[BUG] MCP stdio server notifications/tools/list_changed does not refresh the tool catalog mid-session

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?

Environment: Claude Code VS Code extension · model claude-opus-4-8 · stdio MCP server (custom Node bridge)

Summary: When a connected stdio MCP server emits notifications/tools/list_changed during a session, the newly advertised tools do not become available for invocation. The same tools are picked up if they're present in tools/list at (re)connection time.

Impact: Breaks dynamic MCP tool catalogs — e.g. a bridge that exposes context-scoped tools after an attach/handshake step. The server correctly merges the tools into tools/list and emits the spec'd notification, but they remain unreachable.

Verified server-side: the bridge emits notifications/tools/list_changed and includes the new tools in subsequent tools/list responses; the standard MCP listChanged capability flow.

What Should Happen?

Client re-issues tools/list, and the B tools become callable within the session.

Error Messages/Logs

Steps to Reproduce

• Connect a stdio MCP server that initially returns catalog A from tools/list.
• Mid-session, the server adds tools (catalog A+B) and emits notifications/tools/list_changed on stdout.
• Ask the model to use a tool from B.

The B tools never become callable (not surfaced as available, not findable). Only a full reconnect (fresh initialize → tools/list) exposes them — which is unusable when the new tools depend on session state established after connect (so they can't be in the initial list).

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.165

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_