diff --git a/pkg/atproto/firehose.go b/pkg/atproto/firehose.go
index 6219b58d6..b7b44040f 100644
--- a/pkg/atproto/firehose.go
+++ b/pkg/atproto/firehose.go
@@ -455,8 +455,17 @@ func (atsync *ATProtoSynchronizer) repoStreamCallbacks(ctx context.Context, rela
 		if err != nil {
 			return
 		}
-		atsync.markEvent(aqt.Time())
-		cursor.observeTime(aqt.Time())
+		at := aqt.Time()
+		// A relay with a clock running ahead must not pin either mark into the
+		// future: max-wins would then blank out lag reporting (and make the
+		// replay cursor look eternally fresh) until that stamp catches up.
+		// Fold it to the receive time instead -- that is still evidence the
+		// relay is delivering, so a later, correctly dated event moves on.
+		if now := time.Now(); at.After(now) {
+			at = now
+		}
+		atsync.markEvent(at)
+		cursor.observeTime(at)
 	}
 	return &events.RepoStreamCallbacks{
 		RepoCommit: func(evt *indigoatproto.SyncSubscribeRepos_Commit) error {
diff --git a/pkg/atproto/firehose_liveness_test.go b/pkg/atproto/firehose_liveness_test.go
index 1ce013ea9..cab607e0a 100644
--- a/pkg/atproto/firehose_liveness_test.go
+++ b/pkg/atproto/firehose_liveness_test.go
@@ -49,4 +49,18 @@ func TestFirehoseLivenessCountsUnindexedCommits(t *testing.T) {
 	// before dedup: a duplicate is still evidence of what the relay sent.
 	require.NoError(t, rsc.RepoCommit(commit(evtTime.Add(-time.Minute))))
 	require.Equal(t, evtTime.UnixNano(), atsync.lastEvent.get())
+
+	// A relay with a clock running ahead must not pin the mark into the
+	// future: that would silence lag reporting until the bogus stamp caught
+	// up. The observation folds to the receive time, so a later, correctly
+	// dated event still advances it.
+	require.NoError(t, rsc.RepoCommit(commit(time.Now().Add(time.Hour))))
+	require.LessOrEqual(t, atsync.lastEvent.get(), time.Now().UnixNano(),
+		"a future stamp must not push the position past the wall clock")
+	before := atsync.lastEvent.get()
+	time.Sleep(2 * time.Millisecond)
+	require.NoError(t, rsc.RepoCommit(commit(time.Now())))
+	require.Greater(t, atsync.lastEvent.get(), before,
+		"correctly dated events keep advancing after a bogus future one")
+	require.Less(t, sinceNanos(atsync.lastEvent.get()), time.Minute)
 }