Nobody documented the operation. How do we regress it before cutover?

The process we want to peel off was never specified. How do we know the new service matches what the host does today?

Identify and save the operation first. AtomIQ can exercise it, record the answers, and write a regression suite, unit tests, and a spec you own. Use that baseline before you cut the process over. The suite is evidence of current behavior. It is not a promise that the new service should copy every quirk.