vim-matchup is a Vim/Neovim plugin that extends the `%` key to navigate between matching language constructs (e.g., if/endif, for/endfor, HTML tags, LaTeX environments) and highlights matching pairs. Its architecture is a classic Vim plugin: `plugin/matchup.vim` is the entry point that initializes configuration, loads modules, and sets up autocommands. Core logic lives in `autoload/matchup/*.vim` files, which are lazy-loaded on demand. The plugin supports both a Vimscript-based matching engine (using `b:match_words` regex patterns) and a Neovim-only treesitter-based engine (Lua code in `lua/treesitter-matchup/`). Key modules include `delim` (delimiter detection and matching), `motion` (movements like `%`, `[%`, `]%`), `text_obj` (text objects `i%`, `a%`), `matchparen` (highlighting and off-screen display), and `perf` (performance timing). It depends on Vim 7.4+ or Neovim 0.5+, and optionally on installed treesitter parsers for enhanced matching. The codebase is well-structured, extensively tested, and demonstrates advanced Vimscript and Lua craftsmanship.