Language Server

The mashin language server (LSP) provides IDE features for any editor that speaks the Language Server Protocol. It is built into the mashin CLI and works with VS Code, Zed, Neovim, Helix, Emacs, and any other LSP-capable editor.

Starting the language server

The language server runs in stdio mode:

mashin lsp

This is what editor extensions call under the hood. You do not need to start it manually if you are using the VS Code or Zed extension.

Features

Completions

The language server suggests:

• Keywords: machine, accepts, responds with, ensures, implements, compute, ask, decide, for_each, and all other mashinTalk keywords
• Step types: With inline documentation for each type
• Stdlib machines: All @mashin/actions/* machines with their input/output schemas
• Context accessors: context.input, context.cell, steps.* with field-level completions
• Config options: Valid options for each step type (using:, with task, returns, etc.)

Diagnostics

Real-time validation as you type:

• Syntax errors with line and column positions
• Unknown keywords or section types
• Missing required fields (e.g., ask without using: or from:)
• Type mismatches in returns declarations
• Semantic validation from the 65-rule validator (SEM003-SEM064)

Hover

Hover over any keyword, step type, or stdlib machine reference to see documentation. Includes:

• Description of what the keyword does
• Expected child structure
• Examples
• Links to the reference docs

Go-to-definition

Navigate to:

• Stdlib machine definitions
• Local machine files (when referenced in ask ... from:)
• Step definitions (when referenced in expressions like steps.my_step)
• Input field declarations

Formatting

The language server formats .mashin files according to the canonical style:

• Consistent indentation (2 spaces)
• Canonical section ordering
• Normalized whitespace around operators

Trigger with your editor’s format command, or from the CLI:

mashin fmt my_machine.mashin

Configuration

Most editors auto-detect the language server from the extension. For manual configuration, point your editor at the mashin lsp command in stdio mode.

Neovim (via nvim-lspconfig)

local lspconfig = require('lspconfig')
local configs = require('lspconfig.configs')

configs.mashin = {
  default_config = {
    cmd = { 'mashin', 'lsp' },
    filetypes = { 'mashin' },
    root_dir = lspconfig.util.root_pattern('mashin.toml', '.mashin'),
  },
}

lspconfig.mashin.setup({})

Helix

Add to ~/.config/helix/languages.toml:

[[language]]
name = "mashin"
scope = "source.mashin"
file-types = ["mashin"]
language-servers = ["mashin-lsp"]

[language-server.mashin-lsp]
command = "mashin"
args = ["lsp"]

Next steps

• Editor Setup - VS Code and Zed extensions
• CLI Reference - All CLI commands