AI & models
Prompt caching
Context caching
Prompt caching saves the model's processed version of text you send repeatedly — a long set of instructions, a big document — so it doesn't have to re-read it from scratch every turn. The next request reuses the cached part, which is much faster and far cheaper, since cached input is billed at a fraction of normal input. In a long Claude Code session, where the same context is reused turn after turn, it's one of the biggest cost savers there is.
Why it matters
Part of What AI costs → It's why a long, context-heavy session doesn't cost a fortune — the expensive part is read once and reused, not re-billed on every message.
see also