build // Bitcoin · Wallets

Regtest CLI Wallet

Ship a descriptor-based CLI that creates addresses, tracks UTXOs, builds change outputs, and broadcasts signed spends on regtest.

Intermediate2 weeks

./open-lesson ls ./roadmap

Overview

Build a command-line wallet that proves you can combine libraries, regtest, and wallet architecture into working software.

A solid single-sig native segwit (or Taproot) wallet beats a half-finished multisig demo. Nail the happy path first: init, address, balance, and send.

Command surface

init - create or import a regtest wallet
address - print a fresh receive address
balance - show confirmed / unconfirmed totals
send - pay an address with a chosen fee rate
bump - optional RBF fee bump for a pending send

Learning objectives

Ship a CLI that creates addresses from a descriptor or seed

Receive coins on regtest and display UTXO balance

Send a payment with correct change and fee handling

Prerequisites

PSBT Workflows
Regtest Development
Wallet Architecture

Required skills

DescriptorsBitcoin Core RPCPSBT basicsTypeScript or Rust

Part of the bitcoin roadmap.

Architecture diagram

cli/        argument parsing
wallet/     descriptors, addresses, coin selection
rpc/        Bitcoin Core client
psbt/       build + sign helpers

Requirements

Works against local regtest without manual RPC pasting
Never uses floating-point for bitcoin amounts
Shows fees before broadcast and confirms user intent
Includes README with setup and demo commands
Has at least one integration test that mines and pays
Creates a change output when leftover exceeds dust threshold

Stretch goals

Optional RBF fee bump (`bump`) for a pending send
Taproot (P2TR) receive addresses by default
Coin control flags for selecting specific UTXOs
Watch-only mode from an xpub / descriptor

Recommended resources

Example repositories

bitcoinjs-lib examples
Reference patterns for payments, addresses, and PSBTs in JavaScript.
BDK CLI
A production-minded CLI wallet built on the Bitcoin Dev Kit.

Submission instructions

Publish a public GitHub repository with a clear README
Include setup steps for Bitcoin Core regtest (or Docker Compose)
Attach a short demo (asciinema, screencast, or GIF) of receive + send
Link the repo from your Pull profile when available
Note your dust policy and fee units in the README
Lab evidence pack: receive+send transcript, fee shown before broadcast, and one failed-send case
Rubric note if this doubles as an OSS portfolio piece

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