diff --git a/scripts/check-maintainability-budgets.mjs b/scripts/check-maintainability-budgets.mjs
index c6f08042..464df05f 100644
--- a/scripts/check-maintainability-budgets.mjs
+++ b/scripts/check-maintainability-budgets.mjs
@@ -2,7 +2,7 @@
 import { readFileSync } from "node:fs";
 
 const budgets = new Map([
-  ["src/components/ClinicalDashboard.tsx", 4160],
+  ["src/components/ClinicalDashboard.tsx", 4140],
   ["src/lib/rag/rag.ts", 5030],
   ["src/components/DocumentViewer.tsx", 1734],
   ["supabase/functions/indexing-v3-agent/index.ts", 2191],
diff --git a/src/components/ClinicalDashboard.tsx b/src/components/ClinicalDashboard.tsx
index 93e48b71..b35f9fce 100644
--- a/src/components/ClinicalDashboard.tsx
+++ b/src/components/ClinicalDashboard.tsx
@@ -31,9 +31,9 @@ import {
   useReducer,
   useRef,
   useState,
-  useSyncExternalStore,
 } from "react";
 import { type DocumentDeleteResult } from "@/components/DocumentManagementActions";
+import { useUploadDesktopLayout } from "@/components/clinical-dashboard/use-upload-desktop-layout";
 import { extractSafetyFindings } from "@/lib/clinical-safety";
 import { resolveScrollBehavior } from "@/lib/scroll-behavior";
 import { isLocalNoAuthMode, resolveClientDemoMode, resolveUploadReadOnlyMode } from "@/lib/client-env";
@@ -123,22 +123,6 @@ const FavouritesHub = dynamic(
   { ssr: false },
 );
 
-const uploadDesktopMediaQuery = "(min-width: 1024px)";
-
-function subscribeToUploadDesktopLayout(callback: () => void) {
-  if (typeof window === "undefined" || typeof window.matchMedia !== "function") return () => {};
-  const media = window.matchMedia(uploadDesktopMediaQuery);
-  media.addEventListener("change", callback);
-  return () => media.removeEventListener("change", callback);
-}
-
-function getUploadDesktopLayoutSnapshot() {
-  return (
-    typeof window !== "undefined" &&
-    typeof window.matchMedia === "function" &&
-    window.matchMedia(uploadDesktopMediaQuery).matches
-  );
-}
 const MedicationPrescribingWorkspace = dynamic(
   () =>
     import("@/components/clinical-dashboard/medication-prescribing-workspace").then(
@@ -570,11 +554,7 @@ export function ClinicalDashboard({
   const [documentsDrawerMode, setDocumentsDrawerMode] = useState<DocumentDrawerMode>("library");
   const [uploadDrawerOpen, setUploadDrawerOpen] = useState(false);
   const [uploadMobileTab, setUploadMobileTab] = useState<UploadIndexingTab>("upload");
-  const uploadUsesDesktopRegions = useSyncExternalStore(
-    subscribeToUploadDesktopLayout,
-    getUploadDesktopLayoutSnapshot,
-    () => false,
-  );
+  const uploadUsesDesktopRegions = useUploadDesktopLayout();
   const uploadTabRefs = useRef(new Map<UploadIndexingTab, HTMLButtonElement>());
   const [documentDrawerStatusFilter, setDocumentDrawerStatusFilter] = useState<DocumentDrawerStatusFilter>("indexed");
   const [indexingMonitorFilter, setIndexingMonitorFilter] = useState<IndexingMonitorFilter>("all");
diff --git a/src/components/clinical-dashboard/use-upload-desktop-layout.ts b/src/components/clinical-dashboard/use-upload-desktop-layout.ts
new file mode 100644
index 00000000..1748d1de
--- /dev/null
+++ b/src/components/clinical-dashboard/use-upload-desktop-layout.ts
@@ -0,0 +1,31 @@
+import { useSyncExternalStore } from "react";
+
+// The upload view switches to a two-region desktop layout at >=1024px. This is a
+// useSyncExternalStore-backed media-query subscription so the value stays correct
+// across SSR (no window) and live viewport changes. Extracted from
+// ClinicalDashboard.tsx (maturity X3) as a pure move.
+const uploadDesktopMediaQuery = "(min-width: 1024px)";
+
+function subscribeToUploadDesktopLayout(callback: () => void) {
+  if (typeof window === "undefined" || typeof window.matchMedia !== "function") return () => {};
+  const media = window.matchMedia(uploadDesktopMediaQuery);
+  media.addEventListener("change", callback);
+  return () => media.removeEventListener("change", callback);
+}
+
+function getUploadDesktopLayoutSnapshot() {
+  return (
+    typeof window !== "undefined" &&
+    typeof window.matchMedia === "function" &&
+    window.matchMedia(uploadDesktopMediaQuery).matches
+  );
+}
+
+/**
+ * Whether the upload view has room for its desktop two-region layout (viewport >= 1024px).
+ * Server-safe: the getServerSnapshot returns false during SSR to avoid a hydration
+ * mismatch, and the value updates on viewport changes on the client.
+ */
+export function useUploadDesktopLayout() {
+  return useSyncExternalStore(subscribeToUploadDesktopLayout, getUploadDesktopLayoutSnapshot, () => false);
+}
diff --git a/tests/audit-navigation-auth-regressions.test.ts b/tests/audit-navigation-auth-regressions.test.ts
index cd96f6f2..c9c79904 100644
--- a/tests/audit-navigation-auth-regressions.test.ts
+++ b/tests/audit-navigation-auth-regressions.test.ts
@@ -174,7 +174,12 @@ describe("audit navigation and auth regressions", () => {
     for (const section of ["setup", "upload", "indexing", "quality"]) {
       expect(clinicalDashboardSource).toContain(`id="dashboard-${section}-section-heading"`);
     }
-    expect(clinicalDashboardSource).toContain("subscribeToUploadDesktopLayout");
+    // The viewport-driven region/tabpanel role is wired through the extracted hook, whose
+    // media-query subscription carries the guard with it.
+    expect(clinicalDashboardSource).toContain("useUploadDesktopLayout()");
+    expect(source("src/components/clinical-dashboard/use-upload-desktop-layout.ts")).toContain(
+      "subscribeToUploadDesktopLayout",
+    );
     expect(clinicalDashboardSource).toContain('event.key === "ArrowRight"');
     expect(clinicalDashboardSource).toContain('event.key === "ArrowLeft"');
     expect(clinicalDashboardSource).toContain('event.key === "Home"');