lspmux-rust-analyzer

WARNING: This is mostly vibe coded and works for me (Rain) personally. This may
or may not work for you.

Uses lspmux, a Language Server Protocol multiplexer, to share
a single rust-analyzer instance across multiple LSP clients. This reduces memory and CPU usage when
running multiple editors or Claude Code sessions on the same workspace.

Problem

Each LSP client (editor, Claude Code session, etc.) spawns its own rust-analyzer
process. On systems running multiple editors, this causes significant memory
pressure since rust-analyzer is memory-intensive.

Solution

lspmux acts as an intermediary between LSP clients and language servers:

┌──────────────┐  ┌──────────────┐  ┌──────────────┐
│  Claude Code │  │     Zed      │  │    Neovim    │
│ (LSP client) │  │ (LSP client) │  │ (LSP client) │
└──────┬───────┘  └──────┬───────┘  └──────┬───────┘
       │                 │                 │
       │ stdio           │ stdio           │ stdio
       ▼                 ▼                 ▼
┌────────────────────────────────────────────────────┐
│              lspmux client shim                    │
│        (invoked as "rust-analyzer")                │
└────────────────────────┬───────────────────────────┘
                         │ socket (localhost:27631)
                         ▼
┌────────────────────────────────────────────────────┐
│              lspmux server                         │
│        (systemd user service)                      │
└────────────────────────┬───────────────────────────┘
                         │ manages
                         ▼
┌────────────────────────────────────────────────────┐
│       rust-analyzer (one per workspace)            │
└────────────────────────────────────────────────────┘

Quick start

./setup

The setup script:

1. Downloads rust-analyzer from GitHub releases (with SHA256 verification)
2. Installs lspmux via cargo install --locked if not found
3. Installs systemd services (Linux) or launchd agents (macOS)

After setup completes, configure your editor (see below).

Editor configuration

Claude Code

claude plugin marketplace add /path/to/lspmux-rust-analyzer
claude plugin disable rust-analyzer-lsp@claude-plugins-official --scope user
claude plugin install lspmux-rust@lspmux-plugins --scope user

Zed

In ~/.config/zed/settings.json:

{
  "lsp": {
    "rust-analyzer": {
      "binary": {
        "path": "lspmux",
        "arguments": ["client", "--server-path", "/path/to/.local/share/lspmux-rust-analyzer/current/rust-analyzer"]
      }
    }
  }
}

Replace /path/to with the actual path (e.g., /home/username or the value of $HOME).

Neovim (untested)

With nvim-lspconfig:

require('lspconfig').rust_analyzer.setup {
  cmd = {
    "lspmux", "client", "--server-path",
    vim.fn.expand("$HOME/.local/share/lspmux-rust-analyzer/current/rust-analyzer")
  },
}

Or if using rustaceanvim:

vim.g.rustaceanvim = {
  server = {
    cmd = function()
      return {
        "lspmux", "client", "--server-path",
        vim.fn.expand("$HOME/.local/share/lspmux-rust-analyzer/current/rust-analyzer")
      }
    end,
  },
}

Vim (untested)

With vim-lsp:

if executable('lspmux')
  au User lsp_setup call lsp#register_server({
    \ 'name': 'rust-analyzer',
    \ 'cmd': ['lspmux', 'client', '--server-path', expand('$HOME/.local/share/lspmux-rust-analyzer/current/rust-analyzer')],
    \ 'allowlist': ['rust'],
    \ })
endif

With coc.nvim, in coc-settings.json:

{
  "languageserver": {
    "rust-analyzer": {
      "command": "lspmux",
      "args": ["client", "--server-path", "/path/to/.local/share/lspmux-rust-analyzer/current/rust-analyzer"],
      "filetypes": ["rust"]
    }
  }
}

Requirements

• Linux (systemd) or macOS (launchd)
• Rust toolchain (for cargo install)
• curl, jq

Directory structure

All paths respect the XDG base directory specification:

rust-analyzer

lspmux

Services

Managing services

lspmux server

Linux (systemd):

systemctl --user status lspmux
systemctl --user restart lspmux
journalctl --user -u lspmux -f

macOS (launchd):

launchctl list | grep lspmux
launchctl stop com.lspmux.server
launchctl start com.lspmux.server
tail -f "${XDG_STATE_HOME:-$HOME/.local/state}/lspmux/server.log"

Automatic updates

A daily timer/agent updates rust-analyzer to the latest release.

Linux:

systemctl --user status rust-analyzer-update.timer
systemctl --user start rust-analyzer-update.service  # manual update

macOS:

# Manual update
"${XDG_DATA_HOME:-$HOME/.local/share}/lspmux-rust-analyzer/bin/update-rust-analyzer"

Configuration

lspmux config

${XDG_CONFIG_HOME:-$HOME/.config}/lspmux/config.toml:

instance_timeout = 300       # Keep server for 5 min after last client
gc_interval = 10             # Check for idle servers every 10 sec
listen = ["127.0.0.1", 27631]
connect = ["127.0.0.1", 27631]
pass_environment = ["CARGO_HOME", "RUSTUP_HOME", "PATH", "HOME", "USER"]

Troubleshooting

LSP not working

1. Check lspmux server is running:

   systemctl --user status lspmux  # Linux
   launchctl list | grep lspmux    # macOS

2. Check rust-analyzer works:

   "${XDG_DATA_HOME:-$HOME/.local/share}/lspmux-rust-analyzer/current/rust-analyzer" --version

3. Check lspmux can connect:

   echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{}}' | \
     lspmux client --server-path "${XDG_DATA_HOME:-$HOME/.local/share}/lspmux-rust-analyzer/current/rust-analyzer"

   You should see JSON output. Press Ctrl+C to exit.

4. For Claude Code, check the plugin is installed:

   claude plugin list

Multiple rust-analyzer processes

Verify only one rust-analyzer is running per workspace:

pgrep -a rust-analyzer

If multiple processes exist, lspmux may not be configured correctly in your editor.

Uninstall

# Uninstall Claude Code plugin and marketplace
claude plugin uninstall lspmux-rust@lspmux-plugins --scope user
claude plugin marketplace remove lspmux-plugins
claude plugin enable rust-analyzer-lsp@claude-plugins-official --scope user

# Stop services (Linux)
systemctl --user disable --now lspmux.service rust-analyzer-update.timer

# Stop services (macOS)
launchctl unload ~/Library/LaunchAgents/com.lspmux.server.plist
launchctl unload ~/Library/LaunchAgents/com.rust-analyzer.update.plist

# Remove files
rm -rf "${XDG_DATA_HOME:-$HOME/.local/share}/lspmux-rust-analyzer"
rm -rf "${XDG_STATE_HOME:-$HOME/.local/state}/lspmux-rust-analyzer"
rm -rf "${XDG_STATE_HOME:-$HOME/.local/state}/lspmux"
rm -rf "${XDG_CONFIG_HOME:-$HOME/.config}/lspmux"
rm -rf "${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user/lspmux.service"
rm -rf "${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user/rust-analyzer-update."*
rm -rf ~/Library/LaunchAgents/com.lspmux.server.plist
rm -rf ~/Library/LaunchAgents/com.rust-analyzer.update.plist

License

MIT