Yeah sorry by saying "sender would know the preimage hash first" I meant first besides the receiver. You're right in your understanding there. But it's assumed the reciever is strike (on behalf of merchant), so they wouldn't redeem the kickback themselves. 

TonyGiorgio

SN Scoop: Strike plans to pay open source wallet devs in a sustainable model

nout

Ah, haha, I see I missed the next images. There, it shows H is sent to the routing nodes.

> However, originally only the sender would know the preimage hash first.

Mhh, I don't see this in the images: Doesn't Dave (the receiver) generate R (the preimage) and H (preimage hash) before any payment is done?

So the receiver could claim the potential payment as the first one by sending H to Strike before sending H to the sender. Strike could respond with some kind of token the receiver can then use together with the preimage after payment to proof he was paid. But since he already has the preimage, he can immediately proof he was paid.

So I am still confused.

Also, the sender should get paid, no?