WordPress Playground is a browser-based WordPress runtime that runs entirely client-side via WebAssembly. It compiles the PHP interpreter (versions 5.2 through 8.5) into WASM using Emscripten, enabling WordPress to execute in the browser without a server. The monorepo is organized into several key packages: php-wasm (PHP-to-WASM compilation toolchain, runtime bindings for Node.js and web, extensions, and Xdebug bridge), playground (blueprint engine, CLI, remote access tunneling, MCP server for AI agents, and a full-featured website application for managing WordPress instances), and docs (Docusaurus-based documentation site). The architecture is a dependency-injected, modular monorepo using Nx for builds and Lerna for publishing. The blueprint system allows declarative configuration of WordPress environments (plugins, themes, content, settings) and supports V1 and V2 schema. The project also includes a sync engine for incremental state persistence, OPFS-based storage, and a CORS proxy for network requests. It is actively maintained with comprehensive CI/CD pipelines and extensive test coverage across Node.js and browser runtimes.