diff --git a/app/worker_api.py b/app/worker_api.py
index 5cea9c5d..4ab49742 100644
--- a/app/worker_api.py
+++ b/app/worker_api.py
@@ -945,12 +945,22 @@ def _seconds_to_next_window(now: float | None = None) -> float:
 
 
 async def _activity_cycle() -> None:
-    """One round, if the owner switched Activity on and Docker answers."""
+    """One round, if the owner switched Activity on and Docker answers.
+
+    With Activity off there is no round, but probes other workers left behind
+    are still swept: their logs hold raw addresses and nothing else removes them.
+    """
     global _pending_activity, _activity_seq
-    if not _activity_enabled:
-        return
     if not await asyncio.to_thread(orchestrator.docker_available):
         return
+    if not _activity_enabled:
+        client = await asyncio.to_thread(activity._client)
+        try:
+            await asyncio.to_thread(activity.sweep, client)
+        finally:
+            with contextlib.suppress(Exception):
+                client.close()
+        return
     switches = _activity_switches
     result = await asyncio.to_thread(activity.run_round)
     if not _activity_enabled or _activity_switches != switches:
diff --git a/tests/test_activity_worker.py b/tests/test_activity_worker.py
index 2c26b2ae..74219066 100644
--- a/tests/test_activity_worker.py
+++ b/tests/test_activity_worker.py
@@ -484,9 +484,11 @@ def wapi():
 with (
     patch("app.worker_api.orchestrator.docker_available", return_value=True) as docker_ok,
     patch("app.worker_api.activity.run_round", return_value=None) as run_round,
+    patch("app.worker_api.activity._client", return_value=MagicMock()),
+    patch("app.worker_api.activity.sweep", return_value=[]),
 ):
     asyncio.run(worker_api._activity_cycle())
-    assert not docker_ok.called and not run_round.called, "a round ran before any reply"
+    assert not run_round.called, "a round ran before any reply"
     reply = MagicMock()
     reply.json.return_value = {"activity": {"enabled": True}}
     worker_api._apply_activity_reply(reply, None)
@@ -523,10 +525,39 @@ def test_disabled_never_runs_a_round(self, wapi):
         with (
             patch("app.worker_api.orchestrator.docker_available", return_value=True),
             patch("app.worker_api.activity.run_round") as run_round,
+            patch("app.worker_api.activity._client", return_value=MagicMock()),
+            patch("app.worker_api.activity.sweep", return_value=[]),
         ):
             asyncio.run(wapi._activity_cycle())
         assert not run_round.called
 
+    def test_disabled_still_sweeps_probes_other_workers_left(self, wapi):
+        """With Activity off the sweep at worker start is not the last one: a probe another
+        worker leaves later (it died and came back under a new id) holds raw addresses in
+        its log, and only a sweep removes it."""
+        wapi._activity_enabled = False
+        client = MagicMock()
+        with (
+            patch("app.worker_api.orchestrator.docker_available", return_value=True),
+            patch("app.worker_api.activity.run_round") as run_round,
+            patch("app.worker_api.activity._client", return_value=client),
+            patch("app.worker_api.activity.sweep", return_value=[]) as sweep,
+        ):
+            asyncio.run(wapi._activity_cycle())
+        sweep.assert_called_once_with(client)
+        client.close.assert_called_once()
+        assert not run_round.called
+
+    def test_disabled_without_docker_does_not_sweep(self, wapi):
+        wapi._activity_enabled = False
+        with (
+            patch("app.worker_api.orchestrator.docker_available", return_value=False),
+            patch("app.worker_api.activity._client") as make_client,
+            patch("app.worker_api.activity.sweep") as sweep,
+        ):
+            asyncio.run(wapi._activity_cycle())
+        assert not make_client.called and not sweep.called
+
     def test_enabled_runs_a_round_negative_control(self, wapi):
         """The control for the test above: the same call with the switch on runs."""
         wapi._activity_enabled = True