# Backend Contracts Index — Product Plan v3.1

> **New here? Start with [BACKEND-HANDOFF.md](BACKEND-HANDOFF.md)** — reading order, current infrastructure state, auth surface, and what a working dev environment still needs.
>
> **Want every endpoint in one place? [FRONTEND-API-SURFACE-COMPLETE.md](FRONTEND-API-SURFACE-COMPLETE.md)** — the final handoff doc. Generated directly from source, all 90 endpoints the frontend currently calls plus 3 response-shape additions on existing endpoints, marked Specified / Inferred / Undocumented against the contracts below. Use it to see gaps across all contracts at once; use the individual Phase/Track docs for full entity shapes and invariants.

This directory is the complete set of wire contracts for building the backend behind [Product Plan v3.1](../PRODUCT-PLAN-v3.1-GAP-ANALYSIS.md). Each doc specifies entities, endpoints, and invariants only — never DB schema or service boundaries, which stay backend's own call.

**Read order matches build order.** Every doc after Phase 1 depends on the ones before it (noted at the top of each). All Sprint 0.1 decisions referenced throughout were answered 2026-08-17 — see [PRODUCT-PLAN-v3.1-DELIVERY-PLAN.md](../PRODUCT-PLAN-v3.1-DELIVERY-PLAN.md) Sprint 0.1 for the full record.

## Launch-gate phases (P0 — required before production)

| Doc | Covers | Status |
|---|---|---|
| [PHASE-1-MONEY-FX-PAYMENTS-CONTRACT.md](PHASE-1-MONEY-FX-PAYMENTS-CONTRACT.md) | Money model, FX quote, price snapshot, server-authoritative checkout amount, payment state machine | Ready |
| [PHASE-2-ORDERS-NOTIFICATIONS-CONTRACT.md](PHASE-2-ORDERS-NOTIFICATIONS-CONTRACT.md) | Canonical Order/OrderLine/Fulfillment (unified multi-seller), event bus, Notification Center | Ready |
| [PHASE-3-CATALOG-OFFER-FULFILLMENT-CONTRACT.md](PHASE-3-CATALOG-OFFER-FULFILLMENT-CONTRACT.md) | Product/Offer split, inventory/reservations, publish-time executability | Ready |
| [PHASE-4-CONNECTOR-FRAMEWORK-CONTRACT.md](PHASE-4-CONNECTOR-FRAMEWORK-CONTRACT.md) | Generic external-order connector framework (no fixed marketplace list) | Ready |

## Post-launch-gate phases (P1/P2)

| Doc | Covers | Status |
|---|---|---|
| [PHASE-5-SELLER-PORTAL-CONTRACT.md](PHASE-5-SELLER-PORTAL-CONTRACT.md) | Seller org/user/membership, seller-scoped order/fulfillment views | Ready |
| [PHASE-6-CART-CHECKOUT-CONTRACT.md](PHASE-6-CART-CHECKOUT-CONTRACT.md) | Server-owned cart, checkout session | Ready |
| [PHASE-7-PAYMENTS-RECONCILIATION-CONTRACT.md](PHASE-7-PAYMENTS-RECONCILIATION-CONTRACT.md) | Refunds, reconciliation, settlements | Ready |
| [PHASE-8-IDENTITY-MESSAGING-CONTRACT.md](PHASE-8-IDENTITY-MESSAGING-CONTRACT.md) | Customer identity, VK ID (built first), OTP, MAX/Telegram bots, Notification Orchestrator | Ready |
| [PHASE-9-TENANT-REGISTRY-DOMAINS-CONTRACT.md](PHASE-9-TENANT-REGISTRY-DOMAINS-CONTRACT.md) | Marketplace registry, Hostinger DNS automation, publish/revision model | Ready |
| [PHASE-10-CONTENT-MODULES-CONTRACT.md](PHASE-10-CONTENT-MODULES-CONTRACT.md) | Gorbushka-class mall/directory content entities | Ready, lowest priority |

## Cross-cutting tracks

| Doc | Covers | Status |
|---|---|---|
| [TRACK-A-ANALYTICS-CONTRACT.md](TRACK-A-ANALYTICS-CONTRACT.md) | Event pipeline, funnel, operational/quality metrics, synthetic-traffic separation | Ready — start alongside Phase 1, longest lead time |
| [TRACK-S-SECURITY-RBAC-CONTRACT.md](TRACK-S-SECURITY-RBAC-CONTRACT.md) | 17 roles/3 scopes, enforcement, audit log, secrets, rate limiting, step-up auth | Ready — gates the launch |
| [PARTNER-PROVISIONING-API-CONTRACT.md](PARTNER-PROVISIONING-API-CONTRACT.md) | Inbound partner API: merchant hierarchy provisioning, idempotency, public-key credentials, payment routing context | Draft — mapping decided, needs Company/Project entities |

## What is deliberately not in this directory

- **API namespace migration** — Sprint 0.1 decision: new endpoints only use `/api/v2/...` etc; legacy endpoints (`/cart`, `/orders`, `/items`) are not being migrated as part of this contract set. See `BACKEND-API-REFERENCE.md` for the current live surface.
- **Per-connector adapters** (Ozon, Wildberries, etc.) — Sprint 0.1 decision: no fixed list. [Phase 4](PHASE-4-CONNECTOR-FRAMEWORK-CONTRACT.md) §8 is the onboarding runbook; each partner's adapter is written when that partner is actually onboarded.
- **Additional payment providers** (wallets, BNPL) — open business decision, not yet made. [Phase 7](PHASE-7-PAYMENTS-RECONCILIATION-CONTRACT.md) §4.

## One open item across all of these

**Backend ownership — answered 2026-08-18.** A separate backend developer implements against these contracts. This repository's team owns the frontend and owns *this contract set* — the docs here are the handoff surface between the two, so a change to any contract is a change both sides must see. Keep them current; they are not a one-time deliverable.