metals-lsp

A Claude Code plugin that integrates Metals, the Scala language server, for code intelligence, refactoring, and analysis.

Prerequisites

Install the Metals LSP binary:

# Via Coursier (recommended)
cs install metals

# Or via Homebrew
brew install scalameta/tap/metals

Installation

Load the plugin when starting Claude Code:

claude --plugin-dir /path/to/metals-lsp

Or add it as a local marketplace for permanent installation:

# Inside Claude Code:
/plugin marketplace add /path/to/metals-lsp
/plugin install metals-lsp

Supported file types

Extension	Language
.scala	Scala
.sc	Scala
.sbt	sbt

Troubleshooting

If Metals isn't responding or indexing fails, try resetting the workspace:

1. Delete caches:

   rm -rf .metals/ .bloop/ .bsp/metals.json

2. Regenerate Bloop project files:

   sbt bloopInstall

3. Trigger compilation by issuing any LSP request (e.g. hover or documentSymbol) — Metals then connects to Bloop, indexes the workspace (~22s), and compiles all sources (~71s total).

Features

Once installed, Claude Code gains LSP-powered capabilities for Scala projects:

• Diagnostics (compiler errors and warnings)
• Hover information (types, documentation)
• Go-to-definition
• Find references
• Code completions