- MONA fp16 causes NaN (gamma=1e-6 underflows in fp16 min subnormal ~6e-8) - Revert MONA forward to fp32 with autocast(enabled=False), cast output back - Fix loss CSV: save raw_loss before backward() (tensor consumed after backward) - Verified: loss=3.78, no NaN, bs=48 peak=21.4 GB Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>