Does 12-hour prompt caching guarantee a cache hit for twelve hours?
No. OpenAI describes a 12-hour minimum cache lifetime for supported Responses API models. The documentation says this controls eligibility for cache-read pricing and does not guarantee every request reuses stored tensors or has lower latency.
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OpenAI’s 12-Hour Prompt Cache Trades Cheaper Reuse for a Pricier WriteOpenAI adds a 12-hour cache option to Responses API. Learn when the higher write charge can pay back and what to measure.
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