Anthropic's automatic caching billed us $0.022 per turn for the same 8,400 tokens that cost $0.003 once we placed the cache marker by hand
Automatic caching means one switch, and the system decides what to save. Manual caching means you mark the exact block yourself, so nothing varying ever poisons the entry. That single difference explains the whole gap, and our meter confirmed it across every repeat.
So we wrote down every trick that moved the bill, and each one ships with code you can paste. Every figure below comes from our own runs
> Mark the stable prefix
> Buy minutes, not hours
> Read the usage meter
> Batch the night shift
Then come the two that need explaining. Split planner from executor across two sessions. Cap thinking before it eats its own output.
Our mid-thread model switch billed $0.197 with zero hits. The two-session version read its cache for $0.011, which means the second prefix never charged twice.
Anthropic's docs describe all six features. Our meter readings show what each one actually saves.
The full tutorial walks through every trick with Python and cURL.
Full breakdown ↓↓
context window — The maximum amount of text a model can consider at once — its working memory for the current conversation or task.
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
Why it matters
Argues manual cache-breakpoint placement and splitting planner from executor across sessions can cut prompt-caching cost roughly 7x versus relying on Claude's automatic caching alone, a concrete lever for repeated-large-context windowThe maximum amount of text a model can consider at once — its working memory for the current conversation or task.Full definition →AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition → workloads.
Key quotes
“Anthropic's automatic caching billed us $0.022 per turn for the same 8,400 tokens that cost $0.003 once we placed the cache marker by hand”
“Automatic caching means one switch, and the system decides what to save.”
“Our mid-thread model switch billed $0.197 with zero hits.”
“The two-session version read its cache for $0.011, which means the second prefix never charged twice.”
