Mirrors commit 872bd7392 (aux next_bar stop-gradient) for the
5-class regime CE head. Same architectural conflict: regime backward
propagated dh_s2 SAXPY back to shared trunk h_s2, conflicting with
Q-loss for trunk representation control.
Today's next_bar fix landed with regime documented as a deferred
follow-up. Audit confirmed regime head has the IDENTICAL kernel
structure (same Linear→ELU→Linear→softmax→CE topology, same dh_s2
SAXPY at lines 732-742). Fix is mechanical — zero-fill the dh_s2
write block.
Combined with 872bd7392, this completes the trunk-isolation pair:
both auxiliary heads now train their own params from CE loss without
pulling on shared h_s2.
Verification: cargo check clean; sp14_oracle_tests 7/7 pass.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
411a304731