cost-tracking

Topics in the source

• Cost Tracking
• Where the data lives
• When to Use
• How It Works
• Example — summary, by model, last 7 days
• Reporting Guidance
• Anti-Patterns
• Related

Use this skill to analyze Claude Code cost and usage history from the metrics log that ECC's stop:cost-tracker hook writes. 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 sessionid and sum across sessions — summing every row multiply-counts. ECC also maintains internal per-session files under /.claude/metrics/cost-snapshots/ so runtime hooks can read the current session total without rescanning all history. Treat those files as a rebuildable cache; each snapshot stores a byte cursor so only newly appended rows are scanned. Stable reads are O(1), while updates are O(new bytes). Stale entries are pruned after 30 days or when the directory exceeds 512 sessions. Cold catch-up work is limited to 16 MiB per hook invocation, and malformed unterminated rows larger than 1 MiB are discarded with a resumable cursor. Reports and exports should continue to use costs.jsonl. Row schema: | Field | Meaning | | --- | --- | | timestamp | ISO timestamp of the snapshot | | sessionid | Claude Code session identifier | | transcriptpath | Path to the session transcript |

This is an excerpt. Refer to the complete source and its current requirements.