neovim

Neovim RPC

When Claude Code runs inside a Neovim terminal, the $NVIM environment variable points to the parent Neovim's Unix socket. This gives full access to Neovim's msgpack-RPC API without any plugins or HTTP servers.

Prerequisites

Before sending any commands, verify the socket is available:

echo "$NVIM"

If $NVIM is empty, you are not running inside a Neovim terminal and cannot communicate with a Neovim instance.

Important: When NVIM_APPNAME is set, all nvim --server commands emit a Warning: Using NVIM_APPNAME=... message on stdout (not stderr). This corrupts parsed output (especially JSON). To suppress it, capture the output first, then filter:

result=$(nvim --server "$NVIM" --remote-expr 'EXPR') && echo "$result" | grep -v '^Warning: Using NVIM_APPNAME='

Note: Piping nvim directly (e.g. nvim --server "$NVIM" ... | grep ...) can fail because $NVIM may not expand correctly in pipe contexts. Always use command substitution ($(...)) as shown above.

Evaluating expressions

All examples below use the command substitution pattern from Prerequisites to filter the NVIM_APPNAME warning. The shorthand nvimx EXPR means:

result=$(nvim --server "$NVIM" --remote-expr 'EXPR') && echo "$result" | grep -v '^Warning: Using NVIM_APPNAME='

Use --remote-expr to evaluate a Vimscript expression and get the result back:

result=$(nvim --server "$NVIM" --remote-expr 'v:version') && echo "$result" | grep -v '^Warning: Using NVIM_APPNAME='

For Lua expressions, wrap them in luaeval():

result=$(nvim --server "$NVIM" --remote-expr 'luaeval("vim.api.nvim_buf_get_name(0)")') && echo "$result" | grep -v '^Warning: Using NVIM_APPNAME='

For multi-statement Lua that returns a value, use an IIFE:

result=$(nvim --server "$NVIM" --remote-expr 'luaeval("(function() local x = vim.api.nvim_get_current_win(); return vim.api.nvim_win_get_number(x) end)()")') && echo "$result" | grep -v '^Warning: Using NVIM_APPNAME='