DictionaryCaching
Cache Write
The one-time extra fee to store part of your request for reuse, like paying to rent a locker.
Definition
The cost of storing a prompt prefix in the cache for the first time. On Claude, 5-minute cache writes cost 1.25x base input (Claude Sonnet 5.5: $2.50/MTok vs. $2/MTok) and 1-hour cache writes cost 2x base input. The write pays for itself once the same prefix is read back.
Example
On Claude Sonnet 5.5, caching a 100K-token prefix for 5 minutes costs $0.25 (at $2.50/MTok) instead of $0.20 uncached.