nix-blueprint

name	nix-blueprint
description	numtide/blueprint — Nix flake framework that maps a fixed directory structure to flake outputs with zero glue code. Apply when a repo's flake.nix calls `inputs.blueprint { ... }`; when deciding where a package, devshell, host, module, check or template file must live; when a package/devshell/host is missing from `nix flake show` or `nix build` says the attribute doesn't exist; when adding the `prefix` option; when writing packages/<name>/default.nix, devshell.nix or modules/<class>/<name>.nix. Do NOT use for generic Nix flakes without blueprint (hand-written outputs, flake-parts, flake-utils), for nixpkgs contributions, or for NixOS module semantics unrelated to file placement. Prefer nix-project-scaffold for creating a NEW project, nix-treefmt-formatter for formatter.nix internals, and nixos-host-provisioning for adding hosts with disko/facter.
user-invocable	true
license	MIT
compatibility	Designed for Claude Code, Codex or similar harness, and for projects using Nix flakes with numtide/blueprint.
metadata	{"author":"aldoborrero","version":"1.0.0","openclaw":{"emoji":"🧭","homepage":"https://github.com/aldoborrero/cc-skills-nix","requires":{"bins":"[Truncated]"},"install":[]}}
allowed-tools	Read Edit Write Glob Grep Bash(nix:*) Bash(git:*) Agent
paths	["**/flake.nix","**/*.nix"]

numtide/blueprint

Blueprint generates all flake outputs from the directory layout. The structure IS the API: there is no place to "register" an output — you create a file at the right path and the output exists. Source of truth for every mapping below: lib/default.nix in numtide/blueprint.

A blueprint flake.nix is ~10 lines and rarely changes:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-unstable";
    blueprint.url = "github:numtide/blueprint";
    blueprint.inputs.nixpkgs.follows = "nixpkgs";
  };
  outputs = inputs: inputs.blueprint {
    inherit inputs;
    prefix = "nix";                        # optional: load tree from ./nix/ instead of repo root
    # systems = [ "x86_64-linux" ];        # default: x86_64-linux, aarch64-linux, x86_64-darwin, aarch64-darwin
    # nixpkgs.config.allowUnfree = true;   # forces a fresh nixpkgs import per system
    # nixpkgs.overlays = [ ... ];
  };
}

With prefix = "nix" every path below lives under nix/ (e.g. nix/packages/foo/default.nix); without it, at the repo root. Convention observed in real repos: application/library projects use prefix = "nix" to keep Nix out of the way; NixOS/system config repos skip the prefix since the whole repo is Nix.

Directory → output map (condensed)

Path (under prefix)	Flake output
devshell.nix	devShells.<sys>.default
devshell.toml	devShells.<sys>.default (needs devshell input)
devshells/<name>.nix or devshells/<name>/default.nix	devShells.<sys>.<name>
devshells/<name>.toml	devShells.<sys>.<name> (needs devshell input)
package.nix	packages.<sys>.default
packages/<name>.nix or packages/<name>/default.nix	packages.<sys>.<name> + checks.<sys>.pkgs-<name>
formatter.nix	formatter.<sys> (also registered as )