One Claude Code session cost $481. Nobody noticed for three weeks.

While building claudebill we ran it over our own Claude Code history: 81 sessions, 7 billion tokens, about $7,600 in API-equivalent spend. Three things we did not expect:

- One session cost $481. It was a long homelab automation task that kept a huge context alive for hours. Nobody noticed at the time, because on a Max plan nothing shows a dollar figure.

- One project was 96% of all spend. Everything else combined was 4%.

- Prompt caching saved about $44,000. Without it the same work would have cost six times more.

The tool launches here on Friday. It reads the transcripts Claude Code already keeps on disk, so it works on history you already have: npx claudebill

The question for this thread: do you know what your most expensive session was? Not roughly, the actual number. If you run it before Friday, post the figure here. We are curious whether $481 is unusual or normal.