diff --git a/foundry/packages/backend/src/services/better-auth.ts b/foundry/packages/backend/src/services/better-auth.ts
index 1f1ae4c..ea9d95a 100644
--- a/foundry/packages/backend/src/services/better-auth.ts
+++ b/foundry/packages/backend/src/services/better-auth.ts
@@ -549,6 +549,9 @@ export function initBetterAuthService(actorClient: any, options: { apiUrl: strin
         strategy: "compact",
       },
     },
+    onAPIError: {
+      errorURL: stripTrailingSlash(options.appUrl) + "/signin",
+    },
     socialProviders: {
       github: {
         clientId: requireEnv("GITHUB_CLIENT_ID"),