execute-code

A code-execution workflow that runs JavaScript or Python in an isolated virtual machine.

In plain words
What is it for?
Executing scripts, checking calculations, testing algorithms, and demonstrating code behavior with actual output.
Why use it?
It lets you test code and calculations without running that code directly in the surrounding environment.

Skill for Claude CodeCodex

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/jsturtevant/local-code-interpreter-tool/execute-code
Any agent
npx skills add jsturtevant/local-code-interpreter-tool --skill execute-code
Clone the repo
git clone --depth 1 https://github.com/jsturtevant/local-code-interpreter-tool

Made for: Claude Code, Codex.

Per session 42 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 947 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 2 findings. 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.

ModelPer sessionOnce invoked
Fable 5 $0.00042 $0.00947
Opus 5 $0.00021 $0.00474
Sonnet 5 $0.00008 $0.00189
Haiku 4.5 $0.00004 $0.00095

Measured yesterday against content hash 7efe887d1597, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

execute-code scanned grade C with 2 findings 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 2 executable files (scripts/run.py, scripts/setup.sh), 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.

Downloads and executes remote codehighSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Makes network callslowCapability

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

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
.claude/skills/execute-code/SKILL.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Execute Code Skill

Execute JavaScript or Python code in a secure Hyperlight VM sandbox with full isolation.

This skill is standalone and shareable - it can be copied to any .claude/skills/ directory and works independently of the original repository.

Requirements

  • Linux with KVM support (/dev/kvm)
  • Python 3.8+
  • Git (for cloning hyperlight-nanvix)
  • Rust toolchain (installed automatically by setup script)

When to Use

Use this skill when:

  • The user asks to run, execute, or test code
  • You need to verify calculations or algorithm correctness
  • You want to demonstrate code behavior with actual output

Standalone Installation

To use this skill in a new project or share it with others:

1. Copy the Skill

# Copy the entire execute-code directory to your project
cp -r /path/to/execute-code ~/.claude/skills/
# Or for project-specific use:
cp -r /path/to/execute-code /your/project/.claude/skills/

2. Run Setup

cd ~/.claude/skills/execute-code
./scripts/setup.sh

The setup script will:

  • Create a virtual environment in .venv
  • Install Rust nightly toolchain (if not present)
  • Clone and build hyperlight-nanvix from source
  • Configure everything for standalone use

3. Activate and Use

source .venv/bin/activate
python3 scripts/run.py --lang javascript --code 'console.log("Hello!");'

Quick Start

JavaScript

python3 scripts/run.py --lang javascript --code 'console.log(2 + 2);'

Python

python3 scripts/run.py --lang python --code 'print(2 + 2)'

Usage Notes

  • JavaScript: Use console.log() to see output
  • Python: Use print() to see output
  • Code runs in VM-isolated sandbox (hyperlight-nanvix)
  • The skill is self-contained with its own virtual environment

Examples

Calculate Fibonacci

python3 scripts/run.py --lang javascript --code '
const fib = n => n <= 1 ? n : fib(n-1) + fib(n-2);
for (let i = 0; i < 10; i++) console.log("fib(" + i + ") =", fib(i));
'

Read the full file on GitHub · 135 lines

Files

What ships with it

4 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.

  1. yesterday First seen · 135 lines · 42 tokens per session scan C 7efe887d1597

Subscribe to this mod's changes

execute-code is a skill published in the GitHub repository jsturtevant/local-code-interpreter-tool (2 stars, last pushed 7mo ago), licensed MIT. It adds 42 tokens to every session and 947 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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