Show HN: I built a quickstart for the new OpenAI apps-SDK-UI (github.com)

A developer released sunpeak, a quickstart toolkit and component library for the new OpenAI apps-SDK-UI that helps you build and test ChatGPT App UIs locally. It bundles a ChatGPTSimulator for iterative component development, a basic MCP server to serve your UI to ChatGPT production, a testing framework that reproduces advanced ChatGPT behaviors locally, and a set of pre-built React/Tailwind components (OpenAICard example shown). The package targets cross-platform MCP UI workflows and aims to accelerate shipping ChatGPT Apps with a CLI-driven template project (pnpm dlx sunpeak init) and simple installation (pnpm add sunpeak). Requirements include Node 20+, pnpm 10+, React 18+ and Tailwind 4. Technically, sunpeak is an npm package containing a CLI, a library with runtime APIs and testing utilities (including the simulator), and a templated project with ready-to-use components and App scaffolding. Components are built on openai/apps-sdk-ui and importable styles (import 'sunpeak/style.css'). It fully supports the OpenAI ChatGPT design guidelines now, with design systems for Google Gemini and Anthropic Claude (SDK support coming soon), and allows custom platform adapters. The project is open to contributions and includes a DEVELOPMENT.md for deeper setup and development guidance, making it a practical tooling layer for teams building ChatGPT Apps.