I always wanted to be able to use Cashu in a web widget that can be used to pay for services on a web page (imagine a tiny javascript wallet that loads once you visit a site). This is a huge head ache with ecash since the actual ecash is non-custodial and browsers do not easily support synching state across different pages (for very good reasons). I've been trying to come up with ways how this widget hosted on different webpages could use the same ecash balance and all of them involved some sort of "carrying over state" – either by downloading the ecash from a server that stores it for you, or by synchronizing the derivation path counter and "restoring" the ecash every time you open the page.

I've spent way too much time thinking about this problem. Very very very bad vibes. None of these would have worked without serious issues.

But – I've finally seen the light.