_{No AI was used to write this post.}

I just recently finished up the first month of the 2026 BOSS Challenge, which is a multi-month initiative, hosted by Chaincode Labs, to get people interested in Bitcoin open-source software (BOSS) development. It consists of programming challenges and open source contributions to projects in the Bitcoin ecosystem.

In the first challenge, you are required to build Bitcoin Core and run tests. In the remaining challenges you need to use Bitcoin Core to complete tasks. I've already built it before using Guix, so I was well-prepared, such that I only had to copy over a few files from my bitcoin fork.

Using Guix as a package manager to build Bitcoin Core for development fits perfectly, because actual Core builds already use Guix for its reproducible nature and bootstrapability (see this presentation by Carl Dong).

• Guix - the package manager
• direnv - for per directory environments

You can ignore direnv and the .envrc file if you just want to use guix shell instead. Direnv will automatically call guix shell for you when you enter the directory. This is really useful for editor integration so the editor can get the correct environment, or just to set some env vars automatically.

We will put the manifest.scm and .envrc in a parent dir "bitcoin-dev", so that we don't need to track these files in the bitcoin repo.

$ mkdir bitcoin-dev && cd bitcoin-dev
$ git clone git@github.com:bitcoin/bitcoin.git
$ cd bitcoin

Create an .envrc (optional)

use guix

Create manifest.scm

(use-modules (gnu packages))

(specifications->manifest
 (list
  ;; Build tools
  "make" "automake" "autoconf" "cmake" "libtool"
  ;; Toolchains
  "gcc-toolchain@14"
  "clang"
  ;; Extras
  "perl"
  "pkg-config"
  "python"
  "qttools@5.15"
  "util-linux"

  ;; Bitcoin dependencies
  "boost"
  "capnproto"
  "libevent"
  "qtbase@5"
  "sqlite"
  "zeromq"))

I'm using clang to build cause it seems to be faster and more efficient with memory. Still need gcc for some libs.

Press "Enter" and you should see direnv tell you to direnv allow and then "Enter" again so it loads the environment. This will take a while the first time because Guix will be pulling in dependencies.

If you don't have direnv, or don't want to use it, you can just do guix shell in the bitcoin-dev/ directory and it will give you a shell that has the environment from manifest.scm.

For building, you can refer to the doc/build-unix.md file for specific parameters, but I'm using this:

$ cmake -B build -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang -DENABLE_WALLET=ON -DWITH_ZMQ=ON
$ cmake --build build
# wait a while for build to complete

After that completes, you will find bitcoind, bitcoin-cli and others inside build/bin.

You can update your PATH variable in an .envrc of another project that may require using one of them, like with the BOSS challenges.

Pretty easy and no hunting for dependencies on your specific distro.