OpenUI

What it claims

OpenUI's differentiator over the summary is concrete: its token-efficiency claim (up to 67% fewer than JSON) is measured with tiktoken using the GPT-5 encoder, against two JSON-based streaming formats across seven UI scenarios, with methodology and reproduction in benchmarks/. Component contracts are defined with Zod schemas (typed props and structure), and rendering is restricted to components you explicitly define and register — the model cannot emit arbitrary UI.

How it works

Your component library is the source of truth: you generate a system prompt from it, send that to the model, and stream OpenUI Lang back to the renderer, which parses and paints progressively as tokens arrive.

flowchart LR
    A["Component Library<br/>(Zod schemas)"] --> B["System Prompt"]
    B --> C["LLM"]
    C --> D["OpenUI Lang Stream"]
    D --> E["Renderer"]
    E --> F["Live UI"]

How to use it

Fastest path scaffolds a full streaming app:

npx @openuidev/cli@latest create --name genui-chat-app
cd genui-chat-app
echo "OPENAI_API_KEY=sk-your-key-here" > .env
npm run dev

Piecemeal installs by target:

# React runtime + prebuilt components
npm install @openuidev/react-lang @openuidev/react-ui
# Framework-agnostic / Edge prompt generation
npm install @openuidev/lang-core
# LangChain/LangGraph
npm install @openuidev/langchain @langchain/langgraph
# Other runtimes
npm install @openuidev/vue-lang
npm install @openuidev/svelte-lang
npm install @openuidev/angular-lang
# A2UI protocol payloads
npm install @openuidev/a2ui zod

Agent Skill (Claude Code, Codex, Cursor, Copilot), maintained separately in thesysdev/skills:

npx skills add thesysdev/skills --skill openui

Packages the summary omits and that may matter: react-email (generated email components), assistant-ui renderers, browser-bundle (script-tag/CDN/iframe/no-build embeds), observability (framework-free event bus), and observability-cloud, which ships events to Thesys — relevant if you care about where telemetry goes. devtools provides an "OpenUI Inspect" widget.

Limits

• React is the only officially supported runtime; Vue/Svelte/Angular are community-supported.
• The 67% figure is a ceiling ("up to") from the maintainers' own seven-scenario benchmark against two unnamed JSON formats — verify against your own payloads.
• License is unspecified in the page text (only "see LICENSE"); check before adopting.
• observability-cloud sends data to Thesys (the vendor); the framework is otherwise self-hosted.
• Note the maintainers' disclaimer: no official crypto token exists under the OpenUI name.