How exactly does the API billing with Kagi work?

[SomeOddCodeGuy]

Hey folks! I was looking at the Kagi api documentation found in overview.md, and found myself somewhat confused about how the Pre-Paid API Credit interacts with the usage limit and invoicing.

I can see under billing that there is a Pre-Paid API Credit section; to me, this sounds like the ideal system for me, where I can put N number of dollars in and usage eats the credits as I go. Once I hit $0, I can no longer use it. This means if the API key is ever lost or stolen, I don't run the risk of rampant spending.

However, I then see

You are invoiced when your usage reaches $100 (or your custom limit) or at the end of each monthly billing cycle, whichever comes first.

which reads like pay as you go with an invoice threshold. And the billing screenshot in the doc (api-portal-billing.png) shows the Set Usage Limit section with this text:

Set a spending limit, at which requests will be blocked until payment is cleared.

I understand the mechanics of the limit on its own. What I can't figure out from the docs is how it interacts with the prepaid credit. A concrete example:

Say that my usage limit is set to $80, and I have $60 in prepaid credit.

1. Does the API stop working at $60 because my balance ran out, or does it keep going to $80 with the last $20 owed beyond my balance?
2. Using the spend limit feature: since requests are "blocked until payment is cleared", does the limit reset every time a payment clears? And is that an automatic payment from the stripe account? I'm curious whether the $80 limit in my example would really stop a lost API key from ever costing me more than $80, or if it would just break the attack into chunks: $80 -> stop and auto-charge my card -> $80 -> stop and auto-charge my card.

The reason I ask: I specifically want a setup where a lost or stolen API key has a hard ceiling on what it can ever cost me. If prepaid credit acts as a true cap (the API stops at $60 in my example, and prepaid-only accounts are allowed), that is exactly what I am after. If instead the credit is just a deposit against invoices and the limit resets on every payment, then there is no real ceiling once a card is attached, and I would like to know that before I build around it.

Thank you!