diff --git a/ui/src/lib/inbox.test.ts b/ui/src/lib/inbox.test.ts
index f34f2a7b..2ba6b3d9 100644
--- a/ui/src/lib/inbox.test.ts
+++ b/ui/src/lib/inbox.test.ts
@@ -24,6 +24,7 @@ import {
   loadLastInboxTab,
   normalizeInboxIssueColumns,
   RECENT_ISSUES_LIMIT,
+  resolveInboxNestingEnabled,
   resolveIssueWorkspaceName,
   resolveInboxSelectionIndex,
   saveInboxIssueColumns,
@@ -520,6 +521,19 @@ describe("inbox helpers", () => {
     expect(loadLastInboxTab()).toBe("all");
   });
 
+  it("keeps nesting enabled on desktop when the saved preference is on", () => {
+    expect(resolveInboxNestingEnabled(true, false)).toBe(true);
+  });
+
+  it("forces nesting off on mobile even when the saved preference is on", () => {
+    expect(resolveInboxNestingEnabled(true, true)).toBe(false);
+  });
+
+  it("keeps nesting off when the saved preference is off", () => {
+    expect(resolveInboxNestingEnabled(false, false)).toBe(false);
+    expect(resolveInboxNestingEnabled(false, true)).toBe(false);
+  });
+
   it("defaults issue columns to the current inbox layout", () => {
     expect(loadInboxIssueColumns()).toEqual(DEFAULT_INBOX_ISSUE_COLUMNS);
   });
diff --git a/ui/src/lib/inbox.ts b/ui/src/lib/inbox.ts
index 925870cb..4411a215 100644
--- a/ui/src/lib/inbox.ts
+++ b/ui/src/lib/inbox.ts
@@ -169,6 +169,10 @@ export function saveInboxNesting(enabled: boolean) {
   }
 }
 
+export function resolveInboxNestingEnabled(preferenceEnabled: boolean, isMobile: boolean): boolean {
+  return preferenceEnabled && !isMobile;
+}
+
 export function loadLastInboxTab(): InboxTab {
   try {
     const raw = localStorage.getItem(INBOX_LAST_TAB_KEY);
diff --git a/ui/src/pages/Inbox.tsx b/ui/src/pages/Inbox.tsx
index 9f9704ef..8926dd0e 100644
--- a/ui/src/pages/Inbox.tsx
+++ b/ui/src/pages/Inbox.tsx
@@ -16,6 +16,7 @@ import { projectsApi } from "../api/projects";
 import { useCompany } from "../context/CompanyContext";
 import { useBreadcrumbs } from "../context/BreadcrumbContext";
 import { useGeneralSettings } from "../context/GeneralSettingsContext";
+import { useSidebar } from "../context/SidebarContext";
 import { queryKeys } from "../lib/queryKeys";
 import {
   armIssueDetailInboxQuickArchive,
@@ -87,6 +88,7 @@ import {
   loadInboxIssueColumns,
   loadInboxNesting,
   normalizeInboxIssueColumns,
+  resolveInboxNestingEnabled,
   resolveIssueWorkspaceName,
   resolveInboxSelectionIndex,
   saveInboxIssueColumns,
@@ -579,6 +581,7 @@ function JoinRequestInboxRow({
 export function Inbox() {
   const { selectedCompanyId } = useCompany();
   const { setBreadcrumbs } = useBreadcrumbs();
+  const { isMobile } = useSidebar();
   const navigate = useNavigate();
   const location = useLocation();
   const queryClient = useQueryClient();
@@ -911,9 +914,10 @@ export function Inbox() {
   ]);
 
   // --- Parent-child nesting for inbox issues ---
-  const [nestingEnabled, setNestingEnabled] = useState(() => loadInboxNesting());
+  const [nestingPreferenceEnabled, setNestingPreferenceEnabled] = useState(() => loadInboxNesting());
+  const nestingEnabled = resolveInboxNestingEnabled(nestingPreferenceEnabled, isMobile);
   const toggleNesting = useCallback(() => {
-    setNestingEnabled((prev) => {
+    setNestingPreferenceEnabled((prev) => {
       const next = !prev;
       saveInboxNesting(next);
       return next;