fix(scanner): reject terminal leadership epochs

crates/scanner/src/scanner/leadership.rs

@@ -196,7 +196,7 @@ pub(super) async fn claim_scanner_leadership(
         if ctx.is_cancelled() {
             return false;
         }
-        let Some(claimed_epoch) = persisted_epoch.checked_add(1) else {
+        let Some(claimed_epoch) = persisted_epoch.checked_add(1).filter(|epoch| *epoch < u64::MAX) else {
             error!(
                 target: "rustfs::scanner",
                 event = EVENT_SCANNER_PERSIST_STATE,

crates/scanner/src/scanner/tests.rs

@@ -1410,6 +1410,22 @@ async fn test_leadership_claim_preserves_usage_epoch_floor_across_old_epoch_conf
     assert_eq!(store.put_counts.lock().await.get(&key), Some(&3));
 }
 
+#[tokio::test]
+async fn test_leadership_claim_rejects_terminal_epoch() {
+    let store = Arc::new(MemoryConfigStore::default());
+    let ctx = CancellationToken::new();
+    let mut revision = DataUsageCacheRevision::Missing;
+    let mut cycle = CurrentCycle {
+        next: 12,
+        ..Default::default()
+    };
+    let mut persisted_epoch = u64::MAX - 1;
+
+    assert!(!claim_scanner_leadership(&ctx, store.clone(), &mut cycle, &mut revision, &mut persisted_epoch).await);
+    assert_eq!(persisted_epoch, u64::MAX - 1);
+    assert!(read_config(store, &DATA_USAGE_BLOOM_NAME_PATH).await.is_err());
+}
+
 #[tokio::test]
 async fn test_leadership_claim_confirms_commit_after_returned_error() {
     let store = Arc::new(MemoryConfigStore::default());