The mdx-js/eslint-mdx repository provides ESLint integration for MDX (Markdown with JSX) files. It consists of two main packages: `eslint-mdx`, which serves as an ESLint parser capable of converting MDX syntax into an ESTree Abstract Syntax Tree (AST) that ESLint can process, and `eslint-plugin-mdx`, which offers a plugin containing processors, configurations, and rules to enable linting of both JavaScript/JSX code and Markdown content within MDX files via remark-lint integration. The architecture centers around a parser that transforms MDX into an ESTree AST, preserving the structure of both Markdown and JSX elements. This parser employs a sophisticated token restoration mechanism (located in `tokens.ts`) to ensure that the token stream matches the original source code, which is essential for ESLint rules that rely on token-level analysis (such as semicolon or quoting rules). The plugin complements this by providing a processor that integrates with remark-lint to lint Markdown content, allowing users to apply Markdown-specific linting rules alongside standard JavaScript linting. Additionally, the plugin includes configurations for code block linting, enabling ESLint rules to be applied to code snippets embedded within Markdown fenced code blocks. The project demonstrates strong engineering practices, including strict type coverage enforcement, comprehensive testing with 100% coverage thresholds, and active maintenance with up-to-date dependencies. It supports modern ESLint versions (8, 9, and 10) and Node.js versions (>=18), ensuring compatibility with contemporary toolchains. The separation of concerns between the parser and plugin, along with the isolation of complex logic like token restoration into dedicated modules, contributes to a clean and maintainable codebase that is well-suited for reuse in similar tooling scenarios.