Don't let a long session idle past the one-hour cache lifetime
Claude Code re-reads your whole conversation at the cached rate. Come back after a long lunch and the first message reprocesses all of it at full price.
The problem
A session left open all day feels free until you send a one-line question and it draws usage for the entire conversation, because the break was long enough to lose the cache.
The hack
Treat the cache lifetime as a real deadline. On a subscription it is an hour of inactivity; if you are going to be away longer, close the session out deliberately rather than leaving a huge context to go cold.
Why it works
Claude Code sends your full conversation with every request and reads that history at the cached token rate. The first message after a break longer than the cache lifetime misses the cache and reprocesses everything at the uncached rate.
Setup
1. Run `/usage` and check the behavior flags — cache misses and long context are flagged when either accounts for 10% or more of recent usage. 2. Before stepping away from a large session, finish the thread: commit, and write anything worth keeping to a file. 3. Coming back to a big session, prefer `/clear` and let Claude re-read the repo over paying to reprocess the whole history. 4. On Pro and Max, accept the offer to resume from a summary when it appears. 5. Watch out for scheduled tasks on an idle session — they fire on their interval and send your full context each time.
Discussion
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