Referral app that automatically applies bonus to subscription renewal

[FastFedora]

I'm looking for a referral solution for a client who is launching a Shopify store. It's for a subscription box business where their customers have auto-renewing subscriptions.

Do you know if there's any app that supports referral bonuses that are automatically applied to the next subscription renewal? Or how this might be done using a tool like Mechanic?

For example, if Bob refers Alice, they would like it if Bob's referral bonus is automatically applied to his next subscription renewal amount without needing to take an explicit action to do so. Alice would use her referral bonus in the normal way, since she would be creating a new subscription/order.

It's ideal if the app can handle affiliates as well, since they'll also be running an affiliate program. But if we have to use two separate apps, that's fine too.