GML Language Server

GMLoop provides gmloop-lsp, a Language Server Protocol server for .gml files.

The LSP workspace owns protocol transport, document synchronization, range conversion, and session lifecycle. It delegates domain behavior to the owning workspaces:

• @gmloop/parser for parse diagnostics.
• @gmloop/lint for lint diagnostics and quick-fix surfaces.
• @gmloop/format for document formatting.
• @gmloop/semantic for project index facts, symbols, definitions, and references.
• @gmloop/refactor for rename/edit safety.

Editor Usage

Build the workspace, then run GMLoop's LSP server:

# Start the LSP server over stdio
gmloop lsp

The server explicitly wires standard input and standard output (process.stdin / process.stdout) to speak JSON-RPC over stdio by default, without requiring any command-line flags. It targets .gml files only.

VSCode Usage

GMLoop provides a first-party VSCode extension package in src/vscode. The extension registers .gml files as the gml language and starts the existing stdio server with:

gmloop lsp

The extension contributes:

• gmloop.serverPath - path or command name for the GMLoop CLI executable. It defaults to gmloop; the extension always appends the fixed lsp argument.
• GMLoop: Restart Language Server
• GMLoop: Show Language Server Output

For semantic navigation features such as definitions, references, workspace symbols, and rename, open a folder that contains or is nested under a GameMaker .yyp project so the semantic project root can be discovered.

Hover distinguishes inspectable symbols from language syntax. Project symbols and documented runtime built-ins such as functions, sprite_index, and visible provide tooltips; keywords such as function, var, constructor, if, else, and repeat do not. Constructor-owned instance variables resolve from both bare references and self-qualified references inside static methods, and their tooltips link to the defining assignment. For documented callable project symbols, including constructor static methods, the tooltip includes the description, parameter names and types, and return information.

Comments, strings, and function-documentation contents such as @desc, @param, and @returns do not produce GMLoop hover results. VSCode can still merge a hover from another installed extension; in particular, GitHub Pull Requests treats raw @name text in comments as GitHub user mentions. Disable that extension for the workspace if those external profile cards conflict with GML documentation tags.

Game projects initialized with gmloop agent-pack init --vscode receive project-local .vscode/settings.json and .vscode/extensions.json files for this setup. The command also makes a best-effort attempt to install the GMLoop VSCode extension through the code CLI.

Before Marketplace publishing, the installable VSCode extension artifact is a local .vsix:

pnpm run package:vscode
code --install-extension src/vscode/dist/gmloop-0.0.1.vsix

The generated VSIX contains the VSCode client and its runtime vscode-languageclient dependency. It does not bundle the language server itself; VSCode still launches the configured gmloop.serverPath with the fixed lsp argument.

Active LSP Development In VSCode

For active LSP development, install the VSIX once, keep gmloop.serverPath pointed at your local compiled CLI, run pnpm run build:ts, then restart the language server in VSCode.

Use this loop when editing the language server or the workspaces it delegates to:

pnpm run build:ts

Then run this command from VSCode's Command Palette:

GMLoop: Restart Language Server

The VSCode extension is a thin client and does not bundle the LSP implementation, so rebuilding and restarting the server is enough for normal LSP changes. Rebuild and reinstall the VSIX only when the VSCode extension workspace itself changes.

The extension does not currently auto-refresh after GMLoop code changes. Automatic refresh would need a development-only watcher that rebuilds the repository and asks the VSCode client to restart the language server.

Using With lsp-mcp-server

lsp-mcp-server is an MCP bridge. It should launch gmloop-lsp as the language server instead of GMLoop duplicating LSP tools inside the GMLoop MCP server.

Example MCP configuration:

{
  "mcpServers": {
    "lsp": {
      "command": "lsp-mcp-server",
      "env": {
        "LSP_LOG_LEVEL": "info"
      }
    }
  }
}

Configure the bridge's language-server catalog in .lsp-mcp.json or lsp-mcp.json so .gml files use:

{
  "servers": [
    {
      "id": "gml",
      "extensions": [".gml"],
      "languageIds": ["gml"],
      "command": "gmloop-lsp",
      "args": []
    }
  ]
}

GMLoop MCP and GMLoop LSP are companion surfaces: MCP exposes agent workflows, while LSP exposes editor-style code intelligence that MCP bridges can consume.