Tsinghua & CUHK propose cache engineering: 27.7% cost cut and +1.7 benchmark for agents

TheTuringPost · x · 2026-10-28

Context engineering can backfire: trimming or summarizing older messages forces KV-cache recomputation and increases compute. Tsinghua and CUHK propose cache engineering instead—keep the text history intact and edit cache availability via two ops alongside append: "drop" (removes KV entries from future attention) and "repos" (adjusts positional encodings). They built AKV, a serving engine managing cache reuse, eviction, and restoration with a stateless API, an extended radix tree tracking operation histories, and segment-batch attention for single-pass restoration. A simple policy that gradually drops older tool responses cut average cost 27.7%, added +1.7 benchmark points, and delivered 1.18× throughput / 1.51× P95 latency; letting agents refine their own cache policies saved another 7.1%. Caveat: it requires specialized serving infrastructure.

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