With fedimint, something similar is achieved by having a lightning gateway serve multiple federations. A lightning gateway is a server that can offer to perform ecash-lightning atomic swaps as a service to federations that it trusts, typically maintaining an ecash balance for all federations it serves so it has liquidity to fulfill swap requests. Under the hood, if a user of Federation A pays an invoice to a user in Federation B, the gateway short-circuits and never even uses lightning. Instead it simply takes the Federation A ecash and pays out Federation B ecash. All of the complexity you’re describing is tucked away into the gateway, eliminating the need for every user to be a part of multiple federations in order to find overlap with counterparties. Instead, the gateway is the only party that needs to trust multiple federations, which it wants to do anyway, since that will lead to more tx volume and therefore more fees.

Although now that i think about it the offline case still fails if you need to do the swap 🤔

You mean if the sender is offline? Yes, offline Cashu transactions always come with some requirements and trade offs. Receiver offline: sender needs to pick the right token (as defined in the payment request) and include DLEQ Sender offline: receiver should accept token from all mints and swap to LN to make sure token are real money Both offline: requires either preparation in advance or a considerable amount of trust

can the payment request be static or is it always interactive?

It can be static. Here is the base spec:

GitHub

nuts/18.md at main · cashubtc/nuts

Cashu protocol specifications https://cashubtc.github.io/nuts/ - cashubtc/nuts

Here is the PR that extends NUT-18 for HTTP402 and defines the protocol:

GitHub

NUT-24: HTTP Payment required by hzrd149 · Pull Request #239 · cashubtc/nuts

This PR adds NUT-24 that describes how the HTTP 402 status code + an X-Cashu header can be used to require payment for http resources readable vers...

Unfortunately Cashu is a shoddily designed protocol

Starts to make sense? I think you are making a lot of assumptions that non-technical people will understand any of this as opposed to simply opting for a completely turnkey black box solution.

I was saying it makes sense from a merchant perspective, assuming customer wallets can do these swaps automatically. I was trying to think of a situation where i would be willing to to accept these with low risk. Yes the biggest problem is like you described, you actually have to think hard about the actual tradeoffs

Talking about merchant , what do you think of MCP square ?

This still reads as if you expect to be receiving cashu tokens as payment. The receiver presents a ln invoice the sender, the sender "melts" their token and their mint pays the ln invoice to your mint of choice, which issues you cashu tokens. You seem to be describing letting users pay you in raw cashu tokens from various mints. Users can send cashu tokens out of band or on nostr but lightning is the bridge between mints. Cashu is better privacy custodian.

In summary, the main advantage of Cashu is that it frees ordinary people, who may not know much about the Lightning Network, from the challenging task of operating a Lightning Network node. Complex issues like inbound and outbound liquidity are handled by specialized mints. The downside, of course, is that it is custodial, meaning there is always a risk that the service could disappear, and this risk primarily falls on the buyer who actually receives the Cashu tokens. As a seller, there is no need to trust random mints (in which case the tokens would essentially have no value); you can choose to only accept tokens from specific mints that you trust. This means that both buyers and sellers can deposit or receive payments through mints they trust. However, this also means that sellers and buyers must rely on their trusted mints to "swap" through the Lightning Network, which still presents the issue of routing failures. Ultimately, even when using Cashu, payment failures can occur. Of course, the liquidity management will be much more professional than that of the buyer or seller.