Fix: "Add another account" button now navigates to sign-in page

app/auth/login/page.tsx

@@ -6,16 +6,27 @@ import { useSearchParams } from 'next/navigation';
 import { LoginForm, DevQuickLogin } from "../../components/forms/login-form"
 import { ModernAuthLayout } from "../../components/layout/modern-auth-layout"
 import { Alert, AlertDescription } from "../../components/ui/alert";
+import { hasSearchParam } from "../../utils/searchParams";
 
 function LoginContent() {
   const searchParams = useSearchParams();
   const action = searchParams?.get('action');
   const message = searchParams?.get('message');
   const isPostingReply = action === 'posting_reply';
   const isSessionRevoked = message === 'session_revoked';
+  const isAddingAccount = hasSearchParam(searchParams, 'switchAccount');
 
   return (
     <ModernAuthLayout afterCard={<DevQuickLogin />}>
+      {isAddingAccount && (
+        <Alert className="mb-4 bg-primary/10 border-theme-medium">
+          <Icon name="UserPlus" size={16} className="text-primary" />
+          <AlertDescription className="text-primary">
+            Sign in with another account to add it to your account switcher.
+          </AlertDescription>
+        </Alert>
+      )}
+
       {isPostingReply && (
         <Alert className="mb-4 bg-primary/10 border-theme-medium">
           <Icon name="AlertCircle" size={16} className="text-primary" />

app/components/forms/login-form.tsx

@@ -13,6 +13,7 @@ import Link from 'next/link';
 import { getEnvironmentType } from '../../utils/environmentConfig';
 import { looksLikeEmail } from '@/utils/validationPatterns';
 import { ChallengeWrapper, useChallengeToken } from '../auth/ChallengeWrapper';
+import { hasSearchParam } from '../../utils/searchParams';
 
 // Constants for rate limiting
 const MAX_ATTEMPTS_BEFORE_WARNING = 3;
@@ -139,10 +140,13 @@ export function LoginForm() {
     setWarning('');
   }, []);
 
-  // Redirect if already authenticated
+  // Redirect if already authenticated (but not when adding another account)
   useEffect(() => {
-    const isAddingAccount = searchParams?.has('switchAccount');
-    if (!authLoading && isAuthenticated && !isAddingAccount) {
+    // searchParams can be null before Next.js resolves the URL; hasSearchParam
+    // also checks window.location as a fallback so we never accidentally redirect
+    // away when the user is in the middle of an add-another-account flow.
+    const urlHasSwitchAccount = hasSearchParam(searchParams, 'switchAccount');
+    if (!authLoading && isAuthenticated && !urlHasSwitchAccount) {
       router.push('/home');
     }
   }, [isAuthenticated, authLoading, router, searchParams]);

app/components/layout/MobileAccountMenu.tsx

@@ -127,9 +127,18 @@ export default function MobileAccountMenu() {
     }
   };
 
-  const addAnotherAccount = () => {
+  const addAnotherAccount = (event: React.MouseEvent) => {
+    event.preventDefault();
+    event.stopPropagation();
     setIsOpen(false);
-    router.push("/auth/login?switchAccount=1");
+    // Use window.location.href instead of router.push so the page performs a
+    // full reload. With router.push (client-side nav) the AuthProvider is
+    // already settled (isLoading=false, isAuthenticated=true) and the login
+    // form's redirect guard can fire before useSearchParams reflects the new
+    // URL, bouncing the user back immediately. A full reload reinitialises the
+    // AuthProvider with isLoading=true, keeping the guard silent while the
+    // params are read correctly from the address bar.
+    window.location.href = "/auth/login?switchAccount=1";
   };
 
   const forgetAccount = async (uid: string) => {

app/utils/searchParams.ts

@@ -0,0 +1,28 @@
+/**
+ * Returns true if the given key exists in the provided Next.js searchParams object
+ * OR in the current browser URL.
+ *
+ * Two failure modes are handled:
+ * 1. `useSearchParams()` returns null before Next.js has resolved the URL during
+ *    client-side navigation — the window.location fallback covers this case.
+ * 2. `useSearchParams()` returns a non-null but *stale* object (from the previous
+ *    page) when the component mounts before the router has flushed the new params —
+ *    the window.location fallback is always checked regardless.
+ */
+export function hasSearchParam(
+  searchParams: { has(key: string): boolean } | null | undefined,
+  key: string
+): boolean {
+  // Always check window.location first — it reflects the address bar immediately
+  // and is immune to any stale searchParams object from the previous render.
+  if (typeof window !== 'undefined') {
+    if (new URLSearchParams(window.location.search).has(key)) {
+      return true;
+    }
+  }
+  // Fall back to the searchParams object (may be null/stale on client-side nav)
+  if (searchParams != null) {
+    return searchParams.has(key);
+  }
+  return false;
+}