A new request often exposes rules that were always present but never tested together in the old workflow.

The practical check

Treat a surprising failure as a question about the underlying model: what assumption did the new feature force into view?

Where AI fits

AI can trace a new failure back to previously untested assumptions or invariants and prepare the questions that would test whether those assumptions still hold.

The human decision

People decide which assumption to change and verify that the repair does not break other valid cases.

The lesson

A new feature is useful evidence when it exposes an old assumption that needs to be tested against the full range of valid work.

That feature-triggered invariant check is worked through in the Build Log companion.