If you use Paper as your MCP server and develop inside a Docker-based dev container (VS Code Dev Containers, Cursor, or any devcontainer-compatible editor), you've probably hit this frustrating wall:

Failed to reconnect to plugin:paper-desktop:paper: ECONNRESET

Your MCP client inside the container tries to reach 127.0.0.1:29979 , but that address points to the container's own loopback — not your host machine where Paper is actually running. This article walks through the exact solution.

Why This Happens

When you run a dev container, your development environment lives inside a Docker container. Your .mcp.json file correctly points to http://127.0.0.1:29979/mcp — and that works fine when running tools directly on the host.…