{"i":19,"slug":"prompt-cache-across-sessions","chart":{"id":"cache-sessions-turn1-cost","title":"Claude Sonnet 5.5 · Claude Code: list-price cost of turn 1, by setup and session (calculation)","subtitle":"The recorded tokens of each call priced at list price; the last bar shows the mean of the 3 calls priced without any cache","kind":"grouped-bar","unit":"usd","xLabel":"Setup","yLabel":"USD (list price)","series":{"$k":["name","points"],"$r":[["Session 1 (first in its setup)",{"$k":["label","value","n"],"$r":[["A: new folder each time",0.02942,1],["B: fixed folder",0.025807,1],["C: fixed folder, ledger in system prompt",0.029242,1]]}],["Session 2",{"$k":["label","value","n"],"$r":[["A: new folder each time",0.025871,1],["B: fixed folder",0.001601,1],["C: fixed folder, ledger in system prompt",0.001597,1]]}],["Session 3",{"$k":["label","value","n"],"$r":[["A: new folder each time",0.025879,1],["B: fixed folder",0.001601,1],["C: fixed folder, ledger in system prompt",0.001597,1]]}],["Same call without a cache (every input token at the input price)",{"$k":["label","value","n"],"$r":[["A: new folder each time",0.015735,3],["B: fixed folder",0.0157,3],["C: fixed folder, ledger in system prompt",0.015664,3]]}]]},"note":"Calculation, not a bill: the calls ran on a subscription. Uncached input at the input price, cache reads at the cache-read price, 1-hour cache writes at 2× the input price (every write in this run was a 1-hour write); Sonnet 5.5 list prices, effective 2026-09-21. A write costs more than plain input, so a session that writes the ledger again costs more than no cache at all.","sourceIds":["agent-cache-sessions","calc-cache-pricing","price-anthropic"]}}