oraios/serena · error · RuntimeError

Failed to locate or download MATLAB Language Server. Please

Error message

Failed to locate or download MATLAB Language Server. Please either:
1. Set MATLAB_EXTENSION_PATH environment variable to the MATLAB extension directory
2. Install the MATLAB extension in VS Code (MathWorks.language-matlab)
3. Ensure internet connection for automatic download

What it means

After checking disk locations and attempting an automatic download, create_launch_command gives up if no MATLAB extension directory could be obtained. The error enumerates the three supported ways to supply the extension: env var, VS Code install, or network download.

Source

Thrown at src/solidlsp/language_servers/matlab_language_server.py:341

            log.info(f"Using MATLAB installation: {matlab_path}")

            self._matlab_path = matlab_path
            return matlab_path

        def create_launch_command(self) -> list[str]:
            # Verify node is installed
            node_path = shutil.which("node")
            if node_path is None:
                raise RuntimeError("Node.js is not installed or isn't in PATH. Please install Node.js and try again.")

            # Find existing extension or download if needed
            extension_path = self._find_matlab_extension()
            if extension_path is None:
                log.info("MATLAB extension not found on disk, attempting to download...")
                extension_path = self._download_and_install_matlab_extension()

            if extension_path is None:
                raise RuntimeError(
                    "Failed to locate or download MATLAB Language Server. Please either:\n"
                    "1. Set MATLAB_EXTENSION_PATH environment variable to the MATLAB extension directory\n"
                    "2. Install the MATLAB extension in VS Code (MathWorks.language-matlab)\n"
                    "3. Ensure internet connection for automatic download"
                )

            # Get the language server script path
            server_script = self._get_executable_path(extension_path)

            if not os.path.exists(server_script):
                raise RuntimeError(f"MATLAB Language Server script not found at: {server_script}")

            # Build the command to run the language server
            # The MATLAB language server is run via Node.js with the --stdio flag
            cmd = [node_path, server_script, "--stdio"]
            return cmd

        def create_launch_command_env(self) -> dict[str, str]:

View on GitHub (pinned to 7fcbca7e62)

Solutions

1. Set MATLAB_EXTENSION_PATH to the directory of the MathWorks.language-matlab extension
2. Install the MATLAB extension in VS Code so it exists on disk under ~/.vscode/extensions
3. Restore network access to the extension download host and retry the automatic download

Example fix

# before
# nothing set, no extension installed
# after
export MATLAB_EXTENSION_PATH=~/.vscode/extensions/MathWorks.language-matlab-1.4.0

import os
def ensure_matlab_extension():
    ext = os.environ.get("MATLAB_EXTENSION_PATH")
    if ext and os.path.isdir(ext):
        return ext
    vscode_ext = os.path.expanduser("~/.vscode/extensions")
    if os.path.isdir(vscode_ext):
        for d in os.listdir(vscode_ext):
            if d.startswith("MathWorks.language-matlab"):
                return os.path.join(vscode_ext, d)
    raise RuntimeError("Install MathWorks.language-matlab or set MATLAB_EXTENSION_PATH")

def extension_located() -> bool:
    ext = os.environ.get("MATLAB_EXTENSION_PATH")
    return bool(ext) and os.path.isdir(ext)

try:
    ls = SolidLSP("matlab")
except RuntimeError as e:
    if "Failed to locate or download MATLAB Language Server" in str(e):
        install_vscode_matlab_extension()  # fallback path
        ls = SolidLSP("matlab")
    else:
        raise

When it happens

Trigger: create_launch_command finds no extension via _find_matlab_extension (MATLAB_EXTENSION_PATH unset/invalid and no MathWorks.language-matlab in VS Code extensions dirs) and _download_and_install_matlab_extension also returns None (download failed or network blocked).

Common situations: Offline/air-gapped machines; GitHub/marketplace downloads blocked by firewall; MATLAB_EXTENSION_PATH typo'd; VS Code not installed so no extensions directory exists; corrupted download leaving no usable directory.

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AI-assisted analysis of oraios/serena@7fcbca7e62 (2026-08-29). Data as JSON: /api/errors/868f65fe311737de. Report an issue: GitHub.