diff --git a/src/db.rs b/src/db.rs
index c8d3dd1..6ee5284 100644
--- a/src/db.rs
+++ b/src/db.rs
@@ -117,22 +117,10 @@ pub async fn list_accounts(pool: &AnyPool) -> Result<Vec<AccountRow>> {
         .collect())
 }
 
-/// Advance the scan height of already-caught-up accounts (scan_height at/above
-/// the previous tip) to the new tip after a forward scan pass.
-pub async fn advance_caught_up_scan_heights(
-    pool: &AnyPool,
-    to_height: i64,
-    from_height: i64,
-) -> Result<()> {
-    sqlx::query("UPDATE accounts SET scan_height = $1 WHERE scan_height >= $2")
-        .bind(to_height)
-        .bind(from_height)
-        .execute(pool)
-        .await?;
-    Ok(())
-}
-
-/// Set one account's scan height (used after its backfill completes).
+/// Set one account's scan height (after a forward-scan pass covers it, or after
+/// its backfill completes). Advancing per-account (rather than a blanket
+/// UPDATE-by-height) is deliberate: it must never mark an account that was not
+/// actually scanned as caught-up.
 pub async fn set_account_scan_height(pool: &AnyPool, rewind_hash: &str, height: i64) -> Result<()> {
     sqlx::query("UPDATE accounts SET scan_height = $1 WHERE rewind_hash = $2")
         .bind(height)
diff --git a/src/scanner.rs b/src/scanner.rs
index 4798284..4b4cd8e 100644
--- a/src/scanner.rs
+++ b/src/scanner.rs
@@ -100,10 +100,19 @@ async fn tick(pool: &AnyPool, node: &GrinNode) -> crate::error::Result<()> {
     // ── Phase 2: spend reconcile (by absence from the unspent set) ──────────
     reconcile_spends(pool, node, tip_height).await?;
 
-    // ── Phase 3: advance the cursor + caught-up accounts ────────────────────
+    // ── Phase 3: advance the cursor + the accounts we actually scanned ──────
     // (Only after discovery AND reconcile succeeded — Risk R1.)
     db::set_cursor(pool, new_mmr_index as i64, tip_height as i64, &tip_hash).await?;
-    db::advance_caught_up_scan_heights(pool, tip_height as i64, prev_tip as i64).await?;
+    // Advance ONLY the accounts that were in this tick's `caught_up` set — i.e.
+    // the ones the forward scan above actually covered. A blanket
+    // UPDATE-by-height would also mark an account that REGISTERED DURING this
+    // tick's scan (so it was never in `caught_up`, never scanned) as caught-up,
+    // leaving it stuck at a 0 balance forever — and the backend's synced gate
+    // would then trust that 0. Such an account instead stays "behind" and is
+    // picked up by the backfill phase on a later tick.
+    for rh in &caught_up {
+        db::set_account_scan_height(pool, rh, tip_height as i64).await?;
+    }
 
     // ── Phase 4: backfill one pending new account (birthday → cursor) ───────
     if let Some(acct) = accounts.iter().find(|a| a.scan_height < prev_tip) {