diff --git a/src/api/client.js b/src/api/client.js
index a460fe2..bfeaa1e 100644
--- a/src/api/client.js
+++ b/src/api/client.js
@@ -17,8 +17,19 @@ class ApiClient {
     const res = await fetch(`${API_BASE_URL}${endpoint}`, { ...options, headers });
     const text = await res.text();
     let data = null;
-    try { data = text ? JSON.parse(text) : null; } catch { throw new Error('Ungültige Server-Antwort'); }
-    if (!res.ok) throw new Error(data?.error || `HTTP ${res.status}`);
+    try {
+      data = text ? JSON.parse(text) : null;
+    } catch {
+      throw new Error(`Server-Antwort nicht lesbar (HTTP ${res.status}): ${text.slice(0, 120)}`);
+    }
+    if (!res.ok) {
+      // Validation-Errors (express-validator) zeigen
+      if (Array.isArray(data?.errors) && data.errors.length) {
+        const msg = data.errors.map(e => e.msg || e.message || JSON.stringify(e)).join(', ');
+        throw new Error(`Eingabe ungültig: ${msg}`);
+      }
+      throw new Error(data?.error || `HTTP ${res.status}`);
+    }
     return data;
   }