Asked about Prompt caching
How do you verify caching is working?
An answer that works
Check the cached token count in usage data on repeated similar requests. Consistently zero means something volatile is in the prefix. It is worth asserting on in a test, because the failure has no behavioural symptom.
Reading an answer is not being able to give one. The section that teaches this is Prompt caching, 5 hours of Prompt caching.
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