fix: keep the account and other query parameters of a mail link Lite replays after a 404 #1352

components/mail/mail-app.tsx

@@ -157,7 +157,7 @@ import {
 import { consumePendingDeepLink, subscribePendingDeepLink } from "@/lib/deep-link-handoff";
 import { useProInterfaceActive } from "@/components/pro/pro-interface-redirect";
 import type { QuoteHeader } from "@/lib/plugin-types";
-import { useLiteLinkSegments } from "@/hooks/use-lite-link-segments";
+import { initialLinkSearch, useLiteLinkSegments } from "@/hooks/use-lite-link-segments";
 
 export interface MailAppProps {
   /**
@@ -1893,7 +1893,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
   // actually opened with on first client render.
   const initialSearchRef = useRef<string | null>(null);
   if (initialSearchRef.current === null && typeof window !== "undefined") {
-    initialSearchRef.current = window.location.search;
+    initialSearchRef.current = initialLinkSearch('mail');
   }
 
   useEffect(() => {

hooks/__tests__/use-lite-link-segments.test.ts

@@ -14,9 +14,41 @@ vi.mock('@/lib/lite', async (importOriginal) => {
   };
 });
 
-import { useLiteLinkSegments } from '@/hooks/use-lite-link-segments';
+import { initialLinkSearch, useLiteLinkSegments } from '@/hooks/use-lite-link-segments';
 import { LITE_PENDING_PATH_KEY } from '@/lib/lite';
 
+// Mail reads the query it was opened with on its first render, while the
+// address bar still shows the surface root the 404 shim jumped to (#1352).
+describe('initialLinkSearch', () => {
+  beforeEach(() => sessionStorage.clear());
+
+  it('takes the query of a parked deep link in the first render', () => {
+    liteState.IS_LITE = true;
+    window.history.replaceState({}, '', '/en/mail/');
+    sessionStorage.setItem(LITE_PENDING_PATH_KEY, '/en/mail/message/m1/?account=bob%40example.org#x');
+
+    const seen: string[] = [];
+    renderHook(() => {
+      useLiteLinkSegments('mail', []);
+      seen.push(initialLinkSearch('mail'));
+    });
+
+    expect(seen[0]).toBe('?account=bob%40example.org');
+    // The restored URL carries it from then on.
+    expect(window.location.search).toBe('?account=bob%40example.org');
+  });
+
+  it('reads the address bar otherwise', () => {
+    liteState.IS_LITE = true;
+    window.history.replaceState({}, '', '/en/mail/message/m1?account=a');
+    sessionStorage.setItem(LITE_PENDING_PATH_KEY, '/en/calendar/week/2026-09-17?view=1');
+    expect(initialLinkSearch('mail')).toBe('?account=a');
+    liteState.IS_LITE = false;
+    sessionStorage.setItem(LITE_PENDING_PATH_KEY, '/en/mail/message/m2?account=b');
+    expect(initialLinkSearch('mail')).toBe('?account=a');
+  });
+});
+
 describe('useLiteLinkSegments', () => {
   beforeEach(() => {
     sessionStorage.clear();

hooks/use-lite-link-segments.ts

@@ -53,3 +53,16 @@ export function useLiteLinkSegments(surface: AppSurface, linkSegments?: string[]
 
   return segments;
 }
+
+/**
+ * The query a surface was opened with, for a caller that reads it during its
+ * first render: until the effect above restores a parked deep link, the
+ * address bar shows the surface root without the link's query (#1352).
+ */
+export function initialLinkSearch(surface: AppSurface): string {
+  const pending = IS_LITE ? peekPendingLitePath(surface, getPathPrefix()) : null;
+  if (pending === null) return window.location.search;
+  const query = pending.split('#')[0];
+  const start = query.indexOf('?');
+  return start === -1 ? '' : query.slice(start);
+}