How to Fix RabbitMQ Management UI Breaking Behind an Nginx Reverse Proxy

Placing RabbitMQ's Management UI behind an Nginx reverse proxy under a /rabbitmq/ path causes queue detail pages and API calls to break silently. The root cause is that Nginx decodes the URL-encoded forward slash %2F into a literal slash before forwarding requests, corrupting API paths that RabbitMQ uses to reference its default virtual host. Common fixes like merge_slashes off or rewrite directives fail because they still operate on the decoded $uri variable. The solution is to use $request_uri inside an if block for API location blocks, since this variable preserves the raw, undecoded URI exactly as the client sent it. Static assets and general UI routes can be handled separately with a standard rewrite-based proxy block that does not require raw URI preservation.