{"i":19,"slug":"prompt-cache-across-sessions","chart":{"id":"cache-sessions-turn1-read-share","title":"Claude Sonnet 5.5 · Claude Code: share of turn-1 input read from the cache, by setup and session","subtitle":"One bar per call: turn 1 of one session; 3 sessions per setup, run back to back; read-share calculation","kind":"grouped-bar","unit":"rate","polarity":"none","xLabel":"Setup","yLabel":"Input tokens read from cache","series":{"$k":["name","points"],"$r":[["Session 1 (first in its setup)",{"$k":["label","value","n"],"$r":[["A: new folder each time",0.0676,1],["B: fixed folder",0.1867,1],["C: fixed folder, ledger in system prompt",0.0691,1]]}],["Session 2",{"$k":["label","value","n"],"$r":[["A: new folder each time",0.1863,1],["B: fixed folder",0.9997,1],["C: fixed folder, ledger in system prompt",0.9997,1]]}],["Session 3",{"$k":["label","value","n"],"$r":[["A: new folder each time",0.1863,1],["B: fixed folder",0.9997,1],["C: fixed folder, ledger in system prompt",0.9997,1]]}]]},"note":"Session 1 was the first session to use its setup’s ledger. Sessions 2 and 3 used that same ledger. Different seeds prevent full ledger-prefix reuse between setups; shared CLI-prefix reads remain possible. We interpret session-1 reads as a shared CLI prefix; no token-level trace proves this. Read share (calculation) = cache reads ÷ (uncached input + cache reads + cache writes), as the provider reports them. Each bar is one call, not a rate; the counts per setup are in the table. 2 later sessions per setup is a small number.","sourceIds":["agent-cache-sessions"]}}