VSCode hangs at "Waiting for server to respond to initialize" with nuxt-mcp server

[blouflashdb]

Describe the bug

When launching the nuxt app with the nuxt-mcp module, the output logs show that the server starts successfully, but VSCode never receives a response to the LSP initialize request.

Reproduction

https://github.com/blouflashdb/nuxt-mcp-reproduction

System Info

System:
    OS: Windows 11 10.0.22631
    CPU: (16) x64 11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz
    Memory: 18.30 GB / 31.73 GB
Binaries:
    Node: 24.0.1
    npm: 11.3.0

Version: 1.101.0-insider (user setup)
Commit: 747d0bd66a4699a53e720cf7a61dcd10f664e667
Date: 2025-05-23T06:35:04.132Z
Electron: 35.4.0
ElectronBuildId: 11602177
Chromium: 134.0.6998.205
Node.js: 22.15.0
V8: 13.4.114.21-electron.0

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A, please open a GitHub Discussion instead.
• The provided reproduction is a minimal reproducible of the bug.

Contributions

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests (actually just go ahead and do it, thanks!)

[antfu]

Can you double-check if that happens at other editors or tools as well? If not, I think it's most likely the issue of VS Code

[blouflashdb]

Works in the MCP Inspector. I also think its most likely a bug in VSCode.

[blouflashdb]

Your MCP server:

1. Only supports the legacy SSE strategy for connection
2. Responds to POST requests to the MCP endpoint with a legacy SSE stream. SSE should only be served as GET. Because POST works, we asssume the server supports Streamable HTTP.

The fix for this is to have your server return an appropriate status code (405) when trying to post to your SSE endpoint. Or update to streamable HTTP.

microsoft/vscode#246753 (comment)

I think this package should be updated to use streamable HTTP as right now it uses legacy SSE.

[DefinitelyMaybe]

works with vscode insiders so most likely will be sorted in next stable release