diff --git a/src/modules/auth/pages/OAuthCallback.jsx b/src/modules/auth/pages/OAuthCallback.jsx
index bb1b6bc..1f71f72 100644
--- a/src/modules/auth/pages/OAuthCallback.jsx
+++ b/src/modules/auth/pages/OAuthCallback.jsx
@@ -73,7 +73,10 @@ export default function OAuthCallback() {
       // already set by the backend; restoreSession() just picks it up.
       const { success, user } = await restoreSession()
       if (cancelled) return
-      navigate(success ? getRoleHomePath(user) : '/login', { replace: true })
+      navigate(success ? getRoleHomePath(user) : '/login', {
+        replace: true,
+        state: success && pending.justLinkedGoogle ? { justLinkedGoogle: true } : undefined,
+      })
     })()
 
     return () => { cancelled = true }
@@ -89,7 +92,10 @@ export default function OAuthCallback() {
         <div className="w-full max-w-sm">
           <OtpVerifyForm
             email={email}
-            onSuccess={(user) => navigate(getRoleHomePath(user), { replace: true })}
+            onSuccess={(user) => navigate(getRoleHomePath(user), {
+              replace: true,
+              state: result?.justLinkedGoogle ? { justLinkedGoogle: true } : undefined,
+            })}
             title="Verify your sign-in"
             description={`We sent a 6-digit code to ${email} to finish signing in with Google. It expires in 10 minutes.`}
           />
diff --git a/src/modules/client/pages/Dashboard.jsx b/src/modules/client/pages/Dashboard.jsx
index 978c3d3..a8c6c52 100644
--- a/src/modules/client/pages/Dashboard.jsx
+++ b/src/modules/client/pages/Dashboard.jsx
@@ -240,6 +240,17 @@ const Client = () => {
         window.history.replaceState({}, '');
     }, []);
 
+    // Show a one-time notice the first time a manually-registered account
+    // gets folded into a Google sign-in with the same email.
+    useEffect(() => {
+        if (!navState?.justLinkedGoogle) return;
+        toast('Your Google account is now affiliated with this account.', {
+            description: 'You can sign in with Google going forward.',
+            duration: 6000,
+        });
+        window.history.replaceState({}, '');
+    }, []);
+
     useEffect(() => {
         getCourses();
         getUnits();