ChatGPT throws away the standard MCP session on every tool call. But it carries its own session ID inside the JSON-RPC body, in a place no header-based proxy can see. Here's where it lives, why OpenAI put it there, and how mcpr surfaces it.
I caught ChatGPT and Claude red-handed using the same MCP server completely differently. One creates a fresh session per tool call. The other reuses one. Here's the data from the proxy dashboard, and why it matters for every MCP server developer.
Your MCP App widget loads a blank iframe. No error. No hint. Here's exactly what's happening: the five CSP domain arrays, the mistakes that break your widget, and how to debug them.
MCPR is an open-source, MCP-aware reverse proxy that fixes CSP issues, handles auth, and observes every tool call, so you can ship MCP apps without the infrastructure headaches.
