Who is typically designated as the primary custodial parent in a divorce or separation agreement, and what factors are considered in determining this role?

In a divorce or separation agreement, the primary custodial parent is typically the parent who has the majority of physical custody of the child. Factors considered in determining this role include the child's best interests, the parent's ability to provide a stable and nurturing environment, the parent's relationship with the child, and any history of abuse or neglect.