init-flake

name	init-flake
description	Initialize a Nix flake for any project to set up a reproducible development environment with nix develop. Use when a project needs flake.nix, devShell, or Nix-based development setup.
argument-hint	<project-directory>
disable-model-invocation	true
allowed-tools	WebSearch, WebFetch(domain:github.com), WebFetch(domain:nix.dev), WebFetch(domain:wiki.nixos.org), Bash(nix flake *), Bash(nix develop *), Bash(ls *), Bash(git *), Read, Edit, Write, Glob, Grep

Initialize Nix Flake

Set up a Nix flake for the project at: $ARGUMENTS

1. Project Analysis

Inspect the target directory to determine the tech stack:

• Check for language-specific manifest files (package.json, Cargo.toml, pyproject.toml, go.mod, Gemfile, pom.xml, mix.exs, CMakeLists.txt, *.cabal, deno.json, etc.)
• Identify build tools and dependency managers in use
• Note any existing Nix files (flake.nix, shell.nix, default.nix)

If a flake.nix already exists, ask the user before overwriting.

2. Generate flake.nix

Create a flake.nix tailored to the detected stack. Use this base structure:

{
  description = "Development environment for <project>";

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

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
      in {
        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            # language runtime, build tools, LSP, linters
          ];
          shellHook = ''
            echo "dev shell ready"
          '';
        };
      }
    );
}

Language-specific packages

Stack	Typical packages
Node.js	nodejs, pnpm or yarn, nodePackages.typescript
Python	python3, uv or python3Packages.pip
Rust	rustc, cargo, rust-analyzer, clippy, rustfmt
Go	go, gopls, gotools
C/C++	gcc or clang, cmake, gnumake, pkg-config
Ruby	ruby, bundler
Java	jdk, maven or gradle
Haskell	ghc, cabal-install, haskell-language-server
Elixir	elixir, erlang
Deno	deno

For mixed-language projects, combine the relevant packages.

3. direnv integration (optional)

Ask the user if they want direnv support. If yes:

• Create .envrc containing use flake
• Remind them to run direnv allow

4. Update .gitignore

Append these entries if missing:

# Nix
result
result-*
.direnv/

5. Validate

Run validation to ensure the flake is correct:

cd "$ARGUMENTS" && nix flake check --extra-experimental-features 'nix-command flakes pipe-operators'

Then test the dev shell:

cd "$ARGUMENTS" && nix develop --extra-experimental-features 'nix-command flakes pipe-operators' --command echo "Shell works!"

Notes

• Ask the user if they need additional tools or libraries
• Include language servers for IDE integration where appropriate
• For projects with native dependencies, add the required system libraries
• Use --extra-experimental-features flag so it works on systems without flakes enabled globally