Import AI 464: Claude Fable Autonomously Writes the Fastest Megakernel Ever Submitted to KernelBench-Mega

Import AI (Jack Clark)·high signal

Jack Clark's Import AI 464 (~July 6, 2026) leads with Claude Fable autonomously writing 'the first genuine (and fastest) megakernel' submitted to the KernelBench-Mega leaderboard — an 18.71x speedup in hand-written CUDA on an RTX PRO 6000 Blackwell vs. an optimized PyTorch baseline, with torch.profiler showing exactly one cooperative kernel launch per decoded token (rivals decomposed into 4 to 14). It beat other frontier models writing Triton: Opus 4.8 (14.4x), GLM-5.2 (11.14x), GPT-5.5 (4.34x). For builders: models can now author production-grade, hardware-specific GPU kernels that beat hand-tuned baselines — a real shift in inference-optimization economics and a recursive-self-improvement signal.