.github/lsp.json and .github/mcp.json do not work

[leymbda]

Describe the bug

I have the following .github/lsp.json:

{
  "lspServers": {
    "fsautocomplete": {
      "command": "dotnet",
      "args": ["fsautocomplete", "--stdio"],
      "fileExtensions": {
        ".fs": "fsharp",
        ".fsx": "fsharp"
      }
    }
  }
}

and .github/mcp.json:

{
  "mcpServers": {
    "mslearn-mcp": {
      "type": "http",
      "url": "https://learn.microsoft.com/api/mcp",
      "headers": {},
      "tools": ["*"]
    }
  }
}

When I run copilot from the project root, neither of these work.

If I use these exact same configs in .copilot/lsp-config.json and .copiloty/mcp-config.json they do work, and if I explicitly say --additional-mcp-config @.github/mcp.json it also works. Moving the mcp config to .mcp.json at the project root also gets picked up.

You will also notice that the fsautocomplete lsp is being detected (so clearly its finding the file) yet its missing a word in the format, which you can see in this example where I have it working in copilot config but failing in github config (in this case attempting to use fsautocomplete directly as a globally installed dotnet tool instead of a local one via dotnet fsautocomplete:

Affected version

GitHub Copilot CLI 1.0.2

Steps to reproduce the behavior

1. Copy above json snippets into their respective files in a .github directory
2. Launch copilot cli with copilot from the directory above
3. Use /lsp test fsautocomplete and inspect /mcp show to see the problem occurring

Expected behavior

These files are documented as though they should work as is. Intended behaviour is the lsp starting up successfully and the mslearn mcp connecting as normal.

Additional context

I have attempted this on Windows, Debian WSL, and an Ubuntu based image in a Github Codespace, and all behave the same.

[leymbda]

#1323 and #1373 seem to be experiencing this issue as well with other LSPs running older versions of copilot, but this is still an issue in this 1.0.2 release

[jtrenaud1s]

Also having exact same issue in 1.0.5 release trying to use typescript-language-server

{
  "lspServers": {
    "typescript": {
      "command": "npx",
      "args": ["typescript-language-server", "--stdio"],
      "fileExtensions": {
        ".ts": "typescript",
        ".tsx": "typescriptreact",
        ".js": "javascript",
        ".jsx": "javascriptreact"
      }
    }
  }
}

LSP Server Status:


  Project-configured servers:
    • typescript: (.ts, .tsx, .js, .jsx)

  User config: C:\Users\xxxxxx\.copilot\lsp-config.json
  Project config: C:\Users\xxxxxx\projects\xxxxxx\.github\lsp.json

✗ Server "typescript" not found. Available: (none)

[sea-st]

Reproduced on Copilot CLI 1.0.9 on Windows / PowerShell 7 with typescript-language-server.

With this server defined only in .github/lsp.json, /lsp correctly shows the project-configured typescript server, but /lsp test typescript fails with:

✗ Server "typescript" not found. Available: (none)

I also tested whether the issue was just a missing user config file. It is not:

• no user config: fails
• user config present but empty ({ "lspServers": {} }): still fails
• same typescript server duplicated into C:\Users\<user>\.copilot\lsp-config.json: succeeds immediately

✓ Server "typescript" started successfully!

So the bug seems narrower than "project config not detected": /lsp status can see .github/lsp.json, but /lsp test <name> appears not to resolve servers from the same effective config set.

This looks like a config lookup / merge inconsistency between the status path and the /lsp test execution path.