Cost per Conversation and aggregate by agent and model . This skill aggregates by conversation (session) — a different lens that surfaces which conversations cost the most . Useful for retrospectives ("which sessions ran long on Opus?") and for evaluating whether a given project's session pattern is sustainable. When to use - After multiple sessions, to see total spend per conversation. - Before scoping a long session, to understand typical cost-per-conversation. - For per-project rollups via . Steps 1. Run the script from anywhere: Optional env: - — emit JSON instead of markdown - — show onl…