{
  "after": "C289",
  "chosen_next_step": "C290: test fixed25/23 dilation of the complete four-node source pattern, retaining center and seasonal distinctions.",
  "reason": "The pure-K coefficients suggest529→575, but a valid scalar replacement must be checked against source identities and physical pair widths.",
  "next_step_executed_within_this_step": false,
  "effort": "High sufficient",
  "limits": [
    "Pure-K constants restate the retained placement rather than independently requiring it.",
    "A congruence does not choose the common translation uniquely.",
    "Missing Noah source identities remain missing."
  ]
}