A toolkit for debugging software in disposable macOS, Windows, and Linux virtual machines. Virtual machines are isolated guest computers running on the developer’s Mac or other host.

Use it to reproduce bugs across operating systems, inspect running processes, networks, files, or memory, check code signing, and perform dynamic debugging with Parallels, VirtualBox, or VMware.

It provides a repeatable way to reproduce operating-system-specific problems without changing the main computer, while connecting to each guest over SSH.

vm-lab — Skill for Claude Code and Codex by forefy: A toolkit for debugging software in disposable macOS, Windows…

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.

agentmods

npx agentmods add skills/forefy/.context/vm-lab

Any agent

npx skills add forefy/.context --skill vm-lab

Clone the repo

git clone --depth 1 https://github.com/forefy/.context

Made for: Claude Code, Codex.

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/forefy/.context/vm-lab.svg)](https://agentmods.dev/skills/forefy/.context/vm-lab)

Your own site

<a href="https://agentmods.dev/skills/forefy/.context/vm-lab"><img src="https://agentmods.dev/badge/skills/forefy/.context/vm-lab.svg" alt="Measured on agentmods" height="20"></a>

Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,112 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 1 finding. Scan, not verified.

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	$0.00038	$0.02112
Opus 5	$0.00019	$0.01056
Sonnet 5	$0.00008	$0.00422
Haiku 4.5	$0.00004	$0.00211

Measured yesterday against content hash aa3161529f97, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

vm-lab 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 yesterday.

The scan reads SKILL.md. This mod also ships 16 executable files (bootstrap/linux.sh, bootstrap/macos.sh, bootstrap/windows.ps1, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

rc_sudo mac 'fs_usage -w' # sudo on mac/linux (echoes the guest pw via -S)

skills/hunter-utils/vm-lab/SKILL.md · 125 lines

How it starts

The opening of the file, as written. The whole thing — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.

VM Lab - cross-OS debugging on any free hypervisor

Disposable local VMs - real macOS, Windows, and Linux, isolated from this host - for cross-OS repro, live process/network/file/memory triage, code-signing checks, and dynamic instrumentation. Works on Parallels, VirtualBox, or VMware with no paid tooling.

The core idea

SSH is the universal substrate. The hypervisor only ever does four things - list, get-ip, power, snapshot - and each of the three has a free way to do all four (providers/*.sh). Everything valuable (the debug toolkit) runs over SSH and is hypervisor-agnostic; it only varies by guest OS and CPU arch. So this skill is a thin swappable provider layer + a big OS/arch-specific debugging core.

On every invocation - ask first, then route

This skill serves three OSes and three providers. Before doing anything, establish:

Which guest - macOS, Windows, or Linux? (drives toolkits/<os>.md + SSH gotchas)
Which provider - Parallels / VirtualBox / VMware? (drives providers/<name>.sh)
Set up fresh, or use an existing guest?
- Existing → confirm it's in config.local.env, ./ctl.sh <tag> up, ./verify.sh <tag>, go.
- Fresh → bootstrap/ (Path A one-liner, or Path B unattended), then add to config, verify, snapshot.

If a config.local.env already defines the guest the task needs, skip the questions and use it. Ask only what's genuinely unresolved.

Config & connect

All mutable details live in config.local.env (copy from config.example.env; it's gitignored so your IPs/keys never get shared). Then:

source lib.sh                 # loads config + helpers (rc, rc_sudo, ssh_cmd, prov, ctl)
rc mac 'uname -a'             # run on the macOS guest
rc win 'whoami'              # Windows: auto-wrapped as base64 PowerShell
rc lin 'uname -a'            # Linux
rc_sudo mac 'fs_usage -w'    # sudo on mac/linux (echoes the guest pw via -S)
./verify.sh                   # every guest: tools present + callable, with hints
./ctl.sh doctor               # host preflight: which providers/tools are present here
./ctl.sh win up               # boot + WAIT for sshd; then down|ip|ssh|snaps|vms
push mac ./tool /tmp/tool     # copy to guest (scp); pull mac /tmp/x.pcap ./  to fetch
tun  mac -L 8080:127.0.0.1:8080   # port-forward (MITM/reach a guest service)
./ctl.sh mac reset            # restore the clean snapshot (RESET_SNAPSHOT) - the disposable loop

Guests are tags (mac/win/lin, your choice) with {PROVIDER, OS, ARCH, VMNAME, IP, USER, AUTH, KEY/PW}. Leave IP blank to auto-discover (provider → mDNS → ARP).

Read the full file on GitHub · 125 lines

Files

What ships with it

23 files 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.

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.

yesterday Changed · +1 lines aa3161529f97
5d ago First seen · 124 lines · 38 tokens per session scan B 4ac928d65668

Subscribe to this mod's changes

vm-lab is a skill published in the GitHub repository forefy/.context (144 stars, last pushed today), licensed MIT. It adds 38 tokens to every session and 2,112 once invoked, about $0.0002 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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