{
  lib,
  stdenv,
  fetchurl,
  autoPatchelfHook,
  versionCheckHook,
}:

let
  version = "0.75.5";

  # jcode is a large Rust workspace, but every release ships prebuilt binaries,
  # so we install those rather than paying for a full cargo build. Hashes were
  # cross-checked against the release's own SHA256SUMS.
  #
  # The Linux tarballs contain two files: the ELF (<asset>.bin) plus a launcher
  # shell script that only exists to put its own directory on LD_LIBRARY_PATH.
  # Nothing ships alongside the ELF, and autoPatchelfHook writes a real RPATH,
  # so the launcher is dropped and the ELF installed directly. The macOS
  # tarballs ship the bare binary with no launcher and no .bin suffix.
  sources = {
    x86_64-linux = {
      asset = "jcode-linux-x86_64";
      binary = "jcode-linux-x86_64.bin";
      hash = "sha256-HDrk3JsObqqYI4NZxEEQ49w0fJbXNpOag5NH6VqRRZ4=";
    };
    aarch64-linux = {
      asset = "jcode-linux-aarch64";
      binary = "jcode-linux-aarch64.bin";
      hash = "sha256-xmE8Qed02pK1Lb+wrRNmKrBm7JlIaAXK0Dd1Z+XlhxI=";
    };
    x86_64-darwin = {
      asset = "jcode-macos-x86_64";
      binary = "jcode-macos-x86_64";
      hash = "sha256-jsJwLlevJvmDbkrZnPRX5ryyDA9mmo9qsigN9t8qb/k=";
    };
    aarch64-darwin = {
      asset = "jcode-macos-aarch64";
      binary = "jcode-macos-aarch64";
      hash = "sha256-1v7sL5Tt8Dq6ybZTJh30+4DfpRAG2P1V0/mo+mLvzfI=";
    };
  };

  source =
    sources.${stdenv.hostPlatform.system}
      or (throw "nix-bin/jcode.nix: no prebuilt jcode release for ${stdenv.hostPlatform.system}");
in
stdenv.mkDerivation {
  pname = "jcode";
  inherit version;

  src = fetchurl {
    url = "https://github.com/1jehuang/jcode/releases/download/v${version}/${source.asset}.tar.gz";
    inherit (source) hash;
  };

  # The tarball has no top-level directory.
  sourceRoot = ".";

  nativeBuildInputs = [
    versionCheckHook
  ] ++ lib.optionals stdenv.hostPlatform.isLinux [ autoPatchelfHook ];

  # The ELF needs libgcc_s.so.1; everything else it pulls in is glibc.
  buildInputs = lib.optionals stdenv.hostPlatform.isLinux [ stdenv.cc.cc.lib ];

  installPhase = ''
    runHook preInstall
    install -Dm755 ${source.binary} $out/bin/jcode
    runHook postInstall
  '';

  doInstallCheck = true;
  versionCheckProgramArg = "--version";

  meta = {
    description = "RAM-efficient AI coding agent harness";
    homepage = "https://github.com/1jehuang/jcode";
    license = lib.licenses.mit;
    mainProgram = "jcode";
    sourceProvenance = with lib.sourceTypes; [ binaryNativeCode ];
    platforms = builtins.attrNames sources;
  };
}