javascriptkit

Guidance for Swift developers building WebAssembly applications with JavaScriptKit, a library that lets Swift code interact with JavaScript in web pages.

In plain words
What is it for?
Use it to set up the WebAssembly SDK, connect Swift and JavaScript, and follow common JavaScriptKit development practices.
Why use it?
It provides project setup help, language-bridging patterns, and environment checks for Swift and WebAssembly development.

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/swiftwasm/swift-wasm-agent-skill/javascriptkit
Any agent
npx skills add swiftwasm/Swift-Wasm-Agent-Skill --skill javascriptkit
Clone the repo
git clone --depth 1 https://github.com/swiftwasm/Swift-Wasm-Agent-Skill

Made for: Claude Code, Codex.

Per session 15 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 150 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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 $0.00015 $0.00150
Opus 5 $0.00008 $0.00075
Sonnet 5 $0.00003 $0.00030
Haiku 4.5 $0.00002 $0.00015

Measured 2d ago against content hash 1ca57fd85e55, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

javascriptkit 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 2d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/doctor.py, scripts/install-sdk.py), 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.

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.

javascriptkit/SKILL.md · 20 lines

What it actually says

Instructions

You are an expert in Swift and WebAssembly development using JavaScriptKit. Your goal is to help users build web applications in Swift by bridging the gap between the two languages.

References

Scripts

  • scripts/doctor.py: Check the environment for Swift and Wasm SDK.
  • scripts/install-sdk.py: Automatically find and install the matching Swift SDK for WebAssembly based on the current toolchain.
Files

What ships with it

5 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. 2d ago First seen · 20 lines · 15 tokens per session scan A 1ca57fd85e55

Subscribe to this mod's changes

javascriptkit is a skill published in the GitHub repository swiftwasm/Swift-Wasm-Agent-Skill (47 stars, last pushed 23d ago), licensed MIT. It adds 15 tokens to every session and 150 once invoked, about $0.0001 per session on Opus 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.

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