Data Action returns undefined despite 200 OK and valid JSON payload

I’ve got a Data Action calling an internal endpoint to fetch customer tenure. The HTTP status is 200 and the response body is valid JSON.

{"years": 5, "status": "active"}

The mapping uses $.years for the output field. Architect shows the step succeeds, but the variable comes back as undefined downstream. I’ve tried response.body.years and $.years in the mapping. Both fail. Is there a specific way to parse the JSON body in the success output configuration?