{
  description = "Progressive LLM Training for 松尾研LLMコンペ2025 (Minimal)";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          config = {
            allowUnfree = true;
            cudaSupport = true;
          };
        };
        
        # Python 3.11 for better compatibility
        python = pkgs.python311;
        
        # Minimal Python packages
        pythonWithPackages = python.withPackages (ps: with ps; [
          # Core essentials only
          torch
          transformers
          numpy
          
          # Essential dependencies
          pyyaml
          
          # Build tools
          pip
          setuptools
          wheel
        ]);
        
      in
      {
        devShells.default = pkgs.mkShell {
          buildInputs = with pkgs; [
            # Python with packages
            pythonWithPackages
            
            # Build tools
            gcc
            cmake
            ninja
            pkg-config
            
            # Git
            git
            git-lfs
            
            # Libraries needed for Python packages
            openssl
            zlib
            glib
            stdenv.cc.cc.lib
            
            # CUDA support
            cudaPackages.cudatoolkit
            cudaPackages.cudnn
          ];
          
          shellHook = ''
            echo "🚀 Progressive LLM Training Environment (Minimal)"
            echo "Python version: $(python --version)"
            echo "PyTorch version: $(python -c 'import torch; print(torch.__version__)')"
            echo "CUDA available: $(python -c 'import torch; print(torch.cuda.is_available())')"
            
            # Set up CUDA environment
            export CUDA_HOME=${pkgs.cudaPackages.cudatoolkit}
            export CUDA_PATH=${pkgs.cudaPackages.cudatoolkit}
            export LD_LIBRARY_PATH=${pkgs.cudaPackages.cudatoolkit}/lib:${pkgs.cudaPackages.cudnn}/lib:${pkgs.stdenv.cc.cc.lib}/lib:$LD_LIBRARY_PATH
            
            # Set Python path
            export PYTHONPATH=$PWD/src:$PYTHONPATH
            
            echo ""
            echo "Note: This is a minimal configuration. Install additional packages with pip as needed:"
            echo "  pip install accelerate peft trl datasets bitsandbytes wandb jsonlines scikit-learn sentencepiece protobuf"
            echo "  pip install flash-attn --no-build-isolation"
          '';
          
          # Environment variables
          CUDA_HOME = "${pkgs.cudaPackages.cudatoolkit}";
          CUDA_PATH = "${pkgs.cudaPackages.cudatoolkit}";
          NIX_SHELL_PRESERVE_PROMPT = 1;
          LOCALE_ARCHIVE = "${pkgs.glibcLocales}/lib/locale/locale-archive";
          LC_ALL = "en_US.UTF-8";
        };
      });
}