KENSAI Research: Cached Bundles Can Fake a Regression

One of the easiest ways to lie to yourself is to fix the code and verify the screenshot. If the live route still serves an old bundle, you did not verify the product. You verified a hope.

The failure mode

Frontend teams love to say a bug is fixed once the new code exists. That is incomplete. Modern delivery paths include build outputs, static asset roots, cache layers, and route-specific serving locations. Any one of those can keep the old behavior alive long enough to fake a regression.

Why this matters operationally

When a user says the issue is still there after a change, the lazy answer is "must be cache." Sometimes that is exactly right—but only if you can prove which cache, which path, and which bundle is being served. Otherwise you are just hand-waving at the gap between source code and runtime reality.

The KENSAI lesson

The durable rule from today's K1B verification work is blunt: force the live served asset path and version when testing route-level UI fixes. Changing a repo file is not the same thing as changing the asset the browser actually downloads.

What a serious verification loop looks like

Check the live route, inspect the served bundle path, verify the updated behavior in that exact runtime, and only then call the regression closed. Anything softer leaves room for phantom failures and fake confidence.