The Parity Gate: Proving Your Rewrite Didn't Drop Anything

The silent failure mode

A rewrite rarely fails by crashing. It fails quietly: a screen that used to write an audit row now doesn't, a PII field that used to be masked now isn't, an edge case that used to be handled now falls through. You find out months later, from a customer or an auditor.

Contract in, contract out

Because CodeIQ Pro already extracted the legacy system's contract — every table written, every relationship, every PII path — it has something concrete to check the new build against.

How the gate works

The parity gate runs a graph diff between the legacy slice and its modern replacement. It asks: does the new code still write every table the old one did? Preserve every reconstructed relationship? Cover every PII path? Anything the rewrite silently dropped shows up as a failed check, with specifics.

Confidence you can ship on

Instead of "we think it's equivalent," you get "these 90 tables are all preserved and zero PII paths were dropped." That's the difference between hoping a migration is safe and knowing it is.