diff --git a/apps/rebreak-native/hooks/useCustomDomains.ts b/apps/rebreak-native/hooks/useCustomDomains.ts
index 8e7b2b5..c05cc11 100644
--- a/apps/rebreak-native/hooks/useCustomDomains.ts
+++ b/apps/rebreak-native/hooks/useCustomDomains.ts
@@ -145,8 +145,20 @@ export function useCustomDomains(plan: Plan): UseCustomDomainsReturn {
       const resolvedKind: 'web' | 'mail' = kind ?? (input.includes('@') ? 'mail' : 'web');
       if (resolvedKind === 'web' && !isValidDomain(input)) return { ok: false, error: 'invalid_domain' };
       if (resolvedKind === 'mail' && !input.trim()) return { ok: false, error: 'invalid_pattern' };
-      const tier = deriveTier(plan, domains);
-      if (tier.atLimit) return { ok: false, error: 'limit_reached' };
+      // Per-Bucket-Limit-Check via Backend-counts/limits (Single Source of Truth).
+      // Wenn API noch keine counts/limits geliefert hat (Legacy-Response) → skip,
+      // Backend rejected dann mit WEB_LIMIT_REACHED / MAIL_LIMIT_REACHED.
+      if (apiCounts && apiLimits) {
+        const bucket = resolvedKind;
+        const used = apiCounts[bucket] ?? 0;
+        const cap = apiLimits[bucket] ?? Infinity;
+        if (used >= cap) {
+          return {
+            ok: false,
+            error: bucket === 'mail' ? 'mail_limit_reached' : 'web_limit_reached',
+          };
+        }
+      }
       const pattern = resolvedKind === 'web' ? normalizeDomain(input) : input.trim();
       const body: Record<string, string> = { pattern };
       if (kind !== undefined) body.kind = kind;