The Cost of Sending One Message After a Long Lunch Break
You leave a Claude Code session open over a long lunch, then send one short follow-up question.
Why can that single short message end up costing far more than a similar message sent earlier in the same session?
The correct answer is "The gap exceeded the cache lifetime, so it reprocessed uncached."
Prompt caching normally lets the accumulated conversation be re-read at a cheaper cached rate, but a gap longer than the cache's lifetime causes the next message to reprocess the entire context at full, uncached rates — so one short question can draw usage for the whole conversation. Pricing doesn't literally double on a fixed schedule after 30 minutes, the model doesn't auto-upgrade during idle time, and idle time itself isn't billed — it's the next message's full reprocessing that costs more.
Share this question