Lightning Is Dead, Long Live Lightning!Lightning Is Dead, Long Live Lightning!

Lightning Grows When We Cultivate It TogetherLightning continues to evolve, but most of the changes we’ve witnessed over the last decade are changes in the technology. What’s happened over the last two years, however, is a change of the technology. We’re not talking about protocol enhancements or new features, but a fundamental reconceptualization of what Lightning is, what it can do, and who uses it for what.

We’ve discussed some of these changes before in isolation, but they can be a little abstract. That’s why we tend to use metaphors like “common language” and “last-mile technology.”

Fortunately, one of our partners, Cake Wallet, has traced this path with us, and their story renders the abstraction of Lightning’s recent transformation marvelously concrete. So let me tell you the story of Lightning, Breez, and Cake.

If We Only Node Then What We Know NowIf We Only Node Then What We Know Now

In 2024, we at Breez were very glad to welcome Cake as an early design partner using our (then) brand-new SDK. Cake implemented the Breez SDK using Greenlight in their wallet. While Greenlight’s remote nodes improved the Lightning UX relative to client nodes running on users’ phones, Cake never put it into production, and we have since deprecated it.

Greenlight was a quality-of-life improvement over earlier implementations of Lightning on mobile devices. Running an actual Lightning node on users’ phones devoured resources and required constant sync with the Bitcoin chain and the Lightning Network, which was very challenging to solve with the restrictions of the contemporary mobile operating systems. By moving users’ nodes into the cloud and shifting many of the moving parts into the background, Greenlight did improve the UX.

However, even with Greenlight, compromises between open, permissionless, borderless Bitcoin and an intuitive, frictionless UX remained. For example, liquidity remained a tough nut to crack for everyone involved. Receiving bitcoin offline still required improvised workarounds using mobile notifications. We thought that Greenlight was the best balance available at the time, comparable in custody and openness with its predecessors and surpassing them in simplicity, but the UX was still too complicated and Greenlight itself proved hard to scale.

It’s for reasons like these that Cake never took the Greenlight implementation of the Breez SDK into production, despite praising its design, simplicity, and functionality. Greenlight was an advance in the technology, but Lightning needed a fundamental change of the technology.

Cake tried the Greenlight solution, and it turned out to be good enough for devs but still lacking for users. They opted not to compromise and rather wait for a better product. And honestly, that’s exactly the feedback we needed.

A Common Language for the Last MileA Common Language for the Last Mile

Times change, and tech changes with them.

More specifically, several last-mile technologies have emerged to improve the experience of the world’s Bitcoin users and the economics of moving bitcoin. These include new-gen statechains like Spark, sidechains like Liquid, federations for friends and family like Fedimint, eCash networks like Cashu, and advanced programming layers like Arkade. They’re all variations on a common theme: just as Lightning improves on Bitcoin’s economics and throughput, these last-mile technologies all improve on Lightning’s payment channels, economics, complexity, and scalability.

Lightning is still a vital part of how we transfer value, but it has evolved to become the common language and payment protocol that connects these last-mile technologies rather than a channels protocol that end users need to master. And Lightning’s connections run deep. Even when bitcoin moves from a Spark entity to Arkade or between a Fedimint federation and Liquid, those various subnetworks speak to each other in fluent Lightning.

Lightning’s transformation seems inevitable to anyone who understands the economics of Lightning and values UX. Poon-Dryja payment channels excel when there’s a constant flow of high-velocity transactions, especially when they’re bi-directional. Even if problems that inherently stem from mobile usage (such as network synchronization and offline receive) are solved, edge nodes will always under-perform at low transaction velocities. Liquidity management and economics is a feature for routing nodes, but a bug when it comes to end-user nodes. Luckily, these last-mile technologies solve such issues and other UX complexities, and with Lightning as the common language that connects them, Bitcoin just works for devs and users alike.

The Return of CakeThe Return of Cake

Talking about the evolution of Lightning is so exciting, I almost forgot to tell you the big news: Cake Wallet is now taking the Breez SDK into production! Huzzah!

Cake continued to research the Bitcoin-UX dilemma and explore various last-mile solutions. The Spark implementation of the Breez SDK provided Cake with a balanced trade-off between a trust-minimized solution and the UX they deserve. It combines the openness, utility, and finality of bitcoin with features that have eluded Lightning until now, like offline payments.

And the UX, which used to be the weak spot, is now the best part. Payments are instant. Offline payments and Lightning addresses are built in. Fees are infinitesimal. Like any fintech app, the complexity behind the scenes is substantial but irrelevant, because users just see money moving where they want, when they want, how they want. It’s bitcoin as digital cash. Users get to have their Cake and eat it too (sorry, I had to).

Of course, we haven’t compromised on the developer experience, which is better than ever. The API of the Breez SDK is designed by developers for developers to be as simple as possible with clear, extensive instructions and rapid, helpful support. With a user-friendly product, Cake is serving its end users, and with a developer-friendly product, we’re serving Cake’s product team.

Lightning Grows When We Cultivate It TogetherLightning Grows When We Cultivate It Together

Breez was among the first to see the promise of Lightning and ship a functional mobile app, but our users pushed us to build a better experience. We worked together with the Blockstream team, who devised Greenlight, to optimize it for users and developers alike. Again, we were proud and with good reason, because our old Greenlight SDK was a significant improvement. But partners like Cake weren’t yet satisfied despite giving the Greenlight implementation a fair chance. They pushed us to build better.

We have, and by “we” I mean the whole Lightning community. Breez is still working with Blockstream on the Liquid implementation of the SDK, and we’re working with Lightspark on the Spark implementation, leveraging it to provide the best-in-class Lightning experience

This is exactly how it’s supposed to work. We build as far as we can with existing technology, and then we release the result out into the market to raise the bar and to determine where we still need to improve. Dedicated partners like Cake tell us how by sharing what they and their users need. Then we meet with our allies who are pursuing the same goal, and we cooperate to build the next miracle and reach the next optimum.

The story of Breez, Lightning, and Cake holds two lessons. First, there’s no alternative but to keep building and testing. Second, even though it’s impossible to tell what the next innovation in Lightning will be or how it will perform, the overall trajectory is obvious: Lightning keeps getting better. It’s now a much more functional technology helping far more people do far more things than it was when we all started.

Don’t you love a story with a happy ending?

Originally posted by Roy on X.