Reusing another agent’s KV cache inside a new prompt scored worse than using no cache at all

KVShareArena, from the University of Central Florida, measured what happens when a coordinator reuses the KV caches of its subagents’ reports. On its numbers, caches stitched naively into a new prompt did worse than no cache at all, scoring minus 0.82 where zero is no cache and one is full recomputation. Fixing positions rescued single-document questions, not multi-hop ones. Every result comes from models of 8 billion parameters or fewer. The verdict: never splice a subagent’s cache into a new prompt without a repair step.