Cashu Dev Kit

The Cashu Development Kit (CDK) is a Rust library for building wallets and mints that implement the Cashu protocol. It provides the core protocol logic, storage backends (SQLite, PostgreSQL, Redb), an Axum-based mint HTTP server, and Lightning backends for CLN, LND, LNbits, and LDK Node. Binaries for a wallet CLI (cdk-cli) and a mint (cdk-mintd) are included.

CDK is the easiest way to get started building Cashu apps. As Bitcoin monetizes, Cashu will be the protocol which day-to-day and online-native payments are settled.

—David Caseria

In 2025, CDK added language bindings for Swift, Kotlin, Go, Flutter, and Python. All of them wrap the same Rust core, so wallet and mint developers can build on any platform without reimplementing the protocol. Multi-mint wallet support is also underway, letting a single wallet manage balances across different mints.

Why fund it?

CDK sits between the Cashu protocol specs and the apps people use. Without it, every wallet and mint would have to implement token issuance, Lightning settlement, storage, and networking from scratch. CDK handles all of that in one place.

OpenSats has supported CDK as highlighted in the Advancements in Ecash impact report and awarded an additional grant for cloud and mint operability work in the sixteenth wave of Bitcoin grants.

What's next?

Mint operators are getting Prometheus and Grafana monitoring, along with Kubernetes controllers and gRPC management backends for running mints in the cloud. On the deployment side, container images and Nitro Enclaves support are making it easier to run mints in production.

For a detailed look at recent progress, see the Advancements in Ecash impact report.