TL;DR: I built Boundary-First Engineering around one annoying question: who verifies the code when AI wrote the checks too? My answer is boundaries, contracts, and evidence that came from outside the implementation loop. I still want agents writing code, I just don't want them grading the final exam.

I watched an agent add a feature, write the tests, fix the failures, and hand me a clean pull request before my coffee cooled.

The diff looked normal. Coverage went up. CI passed. A reviewer could feel the familiar click: green checks, sane code, ship it.

That click is the problem.

I do not think AI coding agents are just faster autocomplete. They have moved the bottleneck from writing code to trusting code. My thesis is simple: in the agentic era, verification has to become boundary-first, because anything generated and checked inside the same implementation loop is vulnerable to circular validation.

Circular validation is the phrase I want stuck in your head.…