Meteor is an ultra-simple full-stack JavaScript framework for building modern web and mobile applications. This monorepo contains the Meteor CLI tool (`meteor`), the build system (isobuild, Rspack integration), core runtime packages (reactive data via DDP, MongoDB integration, accounts, Blaze templating, modules, bundling), and a rich ecosystem of OAuth providers, testing infrastructure, and developer tools (ESLint plugin, Babel preset, installer). The codebase is organized as a monorepo with `tools/` for the CLI and build system, `packages/` for framework packages, and `npm-packages/` for standalone npm packages. It demonstrates a real-time data synchronization pattern using DDP (Distributed Data Protocol), a custom constraint solver for package dependency resolution, and a compiler plugin system for transpilation. Despite being a well-established framework with extensive testing, the codebase shows signs of technical drift: deprecated packages remain in-tree, there is a dual sync/async API surface due to ongoing migration from Fibers to async/await, and the build system is transitioning from a legacy compiler to Rspack.