nix-ai: Instructions file for Claude Code

CLAUDE.md

nix-ai CLAUDE.md is an instructions file for Claude Code from dryvist/nix-ai. It costs 1,985 tokens per session, scanned B, original, MIT.

A Claude Code instruction file for nix-ai, an AI command-line project managed with Nix and home-manager.

In plain words
What is it for?
Use it when changing nix-ai to follow its worktree, branching, Nix configuration, formatting, and validation requirements.
Why use it?
It records project rules and checks that prevent common setup and validation mistakes, including missed regression tests on macOS.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: reads .claude/ paths; mentions CLAUDE.md; mentions Claude Code.

This is dryvist/nix-ai's own configuration. It tells Claude Code how to work on nix-ai 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-ai configures →

Reuse

Borrowing it

Nothing to install: this file belongs to dryvist/nix-ai. 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/dryvist/nix-ai/develop/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/dryvist/nix-ai

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.

agentmods badge for nix-ai CLAUDE.md

README.md
[![agentmods](https://agentmods.dev/badge/instructions/dryvist/nix-ai/claude-md.svg)](https://agentmods.dev/instructions/dryvist/nix-ai/claude-md)
Your own site
<a href="https://agentmods.dev/instructions/dryvist/nix-ai/claude-md"><img src="https://agentmods.dev/badge/instructions/dryvist/nix-ai/claude-md.svg" alt="Measured on agentmods" height="20"></a>
Per session 1,985 This file is loaded in full into every session.
When invoked 1,985 The same file — it is already loaded in full.
Security scan B 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 $0.01985 $0.01985
Opus 5 $0.00992 $0.00992
Sonnet 5 $0.00397 $0.00397
Haiku 4.5 $0.00198 $0.00198

Measured 2d ago against content hash 5a3298aaa23c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade B, and why

nix-ai CLAUDE.md scanned grade B 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 2d 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

sudo darwin-rebuild switch --flake "$HOME/git/nix-darwin/main" \
CLAUDE.md · 161 lines

How it starts

The opening of the file, as written. The whole thing — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.

nix-ai - AI Agent Instructions

AI CLI ecosystem for Claude, Antigravity, Codex, Copilot, and MCP servers via Nix home-manager modules.

Critical Constraints

  1. Flakes-only: Never use nix-env or imperative Nix commands
  2. Module args injection: All flake inputs reach modules via _module.args, not function parameters
  3. Worktrees required: Run /refresh-repo then create a worktree before any work
  4. No direct main commits: Always use feature branches

Validation

Static (every change):

nix fmt            # Fix formatting
nix flake check    # Packages, formatters, devShells

# Regression suite (lib/checks/) — REQUIRED on macOS, see below
nix eval --raw .#checks.x86_64-linux \
  --apply 'cs: builtins.concatStringsSep "\n" (map (c: c.outPath) (builtins.attrValues cs))' \
  >/dev/null

A bare nix flake check on a Mac runs none of lib/checks/. checks is scoped to x86_64-linux (flake.nix), so on aarch64-darwin it omits them, prints green for packages and formatters, and says nothing about the regression suite. A module argument launchd.nix required and default.nix never passed survived a green bare check and failed only at darwin-rebuild.

--all-systems surfaces the assertions but then tries to build Linux derivations on darwin, exiting non-zero for that unrelated reason — so it cannot be routine. The nix eval form above forces every check's outPath: every assertion runs at evaluation time, nothing builds. Verified both ways — passes on a healthy tree, fails on a deliberately broken one.

Workaround; PR #1819 is the structural fix. It builds checks for every supported system, so a plain nix flake check runs the darwin assertions. When it lands, replace the nix eval form above — noting --all-systems on a Linux-only runner then tries to realise the darwin markers and fails.

Assertions only fire when something forces them, so a check that reads a few attributes of a large structure proves nothing about the rest. Where a check covers a nested tree (the launchd agents, for one) it should deepSeq it.

Read the full file on GitHub · 161 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. 2d ago Changed · -5 tokens per session 5a3298aaa23c
  2. 8d ago First seen · 161 lines · 1,990 tokens per session scan B 3b5eb2acbcff

Subscribe to this mod's changes

nix-ai CLAUDE.md is an instructions file published in the GitHub repository dryvist/nix-ai (11 stars, last pushed yesterday), licensed MIT. It adds 1,985 tokens to every session, about $0.0099 per session on Opus 5. A static security scan graded it B with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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