{
  lib,
  buildGoModule,
  fetchFromGitHub,
  fetchurl,
  stdenv,
}:

# Every codeaf ships a furrow inside it: internal/furrowbin embeds a pinned
# Agent-Field/furrow release, and `make build` stages it with
# `fetch -from <file>` instead of downloading, which is the road this build
# takes. The fetcher re-checks the sha256 named in internal/furrowbin/pin.json,
# so the hashes below are a second copy of a pin already in the source. Without
# a staged furrow codeaf still builds, and looks for the binary on PATH instead.
let
  furrow = (
    {
      x86_64-linux = {
        goos = "linux";
        goarch = "amd64";
        source = fetchurl {
          url = "https://github.com/Agent-Field/furrow/releases/download/v0.1.0/furrow-linux-amd64";
          hash = "sha256-x/h+3m81Kq0F066kJRfqychmCa3rYlGHKGQRSSZj4rQ=";
        };
      };
      aarch64-linux = {
        goos = "linux";
        goarch = "arm64";
        source = fetchurl {
          url = "https://github.com/Agent-Field/furrow/releases/download/v0.1.0/furrow-linux-arm64";
          hash = "sha256-ifE9UG8vf1TSyJIMU7V4TwsBiK5w91jpErcb/v3x0dY=";
        };
      };
      x86_64-darwin = {
        goos = "darwin";
        goarch = "amd64";
        source = fetchurl {
          url = "https://github.com/Agent-Field/furrow/releases/download/v0.1.0/furrow-darwin-amd64";
          hash = "sha256-B5mP5JoqoZ9O0IdVud6mWkiwjR/WgLWFKMVbNXnLaFI=";
        };
      };
      aarch64-darwin = {
        goos = "darwin";
        goarch = "arm64";
        source = fetchurl {
          url = "https://github.com/Agent-Field/furrow/releases/download/v0.1.0/furrow-darwin-arm64";
          hash = "sha256-EJN1Fmnla1dqK2WPvZxFKcqvNWfqoJyfduDV2wL4+hY=";
        };
      };
    }
    .${stdenv.hostPlatform.system} or null
  );
in
buildGoModule rec {
  pname = "codeaf";
  version = "0.7.1";

  src = fetchFromGitHub {
    owner = "Agent-Field";
    repo = "CodeAF";
    rev = "v${version}";
    hash = "sha256-F4rRDNrTCF8/cj6g0KM41+gNdzvTWw5Vj2N0OJp+vCc=";
  };

  vendorHash = "sha256-eIocnhp3uGk+wG0kprRie0Csms+Deqxy3K3HuI1vJyM=";

  env.CGO_ENABLED = 0;

  # The shipped binary carries the packed manual rather than the raw Markdown.
  tags = [ "codeaf_packed_manual" ];

  subPackages = [ "cmd/codeaf" ];

  # Upstream's own suite is a CI matrix (make test / make check) with network
  # and timing assumptions; it is not buildGoModule-shaped.
  doCheck = false;

  # `make build` runs two host-side steps before compiling. Both are built for
  # the build machine even when codeaf targets another platform, hence the
  # unset GOOS/GOARCH; the fetcher is told the target platform by hand. The
  # vendoring derivation runs preBuild too, before vendor/ exists, and these two
  # need the vendored dependencies, so they wait for it.
  preBuild = ''
    if [ -d vendor ]; then
      env -u GOOS -u GOARCH go generate ./internal/manual
      ${lib.optionalString (furrow != null)
        "env -u GOOS -u GOARCH go run ./internal/furrowbin/cmd/fetch -goos=${furrow.goos} -goarch=${furrow.goarch} -from ${furrow.source}"
      }
    fi
  '';

  ldflags = [
    "-s"
    "-w"
    "-X github.com/Agent-Field/codeaf/internal/buildinfo.rev=${version}"
    "-X github.com/Agent-Field/codeaf/internal/buildinfo.dirty=false"
  ];

  passthru = {
    category = "AI Coding Agents";
    updateScript = [
      "nix-update"
      "--flake"
      ".#codeaf"
    ];
  };

  meta = with lib; {
    description = "Coding harness and software factory for open models: hand off work and watch every project from one terminal";
    homepage = "https://github.com/Agent-Field/CodeAF";
    changelog = "https://github.com/Agent-Field/CodeAF/blob/v${version}/CHANGELOG.md";
    license = licenses.asl20;
    # Not fromSource all the way down: the binary embeds the prebuilt furrow
    # release named in internal/furrowbin/pin.json.
    mainProgram = "codeaf";
    platforms = platforms.linux ++ platforms.darwin;
  };
}