Architect Data Action success output returning undefined despite 200 OK

I’m hitting a wall with a custom Data Action in Architect. We’re making a simple GET request to an internal microservice to fetch user preferences. The HTTP call succeeds with a 200 status, and the response body is definitely JSON.

Here’s the response payload we’re getting back:

{
 "status": "success",
 "data": {
 "theme": "dark",
 "lang": "en"
 }
}```

The issue is the output mapping. I've tried mapping `theme` to `$.data.theme` and just `$.theme`. Both result in `undefined` in the success output block. The documentation says the root object is passed in, so `$.data` should work. 

We've checked the logs. The external service is returning `Content-Type: application/json`. I even tried wrapping the response in a dummy object on the service side just to test, but the Data Action still fails to parse it. 

Is there a known quirk with how Architect handles nested objects in Data Action responses? Or am I missing a specific configuration step in the output mapping UI? The error log just says 'Output variable not set' which isn't helpful. 

We're on the latest platform version. Any pointers?