What is nix-config CLAUDE.md?

Repository instructions for managing a computer’s macOS and Linux settings with Nix, a configuration system that describes software and system setup in files.

Building and applying the macOS setup, testing it without applying changes, updating Nix package inputs, and finding system, user, and application configuration files.

They give the coding agent the commands and folder structure needed to build, test, switch, and update this configuration safely.

How malob/nix-config configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to malob/nix-config. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/malob/nix-config/master/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/malob/nix-config

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/malob/nix-config/claude-md/github.svg)](https://agentmods.dev/instructions/malob/nix-config/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/malob/nix-config/claude-md"><img src="https://agentmods.dev/badge/instructions/malob/nix-config/claude-md/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/malob/nix-config/claude-md"><img src="https://agentmods.dev/badge/instructions/malob/nix-config/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 1,466 This file is loaded in full into every session.

When invoked 1,466 The same file — it is already loaded in full.

Security scan C 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.01466	$0.01466
Opus 5.5	$0.00586	$0.00586
Sonnet 5.5	$0.00293	$0.00293
Haiku 4.5	$0.00147	$0.00147

Measured 1mo ago against content hash 37b281aea22a, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade C, and why

nix-config CLAUDE.md scanned grade C with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

rm -rf ~/.claude/plugins/cache/malos-plugins/<plugin-name>

CLAUDE.md · 132 lines

How it starts

The opening of the file, as written. The whole thing — 132 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Build Commands

# Build and switch to the macOS nix-darwin configuration
nh darwin switch --no-nom

# Build without switching (for testing)
nh darwin build --no-nom

# Update all flake inputs
nix flake update

# Update a specific input
nix flake update nixpkgs-unstable

Architecture

This is a Nix flake that manages system configuration for macOS (via nix-darwin) and Linux (via home-manager).

Key Structure

flake.nix - Main entry point defining inputs, outputs, overlays, and system configurations
darwin/ - nix-darwin modules for macOS system-level configuration
home/ - home-manager modules for user-level configuration
modules/ - Reusable modules (both darwin and home-manager)
lib/ - Helper functions including mkDarwinSystem
configs/ - Application configs (Claude Code) symlinked for live editing
overlays/ - Nixpkgs overlays

System Configurations

darwinConfigurations.MaloBookPro - Primary macOS config, built with lib.mkDarwinSystem
darwinConfigurations.githubCI - CI variant with homebrew disabled
homeConfigurations.malo - Standalone home-manager config for Linux

User Info Pattern

User info is defined once and referenced throughout:

Passed to lib.mkDarwinSystem as username, fullName, email, nixConfigDirectory
Set on users.primaryUser in darwin config
Available as config.home.user-info in all home-manager modules

Example usage in a home module:

{ config, ... }:
let
  inherit (config.home.user-info) email nixConfigDirectory;
in { ... }

Live-Editable Configs

Files in configs/ are symlinked via mkOutOfStoreSymlink, allowing edits without rebuild:

configs/claude/ → ~/.claude/ (CLAUDE-USER.md → CLAUDE.md, settings.json, commands, plugins, etc.)

Claude Code settings use a hybrid approach:

managed-settings.json (Nix-generated at /Library/Application Support/ClaudeCode/): Has highest precedence. Contains only path-dependent settings needing nixConfigDirectory interpolation (additionalDirectories, nix-config permissions, extraKnownMarketplaces). Created by darwin/claude-managed-settings.nix.
settings.json (user-editable symlink from configs/claude/): All other settings using portable ~ paths. Edit directly without rebuild.

Read the full file on GitHub · 132 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

1mo ago First seen · 132 lines · 1,466 tokens per session scan C 37b281aea22a

Subscribe to this mod's changes

nix-config CLAUDE.md is an instructions file published in the GitHub repository malob/nix-config (463 stars, last pushed 3d ago), licensed MIT. It adds 1,466 tokens to every session, about $0.0059 per session on Opus 5.5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

DevOps and cloud dotfiles nix nix-darwin nix-dotfiles nix-expressions nixpkgs

vscode buildNext.instructions.md

Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).

microsoft/vscode · 9,649 tokens

nix-config: Instructions file for Claude Code