diff --git a/server-rs/crates/spacetime-module/src/runtime/active/profile.rs b/server-rs/crates/spacetime-module/src/runtime/active/profile.rs
index fff05e9dd..e37eed3dc 100644
--- a/server-rs/crates/spacetime-module/src/runtime/active/profile.rs
+++ b/server-rs/crates/spacetime-module/src/runtime/active/profile.rs
@@ -4192,6 +4192,18 @@ mod tests {
         assert_eq!(same_period.row.cycle_index, 1);
         assert_eq!(same_period.row.cycle_remaining_points, 120);
 
+        // 期号水位为 0（新列默认值）但账期窗口已存在：只补水期号，不重发本期额度。
+        let mut stale_watermark = row();
+        stale_watermark.cycle_index = 0;
+        let backfilled = advance_profile_membership_cycle_to(
+            stale_watermark,
+            Timestamp::from_micros_since_unix_epoch(anchor + 10 * day),
+            400,
+        );
+        assert!(!backfilled.advanced, "期号水位缺失不应被当成换期");
+        assert_eq!(backfilled.row.cycle_index, 1);
+        assert_eq!(backfilled.row.cycle_remaining_points, 120);
+
         let next_period = advance_profile_membership_cycle_to(
             row(),
             Timestamp::from_micros_since_unix_epoch(anchor + 28 * day),
@@ -9424,7 +9436,13 @@ fn advance_profile_membership_cycle_to(
     // 起点取已落库的期号（水位下限），保证只前进、不后退。
     let mut cycle_index = row.cycle_index.max(1);
     let mut window = membership_cycle_window(anchor_micros, cycle_index);
-    let mut advanced = row.cycle_resets_at.is_none() || row.cycle_index == 0;
+    // `cycle_resets_at` 缺失 = 账期窗口尚未初始化，需要写库补种并发放本期额度；
+    // `cycle_index == 0` 只是期号水位没写（新列默认值），不能据此判定越界、重发额度。
+    let mut advanced = row.cycle_resets_at.is_none();
+    if row.cycle_index == 0 {
+        // 仅补写期号水位：账期额度只应在真正越过边界时重置。
+        row.cycle_index = 1;
+    }
     // 仅当 `at` 已越过当前窗口结束时刻才推进；时钟回拨时条件不成立，整行保持原状。
     while window.1 <= at_micros && cycle_index < max_index {
         cycle_index = cycle_index.saturating_add(1);