Root marker

A data attribute named after a component's id and carried on its root element, such as data-accordion or data-button, so that selectors and identifiers can be scoped to one component and never reach another nested inside it

Needed as soon as two components share a part name. Since Button and Link both carry a treatment, a bare [data-treatment] selector would also reach a button nested in an accordion panel, so the accordion's treatment rules are written [data-accordion][data-treatment=…]. The Core's ADR-0027 (tokens scoped to ds-accordion[data-brand][data-treatment]) and ADR-0028 (instance-unique ids) fix the same class of bug: an unscoped identifier that works with one instance and breaks with two.

Not a cwds field. A Component Contract names no markup hooks (cwds ADR-0005), so the marker is an adapter convention derived from the record's id

cwds' reading of its own decisions, 2026-10-01, not a separate ruling. Record ids are unique and stable, while part names are unique only within a record, so scoping a shared part name by the record's id follows from the records as they stand. If the convention ever needs to bind every adapter, the Component Schema is the place to declare it.