agentmods.dev

modern-js-runtimes

modern-js-runtimes is a skill for Claude Code, Codex from jxoesneon/Ciel. It costs 20 tokens per session (420 once invoked), scanned A, original, Apache-2.0.

A set of rules for developing JavaScript and TypeScript projects with Bun, a runtime, package manager, and test runner. It also distinguishes Ethereum's Keccak-256 hashing from the similar but incompatible SHA3-256 standard.

In plain words
What is it for?
Running TypeScript directly, installing dependencies, testing with Bun, using Bun APIs, and checking Ethereum-related code for the wrong hashing algorithm.
Why use it?
It prevents mixed package managers from breaking lockfiles and avoids incorrect hashes that can silently invalidate Ethereum selectors, signatures, or storage slots.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

not rated 1repo changed 1mo ago A scan 20 tokens original Apache-2.0

Good fit Running TypeScript directly, installing dependencies, testing with Bun, using Bun APIs, and checking Ethereum-related code for the wrong hashing algorithm.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/jxoesneon/ciel/modern-js-runtimes
View source ↗ jxoesneon/Ciel
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 jxoesneon/Ciel --skill modern-js-runtimes
Clone the repo
git clone --depth 1 https://github.com/jxoesneon/Ciel

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 modern-js-runtimes

README.md
[![agentmods](https://agentmods.dev/badge/skills/jxoesneon/ciel/modern-js-runtimes/github.svg)](https://agentmods.dev/skills/jxoesneon/ciel/modern-js-runtimes)
Your own site
<a href="https://agentmods.dev/skills/jxoesneon/ciel/modern-js-runtimes"><img src="https://agentmods.dev/badge/skills/jxoesneon/ciel/modern-js-runtimes/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 modern-js-runtimes

Your own site · 80×15
<a href="https://agentmods.dev/skills/jxoesneon/ciel/modern-js-runtimes"><img src="https://agentmods.dev/badge/skills/jxoesneon/ciel/modern-js-runtimes.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 420 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.
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 $0.00020 $0.00420
Opus 5.5 $0.00008 $0.00168
Sonnet 5.5 $0.00004 $0.00084
Haiku 4.5 $0.00002 $0.00042

Measured 1mo ago against content hash 9b307b3e07b3, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

modern-js-runtimes 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.

skills/modern-js-runtimes/SKILL.md · 36 lines

What it actually says

CIEL ADAPTATION: Modern JS Runtimes (Bun & Keccak)

This skill manages high-speed JS/TS development using Bun and enforces cryptographic correctness for specialized domains (Ethereum).

The Bun Stack

  • All-in-One: Use Bun as the Runtime, Package Manager (bun install), and Test Runner (bun test).
  • Natiive TS: Run .ts files directly without a separate transpilation step.
  • Performance: Prefer Bun's native APIs (e.g., Bun.file(), Bun.serve()) over Node equivalents for hot paths.

Hashing Integrity (Ethereum)

  • Hard Gate: For Ethereum contexts (selectors, signatures, storage slots), NEVER use Node's crypto.createHash('sha3-256') (NIST SHA3).
  • Mandate: Use keccak256 from ethers, viem, or web3.
  • Audit: Grep for createHash.*sha3 in Ethereum-related packages to find silent bugs.

Operational Standards

  • Lockfiles: ALWAYS commit bun.lock (text) or bun.lockb (binary) for reproducible installs.
  • Vercel: Explicitly set the runtime to Bun in project settings for 2x deployment speed.

Anti-Patterns

  • Mixing Managers: Using npm or yarn in a Bun-initialized project (corrupts lockfiles).
  • Amnesiac Hashing: Assuming "SHA3" means "Keccak" in JS (NIST SHA3 != Keccak-256).
  • Silent Bun Failure: Ignoring Bun-specific dependency issues; fallback to Node if compatibility is broken.
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.

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 · -13 lines 9b307b3e07b3
  2. 2mo ago First seen · 49 lines · 20 tokens per session scan A 21bdf31102bd

Subscribe to this mod's changes

modern-js-runtimes is a skill published in the GitHub repository jxoesneon/Ciel (1 stars, last pushed 7d ago), licensed Apache-2.0. It adds 20 tokens to every session and 420 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 2026-09-03.

Autonomous AgentsClaude CodeLanguagesTypeScriptWeb3 and blockchainagentic-workflowsaigemini-climulti-agent-systems
Related

modern-js-runtimes compared with skills from other repositories

modern-js-runtimes next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
modern-js-runtimesjxoesneon/CielSkill17d agoApache-2.0A20Claude Code, Codex
nodejs-keccak256Jamkris/everything-gemini-codeSkill935mo agoMITA51Claude Code, Codex
build-error-resolverKacper0199/Opencode-UltrathinkerSkill25mo agononeC50Claude Code, Codex
starknet-jsstarknet-io/starknet.jsSkill1.3kyesterdayMITA79Claude Code, Codex
adding-personhog-rpcPostHog/posthogSkill41kyesterdaynoneA88Claude Code, Codex
viem-integrationUniswap/uniswap-aiSkill2362d agoMITA69Claude Code
solanaquicknode/solana-finance-claude-pluginSkill101yesterdayMITA76Claude Code