diff --git a/tests/tui_gateway/test_busy_compression_demotion.py b/tests/tui_gateway/test_busy_compression_demotion.py
index bb7d3ba041..b5d93d421c 100644
--- a/tests/tui_gateway/test_busy_compression_demotion.py
+++ b/tests/tui_gateway/test_busy_compression_demotion.py
@@ -220,6 +220,8 @@ def test_submit_during_manual_compress_is_queued_and_reply_persists(monkeypatch)
     assert session["running"] is True
     second = server._methods["session.compress"]("r3", {"session_id": "sid"})  # the locked claim maps to busy
     assert second["error"]["code"] == 4009
+    # tools.configure rebuilds the agent (history_version bump): refused before it reads the action
+    assert server._methods["tools.configure"]("r4", {"session_id": "sid"})["error"]["code"] == 4009
     # "/compress --aggressive" never touches history: answered without claiming (or draining) the busy session
     assert server._compress_live_with_feedback("sid", session, agent, "--aggressive", snapshot_kwargs=True) == \
         ccm.AGGRESSIVE_UNSUPPORTED