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Introducing C1

C1 is an API layer on top of LLMs that builds adaptive UIs in real time.

It turns responses from your model into live interfaces using our React SDK.

C1 Introduction
Automate your frontend in just 3 steps
Step 1
Change URL
Step 2
Integrate SDK
Step 3
Customize UI (Optional)
const { OpenAI } = require('openai')

// Create OpenAI client with TheSys endpoint
const client = new OpenAI({
  apiKey: process.env.THESYS_API_KEY,
  baseURL: 'https://api.thesys.dev/v1/embed'
})

// Now use the client for your AI requests
const response = await client.chat.completions.create({
  model: '<model-name>',
  messages: [
    { role: 'user', content: 'Hello, world!' }
  ]
})
FeaturesBuilt by developers, for developers.
Banner Card Image
Composes UIs in real-time

With C1, LLMs return interactive UI, not just text.

Build engaging interfaces directly from model responses.

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Controllable with promptsUse system prompts to guide C1 for consistent UI patterns and product logic.
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Customizable with easeDeliver polished, on-brand UI using C1's customizable components.
Universal
C1 integrates seamlessly with any language, framework and MCP server.
Performant
C1 renders interfaces in real time without introducing any latency.
Secure
Thesys never stores your data and adheres to industry security standards.
Use CasesEverything you need to know to get started.
AI-Powered Chatbots
Turn static chatbots into rich, interactive experiences that delight users and boost engagement. Whether it's customer support or a ChatGPT-style assistant, C1 adapts to your use case and delivers seamless, dynamic UI.
Chat with C1
Upgrade to Generative UIDon't ship AI with legacy UI.
Shipping delays
Manually developing UI for AI is a slow and painful process.
UI Bottlenecks
Hardcoded UI cannot scale with AI abilities or adapt to user's intent.
Weak engagement
Users churn when interactions are limited to static text and rigid UI.

Traditional apps had fixed paths, so their UIs were hardcoded. AI unlocks infinite user journeys.

We built C1 so that the UI can keep up.

FAQsEverything you need to know to get started.

C1 by Thesys is a Generative UI API that lets you build AI-powered applications with interfaces that generate themselves - based on user input, context, or intent - instead of being hardcoded.

It's an OpenAI-compatible endpoint that returns structured UI components like forms, visualizations and layouts instead of markdown. The output is then parsed by the React SDK to create the UI.

You prompt it like a chat completion API-and it responds with live, usable UI.

Generative UI is for teams building AI-native software-agents, copilots, and tools-where use cases evolve fast, and static UIs fall short.

  • Adapts to logic, state, and user behavior
  • LLMs shape both output and interaction

Perfect for devs, product teams, and builders creating dynamic, task-specific interfaces.

Tools like Lovable or Bolt help you design UI before your app goes live-they turn prompts into mockups or code.

C1 by Thesys is different: it builds and shows the actual interface while the app is running, tailored to each user and situation. Think of it this way:

  • Tools like Lovable or Bolt are coding assistants that help write the code that powers the UI.
  • C1 is the UI - live, flexible, and ready when users need it.

Yes, we currently support Anthropic models and are planning to add support for more LLMs, including OpenAI, soon to give developers even more flexibility.

Yes, C1 lets you customize the UI to match your companys design system.

It's built on top of Crayon's UI library, so any customization supported by Crayon - like themes, tokens, or components - works out of the box.