{"version":"2.1.286","anchor":"prompt-cache-ttl-and-expiry-estimate-now-depends-on-the-usag","canonical_anchor":"prompt-cache-ttl-and-expiry-estimate-now-depends-on-the-usag","heading":"Prompt cache expiry estimate now uses the last response's usage","tier":"internal","area":"Prompt Cache","url":"https:\/\/changelogs.core-directive.com\/v\/2.1.286\/e\/prompt-cache-ttl-and-expiry-estimate-now-depends-on-the-usag","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.286","markdown":"### Prompt cache expiry estimate now uses the last response's usage\n\nClaude Code's estimate of when the prompt cache expires now draws on usage figures from the last response\n\n**Unclear.** How the usage figures change the estimated cache lifetime is not known.\n\n**What**\n\nClaude Code estimates when its prompt cache has probably expired and what rebuilding it would cost. The prompt cache holds the start of your conversation on the server so it does not need to be reprocessed. That estimate is behind `prompt_cache_likely_expired` and the estimated cache write cost.\n\nIt used to depend only on the model and the size of the context. It now also uses the usage figures from the last response, or from saved session details. Claude Code also records when the main conversation's cache was last renewed.\n\n**Why**\n\nThe cache-expired signal and the estimated cost may now match what actually happened more closely.\n\n- Area: Prompt Cache\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 2\/5"}