Replay Doctor identifies prompt cache failures and token re-billing in Claude Code sessions

Replay Doctor, a diagnostic tool available for local use, reads Claude Code transcripts and identifies which turn caused prompt cache expiry or other failures and how many tokens were re-billed at write prices. According to the project, causes of re-billing include cache expiry, tool list changes mid-session, and silent re-reads. The tool writes a single analysis file with counts, ratios, and build identifiers, allowing developers to track token waste across sessions.