diff --git a/client/src/const.ts b/client/src/const.ts
index 9999063..7a84981 100644
--- a/client/src/const.ts
+++ b/client/src/const.ts
@@ -4,6 +4,13 @@ export { COOKIE_NAME, ONE_YEAR_MS } from "@shared/const";
 export const getLoginUrl = () => {
   const oauthPortalUrl = import.meta.env.VITE_OAUTH_PORTAL_URL;
   const appId = import.meta.env.VITE_APP_ID;
+
+  // If OAuth portal URL is not configured (e.g. self-hosted / recette without Manus OAuth),
+  // fall back to the local login page instead of constructing an invalid URL.
+  if (!oauthPortalUrl || !appId) {
+    return "/login";
+  }
+
   const redirectUri = `${window.location.origin}/api/oauth/callback`;
   const state = btoa(redirectUri);