Gate shifted velocity Jets to all-blocked callers

src/CelerisLab/body/jets.py

@@ -189,13 +189,14 @@ def edge_to_node_frame(points):
 
 
 def surface_link_velocity(objects, cfg, flags, fluid_idx, dir, body_id, rx, ry,
-                          jets=(), hits=None):
+                          jets=(), hits=None, *, _shifted_blocked=False):
     """Per-link prescribed surface velocity (n, 2) FP32 and aperture mask.
 
     Host-only and storage-neutral: rows follow the given physical cut-link
     order. Returns (None, None) when neither an object carries surface
     actuation nor a jet is given. Jets need true FP64 ``hits`` (n, 2) and may
     not share a link with each other or with a legacy aperture.
+    Shifted storage is privately enabled only by the all-blocked stepper.
     """
     enabled = [obj for obj in objects if obj.surface_actuation is not None]
     if not enabled and not jets:
@@ -219,7 +220,9 @@ def surface_link_velocity(objects, cfg, flags, fluid_idx, dir, body_id, rx, ry,
         if hits is None or len(hits) != len(dir):
             raise ValueError("Jets require true hit points row-aligned with the cut links")
         if (cfg is None or not cfg.is_d2q9 or cfg.store_precision != "FP32"
-                or cfg.streaming != "double_buffer" or cfg.ddf_shifting):
+                or cfg.streaming != "double_buffer"
+                or (cfg.ddf_shifting and not (_shifted_blocked is True
+                    and cfg.collision == "SRT" and not cfg.les_enabled))):
             raise ValueError("Jets require D2Q9/FP32/unshifted/double_buffer")
         shape, jet_id = jet_link_shapes(jets, hits)
         driven = jet_id >= 0