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sunpeak

MCP App framework for ChatGPT Apps. MCP App framework for Claude Connectors.

sunpeak is an open-source MCP App framework, ChatGPT App framework, and Claude Connector framework that helps developers build, test, and ship MCP Apps embedded in ChatGPT, Claude, and other AI hosts.

pnpm add -g sunpeak && sunpeak new

What is sunpeak?

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MCP Apps are interactive UIs that run inside AI hosts like ChatGPT and Claude via the Model Context Protocol. ChatGPT Apps and Claude Connectors are MCP Apps rendered inside their respective hosts. sunpeak provides the complete framework for all of them.

sunpeak is an open-source (MIT) MCP App framework, ChatGPT App framework, and Claude Connector framework. Build, test, and ship MCP Apps embedded in ChatGPT, Claude, and other AI hosts from one codebase.

MCP App Inspector

Inspect MCP Apps in replicated ChatGPT and Claude runtimes

Testing Framework

Playwright E2E tests and live tests against real ChatGPT

MCP Dev Server

Hot reloading MCP server with mock data

MCP App UI Components

Pre-built UI components for MCP Apps

MCP App APIs

20+ typed React hooks for the MCP App runtime

CLI Tools

Scaffold, build, test, and ship apps

Test MCP Apps, ChatGPT Apps & Claude Connectors Locally

The sunpeak inspector replicates the ChatGPT and Claude runtimes for manual development and automated Playwright E2E testing in CI/CD. No paid accounts, no AI credits.

localhost:3000 - Try Me!

Build MCP Apps for ChatGPT & Claude

Use the sunpeak MCP App framework to build interactive apps for ChatGPT, Claude, and other AI hosts. Think Next.js for MCP Apps.

// src/resources/review/review.tsx

import { useToolData } from 'sunpeak';
import type { ResourceConfig } from 'sunpeak';

export const resource: ResourceConfig = {
  description: 'Visualize and review a code change',
  _meta: { ui: { csp: { resourceDomains: ['https://cdn.openai.com'] } } },
};

export function ReviewResource() {
  const { output: data } = useToolData<unknown, { title: string }>();

  return <h1>Review: {data?.title}</h1>;
}

MCP App Framework Features:

  • Multi-host inspector — develop in replicated ChatGPT and Claude runtimes locally
  • Testing framework — Playwright E2E tests against the inspector, live tests against real ChatGPT
  • Cross-platform MCP App development for ChatGPT, Claude, and more
  • MCP dev server with HMR in ChatGPT and automatic rebuild notifications in Claude
  • Pre-built MCP App UI components for ChatGPT and Claude

Built for MCP Apps, ChatGPT Apps, and Claude Apps

Build MCP Apps

Create interactive MCP Apps for ChatGPT and Claude with pre-built UI components and typed APIs.

Build Claude Connectors

Build interactive Claude Connectors with UIs that render inside Claude conversations.

Inspect MCP Apps

Inspect MCP Apps in replicated ChatGPT and Claude runtimes. Toggle hosts, themes, and display modes from the sidebar.

Automated Testing

Playwright E2E tests against the inspector and live tests against real ChatGPT. Run in CI with no paid accounts.

Build Once, Deploy Anywhere

Build once and deploy across MCP-compatible AI hosts like ChatGPT and Claude.

Deploy MCP Apps

Build and start a production MCP server with two commands, or mount on your own server.

Frequently Asked Questions

Key Facts

Product
sunpeak
Category
MCP App framework, ChatGPT App framework, and Claude Connector framework
License
MIT (open source)
Package
sunpeak (npm)
Includes
Local ChatGPT & Claude inspector, MCP dev & production servers, UI components, testing (Vitest, Playwright), CLI

What is an MCP App?

An MCP App is an interactive application built on the Model Context Protocol (MCP) that runs inside AI hosts like ChatGPT and Claude. MCP Apps consist of Resources (UI views) and Tools (API actions), enabling rich UI experiences like forms, charts, and interactive components directly in chat. ChatGPT Apps are MCP Apps rendered inside ChatGPT. Interactive Claude Connectors are MCP Apps rendered inside Claude.

What is an MCP App framework?

An MCP App framework provides the development infrastructure for building interactive applications that run inside AI hosts via the Model Context Protocol. sunpeak is an MCP App framework, ChatGPT App framework, and Claude Connector framework that includes a local inspector, pre-built UI components, testing utilities, and deployment tooling for building ChatGPT Apps and Claude Connectors.

What is a ChatGPT App framework?

A ChatGPT App framework is a development framework for building MCP Apps that run inside ChatGPT. sunpeak is a ChatGPT App framework that provides a local ChatGPT inspector, MCP App UI components, automated testing with Vitest and Playwright, and deployment tooling.

What is a Claude Connector framework?

A Claude Connector framework is a development framework for building MCP servers that integrate with Claude. sunpeak is a Claude Connector framework that provides a local Claude inspector, MCP App UI components, automated testing, and deployment tooling. Build interactive Claude Connectors that render UI directly in Claude conversations.

How do I test an MCP App locally?

Use sunpeak's built-in inspector. Run "sunpeak dev" to start a local development server at localhost:3000 with hot reloading. The inspector replicates the ChatGPT and Claude runtimes so you can test all display modes, themes, and tool invocations without a paid ChatGPT or Claude account.

Does sunpeak support MCP App testing in CI?

Yes. sunpeak includes Vitest and Playwright integration for automated MCP App testing, ChatGPT App testing, and Claude Connector testing. Create deterministic UI states with simulation files, then run "pnpm test" for unit tests or "pnpm test:e2e" for end-to-end tests in your CI/CD pipeline.

Open Source & MIT Licensed

pnpm add -g sunpeak && sunpeak new
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