kotlin-multiplatform

Guidance for sharing Kotlin code across Android, desktop, JVM, and iOS while deciding which parts should remain platform-specific. It covers shared source folders and Kotlin's expect/actual pattern for platform-dependent code.

In plain words
What is it for?
Use it when structuring an Amethyst Kotlin Multiplatform project, choosing between common and platform-specific code, or planning support for Android, JVM/Desktop, iOS, and possible web or WebAssembly targets.
Why use it?
It helps avoid putting code in the wrong source folder or sharing code that depends too heavily on one platform. It also clarifies when to share an abstraction and when to keep separate implementations.

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/maxrave-dev/simpmusic/kmp
Any agent
npx skills add maxrave-dev/SimpMusic --skill kmp
Clone the repo
git clone --depth 1 https://github.com/maxrave-dev/SimpMusic

Made for: Claude Code, Codex.

Per session 114 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,309 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00114 $0.03309
Opus 5 $0.00057 $0.01655
Sonnet 5 $0.00023 $0.00662
Haiku 4.5 $0.00011 $0.00331

Measured 3d ago against content hash 4a7d457dc267, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

kotlin-multiplatform 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 3d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/suggest-kmp-dependency.sh, scripts/validate-kmp-structure.sh), 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.

.claude/skills/kmp/SKILL.md · 403 lines

The source is not reproduced here

Licensed GPL-3.0

The repository is licensed GPL-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

6 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. 3d ago First seen · 403 lines · 114 tokens per session scan A 4a7d457dc267

Subscribe to this mod's changes

kotlin-multiplatform is a skill published in the GitHub repository maxrave-dev/SimpMusic (10,880 stars, last pushed yesterday), licensed GPL-3.0. It adds 114 tokens to every session and 3,309 once invoked, about $0.0006 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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