Swarm-notification version bump belongs in deform(), not the internal primitive

src/underworld3/discretisation/discretisation_mesh.py

@@ -3456,6 +3456,15 @@ def _do_move():
         result = remesh_with_field_transfer(
             self, _do_move, dt=dt, extra_zero=zero, verbose=verbose)
 
+        # Notify registered swarms: solve-entry sync compares this version
+        # and marks them for deferred migration (#379 item 1 retired the
+        # read-trigger that consumed this channel). The bump lives HERE,
+        # not in _deform_mesh: the internal primitive also runs on
+        # snapshot restore, whose integrity check treats a moved version
+        # as invalidation and would refuse its own recovery.
+        if result:
+            self._mesh_version += 1
+
         # Refresh deformation-tracking per-boundary normals so Nitsche/penalty
         # BCs that captured ``boundary_normal(...).sym`` at setup read the new
         # geometry (the JIT reads the variable's .data, which would otherwise
@@ -3560,13 +3569,6 @@ def _deform_mesh(self, new_coords: numpy.ndarray, verbose=False,
                 if solver is not None and hasattr(solver, "is_setup"):
                     solver.is_setup = False
 
-            # Notify registered swarms: solve-entry sync compares this
-            # version and marks them for deferred migration (#379 item 1
-            # retired the read-trigger that used to consume this channel).
-            # The mesh.X.coords callback path bumps again after this
-            # returns — harmless, the consumer checks inequality.
-            self._mesh_version += 1
-
             # Invalidate caches whose contents become stale when mesh
             # coordinates change. Matches the cache hygiene already
             # performed by mesh.adapt() and _legacy_access. Without