Neovim Not Working? Common Errors & Fixes

Usually the language server isn't installed/on PATH, the project has no root marker, or the config still uses the deprecated lspconfig setup(). Run :checkhealth vim.lsp, then enable the server with vim.lsp.enable().

On Neovim 0.11+, the legacy nvim-lspconfig setup() framework is deprecated in favor of built-in vim.lsp.config() and vim.lsp.enable(). Replace each setup{} call with vim.lsp.config + vim.lsp.enable.

nvim-treesitter's default 'main' branch is an incompatible rewrite: it needs Neovim 0.12+, tree-sitter-cli and a C compiler, and no longer enables highlighting itself. Install parsers with require('nvim-treesitter').install() and call vim.treesitter.start().

Neovim doesn't talk to the system clipboard itself; it shells out to a tool like wl-copy, xclip, pbcopy or clip.exe. Install one (or use OSC 52 / the WSL g:clipboard config) and set clipboard=unnamedplus.

Colorschemes look washed-out or different inside tmux because true color (RGB) isn't passed through. Set tmux's default-terminal to tmux-256color and add an RGB terminal-features entry.

A noticeable lag when pressing Esc to leave insert mode inside tmux comes from tmux's escape-time. Lower it to about 10ms.

mason.nvim downloads servers using external tools (npm, pip, cargo, go, curl, unzip). If one is missing or misconfigured, installs fail. Check :checkhealth mason and :MasonLog for the missing tool.

Neovim itself is fast; slowness almost always comes from plugins, syntax/Treesitter on huge files, LSP in big projects, or a slow terminal. Compare with nvim --clean, then profile.

Completion menus that show only buffer words, or nothing, usually mean the LSP isn't attached or the completion plugin's capabilities aren't passed to the server. Confirm the LSP first, then wire capabilities.

Neovim 0.12 removed APIs deprecated in 0.10 and changed several defaults, so old plugins and copied configs can throw Lua errors. Update plugins, fix deprecated calls from the 0.12 news, and check health.

Python-based plugins need the pynvim module available to Neovim. Install it with uv or pipx and, if a virtualenv interferes, point g:python3_host_prog at the right interpreter.