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Shokunin
1da2055078
Clang on arm64 contracts a*b+c into an FMA by default; x86-64 GCC without -mfma never does. The software rasterizer's float edge/shading math then rounded differently on a Mac and a Windows peer: +-1 colour steps on single pixels, so VRAM (the av digest) diverged from ~sim 1800 in every cross-machine R4 rollback race while the core digest still matched. Each rollback baseline compare then aborted on "baseline av mismatch", and the realigns forked the session (3P never reached the race; 4P diverged mid-race). VRAM dumps from the same Mac-host 2P race at 16 ticks between sim 1600 and 2080: 1-3 differing pixels in 5 of 16 frames before, 0 after. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>