{
  lib,
  stdenv,
  pkgs,
  python3,
  fetchFromGitHub,
  makeWrapper,
  rocmPackages,
}:

let
  py = python3.pkgs;

  # Kyojin is the Yamz fork of ExLlamaV3: a Python package plus a C++ extension
  # that torch's cpp_extension cross-compiles to HIP code objects. Upstream
  # only supports AMD Strix Halo, so the kernels are built for gfx1151 alone.
  rocmArch = "gfx1151";

  version = "1.3";

  src = fetchFromGitHub {
    owner = "Yamz-Labs";
    repo = "kyojin";
    rev = "v${version}";
    hash = "sha256-/DPoqW/iaLXRAH8XF5RdE+K5YS4jZT6Sic6QeCDQMlU=";
  };

  # setup.py passes EXL3_ROCM_DEV_INCLUDE as -I to every translation unit. The
  # AMD wheels ship one devel tree holding hipsparse/ and thrust/; nixpkgs
  # splits them per package, so join the include dirs. torch's public HIP
  # headers also pull hipsolver/, and it no longer vendors pybind11.
  rocmDevInclude = pkgs.symlinkJoin {
    name = "kyojin-rocm-dev-include";
    paths = map lib.getDev (
      [ py.pybind11 ]
      ++ [
        rocmPackages.clr
        rocmPackages.hipblas
        rocmPackages.hipblaslt
        rocmPackages.hipcub
        rocmPackages.hipfft
        rocmPackages.hiprand
        rocmPackages.hipsparse
        rocmPackages.hipsolver
        rocmPackages.rocblas
        rocmPackages.rocprim
        rocmPackages.rocrand
        rocmPackages.rocsolver
        rocmPackages.rocsparse
        rocmPackages.rocthrust
      ]
    );
  };

  # torch's HIP path in cpp_extension expects one ROCM_HOME holding bin/hipcc,
  # the headers and the amdgcn bitcode; nixpkgs ships them separately.
  rocmToolkit = pkgs.symlinkJoin {
    name = "kyojin-rocm-toolkit";
    paths = [
      rocmPackages."rocm-core"
      rocmPackages."rocm-runtime"
      rocmPackages."rocm-device-libs"
      rocmPackages."rocm-comgr"
      rocmPackages.clr
      (lib.getBin rocmPackages.hipcc)
      rocmPackages.rocblas
      rocmPackages.hipblas
      rocmPackages.hipblas-common
      rocmPackages.hipblaslt
      rocmPackages.hipsparse
      rocmPackages.hipsolver
      rocmPackages.hiprand
      rocmPackages.rocrand
      rocmPackages.hipfft
      rocmPackages.rocsparse
      rocmPackages.rocsolver
      rocmPackages.rocthrust
      rocmPackages.rocprim
      rocmPackages.hipcub
    ];
    # The setup hooks of the joined packages would rewrite build flags; the
    # compiler only needs the files.
    postBuild = ''
      rm -rf $out/nix-support
    '';
  };

  # The library: exllamav3 plus the compiled exllamav3_ext module.
  library = py.buildPythonPackage {
    inherit src version;
    pname = "kyojin";

    format = "pyproject";
    build-system = with py; [
      setuptools
      wheel
    ];

    nativeBuildInputs = [
      py.ninja
      rocmPackages."rocm-runtime"
    ];

    buildInputs = [ (lib.getBin rocmPackages.hipcc) ];

    propagatedBuildInputs = with py; [
      aiohttp
      huggingface-hub
      jinja2
      llguidance
      marisa-trie
      numpy
      pillow
      pydantic
      pyyaml
      rich
      safetensors
      tokenizers
      torchWithRocm
      typing-extensions
    ];

    env = {
      PYTORCH_ROCM_ARCH = rocmArch;
      ROCM_PATH = "${rocmToolkit}";
      ROCM_HOME = "${rocmToolkit}";
      HIP_PATH = "${rocmToolkit}";
      HIPCC = "${rocmToolkit}/bin/hipcc";
      HIP_DEVICE_LIB_PATH = "${rocmPackages."rocm-device-libs"}/amdgcn/bitcode";
      # Upstream build scripts look these up to find the ROCm devel tree.
      EXL3_ROCM_SDK = "${rocmToolkit}";
      EXL3_ROCM_DEV_INCLUDE = "${rocmDevInclude}/include";
      # Default defines of upstream build.sh (tools/strix_halo/rebuild.sh).
      EXL3_HIP_DEFINES = "EXL3_HIP_STG_PAD";
    };

    # setup.py pulls the extension source list and the arch helper with
    # `from exllamav3...import ...`, which runs the package __init__ and
    # therefore exllamav3/ext.py. That module JIT-compiles the extension when no
    # precompiled exllamav3_ext is importable, i.e. during every wheel build
    # (and it wants a writable $HOME for it). Register an empty `exllamav3`
    # package first so only the two leaf modules are imported, and load
    # build_config without the package wrapper.
    postPatch = ''
      sed -i '1i import sys as _sys, types as _types; _exl3_pkg = _types.ModuleType("exllamav3"); _exl3_pkg.__path__ = ["exllamav3"]; _sys.modules.setdefault("exllamav3", _exl3_pkg)' setup.py
      sed -i 's|^from exllamav3\.exllamav3_ext\.build_config import get_sources as _get_sources$|import sys as _exl3_sys; _exl3_sys.path.insert(0, "exllamav3/exllamav3_ext"); from build_config import get_sources as _get_sources; _exl3_sys.path.pop(0)|' setup.py
      grep -q 'from build_config import' setup.py
    '';

    # tests/ needs a real gfx1151 GPU and the published model packs.
    doCheck = false;

    meta = with lib; {
      description = "Inference engine for 100 GB-class EXL3 MoE models on AMD Strix Halo (gfx1151, ROCm 7)";
      homepage = "https://github.com/Yamz-Labs/kyojin";
      changelog = "https://github.com/Yamz-Labs/kyojin/releases";
      license = licenses.mit;
      sourceProvenance = with sourceTypes; [ fromSource ];
      # HIP code objects are gfx1151-only and ROCm is Linux-only.
      platforms = platforms.linux;
    };
  };

  python = py.python.withPackages (_: [ library ]);
in
stdenv.mkDerivation {
  inherit src version;
  pname = "kyojin";

  # Only the wrappers are installed here: the serve scripts are plain scripts,
  # they import their siblings by path, and the module itself is in `library`.
  dontConfigure = true;
  dontBuild = true;

  nativeBuildInputs = [ makeWrapper ];

  installPhase = ''
    runHook preInstall

    mkdir -p $out/bin
    for model in glm mimo qwen; do
      makeWrapper ${python}/bin/python $out/bin/kyojin-serve-$model \
        --set PYTORCH_ROCM_ARCH ${rocmArch} \
        --add-flags "${src}/tools/$model/serve.py"
    done

    runHook postInstall
  '';

  passthru = {
    inherit python rocmArch;
    pythonPackage = library;
    category = "AI Inference";
    updateScript = [
      "nix-update"
      "--flake"
      ".#kyojin"
    ];
  };

  meta = library.meta // {
    mainProgram = "kyojin-serve-qwen";
  };
}