copilot lsp process crashes when containing package.json type is module

[alexjball]

Describe the bug

Related to #4263 (comment), but I think that issue is about the marimo lsp "launcher", which based on ps -ef is using a cjs file. This issue is with the copilot language server itself, which runs as node /home/foo/.venv/lib/python3.12/site-packages/marimo/_lsp/copilot/language-server.js --stdio

When there is a package.json with "type": "module" in the parent folder of the .venv running marimo, the copilot process crashes silently. The lsp logs just show dropped connections:

# ~/.cache/marimo/logs/github-copilot-lsp.log
[INFO] Parsed LSP command: node /home/foo/.venv/lib/python3.11/site-packages/marimo/_lsp/copilot/language-server.js --stdio
[INFO] New connection from ::ffff:127.0.0.1
[INFO] WebSocket closed with code 1005: 

When I run the language server directly I get the actual error:

❯ node /home/foo/.venv/lib/python3.11/site-packages/marimo/_lsp/copilot/language-server.js --version
file:///home/foo/.venv/lib/python3.11/site-packages/marimo/_lsp/copilot/language-server.js:23
require('./main').main();
^

ReferenceError: require is not defined in ES module scope, you can use import instead
This file is being treated as an ES module because it has a '.js' file extension and '/home/foo/package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.
    at file:///home/foo/.venv/lib/python3.11/site-packages/marimo/_lsp/copilot/language-server.js:23:1
    at ModuleJob.run (node:internal/modules/esm/module_job:377:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:689:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:101:5)

Node.js v24.9.0

removing "type": "module" from my workspace package.json fixes it but the lsp should not be dependent on the containing folder.

Other errors also cause silent failures, such as a misformatted package.json. So ideally the fix isolates the lsp process and bubbles crashes up to the lsp or marimo logs.

Will you submit a PR?

• Yes

Environment

{
  "marimo": "0.16.5",
  "editable": false,
  "location": "/home/foo/.venv/lib/python3.11/site-packages/marimo",
  "OS": "Linux",
  "OS Version": "6.8.0-85-generic",
  "Processor": "x86_64",
  "Python Version": "3.11.13",
  "Locale": "en_US",
  "Binaries": {
    "Browser": "140.0.7339.207",
    "Node": "v24.9.0"
  },
  "Dependencies": {
    "click": "8.3.0",
    "docutils": "0.22.2",
    "itsdangerous": "2.2.0",
    "jedi": "0.19.2",
    "markdown": "3.9",
    "narwhals": "2.7.0",
    "packaging": "25.0",
    "psutil": "7.1.0",
    "pygments": "2.19.2",
    "pymdown-extensions": "10.16.1",
    "pyyaml": "6.0.3",
    "starlette": "0.48.0",
    "tomlkit": "0.13.3",
    "typing-extensions": "4.15.0",
    "uvicorn": "0.35.0",
    "websockets": "15.0.1"
  },
  "Optional Dependencies": {
    "loro": "1.8.1"
  },
  "Experimental Flags": {}
}

Code to reproduce

mkdir tmp
cd tmp
# confirm that this does not have "type": "module"
npm init -y
uv init
uv add marimo
uv run marimo edit scratch.py

set up copilot and observe that it connects.

Now edit package.json and set "type": "module" then rerun uv run marimo edit scratch.py. Observe in the browser that you get a connection error after 5-10 seconds.

[mscolnick]

Thanks for pointing this out. Likely a newer version of node since now it supports esm and cjs. We will update this on our end to properly update the extension