对于缓存诊断，API 现在仅在请求包含 diagnostics 对象时才存储请求的指纹。

对于缓存诊断，API 现在仅在请求包含 diagnostics 对象时才存储请求的指纹。仅发送 cache-diagnosis-2026-04-07 beta 标头的请求仍会被接受，但不会存储指纹。后续轮次若将 previous_message_id 指向该请求，则会报告 previous_message_not_found。请在每一轮都包含 diagnostics，并在第一轮中设置 "previous_message_id": null。

For cache diagnostics, the API now stores a request’s fingerprint only when the request includes the diagnostics object. A request that sends only the cache-diagnosis-2026-04-07 beta header is still accepted, but no fingerprint is stored. A later turn that points previous_message_id at it reports previous_message_not_found. Include diagnostics on every turn, with "previous_message_id": null on the first.