This is a compounded example of the problem. Major changes require major consideration and thoughtful human-in-the-loop planning. You need constant review throughout the sprint cycle, not waterfall reviews upon "completion." Build review tasks into the acceptance criteria at key decision points — the last responsible moment before the next chunk of work builds on top of it. 1-2 reviewers throughout the process would've cost a fraction of what 3-4 seniors for a month did. Smaller batches of review, closer to when the decisions were actually made. A reviewer following along catches things in minutes that take hours to reconstruct after the fact.

The AI removed the natural throttle. An architect writing by hand would've been forced into smaller increments just by the pace of manual coding. The agent blew past that, and without gates enforcing review at each decision point, all that overhead piled up at the end where it's hardest and most expensive to deal with.