Cost Track

Reads the active Claude Code session jsonl (~/.claude/projects/<encoded-cwd>/<session>.jsonl), tallies assistant-message usage per model, computes USD cost using REFERENCE.md pricing, and writes a structured record to the cost-tracking AgentDB namespace. This is the producer that gives cost-report and cost-optimize real data to consume.

When to use

• After a meaningful chunk of work, to capture spend for the report.
• At session-end to persist the final tally.
• Periodically during long sessions (cron-friendly — see /loop 30m).

Steps

1. Run the tracker from the project root:

   node plugins/ruflo-cost-tracker/scripts/track.mjs
   

   The script auto-discovers the session jsonl from the current working directory. To pin a specific session: TRACK_SESSION=/path/to/session.jsonl. To dry-run (no memory write): TRACK_DRY_RUN=1.

2. Inspect the markdown summary — total cost, per-model and per-tier breakdowns, and the persisted memory key.

3. Verify persistence — mcp__plugin_ruflo-core_ruflo__memory_search({ query: "session-", namespace: "cost-tracking" }) should list the new record. cost-report step 1 reads from this namespace.

Record shape (in cost-tracking namespace)

Key: session-<sessionId>. Value (JSON):

{
  "sessionId": "1dba3b8c-...",
  "cwd": "/Users/cohen/Projects/ruflo",
  "startedAt": "2026-05-04T...",
  "endedAt": "2026-05-05T...",
  "messageCount": 234,
  "byModel": {
    "claude-opus-4-7": {
      "tier": "opus",
      "input_tokens": 12345,
      "output_tokens": 6789,
      "cache_creation_input_tokens": 800000,
      "cache_read_input_tokens": 2000000,
      "messages": 50,
      "cost_usd": 1.23
    }
  },
  "byTier": { "haiku": 0.0, "sonnet": 0.45, "opus": 1.23, "unknown": 0 },
  "total_cost_usd": 1.68,
  "capturedAt": "2026-05-05T..."
}

Pricing source of truth

The script's PRICING constant mirrors REFERENCE.md "Model pricing (USD per 1M tokens)". Update both together when prices change. Cache-write tokens are billed at cache_write rate; cache-read tokens at cache_read (per Anthropic billing docs).

Env overrides

Env	Default	Purpose
TRACK_CWD	process.cwd()	Override which project's sessions to scan
TRACK_SESSION	most-recent jsonl	Pin a specific session file
TRACK_OUT	unset	Also write the JSON summary to this path
TRACK_DRY_RUN=1	unset	Skip the memory store call
TRACK_QUIET=1	unset	Suppress markdown output
TRACK_NAMESPACE	cost-tracking	Override target namespace

Cross-references

• cost-report (consumer) — reads records produced by this skill
• REFERENCE.md "Cost attribution formula" — the math the script implements
• cost-budget-check (consumer; landing in P2) — reads totals to evaluate alerts