diff --git a/src/app/api/v1/me/route.ts b/src/app/api/v1/me/route.ts
index a5bbeaa8..ea753ec3 100644
--- a/src/app/api/v1/me/route.ts
+++ b/src/app/api/v1/me/route.ts
@@ -42,6 +42,15 @@ const updateProfileSchema = z.object({
       dark_mode: z.boolean().optional(),
       locale: z.string().optional(),
       timezone: z.string().optional(),
+      // multi-port-auditor C3: super-admins land on whichever port
+      // sorts alphabetically-first when there's no header + no
+      // preference. Persisting their last-picked port here makes
+      // the dashboard "remember" their context across tabs.
+      // `withAuth` (helpers.ts) already reads this as the
+      // X-Port-Id fallback; previously the value could only ever
+      // be set via hand-rolled SQL because the allow-list at line
+      // 154 silently stripped unknown keys.
+      defaultPortId: z.string().uuid().optional(),
       // Per-table column visibility. Keyed by entity type — entries
       // with an empty `hiddenColumns` mean "all visible". The validator
       // caps total entries / IDs so a malicious client can't bloat the
@@ -146,7 +155,13 @@ export const PATCH = withAuth(async (req, ctx: AuthContext) => {
       // .passthrough(); the merge prunes them so legacy bloat doesn't
       // accumulate forever, and a future schema regression that tries
       // to ship arbitrary keys still gets dropped here at write time.
-      const ALLOWED_PREF_KEYS = new Set(['dark_mode', 'locale', 'timezone', 'tablePreferences']);
+      const ALLOWED_PREF_KEYS = new Set([
+        'dark_mode',
+        'locale',
+        'timezone',
+        'tablePreferences',
+        'defaultPortId',
+      ]);
       const existing = (profile.preferences as Record<string, unknown>) ?? {};
       const merged = Object.fromEntries(
         Object.entries({ ...existing, ...body.preferences }).filter(([k]) =>
diff --git a/src/components/layout/mobile/mobile-layout.tsx b/src/components/layout/mobile/mobile-layout.tsx
index fcafa353..ee0c4dfc 100644
--- a/src/components/layout/mobile/mobile-layout.tsx
+++ b/src/components/layout/mobile/mobile-layout.tsx
@@ -21,12 +21,12 @@ export function MobileLayout({ children }: { children: ReactNode }) {
   const [searchOpen, setSearchOpen] = useState(false);
 
   return (
-    <div data-shell="mobile" className="min-h-screen bg-background">
+    <div data-shell="mobile" className="min-h-[100dvh] bg-background">
       <MobileLayoutProvider>
         <MobileTopbar />
         <main
           className={cn(
-            'px-4 min-h-screen',
+            'px-4 min-h-[100dvh]',
             // 56px topbar + safe-area + 16px breathing room
             'pt-[calc(56px+env(safe-area-inset-top)+1rem)]',
             // 56px tab bar + safe-area + 32px breathing room
diff --git a/src/lib/api/client.ts b/src/lib/api/client.ts
index fb5a7c76..c0f23fdd 100644
--- a/src/lib/api/client.ts
+++ b/src/lib/api/client.ts
@@ -40,23 +40,35 @@ async function resolvePortIdFromSlug(slug: string): Promise<string | null> {
 }
 
 /**
- * Client-side fetch wrapper that attaches the `X-Port-Id` header from the
- * UI store to every request. Used by all queryFn/mutationFn callbacks.
+ * Client-side fetch wrapper that attaches the `X-Port-Id` header to
+ * every request.
  *
- * Falls back to extracting the port slug from `window.location.pathname` and
- * resolving it via `/api/v1/admin/ports` when the Zustand store hasn't been
- * populated yet (fresh page load before `PortProvider`'s effect has fired).
+ * multi-port-auditor C1: the URL slug is authoritative — Zustand
+ * is a cache that lags by one render after `PortProvider`'s reconcile
+ * effect commits. The previous Zustand-first lookup caused first-load
+ * queries on a freshly-navigated port to fire with the PRIOR port's
+ * id and render cross-port data inside the new shell. Now we resolve
+ * the slug from `window.location.pathname` first and fall back to
+ * Zustand only when the URL doesn't carry a port slug (e.g. /dashboard
+ * / non-portSlug routes).
  */
 export async function apiFetch<T = unknown>(url: string, opts: ApiFetchOptions = {}): Promise<T> {
-  let portId = useUIStore.getState().currentPortId;
+  let portId: string | null = null;
 
-  if (!portId && typeof window !== 'undefined') {
+  if (typeof window !== 'undefined') {
     const slug = window.location.pathname.split('/').filter(Boolean)[0];
-    if (slug && slug !== 'login' && slug !== 'portal' && slug !== 'api') {
+    if (slug && slug !== 'login' && slug !== 'portal' && slug !== 'api' && slug !== 'dashboard') {
       portId = await resolvePortIdFromSlug(slug);
     }
   }
 
+  // Fall back to the Zustand cache when the URL didn't yield a port —
+  // e.g. global routes (/dashboard) where the rep hasn't picked a port
+  // yet but a previous session set one.
+  if (!portId) {
+    portId = useUIStore.getState().currentPortId;
+  }
+
   const headers = new Headers(opts.headers);
   if (portId) {
     headers.set('X-Port-Id', portId);