtreeHasVisibleLink(item.container.items, edition);
+}
+
+/** A stable key for a top-level entry, for React lists. */
+export function topItemKey(item: LayoutItem): string {
+  return 'link' in item ? item.link.viewName : item.container.name;
+}
+
+/** Whether this layout is shallow enough to be drawn as a menu bar at all. */
+export function fitsSectionNav(layout: Layout, edition: string): boolean {
+  return layout.items.filter((item) => topItemVisible(item, edition)).length <= SECTION_NAV_MAX_ITEMS;
+}
diff --git a/src/pages/AdminPanel.tsx b/src/pages/AdminPanel.tsx
index 8ede198..242fb35 100644
--- a/src/pages/AdminPanel.tsx
+++ b/src/pages/AdminPanel.tsx
@@ -18,6 +18,7 @@ import { loadAccountTheme, setAccountSettingsTarget } from '@/lib/accountSetting
 import { setLocale } from '@/i18n';
 import { TopBar } from '@/components/layout/TopBar';
 import { Sidebar } from '@/components/layout/Sidebar';
+import { SectionNav } from '@/components/layout/SectionNav';
 import { MainContent } from '@/components/layout/MainContent';
 import { ErrorBoundary } from '@/components/layout/ErrorBoundary';
 import { LoadingFallback } from '@/components/common/LoadingFallback';
@@ -31,6 +32,8 @@ import { usePermissions } from '@/hooks/usePermissions';
 import { useDocumentTitle } from '@/hooks/useDocumentTitle';
 import { friendlyName } from '@/hooks/useGlobalSearch';
 import { rememberLastVisited, sectionLandingLink } from '@/lib/lastVisited';
+import { fitsSectionNav } from '@/lib/navTree';
+import { cn } from '@/lib/utils';
 
 const BootstrapWizard = lazy(() =>
   import('@/components/bootstrap/BootstrapWizard').then((m) => ({ default: m.BootstrapWizard })),
@@ -83,6 +86,8 @@ export default function AdminPanel() {
   const accessToken = useAuthStore((s) => s.accessToken);
   const activeAccountId = useAuthStore((s) => s.activeAccountId);
   const setActiveSection = useUIStore((s) => s.setActiveSection);
+  const activeSection = useUIStore((s) => s.activeSection);
+  const adminLayout = useUIStore((s) => s.adminLayout);
   const sidebarOpen = useUIStore((s) => s.sidebarOpen);
   const sidebarCollapsed = useUIStore((s) => s.sidebarCollapsed);
   const { canViewObject } = usePermissions();
@@ -188,6 +193,22 @@ export default function AdminPanel() {
     };
   }, [isSchemaLoaded, setSession, setSchema, setAccountInfo, t]);
 
+  /**
+   * INBUXA: which shell draws the navigation. The modern one puts the layout's
+   * items in a bar under the top bar and drops the sidebar; a layout with too
+   * many top-level groups for a menu bar keeps the sidebar whatever the reader
+   * chose, so Settings never turns into nineteen dropdowns.
+   */
+  const currentLayout = useMemo(() => {
+    if (!schema) return null;
+    const canGet = (prefix: string) => permissions.includes(`${prefix}Get`);
+    const hasPerm = (perm: string) => permissions.includes(perm);
+    const name = (section ?? activeSection ?? '').toLowerCase();
+    return visibleLayouts(schema, edition, canGet, hasPerm).find((l) => l.name.toLowerCase() === name) ?? null;
+  }, [schema, edition, permissions, section, activeSection]);
+
+  const useSectionNav = adminLayout === 'modern' && currentLayout !== null && fitsSectionNav(currentLayout, edition);
+
   const isBootstrapMode = useMemo(() => {
     if (!schema) return false;
     if (!canViewObject('x:Bootstrap')) return false;
@@ -288,10 +309,14 @@ export default function AdminPanel() {
   return (
     <div className="flex min-h-screen flex-col">
       <TopBar />
+      {useSectionNav && currentLayout && <SectionNav layout={currentLayout} />}
       <div className="flex flex-1">
-        <Sidebar />
+        <Sidebar mobileOnly={useSectionNav} />
         <main
-          className={`flex-1 overflow-auto bg-content-background p-6 transition-[margin] ${sidebarOpen ? (sidebarCollapsed ? 'md:ml-[4.5rem]' : 'md:ml-64') : ''}`}
+          className={cn(
+            'flex-1 overflow-auto bg-content-background p-6 transition-[margin]',
+            !useSectionNav && sidebarOpen && (sidebarCollapsed ? 'md:ml-[4.5rem]' : 'md:ml-64'),
+          )}
         >
           <ErrorBoundary key={activeAccountId ?? 'none'}>
             <MainContent viewName={viewName} id={id} section={section} />
diff --git a/src/stores/uiStore.ts b/src/stores/uiStore.ts
index 1e82221..82e57dd 100644
--- a/src/stores/uiStore.ts
+++ b/src/stores/uiStore.ts
@@ -12,10 +12,26 @@ import { persist } from 'zustand/middleware';
 
 type Theme = 'light' | 'dark';
 
+/**
+ * INBUXA: which shell draws the navigation. "modern" is the two-tier shell —
+ * the layout switcher in the top bar over a section bar carrying that layout's
+ * own items, and no sidebar. "legacy" is the sidebar the old web UI had. A
+ * layout too deep for a menu bar keeps the sidebar under either setting.
+ */
+export type AdminLayout = 'modern' | 'legacy';
+
+export const DEFAULT_ADMIN_LAYOUT: AdminLayout = 'modern';
+
+export function isAdminLayout(value: unknown): value is AdminLayout {
+  return value === 'modern' || value === 'legacy';
+}
+
 interface UIState {
   theme: Theme;
   /** INBUXA: the color palette, the same set INBUXA webmail offers. */
   palette: PaletteId;
+  /** INBUXA: the navigation shell, the reader's own choice. */
+  adminLayout: AdminLayout;
   sidebarOpen: boolean;
   /** INBUXA: the sidebar folded to a rail of icon tiles, on wide screens. */
   sidebarCollapsed: boolean;
@@ -24,6 +40,7 @@ interface UIState {
   toggleTheme: () => void;
   setTheme: (theme: Theme) => void;
   setPalette: (palette: PaletteId) => void;
+  setAdminLayout: (layout: AdminLayout) => void;
   /** INBUXA: take the theme stored with the account, without writing it back. */
   applyAccountTheme: (palette: PaletteId | null, mode: 'system' | 'light' | 'dark' | null) => void;
   toggleSidebar: () => void;
@@ -48,6 +65,7 @@ export const useUIStore = create<UIState>()(
       sidebarOpen: typeof window !== 'undefined' ? (window.matchMedia?.('(min-width: 768px)').matches ?? true) : true,
       sidebarCollapsed: false,
       palette: DEFAULT_PALETTE,
+      adminLayout: DEFAULT_ADMIN_LAYOUT,
       activeSection: '',
 
       toggleTheme: () => {
@@ -77,6 +95,10 @@ export const useUIStore = create<UIState>()(
         queueAccountTheme(palette, null, get().theme);
       },
 
+      setAdminLayout: (layout) => {
+        set({ adminLayout: layout });
+      },
+
       applyAccountTheme: (palette, mode) => {
         const next: Partial<UIState> = {};
         if (palette) {
@@ -105,6 +127,7 @@ export const useUIStore = create<UIState>()(
       partialize: (state) => ({
         theme: state.theme,
         palette: state.palette,
+        adminLayout: state.adminLayout,
         sidebarCollapsed: state.sidebarCollapsed,
       }),
       onRehydrateStorage: () => {
@@ -112,6 +135,7 @@ export const useUIStore = create<UIState>()(
           if (state) {
             applyThemeClass(state.theme);
             applyPalette(isPaletteId(state.palette) ? state.palette : DEFAULT_PALETTE);
+            if (!isAdminLayout(state.adminLayout)) state.adminLayout = DEFAULT_ADMIN_LAYOUT;
           }
         };
       },