Prompt Caching

Learn why any byte change in a cached prefix invalidates everything after it.

Add a cache_control breakpoint to a system prompt and verify a cache hit.

Order tools, system, and messages correctly so breakpoints cache the right prefix.

Reference table for 5-minute and 1-hour TTLs and their write cost multipliers.

Check usage.cache_read_input_tokens on every response to confirm the cache is working.

Numbered practices for breakpoint placement, TTL choice, and avoiding cache misses.