Function decode_path_cursor 

pub fn decode_path_cursor(
    cursor: &str,
    surface: &str,
    arity: usize,
) -> Result<Vec<String>>

decode_cursor for the keysets whose FIRST part is a document path (query’s [path, id], docs_list/docs_tree’s [path]). Since spec/surface 2.0 the surface speaks the reference form, so an issued cursor’s path is /-rooted; a bare path can only come from a 1.x cursor, whose keyset would sort before every rooted row and silently replay the first page — it is refused with a reason that names the cause.