How do I change variable on outgoing request without updating cache


I’m using a Link to parse a field for responses and requests. Specifically, the field is a JSON string. When data is fetched, the Link calls JSON.parse() on that field and sets it on the same field. This works, and I can work with the field in my app as a JS object. When saving that field, the Link calls JSON.stringify() and sets it as the same key on operation.variables. The server accepts this, however, the problem is this also updates the cache with the stringified field. What’s the best way to change the outgoing request without modifying the cache?