Document the consumer EngineCore crash chain (D-pool 97% -> 112k-token KV transfer fails -> negative prompt-token counter -> prometheus ValueError -> engine dead -> cliff failure). Explains the round-robin 6P+2D rep variance (100/56/80%) as intermittent consumer death, and notes the counter-clamp patch needed to compare routing arms fairly. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>