Connect GitHub Copilot in VS Code to Semlith over MCP

How to connect GitHub Copilot in VS Code to Semlith over MCP, the command or file that adds it, and how to check the connection works.

Every stanza writes ${SEMLITH_BIN} where the binary goes, the path which semlith prints. Set up your agent client explains it and the HTTP form.

GitHub Copilot in VS Code — .vscode/mcp.json for a workspace, or the profile copy that MCP: Open User Configuration opens. The root key is servers, not mcpServers. The JSON below is the per-project workspace file, so it is not written for you; the CLI covers every workspace. code --add-mcp has no scope flag and needs none: it saves into the user profile’s mcp.json, which every workspace sees (https://code.visualstudio.com/docs/agent-customization/mcp-servers).

{
  "servers": {
    "semlith": {
      "type": "http",
      "url": "http://127.0.0.1:7365/mcp",
      "headers": { "Authorization": "Bearer ${SEMLITH_AGENT_KEY}" }
    }
  }
}

code --add-mcp '{"name":"semlith","type":"http","url":"http://127.0.0.1:7365/mcp","headers":{"Authorization":"Bearer ${SEMLITH_AGENT_KEY}"}}'

code --add-mcp '{"name":"semlith","command":"${SEMLITH_BIN}","args":["mcp"]}'

code is on PATH after a Linux or Windows install (code.cmd on Windows), and on macOS only after Shell Command: Install ‘code’ command in PATH. Without it, semlith setup --register-all writes the profile’s mcp.json directly, at the path for your system:

{
  "servers": {
    "semlith": {
      "type": "stdio",
      "command": "${SEMLITH_BIN}",
      "args": ["mcp"]
    }
  }
}

~/.config/Code/User/mcp.json (Linux)

{
  "servers": {
    "semlith": {
      "type": "stdio",
      "command": "${SEMLITH_BIN}",
      "args": ["mcp"]
    }
  }
}

%APPDATA%\Code\User\mcp.json (Windows)

{
  "servers": {
    "semlith": {
      "type": "stdio",
      "command": "${SEMLITH_BIN}",
      "args": ["mcp"]
    }
  }
}

With your own model key (BYOK) and no GitHub sign-in, Copilot Chat also needs chat.utilitySmallModel pointed at one of your own models; the registration alone is not enough.