New release v0.3.0 breaking connectivity

[silvercondor]

Using this mcp via claude code

"staging-elastic": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@elastic/mcp-server-elasticsearch"         // using @elastic/mcp-server-elasticsearch@v0.2.0 works 
      ],
      "env": {
        "ES_URL": "https://localhost:9200",
        "ES_API_KEY": "KEY",
        "NODE_TLS_REJECT_UNAUTHORIZED": "0",
        "ES_VERSION": "8"
      }
    },

logs

[DEBUG] MCP server "staging-elastic": Connection failed: McpError: MCP error -32000: Connection closed
[DEBUG] MCP server "staging-elastic": Error message: MCP error -32000: Connection closed
[DEBUG] MCP server "staging-elastic": Error stack: McpError: MCP error -32000: Connection closed
    at Xn1._onclose (file:///home/user/.nvm/versions/node/v20.19.1/lib/node_modules/@anthropic-ai/claude-code/cli.js:1333:14912)
    at _transport.onclose (file:///home/user/.nvm/versions/node/v20.19.1/lib/node_modules/@anthropic-ai/claude-code/cli.js:1333:14231)
    at ChildProcess.<anonymous> (file:///home/user/.nvm/versions/node/v20.19.1/lib/node_modules/@anthropic-ai/claude-code/cli.js:1335:1444)
    at ChildProcess.emit (node:events:524:28)
    at ChildProcess.emit (node:domain:489:12)
    at maybeClose (node:internal/child_process:1104:16)
    at ChildProcess._handle.onexit (node:internal/child_process:304:5)

[eggdev]

+1 to this happening using my remote/managed elastic server as of this 0.3.0 version

[radoondas]

+1, this is happening since the 0.3.0 was released. In my logs I can see many messages about incorrect JSON structure. I am using Claude desktop client (Claude 0.11.6 (0aa9ce) 2025-06-29T21:59:05.000Z) on MacOS (15.5).

...
...
...
2025-07-01T12:30:49.332Z [elasticsearch-mcp-server] [error] Unexpected token 's', "specify a "... is not valid JSON {
  metadata: {
    context: 'connection',
    stack: `SyntaxError: Unexpected token 's', "specify a "... is not valid JSON\n` +
      '    at JSON.parse (<anonymous>)\n' +
      '    at bqe (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:206)\n' +
      '    at _qe.readMessage (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:133)\n' +
      '    at GK.processReadBuffer (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:2098)\n' +
      '    at Socket.<anonymous> (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:1652)\n' +
      '    at Socket.emit (node:events:518:28)\n' +
      '    at addChunk (node:internal/streams/readable:561:12)\n' +
      '    at readableAddChunkPushByteMode (node:internal/streams/readable:512:3)\n' +
      '    at Readable.push (node:internal/streams/readable:392:5)\n' +
      '    at Pipe.onStreamRead (node:internal/stream_base_commons:189:23)'
  }
}
2025-07-01T12:30:49.332Z [elasticsearch-mcp-server] [error] Unexpected token 'o', "format name"... is not valid JSON {
  metadata: {
    context: 'connection',
    stack: `SyntaxError: Unexpected token 'o', "format name"... is not valid JSON\n` +
      '    at JSON.parse (<anonymous>)\n' +
      '    at bqe (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:206)\n' +
      '    at _qe.readMessage (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:133)\n' +
      '    at GK.processReadBuffer (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:2098)\n' +
      '    at Socket.<anonymous> (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:1652)\n' +
      '    at Socket.emit (node:events:518:28)\n' +
      '    at addChunk (node:internal/streams/readable:561:12)\n' +
      '    at readableAddChunkPushByteMode (node:internal/streams/readable:512:3)\n' +
      '    at Readable.push (node:internal/streams/readable:392:5)\n' +
      '    at Pipe.onStreamRead (node:internal/stream_base_commons:189:23)'
  }
}
2025-07-01T12:30:49.332Z [elasticsearch-mcp-server] [error] Unexpected token 'h', "the filenam"... is not valid JSON {
  metadata: {
    context: 'connection',
    stack: `SyntaxError: Unexpected token 'h', "the filenam"... is not valid JSON\n` +
      '    at JSON.parse (<anonymous>)\n' +
      '    at bqe (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:206)\n' +
      '    at _qe.readMessage (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:133)\n' +
      '    at GK.processReadBuffer (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:2098)\n' +
      '    at Socket.<anonymous> (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:1652)\n' +
      '    at Socket.emit (node:events:518:28)\n' +
      '    at addChunk (node:internal/streams/readable:561:12)\n' +
      '    at readableAddChunkPushByteMode (node:internal/streams/readable:512:3)\n' +
      '    at Readable.push (node:internal/streams/readable:392:5)\n' +
      '    at Pipe.onStreamRead (node:internal/stream_base_commons:189:23)'
  }
}
2025-07-01T12:30:49.332Z [elasticsearch-mcp-server] [error] Unexpected token 's', "standard i"... is not valid JSON {
  metadata: {
    context: 'connection',
    stack: `SyntaxError: Unexpected token 's', "standard i"... is not valid JSON\n` +
      '    at JSON.parse (<anonymous>)\n' +
      '    at bqe (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:206)\n' +
      '    at _qe.readMessage (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:187:133)\n' +
      '    at GK.processReadBuffer (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:2098)\n' +
      '    at Socket.<anonymous> (/Applications/Claude.app/Contents/Resources/app.asar/.vite/build/index-BV1dxcNB.js:188:1652)\n' +
      '    at Socket.emit (node:events:518:28)\n' +
      '    at addChunk (node:internal/streams/readable:561:12)\n' +
      '    at readableAddChunkPushByteMode (node:internal/streams/readable:512:3)\n' +
      '    at Readable.push (node:internal/streams/readable:392:5)\n' +
      '    at Pipe.onStreamRead (node:internal/stream_base_commons:189:23)'
  }
}
2025-07-01T12:30:49.337Z [elasticsearch-mcp-server] [info] Server transport closed { metadata: undefined }
2025-07-01T12:30:49.337Z [elasticsearch-mcp-server] [info] Client transport closed { metadata: undefined }
2025-07-01T12:30:49.338Z [elasticsearch-mcp-server] [info] Server transport closed unexpectedly, this is likely due to the process exiting early. If you are developing this MCP server you can add output to stderr (i.e. `console.error('...')` in JavaScript, `print('...', file=sys.stderr)` in python) and it will appear in this log. { metadata: undefined }
2025-07-01T12:30:49.338Z [elasticsearch-mcp-server] [error] Server disconnected. For troubleshooting guidance, please visit our [debugging documentation](https://modelcontextprotocol.io/docs/tools/debugging) { metadata: { context: 'connection', stack: undefined } }
2025-07-01T12:30:49.338Z [elasticsearch-mcp-server] [info] Client transport closed { metadata: undefined }

[JoshMock]

0.3.1 has been published to npm with this fixed.