Contents

21-dot-dev/swift-bitcoinkernel

Swift package for Bitcoin consensus validation, optionally embedding a full Bitcoin node in-process. The BitcoinKernel product wraps libbitcoinkernel from Bitcoin Core; the `Bit

Contents

Which product?

| Goal | Product | Demo app | Getting started | |------|---------|----------|-----------------| | Validate consensus or sync a chain, no networking | BitcoinKernel | KernelApp | Guide | | Run a full node with in-process RPC | Bitcoin | NodeApp | Guide |

Features

  • Wrap Bitcoin Core's libbitcoinkernel for consensus validation without a daemon
  • Embed bitcoind in-process via a typed BitcoinConfig builder and Daemon lifecycle
  • Cover all 171 Bitcoin Core v31.0 JSON-RPCs through an async/await RPCClient
  • Route RPCs through pluggable transports: direct in-process, HTTP, cookie-file, or auto-detect
  • Ship a BlockchainSync engine and a BlockSource protocol for custom block providers
  • Track chain-sync progress with KVO-observable Foundation.Progress for SwiftUI bindings and BGContinuedProcessingTask budgets
  • Route block downloads or RPC traffic through Tor with a SOCKS5-configured URLSession

Installation

Add to your Package.swift:

.package(url: "https://github.com/21-DOT-DEV/swift-bitcoinkernel.git", exact: "0.1.0"),

Include BitcoinKernel in your target:

.target(name: "<target>", dependencies: [
    .product(name: "BitcoinKernel", package: "swift-bitcoinkernel"),
]),

For the Bitcoin product (embedded daemon and RPC client), opt your target into Swift's C++ interoperability mode:

.target(name: "<target>",
    dependencies: [
        .product(name: "Bitcoin", package: "swift-bitcoinkernel"),
    ],
    swiftSettings: [
        .interoperabilityMode(.Cxx),
    ]
),

Or use Xcode: File → Add Packages…, then enter https://github.com/21-DOT-DEV/swift-bitcoinkernel. For the Bitcoin product in Xcode, set C++ and Objective-C Interoperability to C++/Objective-C++ in the target's Build Settings.

Pin with a version tag. At a tagged release the package excludes its development plugins (tuist, subtree, docc); pinning a commit or branch instead resolves that full toolchain into your dependency graph.

Package Traits

The package uses SE-0450 Package Traits to gate optional functionality. No traits are enabled by default.

wallet

Opts into Bitcoin Core's wallet RPCs (createwallet, sendtoaddress, walletProcessPSBT, etc.). Off by default to keep the dependency graph small.

.package(
    url: "https://github.com/21-DOT-DEV/swift-bitcoinkernel.git",
    exact: "0.1.0",
    traits: ["wallet"]
),

[!NOTE] The wallet trait is a dependency and binary-size optimization, not a security boundary. Under swift build the trait is honored fully. Under Xcode it is not: Xcode doesn't resolve SwiftPM trait conditions, so wallet sources guarded by #if Xcode || ENABLE_WALLET always compile and the wallet API surface is always present. If your threat model requires wallet code to be absent, do not rely on the trait; run the daemon with -disablewallet.

Platform notes

  • tvOS builds BitcoinKernel only. The Bitcoin product depends on execvp (marked __TVOS_PROHIBITED) and does not compile for tvOS.
  • Linux consumers of Bitcoin link the system SQLite. Install libsqlite3-dev (Debian/Ubuntu) or sqlite-devel (Fedora/RHEL).
  • Storage: regtest and signet stay in the tens of MB. Pruned mainnet keeps roughly 12 GB of UTXO chainstate plus the pruned block target (≥ 550 MiB). A full mainnet node is ~700 GB and growing.

Usage Examples

Validate consensus with BitcoinKernel

Boot the validation engine against a fresh regtest data directory and read the tip height to confirm the chainstate loaded. Context(chain:) wraps the options builder for the common case:

import BitcoinKernel
import Foundation

let context = try Context(chain: .regtest)

let dataDirectory = FileManager.default.temporaryDirectory
    .appendingPathComponent(UUID().uuidString)
    .path(percentEncoded: false)

let manager = try ChainstateManager(context: context, dataDirectory: dataDirectory)

print(manager.bestEntry.height)  // 0 on a fresh regtest directory

→ Full guide: Getting Started — BitcoinKernel

Embed bitcoind and query it with RPCClient

Start an embedded bitcoind on regtest and call a typed JSON-RPC method. Cookie authentication derives the endpoint and credentials from the config, so they are supplied once and no RPC password lives in your code:

import Bitcoin
import Foundation

// Bitcoin Core requires the data directory to exist before startup.
let dataDir = URL.temporaryDirectory.appending(path: "bitcoin-regtest")
try FileManager.default.createDirectory(at: dataDir, withIntermediateDirectories: true)

let config = BitcoinConfig
    .regtest()
    .server()
    .dataDir(dataDir.path(percentEncoded: false))

let client = try await Daemon.startAndConnect(with: config)

let info = try await client.getBlockchainInfo()
print("Chain: \(info.chain), blocks: \(info.blocks)")

_ = try await client.stop()
Daemon.waitUntilStopped()

→ Full guide: Getting Started — Bitcoin

Demo Apps

Two SwiftUI apps in the Projects/ Tuist workspace exercise the package end to end. NodeApp drives the embedded bitcoind lifecycle, the typed RPCClient, and an optional Tor SOCKS proxy. KernelApp runs a BitcoinKernel chain sync through BlockchainSync over an Esplora block source.

swift package --disable-sandbox tuist generate -p Projects/ --no-open
open Projects/Bitcoin.xcworkspace

Pick the NodeApp or KernelApp scheme and run. Projects/README.md has the full tour, including the Tor wiring and the macOS/iOS build-and-test commands.

Documentation

The DocC catalogs for Bitcoin and BitcoinKernel cover the embedded daemon and consensus-validation surfaces:

Build the hyperlinked archive locally:

swift package generate-documentation --target Bitcoin
swift package generate-documentation --target BitcoinKernel

Each tagged release also publishes a downloadable .doccarchive.zip on the corresponding GitHub Release.

Contributing

Contributions are welcome. Read AGENTS.md for project architecture and the subtree extraction flow, Projects/AGENTS.md for the Tuist workspace, and the 21-DOT-DEV contributing guidelines for branching conventions.

[!IMPORTANT] Files under Sources/{bitcoind,libbitcoinkernel,secp256k1,leveldb,minisketch,crc32c}/ are extracted from upstream and overwritten on every subtree sync. Local changes for SPM/embedded use live in patches/ — see patches/README.md.

Security

For vulnerability reports, see SECURITY.md. Patches to the vendored Bitcoin Core never touch consensus code; see the patch policy.

License

Released under the MIT License — see LICENSE. Vendored dependencies carry their own licenses:

Package Metadata

Repository: 21-dot-dev/swift-bitcoinkernel

Default branch: main

README: README.md