Auto-sizer inflated replay buffer to 15.8M entries on H100 (45% of 80GB VRAM). The PER prefix scan inside the CUDA graph processes ALL 15.8M entries every step, dominating step time. With buffer_size=500K, the scan processes 500K entries instead. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>