TL;DR — Sunpeak
Sunpeak is an open-source MCP App framework that helps developers build, test, and ship MCP Apps embedded in ChatGPT, Claude, and other AI hosts. MCP Apps combine Resources (UI views like forms, charts, and interactive components) with Tools (API actions) to create rich experiences directly in chat. Sunpeak includes a local simulator for both ChatGPT and Claude, pre-built UI components, testing utilities with Vitest and Playwright, and deployment tooling to ship from one codebase to multiple AI platforms.
Table of Contents
What is Sunpeak?
Sunpeak is an open-source MCP App framework that helps developers build, test, and ship MCP Apps embedded in ChatGPT, Claude, and other AI hosts. MCP Apps combine Resources (UI views like forms, charts, and interactive components) with Tools (API actions) to create rich experiences directly in chat. Sunpeak includes a local simulator for both ChatGPT and Claude, pre-built UI components, testing utilities with Vitest and Playwright, and deployment tooling to ship from one codebase to multiple AI platforms.
Screenshot of Sunpeak homepage — captured March 21, 2026 by PopularAiTools.ai
Key Features of Sunpeak
ChatGPT and Claude App Building
Build MCP Apps that work in both ChatGPT and Claude from a single codebase using the MCP protocol standard.
Local Simulator
Test MCP Apps locally without a paid ChatGPT account using simulators for both ChatGPT and Claude hosts.
Pre-Built UI Components
Access ready-made UI components including forms, charts, and interactive elements for building rich chat experiences.
Automated Testing
Built-in testing utilities using Vitest and Playwright for local and automated testing of MCP Apps.
One-Codebase Deployment
Ship to both ChatGPT and Claude from a single codebase, eliminating platform-specific development.
MIT Open Source
Completely free under the MIT license with full access to source code and community contributions.
How to Use Sunpeak
1
Install Sunpeak
Install from npm or clone the repository. Sunpeak is fully open source under MIT license.
2
Create Your MCP App
Use the framework to define Resources (UI) and Tools (API actions) for your chat-embedded application.
3
Test Locally
Use the built-in simulators for ChatGPT and Claude to test your app without paid accounts.
4
Write Tests
Add automated tests using Vitest and Playwright for reliable, repeatable testing.
5
Deploy
Ship your MCP App to ChatGPT and Claude from a single codebase using the deployment tooling.
Sunpeak Pricing
Free and open source (MIT license)
Pros and Cons
✓ Pros
- ✓Completely free and open source under MIT license
- ✓Single codebase deploys to both ChatGPT and Claude
- ✓Local simulator eliminates need for paid AI accounts during development
- ✓Pre-built UI components speed up development significantly
- ✓Automated testing with Vitest and Playwright ensures quality
- ✓Active development with recent Claude simulator addition
✗ Cons
- ✗Requires developer experience to build MCP Apps
- ✗MCP ecosystem is still emerging and evolving rapidly
- ✗Limited to ChatGPT and Claude hosts currently
- ✗Small community compared to established web frameworks
Sunpeak Alternatives
Vercel AI SDK
Framework for building AI-powered applications with streaming and tool support.
LangChain
Popular framework for building LLM-powered applications with broad tooling.
Streamlit
Python framework for building AI apps with simple UI components.
Gradio
Python library for building ML demos and web interfaces quickly.
Our Verdict
4.2/5
Sunpeak fills a critical gap in the MCP ecosystem by providing a proper development framework for building chat-embedded applications. The ability to develop and test locally, then deploy to both ChatGPT and Claude from one codebase, is exactly what developers need as MCP adoption grows. Being free and open source under MIT removes any barrier to adoption. For developers looking to build MCP Apps, Sunpeak is currently the best framework available. Rating: 4.2/5
Try Sunpeak Today →
Visit the official Sunpeak website to get started
Frequently Asked Questions
Is Sunpeak free?
Yes, Sunpeak is completely free and open source under the MIT license.
What are MCP Apps?
MCP Apps combine Resources (UI views) and Tools (API actions) to create rich experiences embedded in AI chat hosts.
Which AI platforms does Sunpeak support?
Sunpeak supports building apps for ChatGPT and Claude from a single codebase.
Do I need a paid ChatGPT account to develop?
No, Sunpeak includes local simulators for testing without paid accounts.
What testing tools are included?
Sunpeak includes testing utilities for Vitest and Playwright for automated testing.
Can I build UI in chat?
Yes, MCP Apps support rich UI including forms, charts, and interactive components embedded in chat.
What language is Sunpeak built in?
Sunpeak is built with JavaScript/TypeScript for the web development ecosystem.
Is Sunpeak production-ready?
Sunpeak is actively developed with recent updates. Check the repository for stability status.
Last updated: March 21, 2026 | Review by PopularAiTools.ai
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