Retrieved documents no longer need an identical prefix: one document cache survives changing system prompts, lifting hit rate from 3.3% to 63.9%
KV-Repurpose changes KV-cache reuse in large language model serving from requiring an identical prompt prefix to deciding reuse per segment, so a retrieved document can reuse its cached states even when system prompts, conversation histories, or timestamps differ. Under a Zipfian RAG workload at 30 GB cache capacity, the token-level hit rate rises from 3.3% for prefix caching to 63.9%, lowering time to first token; single-document question answering and summarization largely hold, while cross-document reasoning degrades.