How do I install Elm Lsp Rust?

No package has been published for this server, so install it from source: clone the repository and follow its README.

Is Elm Lsp Rust safe to use with an AI agent?

Its trust score is 34 out of 100 (low). It passes 1 of the 1 static security checks run so far. It has no ConduID identity yet, so agent calls to it are not receipted.

Is Elm Lsp Rust still maintained?

Yes — the last commit was 2 months ago. The repository has 5 stars and 4 forks.

About Elm Lsp Rust

Elm Lsp Rust is an MCP server published by CharlonTank in the Developer Tools category: fast Elm Language Server written in Rust with tree-sitter.

The repository has 5 stars and 4 forks, with the last commit 2 months ago. Recent commit activity is the strongest signal that reported issues will get attention.

Install

From source

git clone https://github.com/CharlonTank/elm-lsp-rust

This server has no ConduID identity, so agent calls to it are not receipted. Pin the version you install and review the source before granting it credentials.

Tools (22)

elm_add_variantAdd variant with auto case branch updates

Parameters not published.

elm_apply_code_actionApply a code action

Parameters not published.

elm_code_actionsGet available actions

Parameters not published.

elm_definitionGo to definition

Parameters not published.

elm_diagnosticsGet compiler errors

Parameters not published.

elm_formatFormat file

Parameters not published.

elm_generate_erdGenerate Mermaid ERD from type

Parameters not published.

elm_move_fileMove an Elm file

Parameters not published.

elm_move_functionMove function to module

Parameters not published.

elm_notify_file_changedNotify LSP of external file changes

Parameters not published.

Show all 22 tools

elm_prepare_add_variantCheck what adding a variant would affect

Parameters not published.

elm_prepare_remove_fieldCheck what removing a field would affect

Parameters not published.

elm_prepare_remove_variantCheck what removing a variant would affect

Parameters not published.

elm_referencesFind all references

Parameters not published.

elm_remove_fieldRemove field from type alias

Parameters not published.

elm_remove_variantRemove variant with auto pattern removal

Parameters not published.

elm_rename_fieldRename a record field

Parameters not published.

elm_rename_fileRename an Elm file

Parameters not published.

elm_rename_functionRename a function

Parameters not published.

elm_rename_typeRename a type

Parameters not published.

elm_rename_variantRename a variant

Parameters not published.

elm_symbolsList file symbols

Parameters not published.

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README

elm-lsp-rust

A fast Elm Language Server written in Rust, designed for Claude Code integration via MCP.

Installation

In Claude Code, run:

/plugin marketplace add CharlonTank/elm-lsp-plugin
/plugin install elm-lsp-rust@CharlonTank/elm-lsp-plugin

Then restart Claude Code.

How Plugin Distribution Works

┌─────────────────────────────────────────────────────────────────┐
│                     elm-lsp-plugin                              │
│            (Marketplace Repository)                             │
│     https://github.com/CharlonTank/elm-lsp-plugin              │
│                                                                 │
│  .claude-plugin/marketplace.json                                │
│  └── plugins: [                                                 │
│        { name: "elm-lsp-rust",                                  │
│          source: "CharlonTank/elm-lsp-rust" }                   │
│      ]                                                          │
└─────────────────────────────────────────────────────────────────┘
                              │
                              │ references
                              ▼
┌─────────────────────────────────────────────────────────────────┐
│                     elm-lsp-rust                                │
│              (This Repository - Plugin)                         │
│      https://github.com/CharlonTank/elm-lsp-rust               │
│                                                                 │
│  .claude-plugin/plugin.json ─► Plugin metadata                  │
│  src/                       ─► Rust LSP server                  │
│  mcp-wrapper/               ─► MCP server (bridges MCP↔LSP)     │
│  scripts/setup.sh           ─► Builds Rust binary on install    │
└─────────────────────────────────────────────────────────────────┘

When you install via the marketplace:

Claude Code fetches plugin metadata from elm-lsp-plugin/marketplace.json
The marketplace points to this repository (elm-lsp-rust)
Claude Code clones this repo and runs scripts/setup.sh to build the Rust binary
The MCP wrapper (mcp-wrapper/index.mjs) becomes available as elm-lsp-rust MCP server

Features

Feature	Description
Go to Definition	Jump to symbol definitions
Find References	All usages across workspace
Rename	Safe rename across all files (functions, types, variants, fields)
Document Symbols	List all symbols in a file
Diagnostics	Compiler errors via `elm make` / `lamdera make`
Formatting	Via `elm-format`
Code Actions	Quick fixes and refactorings
Move Function	Move function to another module with import updates
File Rename/Move	Rename or move Elm files with module/import updates
Add Variant	Add variant to custom type with auto case branch updates
Remove Variant	Smart union type variant removal
Remove Field	Remove field from type alias with usage updates
ERD Generation	Generate Mermaid diagrams from types

Smart Type Operations

Add Variant: Adds a variant and automatically inserts branches in all case expressions:

-- elm_add_variant with custom branch code for each case expression
type Route = HomeRoute | AboutRoute | NewRoute
-- All case expressions get new branches with your specified code

Remove Variant: Intelligently removes variants:

Replaces constructor usages with Debug.todo
Auto-removes pattern match branches
Errors if removing the only variant

Remove Field: Removes fields from type aliases:

Updates record literals, patterns, and field accesses
Replaces field access with Debug.todo

MCP Tools (22 total)

Tool	Description
`elm_definition`	Go to definition
`elm_references`	Find all references
`elm_symbols`	List file symbols
`elm_diagnostics`	Get compiler errors
`elm_code_actions`	Get available actions
`elm_apply_code_action`	Apply a code action
`elm_format`	Format file
`elm_rename_variant`	Rename a variant
`elm_rename_type`	Rename a type
`elm_rename_function`	Rename a function
`elm_rename_field`	Rename a record field
`elm_move_function`	Move function to module
`elm_rename_file`	Rename an Elm file
`elm_move_file`	Move an Elm file
`elm_notify_file_changed`	Notify LSP of external file changes
`elm_prepare_add_variant`	Check what adding a variant would affect
`elm_add_variant`	Add variant with auto case branch updates
`elm_prepare_remove_variant`	Check what removing a variant would affect
`elm_remove_variant`	Remove variant with auto pattern removal
`elm_prepare_remove_field`	Check what removing a field would affect
`elm_remove_field`	Remove field from type alias
`elm_generate_erd`	Generate Mermaid ERD from type

Building from Source

cd elm-lsp-rust
cargo build --release

# Binary at: target/release/elm_lsp

Shared MCP Server (Manual HTTP)

Run one MCP server yourself and point multiple Claude Code sessions to it.

cd /path/to/elm-lsp-rust
cargo build --release
cd mcp-wrapper && npm install

cd /path/to/elm-project
node /path/to/elm-lsp-rust/mcp-wrapper/index.mjs --http --host 127.0.0.1 --port 3333

Claude Code config example (in ~/.claude.json or project .mcp.json):

{
  "mcpServers": {
    "elm-lsp-rust": {
      "type": "http",
      "url": "http://127.0.0.1:3333/mcp"
    }
  }
}

Notes:

Start the server from your Elm project root so elm.json is present.
This shares one LSP per workspace; use the same repo across sessions.
Disable the stdio server entry to avoid duplicates.

Architecture

elm-lsp-rust/
├── .claude-plugin/
│   └── plugin.json      # Plugin metadata for marketplace
├── src/
│   ├── main.rs          # Entry point
│   ├── server.rs        # LSP protocol (tower-lsp)
│   ├── workspace.rs     # Indexing, symbols, refactoring
│   ├── document.rs      # Single file representation
│   ├── parser.rs        # Tree-sitter parsing
│   └── diagnostics.rs   # Elm compiler integration
├── mcp-wrapper/         # MCP server (Node.js)
│   └── index.mjs        # Translates MCP <-> LSP
├── scripts/
│   └── setup.sh         # Build script run on plugin install
├── skills/              # Claude Code skills
└── tests/               # Test suite (228 tests)

Key Design Decisions

Workspace Indexing: Indexes all .elm files at startup for immediate cross-file operations
Tree-sitter Parsing: Fast, incremental, error-tolerant parsing
Compiler Diagnostics: Uses elm make --report=json for 100% accurate errors
Evergreen Exclusion: Skips src/Evergreen/ migration files in refactoring

Testing

# Run all tests (228 tests total)
node tests/run_tests.mjs && node tests/test_meetdown_comprehensive.mjs

Tests cover: definition, references, symbols, rename (functions, types, variants, fields), diagnostics, code actions, move function, file rename/move, add/remove variant, add/remove field, and ERD generation.

elm-lsp-plugin - Marketplace that distributes this plugin
elm-language-server - Original TypeScript LSP
tree-sitter-elm - Elm grammar
tower-lsp - Rust LSP framework

Issues

Report bugs at: https://github.com/CharlonTank/elm-lsp-rust/issues

Read full README

README copy captured when this server was indexed; it may lag the repository. The original is authoritative.

About Elm Lsp Rust

Install

Tools (22)

Ask AI

Security checks

README

elm-lsp-rust

Installation

How Plugin Distribution Works

Features

Smart Type Operations

MCP Tools (22 total)

Building from Source

Shared MCP Server (Manual HTTP)

Architecture

Key Design Decisions

Testing

Related

Issues

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