A tool for finding when a particular version of a Nix package appeared in the nixpkgs history. Nixpkgs is the package collection used by the Nix package manager.

Use it to search packages, inspect metadata, view version timelines, find matching nixpkgs commits, and create pinned Nix shells with selected packages.

It removes the need to search many historical package snapshots manually when a project needs an exact package version.

nxv — Skill for Claude Code by utensils

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add utensils/nxv --skill skill

Clone the repo

git clone --depth 1 https://github.com/utensils/nxv

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/skills/utensils/nxv/skill/github.svg)](https://agentmods.dev/skills/utensils/nxv/skill)

Your own site

<a href="https://agentmods.dev/skills/utensils/nxv/skill"><img src="https://agentmods.dev/badge/skills/utensils/nxv/skill/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/skills/utensils/nxv/skill"><img src="https://agentmods.dev/badge/skills/utensils/nxv/skill.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 169 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 7,728 The whole file, excluding the scripts and references it only reads on demand.

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

Origin 100% copy Near-identical to another mod 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	$0.00169	$0.07728
Opus 5.5	$0.00068	$0.03091
Sonnet 5.5	$0.00034	$0.01546
Haiku 4.5	$0.00017	$0.00773

Measured 2mo ago against content hash a5a5534e33c9, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

nxv scanned grade A 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s "https://nxv.urandom.io/api/v1/search?q=python&version=3.11&limit=5" | jq

Origin

This is a copy

100% identical to nxv — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

src/skill/SKILL.md · 544 lines

How it starts

The opening of the file, as written. The whole thing — 544 lines — stays where its author put it; the contents beside it link to each section on GitHub.

nxv — Nix Version Index

nxv is a Rust CLI + HTTP API that indexes nixpkgs channel-release history (2016+) into a local SQLite database with a bloom filter for fast lookups. It answers: "which exact nixpkgs commit shipped version X of package Y?" and produces the nix shell nixpkgs/<commit>#pkg command you need to actually use it.

Quick Reference

nxv search python                        # All python packages (most recent per version)
nxv search python 2.7                    # Filter by version (prefix match)
nxv search python --exact                # Exact attribute name only
nxv search "json parser" --desc          # Full-text search package descriptions
nxv run python 2.7                       # Resolve and open a pinned shell
nxv run python 3.11 --with nodejs@20     # Multi-package shell
nxv info python311                       # Detailed info for current version
nxv info python311 3.11.4                # Detailed info for specific version
nxv history python311                    # Version timeline (first/last seen)
nxv history python311 3.11.4             # When was 3.11.4 available?
nxv stats                                # Index statistics
nxv update                               # Update nxv itself to the latest release
nxv sync                                 # Download or refresh the local package index
nxv sync --force                         # Force a full index re-download
nxv serve --host 0.0.0.0 --port 8080     # Start HTTP API + web UI
nxv completions zsh                      # Generate shell completions
nxv skill install codex                  # Install this skill for one explicit agent
nxv skill install --detected             # Install for detected AI agents
nxv skill list                           # Agents, skill paths, install status

How to Use This Skill

Parse $ARGUMENTS to determine the action:

If arguments look like a subcommand (search, run, info, history, stats, update, sync, serve, completions, skill, and indexer-only index, dedupe, publish, keygen), run that subcommand.
If arguments look like a package name (e.g. python, nodejs 15, ruby 2.6), default to nxv search.
If arguments look like a question ("when was X added", "which commit has Y"), pick search or history accordingly.
If no arguments, run nxv stats to give the user a quick health check of their index.

Read the full file on GitHub · 544 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

mod.rs 18 KB

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.

2mo ago First seen · 544 lines · 169 tokens per session scan A a5a5534e33c9

Subscribe to this mod's changes

nxv is a skill published in the GitHub repository utensils/nxv (140 stars, last pushed 2mo ago), licensed MIT. It adds 169 tokens to every session and 7,728 once invoked, about $0.0007 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to nxv, differing in 0 lines, and is treated as a copy.

cli nix nixos nixpkgs package-manager

nxv next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
nxvutensils/nxv	Skill	140	2mo ago	MIT	A	169	Claude Code
deep-research-teammalob/nix-config	Skill	462	today	MIT	A	132	Claude Code
audit-permissionsmalob/nix-config	Skill	462	today	MIT	A	67	Claude Code
malo-find-skillsmalob/nix-config	Skill	462	today	MIT	A	69	Claude Code, Codex
plan-protocolkdcokenny/ocx	Skill	982	1mo ago	MIT	A	14	Claude Code, Codex
startmalob/nix-config	Skill	462	today	MIT	A	7	Claude Code
stopmalob/nix-config	Skill	462	today	MIT	A	7	Claude Code

nxv