[BUG] `*/list` MCP requests sent before `notifications/initialized` response.

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Can see in our remote MCP server logs that Claude AI sometimes sends tools/list and other list requests before getting notifications/initialized. Both X-Request-Start header and start processing timestamp of notification request are greater than ones of list requests.

When having a server implemented with FastMCP, in accordance with server specs it leads to an error https://github.com/jlowin/fastmcp/issues/1213.

What Should Happen?

According to MCP specification, notifications/initialized should be finished before sending any other requests.

Error Messages/Logs

Steps to Reproduce

I didn't manage to get a minimal reproducible example with "connectors", but once got this issue with Claude Desktop + mcp-remote. In mcp.log can see tools/list being sent right after notifications/initialized, without waiting for the response:

2025-10-02T15:46:58.546Z [bigquery-dev] [info] Message from client: {"method":"notifications/initialized","jsonrpc":"2.0"} { metadata: undefined }
2025-10-02T15:46:58.547Z [bigquery-dev] [info] Message from client: {"method":"tools/list","params":{},"jsonrpc":"2.0","id":1} { metadata: undefined }

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 0.13.37 (bfd4ed) 2025-09-24T22:18:50.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_