Symmetric turbo4 is catastrophic on dense models (KLD=6.86, NIAH 0/15).
Asymmetric K=FP16 fixes everything (KLD=0.003, NIAH 15/15, top-1 98.1%).
Tested on Qwen2.5-7B-Instruct-8bit (28 layers, all KV cache).
Quality test suite added: scripts/mlx_quality_suite.py
Co-Authored-By: Tom Turney <tturney1@gmail.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
