Track and report Claude Code token usage, spending, and budgets from the local ECC cost-tracker metrics log. Use when the user asks about costs, spending, usage, tokens, budgets, or cost breakdowns by model, session, or date.

Cost Tracking Use this skill to analyze Claude Code cost and usage history from the metrics log that ECC's stop:cost tracker hook writes. Where the data lives The tracker appends one JSON object per session stop to ~/.claude/metrics/costs.jsonl . Each row is a cumulative snapshot for that session , so to total spend you take the latest row per session id and sum across sessions — summing every row multiply counts. Row schema: Field Meaning timestamp ISO timestamp of the snapshot session id Claude Code session identifier transcript path Path to the session transcript model Model used input tokens / output tokens Token counts cache write tokens / cache read tokens Prompt cache token counts estimated cost usd Precomputed cumulative cost in USD for the session Prefer estimated cost usd over hand calculating pricing — model and cache prices change, and the tracker is the source of truth. When to Use The user asks "how much have I spent?", "what did this session cost?", or "what is my token usage?" The user mentions budgets, spending limits, overruns, or cost controls. The user wants a cost breakdown by model, session, or date, or a CSV export. How It Works First verify the log exists (use node , not sqlite3 — the tracker writes JSONL, and node is cross platform): If the log is missing, do not fabricate usage data. Tell the user that cost tracking populates after the first session ends with the stop:cost tracker hook enabled. Example — summary, by model, last 7 days For a session drilldown or CSV export, iterate the same latest set (or the raw rows for CSV) and print the fields you need. Reporting Guidance When presenting cost data, include today's spend vs yesterday, total across all sessions, a by model breakdown, and session count. Format sub dollar amounts with four decimals, larger amounts with two. Anti Patterns Do not sum every row — they are cumulative per session; reduce to the latest row per session id first. Do not estimate costs from raw token counts when estimated cost usd is present. Do not assume the log exists without checking. Do not hard code current model pricing in user facing answers. Do not recommend installing unreviewed hooks or plugins that execute arbitrary code. Related /cost report Command form report over the same metrics log. cost aware llm pipeline Model routing and budget design patterns. token budget advisor Context and token budget planning. strategic compact Context compaction to reduce repeated token spend.

cost-tracking