golem-js-runtime

A guide to the JavaScript runtime available to TypeScript and Scala Golem agents. It covers supported programming interfaces, including Node.js and browser APIs, in Golem's QuickJS-based WebAssembly environment.

In plain words
What is it for?
Use it when checking runtime capabilities or deciding whether a Node.js module or browser API will work in an agent.
Why use it?
It clarifies which JavaScript features and libraries an agent can use in that runtime and which may not be available.

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/golemcloud/golem/golem-js-runtime
Any agent
npx skills add golemcloud/golem --skill golem-js-runtime
Clone the repo
git clone --depth 1 https://github.com/golemcloud/golem

Made for: Claude Code, Codex.

Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,507 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 $0.00044 $0.01507
Opus 5 $0.00022 $0.00754
Sonnet 5 $0.00009 $0.00301
Haiku 4.5 $0.00004 $0.00151

Measured 3d ago against content hash 88917558821a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

golem-js-runtime 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 3d 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:child_process`
golem-skills/skills/common/golem-js-runtime/SKILL.md · 143 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 3d ago First seen · 143 lines · 44 tokens per session scan A 88917558821a

Subscribe to this mod's changes

golem-js-runtime is a skill published in the GitHub repository golemcloud/golem (1,509 stars, last pushed today), with no licence file. It adds 44 tokens to every session and 1,507 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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