diff --git a/backend/app/worker/fluksio_worker.py b/backend/app/worker/fluksio_worker.py
index 458f652..4124902 100644
--- a/backend/app/worker/fluksio_worker.py
+++ b/backend/app/worker/fluksio_worker.py
@@ -48,7 +48,24 @@ PROTOCOL = 1
 HEARTBEAT_S = 10.0
 #: Reconnection backs off to this and no further.
 MAX_BACKOFF_S = 30.0
-WORKER_MAIN = Path(__file__).with_name("worker_main.py")
+
+
+def _worker_main() -> Path:
+    """The user-code runner: beside this file once deployed, or in a checkout.
+
+    On a worker host the two files sit together, which is what the install
+    instructions say. Run straight from a clone and the runner is one directory
+    over, in the engine's own package — worth finding, so trying this out does
+    not start with copying files around.
+    """
+    here = Path(__file__).resolve().parent
+    for candidate in (here / "worker_main.py", here.parent / "flow" / "worker_main.py"):
+        if candidate.exists():
+            return candidate
+    return here / "worker_main.py"
+
+
+WORKER_MAIN = _worker_main()
 
 
 class Subprocess: