reset_for_fold cleared q_value_history (the q_mean source) but missed
the kill criterion's prev_epoch_q_mean baseline AND the adaptive_tau
modulation state. So the kill ratio at fold-N epoch 0 was computed
against fold-(N-1) epoch 5's q_mean — a stale cross-fold baseline.
Discovered while diagnosing why Plan C Phase 2 Thompson smoke triggers
Q-drift kill at fold 0 epoch 2 (researcher report 2026-04-29).
Pairs with the existing q_value_history clear; matches the
project_fold_boundary_q_drift_resolved.md pattern (kill criterion's
companion resets were partially missed).
Independent of Plan C — this is a bug in the kill criterion's
fold-boundary contract regardless of which exploration mechanism is
active.
9f226f429d