Show HN: OpenAI hasn't released their Apps SDK so we did (github.com)

A community-built monorepo has shipped a production-ready toolkit that implements an OpenAI Apps SDK–compatible workflow so developers can build interactive ChatGPT widgets today, before OpenAI’s official SDK is released. The project packages everything needed to author, bundle, serve and test Model Context Protocol (MCP) widgets: React UI hooks, an MCP server toolkit, a Vite-powered bundler, CLI tools and Express utilities. It’s MIT-licensed, targets Node 18+/React 18+/TypeScript 5+, and includes full examples showing the end-to-end flow of registering a widget, returning both chat content and structuredContent, and rendering an interactive HTML widget inside ChatGPT. Technically, the toolkit offers @fractal-mcp/oai-hooks (useWidgetProps/useWidgetState, persistent widget state, layout/display mode and ChatGPT global context), @fractal-mcp/oai-server (MCP server with SSE transport, Zod input validation, registerOpenAIWidget API), @fractal-mcp/bundle (bundle React/Vue/Svelte components into single HTML or separate assets, built-in Playwright testing), plus CLI and mcp-express helpers. Developers can bundle components into standalone HTML, serve them via templateUri, and handle real-time interactions and state persistence with the same patterns OpenAI’s examples use—making it a practical drop-in for teams wanting to prototype or deploy ChatGPT-integrated apps now.