Update

frontend/src/lib/authError.ts

@@ -0,0 +1,25 @@
+const PASSTHROUGH_CODES = new Set([
+  'INVALID_CREDENTIALS',
+  'LOGIN_RATE_LIMITED',
+  'GUEST_ACCESS_DISABLED',
+  'GUEST_READ_ONLY',
+  'GUEST_PROJECT_SCOPE_REQUIRED',
+])
+
+export function formatAuthError(error: unknown, fallback: string): string {
+  if (!(error instanceof Error)) return fallback
+
+  const code = (error as { code?: string }).code
+  if (code && PASSTHROUGH_CODES.has(code)) return error.message
+
+  if (
+    code === 'REQUEST_ERROR'
+    || code === 'INTERNAL_ERROR'
+    || code === 'SESSION_CREATION_FAILED'
+    || /request failed|failed to fetch|networkerror/i.test(error.message)
+  ) {
+    return fallback
+  }
+
+  return error.message || fallback
+}