diff --git a/4-fusion.py b/4-fusion.py
index eeac275..22f5873 100644
--- a/4-fusion.py
+++ b/4-fusion.py
@@ -298,6 +298,11 @@ def main(argv: list[str] | None = None) -> int:
         default=None,
         help="Single sitename to fuse (default: all prepared sites)",
     )
+    parser.add_argument(
+        "--skip-blended",
+        action="store_true",
+        help="Skip sites whose fusion directory already exists under data/fusion/{year}/",
+    )
     args = parser.parse_args(argv)
     year = args.evaluation_year
 
@@ -311,17 +316,18 @@ def main(argv: list[str] | None = None) -> int:
 
     print(f"[Fusion] Processing {len(sites)} site(s)")
     for i, sitename in enumerate(sites, 1):
+        fusion_dir = DATA_DIR / "fusion" / str(year) / sitename
+        if args.skip_blended and fusion_dir.exists():
+            print(f"[Fusion] ({i}/{len(sites)}) {sitename} — skipping (fusion directory exists)")
+            continue
         print(f"[Fusion] ({i}/{len(sites)}) {sitename}")
-        try:
-            summary = fuse_site(sitename, year)
-            print(
-                f"[Fusion] {sitename} done — "
-                f"{summary['fusion_dates']} dates, "
-                f"itb={summary['itb_fusion_files']} bti={summary['bti_fusion_files']} "
-                f"bti_gcc={summary['bti_gcc_files']}"
-            )
-        except Exception as exc:
-            print(f"[Fusion] {sitename} FAILED: {exc}")
+        summary = fuse_site(sitename, year)
+        print(
+            f"[Fusion] {sitename} done — "
+            f"{summary['fusion_dates']} dates, "
+            f"itb={summary['itb_fusion_files']} bti={summary['bti_fusion_files']} "
+            f"bti_gcc={summary['bti_gcc_files']}"
+        )
 
     return 0