Cost Tracking

Cost Tracking

Track the exact token cost of any Claude Code operation by marking a start and stop point in the session JSONL.

Start Tracking

When the user invokes /cost-tracking:

1. Determine the current session JSONL path. It lives at:

   ~/.claude/projects/<project-hash>/<session-id>.jsonl
   

   Find the project directory by looking for the most recently modified .jsonl file under ~/.claude/projects/. The project hash is a mangled version of the working directory path (slashes replaced with dashes, e.g., -Users-johndamask-myproject).

2. Determine the cost tracking output directory:

   ~/.claude/projects/<project-hash>/cost-tracking/
   

3. Run the start script:

   python3 <skill-dir>/scripts/start_tracking.py <session_jsonl_path> <cost_tracking_dir>
   

4. Store the returned tracking_id — mention it to the user and remember it for the stop step.

5. Confirm: "Cost tracking started. I'll calculate costs when you say 'stop tracking'."

Stop Tracking

When the user says "stop tracking", "stop cost tracking", or asks about the cost:

1. Run the stop script with the tracking_id from the start step:

   python3 <skill-dir>/scripts/stop_tracking.py <tracking_id> <cost_tracking_dir>
   

2. The script outputs a formatted cost report and writes:

   • tokens.jsonl — per-entry token log with timestamp, model, input_tokens, output_tokens
   • summary.json — aggregated cost breakdown by model

3. Present the report to the user.

Pricing

The stop script fetches pricing live from Anthropic's published page (https://platform.claude.com/docs/en/about-claude/pricing.md) at run time — it parses the "Model pricing" table, maps the session's model id (e.g. claude-opus-4-8) to the matching row, and caches the result for 24h in scripts/.pricing_cache.json. It distinguishes 5-minute vs 1-hour cache writes via the cache_creation.ephemeral_* fields, and picks the correct row when a model has date-scoped pricing (e.g. Sonnet 5's introductory rate).

resources/pricing.json is now only an offline fallback, used if both the live fetch and the cache are unavailable. If neither the page, the cache, nor the fallback can price a model, the script reports an error for it — it never silently substitutes another model's rate (the failure mode that once 3×-overcharged an Opus 4.8 run at legacy Opus rates). Keep resources/pricing.json reasonably current as a backstop, but the live page is the source of truth.