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# Backend Service: metering

This file adds local guidance for `src/api/flaskr/service/metering`. Read the
repository root and `src/api/AGENTS.md` first, then use this file for
module-specific ownership and risk points.

## Scope

- This service owns usage recording, usage reporting routes, and normalization
  constants for billable LLM and TTS activity.

- Primary checked-in entry files today:
  `src/api/flaskr/service/metering/routes.py`,
  `src/api/flaskr/service/metering/recorder.py`,
  `src/api/flaskr/service/metering/consts.py`,
  `src/api/flaskr/service/metering/models.py`

- Keep behavior in this module unless the concern is clearly cross-service and
  shared by multiple backend domains.

- Preferred pytest location: `src/api/tests/service/metering/` already exists
  and should remain the first stop.

## Do

- Start from the local entry files and preserve how this service already
  structures helpers, models, routes, and DTO-like helpers.

- Normalize usage types, scenes, and billable flags in the shared consts and
  recorder helpers before persisting records.

- Keep recorder helpers as the single place that translates runtime events
  into persisted metering rows.

- Preserve reporting filters and date parsing behavior exposed through the
  metering routes.

## Avoid

- Do not let callers write metering rows directly when recorder helpers
  already own the normalization contract.

- Do not introduce new usage-scene semantics without updating both const
  normalization and reporting expectations.

- Do not change billable defaults or record structure without checking
  downstream finance or quota consumers.

- Avoid scattering service-specific rules upward into root docs when the
  behavior only matters inside this module.

## Commands

- `rg -n "metering" src/api/flaskr/service src/api/tests` to locate all
  backend call sites and tests before editing.

- `cd src/api && pytest tests/service/metering/ -q` for the narrowest focused
  regression pass while iterating on this module.

- `cd src/api && FLASK_APP=app.py flask db migrate -m "message"` and review
  the generated revision if schema or indexed business-key changes are made.

- `cd src/api && pytest -q` when a change touches shared DTOs, auth, streaming
  contracts, or other services in addition to this module.

## Tests

- Add or update focused tests around `src/api/tests/service/metering/` for the
  happy path and the highest-risk validation, permission, or failure case.

- Expand coverage when payload shapes, error codes, or shared helper contracts
  used outside this module change.

- Review persistence-related changes manually for indexing, business-key
  semantics, and migration output whenever models move.

- Document any skipped provider, network, or credential-dependent checks in
  the final task summary.

## Related Skills

- `src/api/SKILL.md`

- `SKILL.md`

- Create a new backend skill under `src/api/skills/<topic>/SKILL.md` when this
  module grows a repeatable multi-step debugging workflow.
