blackwall_/prompt cache economics
replaying a recorded run

A dungeon-master agent: a big, byte-stable system prompt and a tiny, changing thing each turn — the time. Watch what happens to your bill depending on where that timestamp goes.

model
timestamp goes

the prompt, one request

cached read · ~10% price cache write · 1.25× premium (Anthropic) full price · recomputed

the session

this turn
running bill (input) $0.000000
if you never cached $0.000000
vs no-cache —

Real calls through OpenRouter, reasoning disabled, billed cost recorded and replayed here — no live API, nothing to spend. Reproduce it yourself: prompt-cache-economics.