The brain layer was scoring high because the test was leaking. The actual capability was being silently rejected by a misconfigured gate. Both findings landed in the same week.
Part 18 ended on a clean diagnosis. The brain layer reasoned correctly when the encoder fed it correct inputs. The encoder didn't always feed it correct inputs. So the path forward was upstream: more physics-shaped training data for the encoder, retrain, re-validate. I wrote the drops, kicked off the retrain, and watched the held-out eval climb.
It hit twenty-three out of twenty-six. Eighty-eight percent. The number I'd been chasing.
I sat with that for an evening. Twenty-three of twenty-six on compositional reasoning probes the model had never seen during training. The Phase 8 cutover gate from Stage D had been sixty percent. I was thirty points past it. The brain layer had not only survived its missing-from-production months, it had come back stronger.
The number was wrong.
