Reasoning at Constant Memory: How a 4B Chinese Open Model Freezes the KV Cache at 72 MiB

Inside EdgeRock-4B’s “Rock Memory Anchors” — and what they mean for anyone serving long-reasoning models Every engineer who has served a reasoning model knows the moment. The model is good, the answers are right, and then someone sends a 64K-token agent trace and the GPU's memory graph turns into a staircase. Reasoning models think out loud, and every token they think costs KV cache. On October 19, 2026, a team from Rock Matrix (岩芯矩阵, a unit of Chinese listed company 岩山科技), working with researchers at HKUST and CMU, open-sourced a model that takes a different route. EdgeRock-4B keeps its atten