trigger ContactTrigger on Contact (after insert, after update) {

    if (Trigger.isAfter) {
        if (Trigger.isInsert || Trigger.isUpdate) {
            // Only run trigger logic if allowed
            if (ContactTriggerHandler.becamePrimary) {
                System.debug('Trigger executed - becamePrimary is TRUE');
                // your logic here if needed
            }
        }
    }
}