Recover a drifting system

Zero Drift builds an executable equivalence boundary first, lands the replacement behind it and keeps a rollback net until the evidence says the old path can retire.

Change without amnesia

A refactor fails when the old system’s behaviour exists only in people’s heads. We capture that behaviour as observations, build an equivalence boundary and make divergence visible before replacing the path underneath it.

The delivery shape

Stabilise first. Measure the current behaviour. Land the new route behind the same boundary. Keep rollback live until the census says the replacement holds.

Architecture Review finds the structural risk. Technical Recovery / Refactor lands the change. Verification Harness Build keeps it honest.