nix

name	nix
description	Nix language, flakes, NixOS, Home Manager, and agent-skills packaging. TRIGGER when: working with .nix files, flake.nix, flake.lock, Nargo.toml (Nix packaging context), NixOS configuration, Home Manager modules, nix-agent MCP tools, agent-skills-nix deployment, or rigup.nix riglets. DO NOT TRIGGER when: only using nix PATH (chezmoi handles that), or working on ZK circuits (use noir skill), or Nix language is incidental to another domain.
metadata	{"author":"DROOdotFOO","version":"1.0.0","tags":"nix, nixos, flakes, home-manager, devshell, agent-skills, rigup"}

nix

Practical patterns for the Nix ecosystem: the language itself, flake architecture, NixOS/Home Manager configuration, package building, and the emerging pattern of packaging AI agent skills as Nix derivations.

What You Get

• Nix language idioms (let/with/inherit, builtins, lazy evaluation)
• Flake architecture (inputs, outputs, lockfiles, overlays)
• NixOS and Home Manager module patterns
• Package builders (mkDerivation, buildGoModule, buildNpmPackage)
• Agent-skills-as-Nix-packages patterns (rigup, nix-agent MCP)

When to use

• Writing or reviewing .nix files (flakes, modules, overlays, packages)
• Configuring NixOS or Home Manager
• Building Nix packages (mkDerivation, buildGoModule, buildNpmPackage, etc.)
• Managing Nix profiles and registries
• Packaging agent skills for Nix-based deployment (agent-skills-nix, rigup)
• Using nix-agent MCP tools for NixOS automation

When NOT to use

• Nix PATH setup in chezmoi -- handled by paths.zsh.tmpl and chezmoi.toml
• ZK circuit design -- use noir skill
• Solidity or Ethereum -- use solidity-auditor or ethskills

Reading guide

Working on	Read
Nix language idioms, builtins, let/with/inherit	references/language
Flake structure, inputs, outputs, lockfiles	references/flakes
NixOS modules, options, services	references/nixos
Home Manager config, programs, activation	references/home-manager
Building packages (mkDerivation, language builders)	references/packaging
Nix profiles, registries, nix-env alternatives	references/profiles
Agent skills as Nix packages (agent-skills-nix, rigup, nix-agent MCP)	references/agent-integration

Key principles

1. Reproducibility first -- pin inputs, use flake.lock, avoid impure operations
2. Composition over mutation -- overlay and override, never patch in place
3. Lazy evaluation -- Nix is lazy; structure code to exploit this
4. Declarative over imperative -- describe the target state, not the steps
5. Module system is the API -- options with types, defaults, and docs

Common pitfalls

Mistake	Fix
Using rec { } when let ... in works	rec pollutes scope and causes infinite recursion -- prefer let
with pkgs; at module level	Shadows names silently -- use pkgs.foo or selective inherit
Forgetting meta.mainProgram	Breaks nix run -- always set it for packages with binaries
builtins.fetchurl in flakes	Impure -- use flake inputs or fetchurl from nixpkgs
Mutable channel references	Pin nixpkgs as a flake input, not <nixpkgs>
nix-env -i for system packages	Use environment.systemPackages or home.packages
Testing with nix-build when flake	Use nix build .#package -- nix-build ignores flake.nix

See also

• droo-stack -- shell patterns for nix-related scripts
• chezmoi templates in droo-stack -- paths.zsh.tmpl nix conditionals