# Shared packages

Workspace packages consumed by `services/*`. Each package is its own Python distribution with its own `pyproject.toml`; services import via the workspace dependency mechanism (`{ workspace = true }`).

| Package | Purpose |
|---------|---------|
| [`domain/`](./domain/) | Shared domain types — `Property`, `BaselinePerformance`, `Plan`, `Scenario`, `EpcPropertyData`, etc. No persistence, no IO, no business logic. |
| [`repos/`](./repos/) | Persistence layer — one repo per aggregate. Owns the SQL. Depends on `domain`. |
| [`fetchers/`](./fetchers/) | External API clients (gov EPC, Ofgem, Google Solar, etc.). Depend on `domain` for response shapes. |
| [`utils/`](./utils/) | Cross-cutting infra — logging, S3, CloudWatch URL builders, SQS task helpers. |

## Adding a new shared package

Only when a real second consumer materialises. Don't pre-shatter (`repos-epc`, `repos-property`, ...) — split when a deployment needs to drop a dep, not before.

See [`../ara_backend_design.md`](../ara_backend_design.md) §11 for the broader monorepo layout and [`../CONTEXT.md`](../CONTEXT.md) for the domain glossary that names the types living in `domain/`.