StemRuntime SDK

Native UI/UX from StemJSON

The runtime that turns a StemJSON payload into native, fully functional module on the device. Schema-validated, deterministic, ready to ship.

iOS v1.1.0 · Available now Android v1.1.0 · Available now

Full native mobile functionality

Everything a screen needs - UI, state, logic, data, navigation - fits in one StemJSON file, rendered natively by StemRuntime. The weather module shown was built in 2 AI iterations, ~250 lines of StemJSON.

Weather module rendered natively on a mobile device - 12.5° in Ivano-Frankivsk with 7-day forecast and details — Rendered output

{
  "module": "weather",
  "page": "detail",
  "stemjson": {
    "lines": 282,
    "size_bytes": 17575,
    "components": 56,
    "expressions": 13,
    "state_keys": 4
  },
  "data_sources": [
    {
      "kind": "remote_repository",
      "id": "repo_geo",
      "endpoint": "https://geocoding-api.open-meteo.com/v1/search"
    },
    {
      "kind": "remote_repository",
      "id": "repo_weather",
      "endpoint": "https://api.open-meteo.com/v1/forecast"
    }
  ],
  "rendering": {
    "framework": "SwiftUI (iOS) / Jetpack Compose (Android)",
    "platform": "iOS 18+, Android 7+",
    "validation": "schema-checked at runtime"
  }
}

weather module - at a glance

See more apps built end-to-end with StemJSON: Swift examples · Kotlin examples.

Built on StemRuntime

Pluri - a Stem AI Area in production

An iOS app where users describe a tool in plain words and the runtime renders a native module on the spot. The clearest proof of what StemRuntime does in a real, shipping app.

See how Pluri uses the runtime →

Three ways to bring it in

Let users build the app

Drop a Stem AI Area into your screen. Users describe what they want; an LLM emits StemJSON; the runtime renders it natively, sandboxed inside your app.

Ship behavior from your backend

Standard SDUI / BDUI - but it's not just layout. Push complete functional modules from your server: state, actions, expressions, navigation, validation, data. Behavior travels with the JSON, not just pixels.

Skip the data plumbing

Use StemJSON as typed config for your network layer - endpoints, auth, parsing, validation. Bind your hand-written native UI to it. Less boilerplate, more shipping.

Pricing

Free

Full runtime, no time limit. A small "Powered by StemJSON" watermark shows on physical devices only - your simulator builds stay clean.

Pro

$99 / year per app

No watermark. Your feature or bug-fix requests carry weight on the roadmap. Early access to new releases.

Contact to subscribe

Enterprise

Custom

Multiple apps, custom contract terms, guaranteed response times, private support channel.

Contact

See FAQ for what counts as a app bundleId, watermark behaviour, evaluation licenses, and renewal. The full End-User License Agreement is published on this site.

Get in touch

Questions, partnerships, licensing

vkrychun@stemjson.com