Claude Desktop: Local DXT connector tool calls never dispatched after MCP handshake (silent timeout)

[CAPN7606]

Describe the bug
Claude Desktop completely silences tool calls to local DXT connectors. After the MCP handshake completes successfully (initialize + tools/list), no tool calls are ever dispatched to the local server. Claude Desktop waits approximately 4 minutes and then returns a silent timeout — with zero tool call traffic reaching the MCP process.

This renders all local DXT connectors completely non-functional in Claude Desktop, regardless of the server implementation.

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To Reproduce

1. Configure any MCP server as a local DXT connector in Claude Desktop.
2. Monitor the MCP server process (e.g., via logs or a debugger).
3. Start a conversation in Claude Desktop and trigger any tool call.
4. Observe that the server receives initialize and tools/list — but no tool calls ever arrive.
5. After ~4 minutes, Claude Desktop returns a timeout error with no explanation.

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Expected behavior
After the MCP handshake (initialize + tools/list), tool calls invoked by Claude Desktop should be dispatched to the local MCP server and return results to the conversation normally.

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Logs
MCP server process log — shows only the handshake, no tool calls received:

[MCP Server] Received: initialize
[MCP Server] Received: tools/list  ← last message ever received
[MCP Server] ... silence ...
[Claude Desktop] Error: No result received after waiting 4 minutes. The local MCP server may be unresponsive, crashed, or not running.

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Additional context

• The exact same MCP server works correctly in Claude Code — tool calls are dispatched and return results as expected.
• The issue is 100% reproducible and independent of the MCP server implementation (tested with multiple servers).
• The problem is isolated to Claude Desktop + local DXT connectors. Remote MCP servers via URL are not affected.
• This appears to be a bug in how Claude Desktop dispatches tool calls after the initial handshake, not in the MCP server itself.