mxpic_router/builder.py

@@ -446,7 +446,22 @@ def _sbend_forward_axis(plan: dict) -> str:
 
 
 def _link_explicit_route_group(link: LinkSpec) -> str:
-    return str(getattr(link, "route_group", "") or "").strip()
+    route_group = str(getattr(link, "route_group", "") or "").strip()
+    if route_group:
+        return route_group
+    bundle = str(getattr(link, "bundle", "") or "").strip()
+    if _is_default_route_bundle(bundle):
+        return ""
+    return bundle
+
+
+def _is_default_route_bundle(bundle: str) -> bool:
+    name = str(bundle or "").strip().lower()
+    if not name:
+        return True
+    if name == "output_bus":
+        return True
+    return name == "free_wires" or name.startswith("free_wires_")
 
 
 def _route_direction_sign(delta: float) -> int: