Sorry for the confusing response before, was short on time. Here are some more details for you.
That error message is expected with the proxy disabled, since the designer/console is a client-side application. We don't enable CORS by default on the mocking service because it is an implementation decision at the API level, and we endeavor to respect your API definition when mocking it.
To make it work, you have two options. You will need to either supply your own proxy that can be reached by the local copy of API Designer, or put CORS headers into your RAML file as part of your response definitions for methods you'd like accessible via CORS.
CORS support can be added to any API by returning the
Access-Control-Allow-Origin header, with either a wildcard value or a specific domain you want to provide CORS access for. In the example below, the
Access-Control-Allow-Origin header will be mocked and return the example value provided for any 200 response for a POST to /example, which allows that resource and method to be accessed via CORS. You can simplify this and avoid repetition across multiple methods by leveraging Traits and ResourceTypes to establish a responses pattern and re-use it.
title: "CORS Example"
I just tested mocking the above with the API Designer and a disabled proxy, and it worked as expected, so I hope this helps unblock you!
edit: @Eric_Price This should answer your previously un-answered question on CORS support! Sorry I missed that one initially.