Make archive discovery deterministic

backend/app/commands.py

@@ -139,6 +139,16 @@ def get_task_status(node: str, upid: str) -> dict:
     return pvesh_json(["get", f"/nodes/{node}/tasks/{upid}/status"]) or {}
 
 
+def _archive_name_timestamp(path: Path) -> datetime:
+    match = re.search(r"-(\d{4}_\d{2}_\d{2}-\d{2}_\d{2}_\d{2})", path.name)
+    if not match:
+        return datetime.min
+    try:
+        return datetime.strptime(match.group(1), "%Y_%m_%d-%H_%M_%S")
+    except ValueError:
+        return datetime.min
+
+
 def discover_archive(local_backup_dir: str, vmid: int, guest_type: str, started_at: str) -> Path:
     base = Path(local_backup_dir)
     prefix = "vzdump-lxc" if guest_type == "lxc" else "vzdump-qemu"
@@ -161,7 +171,7 @@ def discover_archive(local_backup_dir: str, vmid: int, guest_type: str, started_
                 candidates.append(path)
     if not candidates:
         raise FileNotFoundError(f"No backup archive found for VMID {vmid} in {base}")
-    return max(candidates, key=lambda p: p.stat().st_mtime)
+    return max(candidates, key=lambda p: (p.stat().st_mtime_ns, _archive_name_timestamp(p), p.name))
 
 
 def rclone_list_remotes(rclone_path: str) -> list[str]: