Sabi credits

Inspiration

Across East Africa, mobile money agents are the backbone of everyday financial services, helping millions convert cash into digital money and vice versa. As Bitcoin adoption grows, many of these agents are beginning to facilitate Bitcoin transactions manually through messaging apps and paper records. This creates challenges in tracking liquidity, calculating commissions, resolving disputes, and maintaining trustworthy records. We built Sabi to provide these agents with a professional Bitcoin swap desk that combines the familiarity of mobile money with the speed and security of the Lightning Network.

What it does

Sabi is a Progressive Web App that enables mobile money agents to seamlessly exchange KES and Bitcoin over the Lightning Network. It provides:

A two-way swap engine for buying and selling Bitcoin.
Automatic commission calculation based on configurable spreads.
Real-time liquidity tracking for both cash and sats.
Cryptographic proof of every completed swap using Lightning preimages.
A customer request queue for managing walk-in transactions.
Transaction history, dispute management, and daily accounting.
A portable credit passport that helps customers build a verifiable financial reputation through completed transactions.

How we built it

We built Sabi as a Progressive Web App using vanilla JavaScript for the frontend, making it lightweight and installable on any smartphone. The backend was developed with Node.js and Express, while SQLite was used for persistent storage. We integrated LNbits to generate and settle Lightning invoices, MavaPay for KES-to-Bitcoin on-ramping, and Tando for Bitcoin-to-M-Pesa off-ramping. Cryptographic verification is performed using Lightning preimages and SHA-256 hashing to provide tamper-proof transaction receipts.

Challenges we ran into

One of our biggest challenges was designing a workflow that felt familiar to mobile money agents while introducing Bitcoin transactions. Integrating multiple Lightning services into a seamless experience also required careful coordination. We also had to ensure that every transaction could be independently verified through cryptographic proofs without making the user experience overly technical.

Accomplishments that we're proud of

Building a complete end-to-end Bitcoin swap desk for mobile money agents.
Successfully integrating Lightning payments with local currency on-ramp and off-ramp services.
Implementing cryptographic proof verification for every completed swap.
Creating automated commission tracking and accounting tools that eliminate manual calculations.
Introducing the concept of a portable credit passport built from verifiable transaction history.
Delivering the solution as an installable Progressive Web App that works across devices.

What we learned

Through this project, we gained a deeper understanding of the Lightning Network, payment preimages, and how cryptographic proofs can improve trust in financial systems. We also learned how important it is to design technology around existing community workflows instead of expecting users to change their habits. Most importantly, we saw how Bitcoin infrastructure can complement existing mobile money systems rather than replace them.

What's next for Sabi Credits

Our vision is to expand Sabi into a complete operating platform for Bitcoin-enabled mobile money agents across Africa. Next, we plan to add live exchange rates, SMS notifications, multi-agent support with separate wallets, USSD access for feature phones, and accounting exports. In the long term, we aim to build an interconnected network of trusted agents, enable cross-border Lightning remittances, and allow lenders to use Sabi Credit Passports as verifiable credit histories for financial inclusion.