diff --git a/src/app/api/stores/[storeId]/route.ts b/src/app/api/stores/[storeId]/route.ts
index 84977bf..00caac2 100644
--- a/src/app/api/stores/[storeId]/route.ts
+++ b/src/app/api/stores/[storeId]/route.ts
@@ -144,7 +144,12 @@ export async function PATCH(
         // Even if ScriptTag operations fail (missing scopes), the widget still
         // won’t render because /api/storefront-chat/config returns the flag.
         try {
-            const appBaseUrl = (process.env.NEXT_PUBLIC_APP_URL || "").trim()
+            const appBaseUrl = (
+                process.env.NEXT_PUBLIC_APP_URL ||
+                process.env.AUTH_URL ||
+                process.env.NEXTAUTH_URL ||
+                ""
+            ).trim()
             const apiVersion = "2024-01"
             const injectorBase = appBaseUrl ? appBaseUrl.replace(/\/$/, "") : ""
 
diff --git a/src/app/storefront-chat/widget-injector/route.ts b/src/app/storefront-chat/widget-injector/route.ts
index 04cbb6f..24e3d75 100644
--- a/src/app/storefront-chat/widget-injector/route.ts
+++ b/src/app/storefront-chat/widget-injector/route.ts
@@ -11,7 +11,11 @@ export async function GET() {
   try {
     var script = document.currentScript;
     var baseUrl = script && script.src ? new URL(script.src).origin : window.location.origin;
-    var shop = window.location.hostname;
+    // Prefer Shopify-provided shop identifier when available.
+    // On custom domains, window.location.hostname won't match the shop's myshopify domain.
+    var shop =
+      (window.Shopify && (window.Shopify.shop || window.Shopify.myshopifyDomain)) ||
+      window.location.hostname;
 
     var containerId = "juno-storefront-chat-container";
     var iframeId = "juno-storefront-chat-iframe";