How Claude Code uses prompt caching changedprompt-caching
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278278A high read-to-creation ratio means caching is working well. If creation stays high turn after turn, something is changing in your prefix. The [actions that invalidate the cache](#actions-that-invalidate-the-cache) section lists the usual causes.
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280For a per-session summary, run `/usage`. After the main conversation's first response, Claude Code adds a [`Prompt cache (main)` line](/docs/en/costs#prompt-cache-statistics) to the Session block, showing the session's hit ratio, miss count, and whether the cache is warm right now. A status line script can read the same numbers from the [`prompt_cache` object](/docs/en/statusline#prompt-cache-fields). Both require Claude Code v2.1.251 or later.
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280282For visibility across an organization, the OpenTelemetry exporter reports cache read and creation tokens per user and session. See [Monitor usage](/docs/en/monitoring-usage) for the metric and event attribute reference.
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282284## Subagents and the cache
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