Stop Wiping Your Claude Code Cache: The Model-Switch Cost and a Four-Rule Setup
Each Claude model keeps its own prompt cache, so switching models mid-chat makes the next message re-read the whole conversation uncached. What the docs say, the four habits that keep the cache, a CLAUDE.md note, and how to check your hit rate
Claude Code re-sends your whole conversation on every message. Prompt caching lets the API reuse what it already processed and bill the re-read at the cached token rate. The docs say: "Each model has its own cache. Switching with /model means the next request reads the entire conversation history with no cache hits, even though the content is identical." That one slower, more expensive turn is the cost.
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Unlocks: The four-rule setup (from the docs) · What does not break the cache (per the docs) · Other things that start a fresh cache · The catch · Sources
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