diff --git a/web/app/auth/signin/page.tsx b/web/app/auth/signin/page.tsx
index 47296d6ef..4f8d3dd58 100644
--- a/web/app/auth/signin/page.tsx
+++ b/web/app/auth/signin/page.tsx
@@ -1,7 +1,28 @@
 import { Suspense } from 'react';
+import { redirect } from 'next/navigation';
 import SignInForm from './form';
+import { loadConsoleProfile } from '@/lib/services/console-profile';
+
+export const dynamic = 'force-dynamic';
+
+export default async function SignIn({
+  searchParams,
+}: {
+  searchParams: Promise<{ next?: string }>;
+}) {
+  // Auth guard: an already-signed-in user should never sit on the sign-in
+  // screen. On mobile the device Back button pops history to /auth/signin
+  // (the OAuth flow leaves it on the stack), which read as "Back dumps me at
+  // sign-in". Bounce authenticated users forward into the app instead, so Back
+  // effectively returns them to the console.
+  const profile = await loadConsoleProfile();
+  if (profile) {
+    const { next } = await searchParams;
+    // Only honour app-internal paths to avoid an open-redirect via ?next=.
+    const dest = next && next.startsWith('/') && !next.startsWith('//') ? next : '/dashboard';
+    redirect(dest);
+  }
 
-export default function SignIn() {
   return (
     <Suspense fallback={<div style={{ display: "flex", minHeight: "100vh", alignItems: "center", justifyContent: "center", background: "var(--void)", color: "var(--ink-muted)", fontFamily: "var(--font-mono)", fontSize: 12, letterSpacing: "0.08em", textTransform: "uppercase" as const }}>Loading...</div>}>
       <SignInForm />