diff --git a/src/auth/client.ts b/src/auth/client.ts
index 6447cd9..130a43a 100644
--- a/src/auth/client.ts
+++ b/src/auth/client.ts
@@ -25,8 +25,23 @@ export type Schema = {};
 
 type DirectusClient = ReturnType<typeof buildClient>;
 
+/**
+ * Resolve a (possibly relative) URL against the current page origin.
+ *
+ * Runtime config supports relative paths like `/api` because the SPA always
+ * runs same-origin to its backends. The Directus SDK, however, calls
+ * `new URL(...)` internally and requires an absolute URL — so we resolve
+ * before handing it over.
+ *
+ * - `'/api'` → `'http://localhost:5173/api'` (in dev)
+ * - `'https://api.example.com'` → `'https://api.example.com/'` (passes through)
+ */
+function toAbsoluteUrl(maybeRelative: string): string {
+  return new URL(maybeRelative, window.location.origin).toString();
+}
+
 function buildClient(directusUrl: string) {
-  return createDirectus<Schema>(directusUrl)
+  return createDirectus<Schema>(toAbsoluteUrl(directusUrl))
     .with(authentication('cookie', { credentials: 'include', autoRefresh: true }))
     .with(rest({ credentials: 'include' }));
 }