Overview
Thesys is a developer-focused AI infrastructure platform that transforms how applications interface with large language models. At its core is the C1 API, a middleware layer that converts LLM text responses into real-time, interactive user interfaces—including charts, forms, tables, cards, and slides—without requiring frontend engineers to hardcode every possible UI state.
Built for AI-native teams developing assistants, copilots, and agentic applications, Thesys enables developers to ship dynamic interfaces that adapt to user context and behavior. It's compatible with leading LLMs like OpenAI, Anthropic, and Google, integrates seamlessly via OpenAI-compatible endpoints, and offers enterprise-grade security with zero data retention. The platform is compliant with GDPR, SOC2, and ISO27001.
Whether you're building data analytics dashboards, educational platforms, or conversational commerce experiences, Thesys reduces frontend development time by up to 10x. According to Thesys, 83% of users find C1 responses more engaging than traditional text-based outputs.
Key Features
Real-time Generative UI — Automatically converts LLM outputs into live, interactive components like forms, charts, and tables, eliminating the need to pre-build UI for every possible query or scenario.
Universal LLM Compatibility — Works seamlessly with OpenAI, Anthropic, Google Gemini, and other leading models through an OpenAI-compatible endpoint, giving developers flexibility to switch providers without refactoring.
React SDK with Full Customization — Integrates with existing design systems and allows developers to inject custom React components, styling, and logic, ensuring brand consistency and production-ready quality.
Tool-Calling Integration — Supports tool calling so you can connect your own databases, APIs, and data pipelines, pulling real-time information to populate generated UIs dynamically based on user requests.
Enterprise Security & Compliance — Features zero data retention and compliance with GDPR, SOC2, and ISO27001. Self-hosting and VPC deployment options are available on enterprise plans for regulated industries.
Streaming & Error Handling — Supports real-time streaming for incremental UI updates and includes built-in error handling hooks, configurable actions, and callbacks.
Pricing & Plans
Thesys offers flexible pricing designed to scale from prototypes to enterprise deployments:
| Plan | Price | API Calls/Month | Key Features |
|---|---|---|---|
| Free | $0/month | 5,000 C1 calls | $10 in free LLM credits, style customizations, Discord support |
| Build | $49/month | 25,000 calls | $0.002 per additional call, higher rate limits, email support |
| Grow | $499/month | 500,000 calls | $0.001 per additional call, priority Slack support, highest rate limits |
| Scale | Custom pricing | Custom (negotiated) | Self-hosting/VPC deployment, enterprise SLAs, SOC2/ISO27001/GDPR compliance, HIPAA support (BAA available), dedicated solutions engineer |
Additional Pricing:
- Artifacts API: 100 pages free/month, then $0.01 per page operation (for slides and reports)
- LLM Inference: Pass-through pricing with no markups for GPT-5, Claude Sonnet 4, Gemini 3, and others
All plans include access to the React SDK and core C1 functionality. The free plan is ideal for experimentation, while Build and Grow tiers suit production applications with predictable traffic.
Pros & Cons
Pros:
- Dramatically reduces frontend development time (up to 10x faster) and costs (80% cheaper) for AI-powered interfaces
- OpenAI-compatible API makes integration straightforward—often just a baseURL change
- Supports custom React components and design systems for full brand control
- Enterprise-ready with zero data retention, compliant with SOC2, ISO27001, GDPR, with private deployment options on Scale plan
- Works with any LLM provider, avoiding vendor lock-in
Cons:
- Primarily focused on React environments; other frontend frameworks may require additional adaptation
- Generative UI paradigm requires a mental shift from traditional static UI development workflows
- Pricing can scale quickly for high-traffic applications with millions of API calls per month
Best For
- AI-native startups building conversational assistants, copilots, or agents where UI needs to dynamically adapt to unpredictable user queries and workflows.
- Enterprise development teams replacing static dashboards with AI-powered analytics interfaces that generate visualizations and reports on demand.
- SaaS product teams looking to add interactive AI features (forms, data tables, personalized recommendations) without doubling frontend engineering resources.
- EdTech and FinTech platforms requiring compliant, secure AI interfaces with custom branding and real-time data integration.
- Developers experienced with React who want to prototype and ship generative UI features rapidly using familiar tools and component patterns.
FAQ
What is the C1 API by Thesys?
C1 is a middleware API that sits between your application and any LLM (OpenAI, Anthropic, Google, etc.). Instead of returning plain text, it returns structured UI components—forms, charts, tables, cards—that can be rendered directly in your app using the C1 React SDK. This enables real-time, context-aware interfaces without hardcoding every possible UI state.
Is there a free trial available?
Yes, Thesys offers a free plan with 5,000 C1 API calls per month and $10 in free LLM credits. You can start experimenting immediately using the API or the playground environment. Check the console during signup for specific requirements.
Can I use Thesys with models other than OpenAI?
Absolutely. Thesys supports all major LLM providers including OpenAI, Anthropic (Claude), Google (Gemini), and others. The C1 API is OpenAI-compatible, so you can switch between providers by changing the model parameter without rewriting integration code.
Can I customize the UI components to match my brand?
Yes. Thesys is built on top of the Crayon UI library, which supports extensive theming and customization. You can inject your own React components, apply custom styling, and configure interactions to align with your design system.
How does pricing work for LLM inference?
Thesys uses pass-through pricing for LLM inference with no markups. You pay the standard rate charged by your chosen LLM provider (OpenAI, Anthropic, etc.). The C1 API pricing is separate and based on the number of API calls you make, not the number of tokens processed.
Is my data secure and private?
Yes. Thesys maintains zero data retention for prompts and responses—your conversation data is not stored. The platform is compliant with GDPR, SOC2 (Type 2), and ISO27001. For regulated industries, Thesys offers self-hosting and VPC deployment options on enterprise plans, including HIPAA support with Business Associate Agreements available.
What payment methods are accepted?
Thesys accepts major credit cards (Visa, Mastercard, American Express) and offers invoice-based billing for enterprise customers on the Scale plan. Subscription management is handled through the Thesys console.
Can I cancel my subscription anytime?
Yes, you can cancel your subscription at any time through the Thesys console. There are no long-term commitments for the Build and Grow plans. The Scale plan may include contractual terms depending on your enterprise agreement.