Thesys
Generative UI API Turning LLM Responses Into Live Interfaces
by Thesys, Inc. · San Francisco, California, USA · Founded 2024
What is Thesys?
Thesys is an API middleware platform that augments large language models to respond with interactive UI components in real time instead of plain text.
Its flagship product, C1, acts as an API layer on top of LLMs from OpenAI, Anthropic, and Google, converting model outputs into live, adaptive interfaces including charts, forms, tables, cards, and layouts. The C1 React SDK renders these components directly in the browser.
Thesys supports tool calling for external data fetching, custom design system theming via the open-source Crayon UI library, and streaming responses for real-time rendering.
The platform also offers an Artifacts API for generating slides and reports within applications, and Agent Builder, a no-code tool for creating and publishing AI agents that respond with interactive UI.
Developers integrate C1 in as few as two lines of code, making it compatible with any existing AI stack, framework, or MCP server.
Thesys targets engineering teams building AI-native products where static chat interfaces fall short, serving use cases from enterprise analytics dashboards to customer-facing copilots and internal tooling.
Thesys — Generative UI API Turning LLM Responses Into Live Interfaces Whether you're evaluating Thesys for your team or comparing it to alternatives in the AI Productivity Tools category, this in-depth review covers everything: features, pricing, real user reviews, pros and cons, integrations, and direct comparisons against competitors.
Key Features 8
Who Is Thesys For
Pros & Cons
- Two-Line SDK Integration
- Multi-LLM Provider Compatibility
- Open-Source Crayon Component Library
- Real-Time Adaptive UI Rendering
- React-Only SDK Currently Available
- LLM Token Costs Billed Separately
- Early-Stage Enterprise Compliance Features
Frequently Asked Questions
5 questionsAI code generators produce static UI code before an app runs. Thesys C1 generates and renders live, context-aware UI components at runtime, adapting to each user query and application state in real time. C1 is the interface itself, not a code authoring tool.
C1 works with all major LLM providers out of the box, including OpenAI (GPT-5), Anthropic (Claude Sonnet 4), and Google (Gemini 3 Pro and Flash). The API uses an OpenAI-compatible endpoint format, so switching between models requires no code changes.
Yes. C1 is built on top of Crayon, an open-source UI component library. Developers can apply custom themes, tokens, colors, and component overrides so that all generated UI outputs match the host application's existing brand identity and design language.
The Embed endpoint is a drop-in replacement for standard LLM chat completion calls, supporting tool calling and conversation history. The Visualize endpoint takes a raw data object and returns the optimal UI representation for it, without tool calling support.
Agent Builder lets users connect data sources like files, URLs, or databases, set natural language instructions for tone and guardrails, and publish a live agent as an embeddable widget or standalone page. All generated responses render as interactive UI components rather than plain text.
Who is Thesys for?
Thesys is most useful for Full-Stack AI Developers, SaaS Product Engineers, AI Agent Builders and Enterprise Analytics Teams.
Thesys pricing
Thesys uses a freemium model: a usable free tier with optional paid upgrades. Headline pricing: From $49/mo. For the current tier breakdown and any limits, see the pricing section above or check the vendor's pricing page directly — limits and prices change.
What's New
No-code agent builder for creating and publishing AI apps that respond with charts, forms, cards, and interactive UI. Ranked #2 Product of the Day on Product Hunt.
New API endpoint enabling AI apps to generate stunning slides and reports in real time, integrable in three steps or usable as an MCP tool.
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Thesys Pricing
From $49/mo
- 5,000 C1 API calls per month
- LLM credits worth $10 included
- Style customizations
- Supports all popular LLMs
- 25,000 C1 API calls per month
- $0.002 per call after included quota
- Higher request priority
- Higher rate limits
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