diff --git a/worker/lyra_worker/adapters/_slskd.py b/worker/lyra_worker/adapters/_slskd.py
index 8766db4..6e10d9e 100644
--- a/worker/lyra_worker/adapters/_slskd.py
+++ b/worker/lyra_worker/adapters/_slskd.py
@@ -33,6 +33,15 @@ def _max_polls(total_bytes: int) -> int:
     return max(_MIN_XFER_POLLS, min(budget, _MAX_XFER_POLLS))
 
 
+def _needs_enqueue(state: str) -> bool:
+    """Whether a file must be (re)enqueued on slskd. True if it has no transfer yet or its last
+    transfer ended badly (Errored/Cancelled/Rejected); a file already Completed/InProgress/Queued is
+    left alone so a resumed download continues it instead of restarting from zero. Pure — unit-tested."""
+    if not state:
+        return True
+    return any(bad in state for bad in ("Errored", "Cancelled", "Rejected"))
+
+
 def _basename(path: str) -> str:
     return path.rsplit("\\", 1)[-1].rsplit("/", 1)[-1]