livecodes: Skill for Claude Code

.agents/skills/livecodes/headless-mode/SKILL.md

headless-mode is a skill for Claude Code, Codex from live-codes/livecodes. It costs 36 tokens per session (1,044 once invoked), scanned A, original, MIT.

A guide for using LiveCodes, an in-browser coding playground, without displaying its user interface. It shows how to load code, compile it, read the result, and respond to changes through its software interface.

In plain words
What is it for?
Use it to build Markdown compilers, code formatters, or other tools that need compiled output from LiveCodes without a visible playground.
Why use it?
It lets tools compile and process code in the background when showing an interactive editor is unnecessary.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

This is live-codes/livecodes's own configuration. It tells Claude Code and Codex how to work on livecodes 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 livecodes configures →

About the project

live-codes/livecodes is a browser-based code playground for writing and running code in more than 90 languages, frameworks, and processors. It is used to experiment with code, import modules, embed interactive editors in websites, and host playgrounds on a static file server without a backend. The catalogue add-ons support working with LiveCodes.

live-codes/livecodes · 1,525 stars · on GitHub · livecodes.io

Reuse

Borrowing it

Nothing to install: this file belongs to live-codes/livecodes. 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/live-codes/livecodes/develop/.agents/skills/livecodes/headless-mode/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/live-codes/livecodes

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 headless-mode

README.md
[![agentmods](https://agentmods.dev/badge/skills/live-codes/livecodes/headless-mode/github.svg)](https://agentmods.dev/skills/live-codes/livecodes/headless-mode)
Your own site
<a href="https://agentmods.dev/skills/live-codes/livecodes/headless-mode"><img src="https://agentmods.dev/badge/skills/live-codes/livecodes/headless-mode/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.

agentmods 80×15 button for headless-mode

Your own site · 80×15
<a href="https://agentmods.dev/skills/live-codes/livecodes/headless-mode"><img src="https://agentmods.dev/badge/skills/live-codes/livecodes/headless-mode.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 36 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,044 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00036 $0.01044
Opus 5.5 $0.00014 $0.00418
Sonnet 5.5 $0.00007 $0.00209
Haiku 4.5 $0.00004 $0.00104

Measured 1mo ago against content hash 55b94b3bf527, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

headless-mode scanned grade A with 0 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 1mo 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/livecodes/headless-mode/SKILL.md · 191 lines

How it starts

The opening of the file, as written. The whole thing — 191 lines — stays where its author put it; the contents beside it link to each section on GitHub.

This skill builds on sdk-embedding and sdk-methods. Read them first for foundational concepts.

LiveCodes — Headless Mode

Headless mode runs LiveCodes without any visible UI. Use SDK methods to compile code, get output, and react to events.

Setup

import { createPlayground } from 'livecodes';

// Create headless playground - container is optional
const playground = await createPlayground({
  headless: true,
  config: {
    markup: { language: 'markdown', content: '# Hello World' },
  },
});

// Use SDK methods
const code = await playground.getCode();
console.log(code.markup.compiled); // "<h1>Hello World</h1>"
console.log(code.result); // Result page HTML

Core Patterns

Markdown compiler

import { createPlayground } from 'livecodes';

let playground;

async function compileMarkdown(markdown) {
  if (!playground) {
    playground = await createPlayground({
      headless: true,
      config: { autoupdate: false },
    });
  }

  await playground.setConfig({
    markup: { language: 'markdown', content: markdown },
  });

  const code = await playground.getCode();
  return code.markup.compiled;
}

// Usage
const html = await compileMarkdown('# Hello\n\nWorld');
console.log(html); // "<h1>Hello</h1>\n<p>World</p>"

React/JSX compiler

import { createPlayground } from 'livecodes';

let playground;

async function compileJSX(jsxCode) {
  if (!playground) {
    playground = await createPlayground({
      headless: true,
      config: { autoupdate: false },
    });
  }

  await playground.setConfig({
    script: { language: 'react', content: jsxCode },
  });

  const code = await playground.getCode();
  return code.script.compiled;
}

const compiled = await compileJSX(`
  function App() {
    return <h1>Hello</h1>;
  }
`);

Python interpreter

import { createPlayground } from 'livecodes';

let playground;

async function runPython(code) {
  if (!playground) {
    playground = await createPlayground({
      headless: true,
      config: { autoupdate: true },
    });
  }

  // Set up console listener before running
  const outputs = [];
  playground.watch('console', ({ method, args }) => {
    outputs.push({ method, args });
  });

  await playground.setConfig({
    script: { language: 'python', content: code },
  });

  // Python runs automatically with autoupdate: true
  // Or: await playground.run();

  return outputs;
}

// Usage
const outputs = await runPython('print("Hello from Python!")');
// [{ method: 'log', args: ['Hello from Python!'] }]

Read the full file on GitHub · 191 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. 1mo ago Changed · +1 lines · -2 tokens per session 55b94b3bf527
  2. 2mo ago First seen · 190 lines · 38 tokens per session scan A 86028db7f1c2

Subscribe to this mod's changes

headless-mode is a skill published in the GitHub repository live-codes/livecodes (1,525 stars, last pushed 13d ago), licensed MIT. It adds 36 tokens to every session and 1,044 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Related

headless-mode compared with skills from other repositories

headless-mode next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
headless-modelive-codes/livecodesSkill1.5k13d agoMITA36Claude Code, Codex
create-prprisma/ormSkill48kyesterdayApache-2.0A48Claude Code, Codex
publish-npm-versionprisma/ormSkill48kyesterdayApache-2.0A182Claude Code, Codex
contrib-prprisma/ormSkill48kyesterdayApache-2.0A65Claude Code, Codex
github-review-iterationprisma/ormSkill48kyesterdayApache-2.0A60Claude Code
review-implement-phaseprisma/ormSkill48kyesterdayApache-2.0A38Claude Code
angular-developerangular/angularSkill101kyesterdayMITA93Claude Code, Codex