Catenary

A bridge between MCP (Model Context Protocol) and LSP (Language Server Protocol).

Catenary allows LLM-powered tools to access IDE-quality code intelligence by exposing LSP capabilities as MCP tools.

Features

LSP Multiplexing - Run multiple language servers (Rust, Python, Go, etc.) in a single Catenary instance.
Smart Routing - Automatically routes requests to the correct LSP server based on file extension.
Universal LSP support - Works with any LSP server (rust-analyzer, gopls, pyright, typescript-language-server, etc.)
Full LSP coverage - Hover, go-to-definition, find references, completions, diagnostics, rename, formatting, and more
Smart Encoding - Automatically negotiates UTF-8 position encoding for accurate emoji and multi-byte character support
MCP-native - Exposes all features as MCP tools with proper schemas

Installation

cargo install catenary-mcp

Or build from source:

git clone https://github.com/Mark-Wells-Dev/Catenary
cd catenary
cargo build --release

Usage

catenary --lsp "rust:rust-analyzer" --lsp "shellscript:bash-language-server start" --root /path/to/project

Arguments

--lsp, -l - LSP server specification in lang:command format (can be specified multiple times)
--root, -r - Workspace root directory (default: .)
--idle-timeout - Seconds before closing idle documents (default: 300, set to 0 to disable)

Example: Multiplexing

You can run one Catenary instance that handles all your project's languages:

catenary \
  --lsp "rust:rust-analyzer" \
  --lsp "python:pyright-langserver --stdio" \
  --lsp "shellscript:bash-language-server start" \
  --root .

Catenary will automatically detect the language of the file you are working on and route the LSP request to the appropriate server. For workspace-wide operations (like lsp_workspace_symbols), it queries all servers and merges the results.

Available MCP Tools

Tool	Description
`lsp_hover`	Get hover information (documentation, type info) for a symbol
`lsp_definition`	Go to the definition of a symbol
`lsp_type_definition`	Go to the type definition of a symbol
`lsp_implementation`	Find implementations of an interface or trait
`lsp_references`	Find all references to a symbol
`lsp_document_symbols`	Get the symbol outline of a file
`lsp_workspace_symbols`	Search for symbols across the workspace
`lsp_code_actions`	Get available code actions (quick fixes, refactorings)
`lsp_rename`	Rename a symbol (supports dry run or applying to disk)
`lsp_completion`	Get completion suggestions at a position
`lsp_signature_help`	Get function signature help
`lsp_diagnostics`	Get diagnostics (errors, warnings) for a file
`lsp_formatting`	Format a document
`lsp_range_formatting`	Format a range within a document
`lsp_call_hierarchy`	Get incoming/outgoing calls for a function
`lsp_type_hierarchy`	Get supertypes/subtypes of a type

MCP Configuration

Claude Desktop

Add to ~/.config/claude/claude_desktop_config.json (Linux) or ~/Library/Application Support/Claude/claude_desktop_config.json (macOS):

{
  "mcpServers": {
    "rust-lsp": {
      "command": "catenary",
      "args": ["--command", "rust-analyzer", "--root", "/path/to/rust/project"]
    },
    "python-lsp": {
      "command": "catenary",
      "args": [
        "--command",
        "pyright-langserver --stdio",
        "--root",
        "/path/to/python/project"
      ]
    },
    "typescript-lsp": {
      "command": "catenary",
      "args": [
        "--command",
        "typescript-language-server --stdio",
        "--root",
        "/path/to/ts/project"
      ]
    }
  }
}

Claude Code (CLI)

Add to ~/.claude/settings.json:

{
  "mcpServers": {
    "lsp": {
      "command": "catenary",
      "args": ["--command", "rust-analyzer"]
    }
  }
}

Note: --root defaults to the current directory, so it can be omitted when running from the project root.

Generic MCP Client

{
  "mcpServers": {
    "catenary": {
      "command": "catenary",
      "args": ["--command", "<lsp-command>", "--root", "<workspace-path>"]
    }
  }
}

Common LSP Server Commands

Language	Command
Rust	`rust-analyzer`
Go	`gopls`
Python	`pyright-langserver --stdio`
TypeScript	`typescript-language-server --stdio`
C/C++	`clangd`
Lua	`lua-language-server`
Bash	`bash-language-server start`
YAML	`yaml-language-server --stdio`

License

GPL-3.0

catenary-mcp 0.2.0