Bitcoin and Lightning app development, non-custodial by default.
If you are a non-technical founder building on Bitcoin or Lightning, custody and key management are the build, not a feature you add later. We default to non-custodial: zero accounts where we can manage it, multisig escrow where funds are held, and keys split so no single party can move them alone. We have shipped a nostr order book, Lightning streaming payments, and Swiss-regulated Bitcoin-backed loans, and we run several in the open. Fixed price, fixed date, secure-by-design, and you own the code and the IP from day one. We never promise you will not be breached, because no honest builder does. We promise someone who can secure it reads every part before it ships.
01 / The short answer
On Bitcoin, the worst bugs are the ones that move funds. So custody and keys get senior judgment on every line, and the platform holds as little control as your model allows.
We design non-custodial first. Where funds must be held, we use multisig so no one party can move them alone and keep keys split by design. Where they do not, we hold zero custody and require no accounts at all. The AI is held to evals we agree up front, and you own everything from the first commit. No hidden juniors, no opaque subcontractors, no code held hostage.
We have built an aggregated peer-to-peer order book over nostr, Lightning streaming payments that flow to a host by the second, and multisig custody for Bitcoin-backed lending under Swiss regulation. Several run in the open, so anyone can verify them. We build secure-by-design and make the system audit-ready against a framework. We tell you plainly when your model genuinely requires custody, rather than pretending it does not.
02 / Bitcoin we have built
Three builds, in production, client-owned.
Real systems handling sats, Lightning payments, and on-chain collateral. Results are scoped to what we built and run.
| Client / Project | What we built | Result |
|---|---|---|
| P2P Sats | An aggregated peer-to-peer order book that pulls offers from five Bitcoin marketplaces into one live price view over nostr, with no account and an alert the moment a deal matches. Built end to end, run in the open. | 5 P2P markets unified, 9 currencies, 3 languages, zero accounts to create. |
| Satstreamr | A 1:1 live video call where the viewer's Lightning payments flow straight to the host every few seconds while it runs, with no company in the middle, no card, no account. Built end to end, run in the open. | Lightning streaming roughly every 5 seconds, zero platform cut, zero accounts to create. |
| BTC Backed | A Bitcoin-backed stablecoin loan platform: the backend, the Bitcoin wallet, and a 2-of-3 multisig escrow that guards the collateral so no single party can move it alone. | 30+ backend feature modules, VQF-regulated in Zug, zero keys the platform holds alone. |
Want the same on your build? See how we work or start with a Spark audit. Start a conversation.
03 / What we handle on Bitcoin and Lightning
Custody and keys, treated as the build.
Non-custodial by default, multisig where funds are held, verifiable in the open where you want it.
- + Non-custodial designs where the platform holds zero custody and users keep their funds
- + Multisig escrow and key management so no single party can move collateral alone
- + Lightning payments, streaming, and settlement built as production systems, not demos
- + nostr-based order books, alerts, and aggregation across multiple marketplaces
- + Bitcoin wallets and on-chain logic, secure-by-design from the first commit
- + Builds that run in the open and can be verified, when that is what your model needs
- + Regulated custody where required, with the system made audit-ready against a framework
- + Full ownership of repo, docs, prompts, evals, deployment, and IP, with no vendor lock-in
04 / How a Bitcoin build runs
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01
1–2 wks
Spark audit
If you already have something, we read the custody model, the key handling, and where funds could be at risk. If you are starting fresh, we pressure-test the idea and scope the build, for a small fixed fee credited in full to a build.
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02
4–8 wks
Forge build
Fixed scope, fixed price, fixed deadline. Non-custodial and secure-by-design, AI judged on pre-agreed evals, signed acceptance criteria. If a build misses, remediation is free against those criteria for roughly six weeks.
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03
Ongoing
Engine team
An embedded team that runs the system, hardens custody and key management, and keeps it audit-ready as it grows. You stay involved and you keep owning everything.
Reply within a day with a fixed price and a date. See the fixed-price build or browse all case studies. Start a conversation.
05 / Common questions
Can you build non-custodial Bitcoin apps?
Yes, and we default to it. P2P Sats and Satstreamr hold zero custody and require no accounts, and BTC Backed guards collateral in a 2-of-3 multisig escrow no single party can move alone. We design so the platform never holds sole control of user funds unless your model genuinely requires it, and we tell you plainly when it does.
Do you build on Lightning?
Yes. Satstreamr streams Lightning payments to a host roughly every five seconds during a live 1:1 video call, with no card, no account, and zero platform cut. We build Lightning payments, streaming, and settlement as production systems, held to evals we agree with you up front, not as a demo that works once.
How do you handle security for custody and key management?
Security is the build, not a layer on top. For custody we use multisig so no one party can move funds alone, keep keys split by design, and build secure-by-design auth, isolation, and secrets handling from the first commit. We make the system audit-ready against a framework. We never promise you will not be breached, because no honest builder does. We promise someone who can secure it reads every part before it ships.
Do I own the code, and can I run it in the open?
Yes to both. You own the code, the repo, the docs, the deployment, and the IP from day one, with no vendor lock-in. Several of our Bitcoin builds run in the open, like P2P Sats and Satstreamr, which we built end to end and run publicly. If you want a build others can verify, that is a design choice we support rather than work around.
Last updated June 2026 · Talk with Felipe
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