Prompt caching is driven by prefix matching, not by session identity. If the same prefix shows up again, reuse can happen across conversations and sometimes across users.

TTL is the lifetime of a prompt cache entry. Each hit refreshes it. Leave it unused for long enough, and it expires.

Prompt caching cuts the price of repeated prefixes. Tool-result replacement shrinks the prompt itself. Both can save money, but they push on different parts of the bill.

Deep dive into Cursor Rules classification and prompt structure to make AI your top developer assistant