Reading your AI coding logs: cache hits, retry loops, and other signals

Last week I checked my AI coding spend and it was higher than my AWS bill. I'm paying for Claude Code, Codex, Cursor, the occasional Opus burst, and I had no visibility into where any of it went. Just a number going up. Turns out every AI coding tool already writes session data to disk. Claude Code drops JSONL into ~/.claude/projects/. Codex writes to ~/.codex/sessions/YYYY/MM/DD/. Cursor uses a SQLite database. OpenCode uses SQLite. Pi uses JSONL. All of it is sitting there waiting to be read. I started reading mine and the patterns are obvious once you look.