diff --git a/frontend/src/lib/xray/outbound-form-adapter.ts b/frontend/src/lib/xray/outbound-form-adapter.ts
index 3dd5852d..bf331fca 100644
--- a/frontend/src/lib/xray/outbound-form-adapter.ts
+++ b/frontend/src/lib/xray/outbound-form-adapter.ts
@@ -620,7 +620,10 @@ export function formValuesToWirePayload(values: OutboundFormValues): WireOutboun
   }
 
   if (values.sendThrough) result.sendThrough = values.sendThrough;
-  if (values.mux.enabled && muxAllowed(values)) {
+  // mux may be absent when the modal didn't render the Mux switch (non-
+  // stream protocols or when isMuxAllowed gated it out). validateFields()
+  // only returns registered fields, so values.mux can be undefined.
+  if (values.mux?.enabled && muxAllowed(values)) {
     result.mux = values.mux;
   }
   return result;
diff --git a/frontend/src/pages/xray/OutboundFormModal.tsx b/frontend/src/pages/xray/OutboundFormModal.tsx
index 362efdfa..fee094f7 100644
--- a/frontend/src/pages/xray/OutboundFormModal.tsx
+++ b/frontend/src/pages/xray/OutboundFormModal.tsx
@@ -372,6 +372,13 @@ export default function OutboundFormModal({
     if (key === '1' && activeKey === '2') {
       if (!applyJsonToForm()) return;
     }
+    // Blur the currently focused element before AntD marks the outgoing
+    // tab panel aria-hidden. Without this, a focused input inside the
+    // hidden panel triggers a Chrome a11y warning ("Blocked aria-hidden
+    // on an element because its descendant retained focus").
+    if (typeof document !== 'undefined') {
+      (document.activeElement as HTMLElement | null)?.blur?.();
+    }
     setActiveKey(key);
   }