[BUG] Claude Desktop: custom connector intermittently disappears from "+" menu; reconnect restores tools list but tools/call silently fails with no traffic reaching server

Preflight Checklist

• [x] I have searched existing issues
• [x] Single bug report
• [x] Using latest version of Claude Desktop

What's Wrong?

Operating an OAuth 2.1 / Streamable HTTP MCP server (Memory Store, memory.store, FastMCP) that works correctly in Claude Code CLI and Claude.ai web. Two recurring Desktop-only failure modes since at least April 2026 and still reproducing as of May 2026:

1. Connector disappears from the chat composer "+" menu. The Connectors settings screen still lists the connector, but shows "This connector has no tools available."
2. Disconnect/reconnect restores the tool list, but the first tools/call fails. After reconnecting, the tools are listed correctly on the settings screen and the connector reappears in the "+" menu, but invoking any tool produces Unable to reach Memory Store.

What Should Happen?

Once the connector is connected and tools/list succeeds, subsequent tools/call requests should be dispatched to the server, the same way they are by Claude Code CLI and Claude.ai web against the identical URL.

Key Evidence (client-side, not server-side)

• During the failed tools/call, zero traffic reaches the server — no auth attempt, no request, no entry in access logs.
• The initialize and tools/list exchange at reconnect time arrives normally and succeeds.
• The same server backend is exercised continuously by Claude Code CLI (claude mcp add --transport http) and Claude.ai web with no failures.
• Toggling the connector off and on is a temporary workaround for the visibility issue but does not stop the next tools/call from failing.

Related

• #5826 (open, OAuth 2.1 / Custom MCP, no requests reach server)
• #22299 (closed COMPLETED, Windows + stdio — likely same shape, remote OAuth path possibly still affected)
• #23736 (closed COMPLETED, Granola Streamable HTTP — same transport family)
• #14807 (closed stale, "tools not available despite successful connection")
• #38343 (closed invalid, Asana — "connected but tools never load")

Environment

• Client: Claude Desktop (macOS)
• Server: FastMCP, Streamable HTTP transport, OAuth 2.1 (Descope)
• URL: https://mcp.memory.store/
• Other clients verified working: Claude Code CLI, Claude.ai web