Frontend Infrastructure

for AI Agents

Automate your frontend with C1 - Generative UI API

Ship delightful, intelligent interfaces in seconds.

Boring Agent
C1 Agent

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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!' }
  ]
})

Features

Built by developers, for developers.

Composes UIs in real-time

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

Build engaging interfaces directly from model responses.

Controllable with prompts

Use system prompts to guide C1 for consistent UI patterns and product logic.

Customizable with ease

Deliver 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 Cases

Everything 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.

Upgrade to Generative UI

Don'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.

FAQs

Everything you need to know to get started.

C1 by Thesys is a LLM API that turns large language model (LLM) responses into live, adaptive user interfaces in real time.

Instead of returning plain text like traditional completion endpoints, C1 outputs structured UI components - such as forms, tables, charts, and layouts - that can be rendered directly using the C1 React SDK.

It supports multiple LLMs like OpenAI, Anthropic, & more, works out of the box or with your custom design system, and is built for fast, secure, and real-time rendering of dynamic interfaces.

With C1, developers can build intelligent, context-aware frontends for AI-powered apps - without hardcoding the UI for every possible user query or state.

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.