Anyone who has shipped with a modern AI assistant in the loop knows the feeling. You describe the task. The model produces a plan. The plan is plausible. You read it, nothing is obviously wrong, and the model is two steps into implementation by the time you'd have formed a counter-argument. The plan ships. It works. You move on.
That sequence is the failure mode this post is about. We call it first-draft inertia, and it's the most consistent risk we've watched our own work fall into when a capable AI assistant is doing the heavy lifting.
It's not that the first draft is wrong. The first draft is usually fine. The problem is that "fine" sets the bar for the rest of the build. The second-best plan — which, on reflection, was actually best — never gets argued for. The architectural choice that would have made the next six months easier never gets named.
This is harder to see than classic AI failure modes. A model that hallucinates is loud; you catch it. A model that confidently picks a plausible second-best path is quiet, and the cost shows up months later in the work that didn't happen because the foundation didn't support it.
The model is competent. The first plan is plausible. Implementing it is faster than challenging it. Nobody in the loop has the context to push back. By the time the wrong-shape decision is visible, it's already a foundation, not a draft.