diff --git a/services/web/frontend/js/features/ide-react/components/layout/main-layout.tsx b/services/web/frontend/js/features/ide-react/components/layout/main-layout.tsx
index 60512672c2..40b92eb9d5 100644
--- a/services/web/frontend/js/features/ide-react/components/layout/main-layout.tsx
+++ b/services/web/frontend/js/features/ide-react/components/layout/main-layout.tsx
@@ -28,6 +28,16 @@ const mainEditorLayoutModalsModules: Array<{
 
 // Bootstrap md breakpoint — below this we stack panels vertically on mobile
 const MOBILE_MQ = '(max-width: 767px)'
+// Secondary check: browsers that spoof viewport width (e.g. Tor Browser) still
+// expose `pointer: coarse` for real touch hardware.
+const TOUCH_MQ = '(pointer: coarse) and (max-width: 1024px)'
+
+function detectMobile() {
+  return (
+    window.matchMedia(MOBILE_MQ).matches ||
+    window.matchMedia(TOUCH_MQ).matches
+  )
+}
 
 export default function MainLayout() {
   const [resizing, setResizing] = useState(false)
@@ -42,14 +52,17 @@ export default function MainLayout() {
   } = usePdfPane()
   const { view, pdfLayout } = useLayoutContext()
 
-  const [isMobile, setIsMobile] = useState(
-    () => window.matchMedia(MOBILE_MQ).matches
-  )
+  const [isMobile, setIsMobile] = useState(detectMobile)
   useEffect(() => {
-    const mq = window.matchMedia(MOBILE_MQ)
-    const handler = (e: MediaQueryListEvent) => setIsMobile(e.matches)
-    mq.addEventListener('change', handler)
-    return () => mq.removeEventListener('change', handler)
+    const handler = () => setIsMobile(detectMobile())
+    const mq1 = window.matchMedia(MOBILE_MQ)
+    const mq2 = window.matchMedia(TOUCH_MQ)
+    mq1.addEventListener('change', handler)
+    mq2.addEventListener('change', handler)
+    return () => {
+      mq1.removeEventListener('change', handler)
+      mq2.removeEventListener('change', handler)
+    }
   }, [])
 
   // verticalSplit is always vertical; sideBySide becomes vertical on mobile
diff --git a/services/web/frontend/js/shared/context/layout-context.tsx b/services/web/frontend/js/shared/context/layout-context.tsx
index b4ef85685f..feafcfffb9 100644
--- a/services/web/frontend/js/shared/context/layout-context.tsx
+++ b/services/web/frontend/js/shared/context/layout-context.tsx
@@ -86,16 +86,24 @@ function setLayoutInLocalStorage(pdfLayout: IdeLayout) {
 }
 
 const MOBILE_MQ = '(max-width: 767px)'
+// Secondary touch check: catches browsers that spoof viewport width (e.g. Tor
+// Browser's fingerprinting resistance reports ~980px on an Android phone).
+// `pointer: coarse` reflects real hardware and is not spoofed.
+const TOUCH_MQ = '(pointer: coarse) and (max-width: 1024px)'
+
+function isMobileDevice(): boolean {
+  return (
+    window.matchMedia(MOBILE_MQ).matches ||
+    window.matchMedia(TOUCH_MQ).matches
+  )
+}
 
 function getInitialLayout(): IdeLayout {
   const stored = localStorage.getItem('pdf.layout')
-  const isMobile = window.matchMedia(MOBILE_MQ).matches
-  // On mobile, always start in verticalSplit (editor above, PDF below).
-  // We must check isMobile first: a stale 'flat' in localStorage (written by
-  // a previous autoSave race or a desktop session) would otherwise short-circuit
-  // the mobile check and leave the user stuck in a flat/editor-only layout.
-  // The user can still collapse to flat during a session, but it does not persist.
-  if (isMobile) return 'verticalSplit'
+  // Check mobile first — must come before the stored-'flat' check so that a
+  // stale 'flat' (written by an old autoSave race) doesn't block the mobile
+  // default. isMobileDevice() also catches spoofed-viewport browsers.
+  if (isMobileDevice()) return 'verticalSplit'
   if (stored === 'flat') return 'flat'
   if (stored === 'split') return 'sideBySide'
   if (stored === 'vertical') return 'verticalSplit'