>>105641209
There are no partial cache rewrites. It either has to be a perfect match or it writes an entirely new cache.
In your example, if I understand it correctly, nothing would be counted for the cheaper cache price. It would just create a new cache at 1.25x/2x (5m/1h TTL) the cost for the full 1280 tokens.
There is a technical option to insert cache breakpoints, as the official documentation states. https://docs.anthropic.com/en/docs/build-with-claude/prompt-caching#putting-it-all-together-multiple-cache-breakpoints
That would allow you to do something like you described, but that is not supported in the standard caching function of SillyTavern.