Api based group and statuses

we use zamamd via a middleware all tickets are added by using the API instead of via email

who is reponsible for updating the status, is this handled by zammad? i.e. if
a customer adds a response (by adding an article via API) do i have to update the status myself?

Cause it seems like a status of “closed” stays closed even if i add an customer article to it (i.e. a ticket reply) and i would somehow would have expected that the ticket than automatically gets the status “open” again - but it seems like i have to make an extra call? that seems very dangerous cause it means that “my code” would need to manage some but not all of the zammad ticket statuses, i thought the zammad backend would update the ticket status accordingly?