vim-lsp

Vim-lsp is a lightweight Language Server Protocol client for Vim. It connects your editor to language servers for autocompletion, go-to-definition, hover docs, diagnostics, and code actions in any language that has an LSP server (TypeScript, Python, Rust, Go, C++, and dozens more).

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. Setup means installing a language server for each language you use, then adding a few lines to your vimrc telling vim-lsp where to find it. Pair it with vim-lsp-settings for automatic server installation and configuration.

The catch: 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 who want LSP without switching editors. Configuration is manual unless you add helper plugins, and the Vimscript implementation is slower than Lua-based alternatives on Neovim.