[特性]: 在 Bedrock 路径上启用提示缓存 — cache_control 从未设置

openwiki never requests Bedrock prompt caching, so long runs reprocess their whole stable prefix on every model call. On a real CI run against a mid-sized repo, we measured **17,031,960 input tokens across 286 calls with 0 cache reads** — about 59.5K input tokens per call, essentially all of it a re-sent prefix.