The vim9-lean plugin

Warning

As of March 2026, the vim9-lean plugin has only one user (the initial developer). There will likely be some upgrades in early 2026 that will require manual changes to your Vim configuration. If you are not an experienced Vim user, you may want to consider alternatives such as the lean.nvim plugin for Neovim.

The castedo/vim9-lean plugin is a tiny optional plugin for convenience. If you are an experienced Vim user who already uses LSP, you might prefer just copying the minimal Lean-specific vim9script provided at the end of this page and the syntax file (a copy from the lean.nvim plugin).

The vim9-lean plugin is available at both:

• gitlab.com/castedo/vim9-lean
• github.com/castedo/vim9-lean

To install vim9-lean so that it is automatically loaded, run:

cd ~/.config/vim/pack/viagit/start
git clone https://gitlab.com/castedo/vim9-lean.git

Alternative minimal vim9script config

Instead of using the vim9-lean plugin, you might prefer just copying the minimal vim9script below from the vim9-lean plugin.

call LspAddServer([{
  filetype: 'lean',
  path: 'lspleank', args: ['lake'],
}])

There are additional nice touches and non-essential extra configurations in the ftplugin/lean.vim file from the plugin that you might also want to copy.