attn_sdp_fwd and attn_layer_norm_fwd were loaded from attention_kernel.cubin (which only contains the legacy multihead_feature_attention) instead of attention_backward_kernel.cubin where they actually live. This caused CUDA_ERROR_NOT_FOUND on H100, silently disabling attention. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>