diff --git a/ui/src/ui/app-gateway.sessions.node.test.ts b/ui/src/ui/app-gateway.sessions.node.test.ts
index 24421974213..1bc9178fd1c 100644
--- a/ui/src/ui/app-gateway.sessions.node.test.ts
+++ b/ui/src/ui/app-gateway.sessions.node.test.ts
@@ -142,6 +142,22 @@ describe("handleGatewayEvent session.message", () => {
     expect(loadChatHistoryMock).toHaveBeenCalledWith(host);
   });
 
+  it("skips history reload while a chat run is active", () => {
+    loadChatHistoryMock.mockReset();
+    const host = createHost();
+    host.sessionKey = "agent:qa:main";
+    host.chatRunId = "run-123";
+
+    handleGatewayEvent(host, {
+      type: "event",
+      event: "session.message",
+      payload: { sessionKey: "agent:qa:main" },
+      seq: 1,
+    });
+
+    expect(loadChatHistoryMock).not.toHaveBeenCalled();
+  });
+
   it("ignores transcript updates for other sessions", () => {
     loadChatHistoryMock.mockReset();
     const host = createHost();