baya-monorepo/archive/build-chain/working-context/backend/handoff/after-backend-phase-0.md

After backend-phase-0 — what f0/b1 can rely on

The spine is clean and REST works. The inherited Order demo (entity/feature/repo/config/gRPC) and the three pre-marketplace migrations are gone; Identity + JWE auth + dynamic permissions + the CQRS behaviors + observability are untouched and the existing tests stay green. A real REST controller is live and proves the full pipeline.

What the frontend (f0) can rely on now

• The response envelope is fixed. Every endpoint returns the server's ApiResult envelope, not a bare body. Success shape:

  { "isSuccess": true, "statusCode": 0, "message": "Success", "requestId": "<trace>", "data": <T> }
  

  Failure returns 400/401/403/404 with the same envelope (field-level errors for validation). This is what clientFetch/serverFetch must unwrap. JSON casing is the server default (camelCase for the envelope/body properties; URL segments are snake_case).
• A working endpoint to wire the type pipeline against: GET /api/v1/ping/get_status → ApiResult<{ service, status, serverTimeUtc }>.
• Rate limiting exists. Over-limit requests get 429; get_status_rate_limited demonstrates it (first 5/10s OK, then 429).
• swagger.json is published: dev/contracts/openapi/swagger.v1.json (envelope schemas ApiResult, ApiResultStatusCode, PingQueryResult). Generate frontend types from it.

What b1 can rely on now

• Audit base type: BaseEntity/IAuditableEntity (Domain/Common/BaseEntity.cs) with CreatedAt/ModifiedAt (DateTimeOffset) + CreatedById/ModifiedById (int?). New entities that derive BaseEntity get audit stamping for free.
• Audit interceptor: AuditFieldInterceptor (Infrastructure.Persistence/Interceptors/) stamps those fields on save from ICurrentUser + IDateTimeProvider. b1 extends this to also write the append-only audit_logs rows — the stamping plumbing and the clean extension point are in place.
• Cross-cutting seams (DI-registered, mocked): IDateTimeProvider, IFieldEncryptor (use it for every encrypted PII column — phone/national_id/IBAN/addresses/clinical notes; deterministic Hash for *_hash lookup columns), ICacheService (cache platform_configs / read-heavy data through it), IObjectStorage, INotificationDispatcher. Contracts in Application/Contracts/Common; mocks in Infrastructure.CrossCutting/Seams/; registered by AddCrossCuttingSeams.
• Money rule: IRR is long/BIGINT, integer-only, no floats (CONVENTIONS §6).
• Migration baseline: 20260628191947_InitialBaseline. Add the marketplace schema on top of it; generate with the documented dotnet ef migrations add command.
• Rate-limit policies otp/auth/sensitive are defined and ready to apply via [EnableRateLimiting("...")] on the relevant endpoints (b2 auth/OTP).

Known caveat

Non-Development environments route Serilog to the logDb connection (Server=sql_server2022); if that host isn't reachable, the API won't start there. Development logs to console/file and boots cleanly against the configured SqlServer DB. This is pre-existing infra config, unrelated to phase-0 code.