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nix-config: Instructions file for Claude Code

CLAUDE.md

nix-config CLAUDE.md is an instructions file for Claude Code from softinio/nix-config. It costs 2,344 tokens per session, scanned C, original, MIT.

Repository-specific instructions for working on a Nix configuration that manages macOS systems and user settings.

In plain words
What is it for?
Use them when editing the project’s Nix flakes, machine configurations, user profiles, packages, or dotfiles.
Why use it?
They give the coding agent the project’s architecture, file roles, supported Mac types, and coding constraints before it changes the repository.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions CLAUDE.md; mentions Claude Code.

This is softinio/nix-config's own configuration. It tells Claude Code how to work on nix-config itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything nix-config configures →

not rated 11repo 1mo ago C scan 2,344 tokens original MIT
View source ↗ softinio/nix-config
Reuse

Borrowing it

Nothing to install: this file belongs to softinio/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/softinio/nix-config/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/softinio/nix-config

Made for: Claude Code.

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Per session 2,344 This file is loaded in full into every session.
When invoked 2,344 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.02344 $0.02344
Opus 5.5 $0.00938 $0.00938
Sonnet 5.5 $0.00469 $0.00469
Haiku 4.5 $0.00234 $0.00234

Measured 2mo ago against content hash 3fa0379f2b3d, 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 2mo 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.

Reaches for credential fileshighPrivilege escalation

SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.

gitSigningKey = "~/.ssh/id_ed25519.pub"; # SSH pubkey for git+jj commit signing (null disables signing)
CLAUDE.md · 209 lines

How it starts

The opening of the file, as written. The whole thing — 209 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.

Overview

This is a nix-darwin and home-manager configuration for managing macOS systems declaratively. The configuration uses Nix flakes and manages both system-level packages (via nix-darwin) and user-level packages and dotfiles (via home-manager).

Supports both Apple Silicon (aarch64-darwin) and Intel (x86_64-darwin) Macs, with multi-user support for shared machines.

Architecture

Flake Structure

The repository follows a modular architecture:

  • flake.nix: Entry point defining inputs (nixpkgs, nix-darwin, home-manager, nixvim, herdr) and outputs. Uses mkDarwinConfig helper function to generate machine configurations. Threads hostname to home-manager via extraSpecialArgs.
  • home.nix: Main home-manager entry point. Imports the program modules, packages.nix, and local-options.nix; sets the unfree allowlist (allowUnfreePredicate), stateVersion, and sessionVariables; and exposes shared module args (theme). It no longer holds the package list or inline program config.
  • packages.nix: User packages (home.packages), grouped by domain (languages, language servers, formatters, vcs, cli tools, etc.).
  • theme.nix: Shared appearance settings (currently the monospace fontFamily), passed to every module as the theme argument.
  • local-options.nix: Declares repo-local module options under config.local.* (e.g. per-editor useNixPackage toggles).
  • users/*.nix: User profile files containing personal settings (gitignored to keep private).
  • programs/default.nix: List of program module imports (each program has its own subdirectory with default.nix).
  • programs/*/default.nix: Individual program configurations (fish, git, jujutsu, ghostty, nixvim, zed, etc.). Can access the user and theme arguments. Trivial enable = true programs are grouped in programs/cli-tools/default.nix.

Read the full file on GitHub · 209 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.

  1. 2mo ago First seen · 209 lines · 2,344 tokens per session scan C 3fa0379f2b3d

Subscribe to this mod's changes

nix-config CLAUDE.md is an instructions file published in the GitHub repository softinio/nix-config (11 stars, last pushed 1mo ago), licensed MIT. It adds 2,344 tokens to every session, about $0.0094 per session on Opus 5.5. A static security scan graded it C with 1 finding (reaches for credential files). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

CloudDevOps and cloudneovimnixnix-flakenixosnixos-confignixos-configuration
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