diff --git a/steward/core/alerts.py b/steward/core/alerts.py
index f656e9f..573be15 100644
--- a/steward/core/alerts.py
+++ b/steward/core/alerts.py
@@ -250,9 +250,14 @@ async def record_metrics(session: AsyncSession, rows: list[PluginMetric], phases
                          key=lambda r: r.recorded_at)
         muted = _muted_by(windows, rule)
         resumed = _track_samples(alert_state, samples, now)
+        # A silence ends when Steward hears of it: an agent's flushed backlog
+        # brings samples hours old, and stamping their events at their own
+        # times put the resume inside the silence it ends (#5720).
+        back = resumed is not None
         for sample in samples:
+            at = max(sample.recorded_at, now) if back else sample.recorded_at
             notifications = await _evaluate_rule(session, rule, alert_state, sample.value,
-                                                 sample.recorded_at, note=muted, resumed=resumed)
+                                                 at, note=muted, resumed=resumed)
             resumed = None  # said once, with the first sample back
             if muted:
                 continue
@@ -319,7 +324,13 @@ def _track_samples(state: AlertState, samples: list[PluginMetric], now: datetime
     series had been marked no_data, clear the mark and return the note saying
     so ("data resumed after 15m silent"); the first sample's evaluation
     records it, in one event with whatever that sample does to the rule
-    (#5442)."""
+    (#5442).
+
+    A resumed series counts as last heard `now`, when Steward heard it, not at
+    its newest sample's time: a backlog flushed a few samples a post is hours
+    old, and judging silence by it marked the series silent again between
+    posts, so one silence was resumed twice (#5720). The rest of the backlog
+    then reads as late samples, which teach the cadence nothing."""
     for sample in samples:
         if state.last_sample_at is not None:
             if sample.recorded_at <= state.last_sample_at:
@@ -331,6 +342,7 @@ def _track_samples(state: AlertState, samples: list[PluginMetric], now: datetime
         return None
     note = f"data resumed after {human_duration((now - state.no_data_since).total_seconds())} silent"
     state.no_data_since = None
+    state.last_sample_at = max(state.last_sample_at or now, now)
     return note
 
 
diff --git a/tests/core/test_alert_no_data.py b/tests/core/test_alert_no_data.py
index d3bc325..9af8b4a 100644
--- a/tests/core/test_alert_no_data.py
+++ b/tests/core/test_alert_no_data.py
@@ -151,3 +151,19 @@ def test_muted_by_names_the_window_that_covers_the_rule():
     assert _muted_by(windows[:1], rule) is None
     assert _muted_by([NS(name="all", scope_source=None, scope_resource=None)], rule) == (
         "notification muted: maintenance window all")
+
+
+def test_a_flushed_backlog_counts_as_heard_when_it_arrives():
+    """#5720: an agent's backlog, flushed a couple of samples a post, is hours
+    old. Judged by its newest sample, the series read silent again between
+    posts and resumed twice. It counts as heard when Steward heard it, and the
+    rest of the backlog reads as late."""
+    st = _state(last_sample_at=NOW - timedelta(hours=3), sample_interval_s=60,
+                no_data_since=NOW - timedelta(hours=2, minutes=55))
+    note = _track_samples(st, _samples((2 * 3600 + 60, 5.0), (2 * 3600, 5.0)), NOW)
+    assert note == "data resumed after 2h 55m silent"
+    assert st.last_sample_at == NOW
+    assert silent_since(st.last_sample_at, st.sample_interval_s, NOW, NOW) is None
+    # The next post of the same backlog is late: no gap, no second resume.
+    assert _track_samples(st, _samples((2 * 3600 - 60, 5.0)), NOW) is None
+    assert st.last_sample_at == NOW