LEGACY_WREFS_REFUSAL is no longer exported, and client_flags=["legacy-wrefs"] no longer refuses requests. The server has retired the old-grammar compatibility window and ignores the flag, so the SDK sends requests exactly as it does without it. Remove the flag from client_flags. Code that compared a message with warmhub.LEGACY_WREFS_REFUSAL, or checked details.reason == "legacy-wrefs-sdk", should drop that branch.
Old-format operations get the ordinary error. A mapping in the old format (kind, about, collection type/members, no operation) is no longer recognized and refused with a suggested new form; it gets the ordinary error of the check it fails, such as an add that states no Shapes. A mapping revise carrying active is no longer refused locally with a retract suggestion: an operation carrying any key it does not take (kind, shape, active, or any other) is refused locally with unknown key "<key>" on a <verb> operation, as the server's strict operation objects would refuse it. The internal helpers v1_operation_signal, v2_form_of and missing_shapes_refusal are gone.