How does OpenAI's Responses API prompt-cache prewarming work?
openai-python v3.15.0 adds a prewarm field to the Responses API's prompt cache options. Setting it true forces generate to false, writing the cache with no output, at a TTL fixed to 30 minutes. Claude has offered the same effect since launch via a max_tokens=0 request, with a 5 minute default or a paid 1 hour TTL.
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