⚠️ Experimental endpoint — not yet a stable contract. This action ships as experimental / beta. While experimental, its schema and behaviour may change without a version bump — including breaking changes within v1.0 itself. Anyone consuming it does so for evaluation only, or by coordinating adoption with their account manager so changes can be sequenced with them. It graduates to a stable, version-locked contract (where the normal breaking-change rules apply) only when this experimental notice is removed.

Set the applicable custom field values of a user group without changing any other user group properties. This action requires permission to view the user group and the UserGroups.update-custom-fields permission.

Send a JSON object containing only the required customFields object; other body properties and any query parameters return 422 validation errors. Omitted identifiers remain unchanged, while null clears the corresponding value. When custom fields are enabled for user groups, an empty object succeeds as a no-op without an audit event. Invalid or unavailable submitted identifiers and invalid values return 422 validation errors. If custom fields are disabled for the tenant or user groups, the action returns 412 Precondition Failed. Neither rejection changes values or creates an audit event. A 404 response means the user group was not found or is not accessible.