javascript-sandbox

javascript-sandbox is a skill for Claude Code, Codex from mereyabdenbekuly-ctrl/clodex-ide. It costs 38 tokens per session (1,176 once invoked), scanned A, original, AGPL-3.0.

A guide to using a built-in JavaScript sandbox for browser debugging, processing fetched data, attachments, and small app workflows. A sandbox is a restricted place to run code safely.

In plain words
What is it for?
Use it to debug browser behavior, process retrieved data, work with attachments, and coordinate small tasks in the sandbox.
Why use it?
It explains how to use the available JavaScript environment within its supported limits.

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/mereyabdenbekuly-ctrl/clodex-ide/javascript-sandbox
Any agent
npx skills add mereyabdenbekuly-ctrl/clodex-ide --skill javascript-sandbox
Clone the repo
git clone --depth 1 https://github.com/mereyabdenbekuly-ctrl/clodex-ide

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.

agentmods badge for javascript-sandbox

README.md
[![agentmods](https://agentmods.dev/badge/skills/mereyabdenbekuly-ctrl/clodex-ide/javascript-sandbox.svg)](https://agentmods.dev/skills/mereyabdenbekuly-ctrl/clodex-ide/javascript-sandbox)
Your own site
<a href="https://agentmods.dev/skills/mereyabdenbekuly-ctrl/clodex-ide/javascript-sandbox"><img src="https://agentmods.dev/badge/skills/mereyabdenbekuly-ctrl/clodex-ide/javascript-sandbox.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 1,176 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin unknown 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 $0.00038 $0.01176
Opus 5 $0.00019 $0.00588
Sonnet 5 $0.00008 $0.00235
Haiku 4.5 $0.00004 $0.00118

Measured 4d ago against content hash 465aa583af0a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

javascript-sandbox 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 4d 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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

**Node.js built-ins** (via `require()`): `buffer`, `crypto`, `events`, `path`, `querystring`, `stream`, `string_decoder`, `url`, `util`, `zlib`, `assert`. Blocked: `net`, `http`, `https`, `child_process`, `worker_threads
apps/browser/bundled/plugins/javascript-sandbox/SKILL.md · 94 lines

The source is not reproduced here

Licensed AGPL-3.0

The repository is licensed AGPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

Files

What ships with it

2 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. 4d ago First seen · 94 lines · 38 tokens per session scan A 465aa583af0a

Subscribe to this mod's changes

javascript-sandbox is a skill published in the GitHub repository mereyabdenbekuly-ctrl/clodex-ide (864 stars, last pushed yesterday), licensed AGPL-3.0. It adds 38 tokens to every session and 1,176 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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