diff --git a/scripts/data_platform/corpus_download.py b/scripts/data_platform/corpus_download.py
index 05b6e26..47437a4 100644
--- a/scripts/data_platform/corpus_download.py
+++ b/scripts/data_platform/corpus_download.py
@@ -144,6 +144,8 @@ class DomainClient:
         self.cooled = False
         self.n_requests = 0
         self._last = 0.0
+        self._t_first = None
+        self._t_last = None
 
     def _pace(self):
         interval = RATE.get(self.name, 1.0) + random.uniform(*JITTER)
@@ -151,8 +153,18 @@ class DomainClient:
         if wait > 0:
             time.sleep(wait)
         self._last = time.monotonic()
+        if self._t_first is None:
+            self._t_first = self._last
+        self._t_last = self._last
         self.n_requests += 1
 
+    def avg_interval(self):
+        """域内首末请求间隔/(n-1): 真实节奏(lane 总时长跨段失真, 09-07 实锤
+        cninfo n=3 avg=3621s 的乌龙)。"""
+        if self.n_requests < 2 or self._t_first is None:
+            return None
+        return (self._t_last - self._t_first) / (self.n_requests - 1)
+
     def _transport_fail(self, msg):
         self.consecutive_errors += 1
         if self.consecutive_errors >= COOLDOWN_ERRORS:
@@ -1176,9 +1188,10 @@ def run_lane(lane, until=None, limit=None):
         _save_depth(ctx)
         for name, cl in ctx.clients.items():
             if cl.n_requests:
-                log.info("stats %s: n_requests=%d avg_interval=%.2fs%s",
+                avg = cl.avg_interval()
+                log.info("stats %s: n_requests=%d avg_interval=%s%s",
                          name, cl.n_requests,
-                         (time.monotonic() - t0) / cl.n_requests,
+                         f"{avg:.2f}s" if avg is not None else "n/a",
                          " [429]" if cl.rate_limited else
                          " [cooled]" if cl.cooled else "")
         log.info("lane=%s done in %.0fs: units=%d failed=%d rc=%d",