Large code transformations are tricky. Not because we can’t describe them. Not because we can’t apply them. But because, once they run… we’re never entirely sure they did exactly what we intended. In previous articles, I introduced Dennis and DEX: Dennis generates deterministic transformation plans; DEX turns those plans into portable, inspectable artifacts That already solves a big part of the problem: 👉 transformations become visible But something was still missing: "The missing Question": Even with a plan… Even with an artifact… Even with signatures… How do you know the transformation is actually correct? Not “looks correct”. Not “probably correct”. Correct. The Problem With Traditional Diffs: We already have diffs, right? git diff has been around forever. But here’s the uncomfortable truth: Diffs are not deterministic. Two environments can produce slightly different diffs for the same change: different line endings different grouping different context different ordering They are great for humans.…