Inter-process communication in a sandboxed Mac app

Axminster—my graphical software design tool for the AI coding age—is still in beta, and it’s already been through three different technologies for inter-process communication (IPC). What gives? The reason the app needs IPC at all is to support the Model Context Protocol (MCP), which is how your LLM coding assistant reads and manipulates your diagrammatic model. I’ll start by showing you how it works now, which is that there are two components in Axminster—the app itself, and a small MCP helper tool that forwards requests to the app over a UNIX domain socket. My first attempt avoided the helper process, and relied on an HTTP server inside the Axminster app to serve MCP. This was the easiest to get going from the App Sandbox perspective, as it just means adding the incoming network connections entitlement. However, it’s pretty bad from a security perspective. Any process running locally on the Mac can connect to the server, so a different app potentially controlled by a different user…