diff --git a/src/api/checkoutClient.ts b/src/api/checkoutClient.ts
index cfdd652..4a83b55 100644
--- a/src/api/checkoutClient.ts
+++ b/src/api/checkoutClient.ts
@@ -1,7 +1,18 @@
 import axios from 'axios';
 import { logger } from '../utils/logger';
 
-const API_BASE_URL = import.meta.env.VITE_API_BASE_URL || 'http://localhost:3001';
+// Get API base URL from runtime config (window.env) or build-time config
+const getApiBaseUrl = (): string => {
+  // Check window.env first (runtime config from env.sh)
+  if (typeof window !== 'undefined' && window.env?.API_BASE_URL) {
+    return window.env.API_BASE_URL;
+  }
+
+  // Fall back to build-time env or default
+  return import.meta.env.VITE_API_BASE_URL || 'http://localhost:3001';
+};
+
+const API_BASE_URL = getApiBaseUrl();
 
 export interface CreateCheckoutSessionParams {
   tons: number;