mcp/playwright error - "npx" not a valid command

[Harvester62]

Which version of LM Studio?
LM Studio 0.3.34 (build 1)

Which operating system?
Windows 11 Pro 25H2 26200.7171

What is the bug?
The Playwright MCP plugin doesn't load due to the "npx" not being recognized as a valid command.

Screenshots

Logs
2025-12-13 00:39:04 [ERROR]
[Plugin(mcp/playwright)] stderr: "npx" non � riconosciuto come comando interno o esterno,
un programma eseguibile o un file batch.
2025-12-13 00:39:04 [ERROR]
[Plugin(mcp/playwright)] stderr: Error in LM Studio MCP bridge process: _0x6483 [McpError]: MCP error -32000: Connection closed
at _0xea4460._onclose (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:237914)
at . [as onclose] (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:236691)
at ChildProcess. (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:211822)
at ChildProcess.emit (node:events:519:28)
at _0x1caee0. [as emit] (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:1:191158)
at maybeClose (node:internal/child_process:1105:16)
at ChildProcess._handle.onexit (node:internal/child_process:305:5) {
code: -32000,
data: undefined
}
2025-12-13 00:39:04 [ERROR]
[Plugin(mcp/playwright)] stderr: _0x6483 [McpError]: MCP error -32000: Connection closed
at _0xea4460._onclose (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:237914)
at . [as onclose] (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:236691)
at ChildProcess. (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:211822)
at ChildProcess.emit (node:events:519:28)
at _0x1caee0. [as emit] (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:1:191158)
at maybeClose (node:internal/child_process:1105:16)
at ChildProcess._handle.onexit (node:internal/child_process:305:5) {
code: -32000,
data: undefined
}

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

[Harvester62]

Updated to v 0.3.35 (build 1), same behaviour.

[curious-city]

I had a similar issue until I figured out that MCP needs Node.js installed for it to work in LM Studio: https://nodejs.org/en/download
After install and restart of LM Studio it works just fine. But I have no idea if that helps you as well.

[Harvester62]

Thank you very much! I installed NodeJS node-v24.12.0-x64 and it fixed the problem, as per the following screenshot of the first startup of LM Studio after NodeJS installation. If this was a requirement in the installation process of LM Studio, then I should have missed it. Anyway, I also have Python 3.12.10 installed on this laptop.

And these are now the tools available for the LLM:

After reading the available documentation I must admit that perhaps those requirements might be highlighted better, as Python and NodeJS (the "npx" error what due to that) seems to be required for several MCPs to work. Anyway, thank you again @curious-city for sharing your experience.

Since this is NOT a bug of the program, and a solution has been provided, I consider this as resolved from my side.