diff --git a/asset/arena/quantus-arena-exporter.py b/asset/arena/quantus-arena-exporter.py
index 4db2c10..d9aa8b7 100755
--- a/asset/arena/quantus-arena-exporter.py
+++ b/asset/arena/quantus-arena-exporter.py
@@ -369,6 +369,9 @@ ATTRIBUTION_MIN_CONFIDENCE = 0.6
 # restarts or renames (a new telemetry node id) takes over the attribution
 # after a few blocks instead of having to outvote its own history.
 ATTRIBUTION_WINDOW = 20
+# Startup backfill of the rolling window from chain history is capped by
+# wall clock so a slow node cannot hold the exporter's first poll forever.
+BACKFILL_BUDGET_S = 180.0
 
 GAP_BUCKETS = [0.5, 1, 2, 3, 5, 8, 12, 16, 24, 32, 48, 64, 128]
 # Block timestamp minus the moment this exporter first saw the block, seconds.
@@ -534,6 +537,32 @@ class Arena:
             return None
         return self.rpc.call("chain_getHeader", [h])
 
+    def backfill_window(self, height):
+        """Fill the rolling window from chain history at startup, so the
+        per-author series (leaderboard rows, author labels, timing caps) do
+        not start from nothing after every restart. Window only: the authored
+        counter is left alone so `increase()` sees no phantom burst, and no
+        tip timing is observed for blocks we did not watch arrive."""
+        start = max(1, height - self.blocks.maxlen + 1)
+        deadline = time.time() + BACKFILL_BUDGET_S
+        n = start
+        got = 0
+        while n < height and time.time() < deadline:
+            try:
+                hdr = self.header_at(n)
+            except Exception as e:  # noqa: BLE001 - history is best effort
+                LOG.warning("backfill stopped at %s: %s", n, e)
+                break
+            if hdr:
+                pre = author_preimage(hdr)
+                if pre is not None:
+                    with self.lock:
+                        self.blocks.append((n, pre))
+                    got += 1
+            n += 1
+        LOG.info("backfilled %s of %s window blocks (%s..%s) in %.0fs", got, height - start, start, n - 1,
+                 time.time() - (deadline - BACKFILL_BUDGET_S))
+
     def record(self, header, at_tip):
         height = int(header["number"], 16)
         pre = author_preimage(header)
@@ -636,6 +665,8 @@ class Arena:
                 hdr = self.header_at(n)
                 if hdr:
                     self.record(hdr, at_tip=False)
+        if self.last_height is None:
+            self.backfill_window(height)
         if self.last_height is None or height > self.last_height:
             self.record(head, at_tip=not self.syncing)
             self.last_height = height
diff --git a/asset/grafana/quantus.json b/asset/grafana/quantus.json
index 27be047..be70281 100644
--- a/asset/grafana/quantus.json
+++ b/asset/grafana/quantus.json
@@ -9,7 +9,7 @@
   ],
   "timezone": "browser",
   "schemaVersion": 39,
-  "version": 21,
+  "version": 22,
   "refresh": "30s",
   "time": {
     "from": "now-6h",
@@ -1725,7 +1725,7 @@
           },
           "editorMode": "code",
           "refId": "A",
-          "expr": "sort_desc(topk(20, round(increase(quantus_blocks_authored_total[$__range]))))",
+          "expr": "sort_desc(topk(20, round(increase(quantus_blocks_authored_total[$__range])) > 0))",
           "instant": true,
           "range": false,
           "format": "table"