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.
npx skills add ericrisco/rsc-harness --skill compose-multiplatformgit clone --depth 1 https://github.com/ericrisco/rsc-harnessWrote 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.
[](https://agentmods.dev/skills/ericrisco/rsc-harness/compose-multiplatform)<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/compose-multiplatform"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/compose-multiplatform/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.
<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/compose-multiplatform"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/compose-multiplatform.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00080 | $0.02776 |
| Opus 5.5 | $0.00032 | $0.01110 |
| Sonnet 5.5 | $0.00016 | $0.00555 |
| Haiku 4.5 | $0.00008 | $0.00278 |
Grade A, and why
compose-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 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.
How it starts
The opening of the file, as written. The whole thing — 199 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Compose Multiplatform
You write one Compose UI tree in commonMain and let each platform be a thin host. The whole discipline is one sentence: common by default, platform by exception. Every line you put in commonMain ships to Android, iOS, and desktop unchanged; every line you put in a platform source set is a deliberate exception you should be able to justify.
Versions floor (2026)
Pin these or the K2 compiler bites you. Verify against current docs before locking a project — these are the floors, not opinions.
- Compose Multiplatform 1.11.0, bundling Jetpack Compose 1.11.1.
- Kotlin 2.1.0+ required (2.2.20 recommended for evolving iOS/Web targets). Since CMP 1.8.0 the K2 compiler is mandatory, so every dependency must compile against Kotlin 2.1.0+.
- iOS is Stable (production-ready since CMP 1.8.0, May 2025): feature parity for popular cases, type-safe navigation with deep linking, accessibility (VoiceOver, Full Keyboard Access).
- Web is Beta (CMP 1.9.0, Sept 2025), runs on WasmGC browsers. Do not promise Web parity — ship Android/iOS/desktop, pilot Web.
- Platform minimums: Android API 21, iOS 14+, macOS 13 arm64, Windows 10+, Ubuntu 20.04+, desktop JDK 11+ (17+ for
jpackagepackaging).
Where does this code go?
This is the question you answer dozens of times a day. Default to the leftmost column that compiles.
| Source set | Put here | Concrete example | Never here |
|---|---|---|---|
commonMain |
Shared @Composables, ViewModels, business logic, common interfaces, expect declarations |
@Composable fun GreetingScreen(), expect fun platformName(): String |
android.*, platform.UIKit, java.awt, androidx.activity |
androidMain |
Activity, actual using Android Context/Build |
class MainActivity : ComponentActivity |
iOS/desktop-only APIs |
iosMain |
ComposeUIViewController factory, actual via cinterop/platform.* |
fun MainViewController() = ComposeUIViewController { App() } |
android.* |
desktopMain |
application {} window, Swing interop |
application { Window(::exitApplication) { App() } } |
mobile-only APIs |
wasmJsMain (Beta) |
Web entry point | ComposeViewport(document.body!!) { App() } |
anything you can't ship as Beta |
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.
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.
- 1mo ago First seen · 199 lines · 80 tokens per session scan A d801b9003297
compose-multiplatform is a skill published in the GitHub repository ericrisco/rsc-harness (231 stars, last pushed yesterday), licensed MIT. It adds 80 tokens to every session and 2,776 once invoked, about $0.0003 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.
Other skills, from other repositories
mapkit
MapKit + CoreLocation for iOS (iOS 17–26 era). SwiftUI Map with MapContentBuilder (Marker / Annotation / MapPolyline / MapPolygon / MapCircle / UserAnnotation), MapCameraPosition & MapCamera with onMapCameraChange, mapStyle / mapControls / selection, MapReader + MapProxy coordinate conversion, and Look Around…
navigation
Navigation for Android and Kotlin Multiplatform/iOS apps - all three approaches in one place. (A) Jetpack Navigation Compose (androidx.navigation - NavController, NavHost, composable , type-safe @Serializable routes, nested graphs, bottom nav, deep links, results via SavedStateHandle). (B) Jetpack Navigation 3 / Nav3…
kmp-repositories
Repository pattern for Kotlin Multiplatform. Shared interfaces with platform-specific implementations, clean data layer architecture.
shared-coroutines
Coroutines and Flow in Kotlin Multiplatform shared code - expect/actual dispatchers, iOS main-thread/Darwin constraints, a CoroutineScope shared from commonMain, and exposing StateFlow/Flow to Swift (KMP-NativeCoroutines/SKIE). Use for commonMain/iosMain concurrency. For general, non-multiplatform coroutine and Flow…
kmp-networking
Ktor HTTP client for Kotlin Multiplatform - shared API layer in commonMain with per-target engines (OkHttp/Android engine on Android, Darwin on iOS), kotlinx.serialization, and shared error handling. Use for multiplatform or shared networking. For an Android-only Ktor/OkHttp client use ktor-patterns. For deeper…
shared-models
Shared data models for Kotlin Multiplatform using kotlinx.serialization. Cross-platform domain models with validation and serialization.