{"slug": "show-hn-stemjson-a-language-for-llms-to-extend-native-mobile-apps-on-the-fly", "title": "Show HN: StemJSON – a language for LLMs to extend native mobile apps on the fly", "summary": "StemJSON, a new declarative JSON-based language designed for LLMs to generate native mobile app UI and logic, was posted to Hacker News as a Show HN project. The format lets an LLM emit StemJSON from a user prompt, which a runtime validates and renders as a fully native module inside a developer-defined sandbox, with no new binary and no backend round-trip for the UI. The project is patent pending and is positioned for server-driven UI, prototyping tools, and alongside hand-written code.", "body_md": "StemJSON is a declarative language based on JSON, well-suited for AI to generate comprehensive, performant native app UI and logic - whether building new apps or extending existing ones.\n\nThe format is open. Drop it into AI tools, prototyping environments, IDE extensions, or alongside hand-written code to simplify and accelerate native app design, development, and delivery.\n\nA sandboxed area inside your app where end users describe a feature in their own words - and the runtime renders a fully native module on the spot. Apps that adapt to each user, on demand.\n\nAn LLM emits StemJSON from the user's prompt; the runtime validates it, renders it natively, and keeps it inside the sandbox you defined. No new binary, no backend round-trip for the UI.\n\nPatent pending.\n\nUser prompt\n\nLLM\n\nStemJSON\n\nNative module\n\nOther ways to use it\n\nServer-driven UI\n\nPush complete functional modules from your backend - state, actions, expressions, navigation, validation - straight to the device.\n\nyour server → StemJSON → device\n\nPrototyping & design tools\n\nFrom a prompt or a Figma export to a runnable native prototype. Tools emit StemJSON; the runtime renders it on-device - no glue code in between.\n\nFigma / AI tool → StemJSON → runnable app\n\nAlongside hand-written code\n\nDrop StemJSON modules into a native app for the parts that change often - settings, onboarding, content feeds - and keep the rest hand-written.", "url": "https://wpnews.pro/news/show-hn-stemjson-a-language-for-llms-to-extend-native-mobile-apps-on-the-fly", "canonical_source": "https://stemjson.com/", "published_at": "2026-09-14 11:26:45+00:00", "updated_at": "2026-09-14 12:40:25.320522+00:00", "lang": "en", "topics": ["ai-tools", "developer-tools", "generative-ai", "large-language-models", "ai-products"], "entities": ["StemJSON", "Hacker News", "Figma"], "alternates": {"html": "https://wpnews.pro/news/show-hn-stemjson-a-language-for-llms-to-extend-native-mobile-apps-on-the-fly", "markdown": "https://wpnews.pro/news/show-hn-stemjson-a-language-for-llms-to-extend-native-mobile-apps-on-the-fly.md", "text": "https://wpnews.pro/news/show-hn-stemjson-a-language-for-llms-to-extend-native-mobile-apps-on-the-fly.txt", "jsonld": "https://wpnews.pro/news/show-hn-stemjson-a-language-for-llms-to-extend-native-mobile-apps-on-the-fly.jsonld"}}