Per-request cost accumulator backed by SQLite.

Subscribes to [:gateway, :request, :stop] telemetry from Agentic.LLM.Gateway and writes one row per LLM request to ~/.agentic/spend.sqlite3. The Gateway already auto-injects its base URL into Claude Code / OpenCode / Codex subprocesses via Gateway.inject_env/2, so subprocess-driven LLM calls flow through the same telemetry as in-process ones.

Schema

spend_events  — one row per request (audit log for X-Ray)
spend_windows — materialized aggregate per (provider, account_id,
                canonical_id, period, period_start) for dashboards

The window row is upserted in the same transaction that inserts the event, so dashboard queries stay constant-time as the event log grows.

Currency

All amounts are Money.t() from :ex_money. The native currency is preserved in the row; the dashboard normalizes for display. Sub-cent precision is preserved via Decimal (Money's internal representation).