diff --git a/frontend/src/pages/Asistente.tsx b/frontend/src/pages/Asistente.tsx
index 9bb503a..38a476c 100644
--- a/frontend/src/pages/Asistente.tsx
+++ b/frontend/src/pages/Asistente.tsx
@@ -144,7 +144,10 @@ export default function Asistente() {
               variant="outline"
               size="sm"
               onClick={() => setConfirmClear(true)}
-              disabled={!agent || agent.messages.length === 0}
+              // Also disabled mid-run: MAF saves the thread at run END, so
+              // clearing while an answer streams would delete the row only
+              // to have the finishing run write it right back.
+              disabled={!agent || agent.messages.length === 0 || agent.isRunning}
             >
               <MessageSquarePlus />
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