vim-lsp

If you use Vim or Neovim and want code intelligence — autocomplete, go-to-definition, error highlighting — without installing a heavy plugin framework, vim-lsp is a lightweight Language Server Protocol client that does exactly that. It connects your editor to language servers for any language.

It is async (won't freeze your editor), works with both Vim and Neovim, and has no external dependencies beyond Vim 8+ or Neovim. Pure Vimscript.

The catch: 3.3K stars, stable but niche. The Neovim ecosystem has moved toward built-in LSP support (nvim-lspconfig), which makes vim-lsp more relevant for classic Vim users. Configuration is manual — you set up each language server yourself.