{
  "after": "C280",
  "chosen_next_step": "C281: test which Noah600 rectangles and598/602 crosspairs survive in the MT ON+60 realization without importing SP companions.",
  "reason": "The Flood event has start and close in MT, but Noah has no SP companion rail; this is the immediate domain boundary of the successful six-row transport.",
  "next_step_executed_within_this_step": false,
  "effort": "High sufficient",
  "limits": [
    "Equal460 magnitudes have different source operations.",
    "Flood-only covariance does not supply MT Noah companions.",
    "Preserving local images would require a separately stated intercept adjustment."
  ]
}