mcp-remote: Write operations hang intermittently while read operations work fine

[holger539]

Description

When using mcp-remote as a bridge between Claude Desktop and a local MCP server (Tana Local API at http://localhost:8262/mcp), write operations (import_tana_paste) hang intermittently — the loading spinner runs indefinitely with no error, no timeout, and no result. Read operations (list_workspaces, search_nodes, read_node) on the same server work fine at the same time.

Key evidence: Direct HTTP works, mcp-remote doesn't

• Claude Code connects directly via HTTP transport to the same Tana Local API → import_tana_paste always works
• Claude Desktop must go through mcp-remote → import_tana_paste hangs sporadically

Same server, same operation, same payload size — the only difference is the mcp-remote bridge layer.

Environment

• mcp-remote 0.1.38 (pinned)
• macOS (Darwin 25.3.0)
• Claude Desktop (latest)
• MCP server: Tana Local API (http://localhost:8262/mcp)

Config

{
  "tana-desktop": {
    "command": "/opt/homebrew/bin/npx",
    "args": ["-y", "mcp-remote@0.1.38", "http://localhost:8262/mcp"],
    "env": {
      "PATH": "/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
    }
  }
}

Reproduction

• Not reliably reproducible — happens sporadically
• Small payloads (single node import) also affected
• Read operations on the same connection continue to work when writes hang
• Occurs across restarts and reinstalls of Claude Desktop

Workaround

• Claude Desktop Reload (View → Reload) fixes it temporarily
• Deleting stale lock files in ~/.mcp-auth/mcp-remote-*/ sometimes helps (lock files with dead PIDs block new connections)
• Migrating auth cache after silent version updates helps for that specific failure mode

Related issues

This may be related to SSE connection handling in mcp-remote. The connection appears to go stale silently for write operations while maintaining enough state for reads to continue working. No timeout error is ever thrown — the client just waits indefinitely.

[KKonstantinov]

Please provide a reproduction with the @modelcontextprotocol/sdk package and open a new issue if there is such.