---
id: ADR-0006
title: Harvest mechanisms from the parallel platform, keep our architecture
status: active
date: 2026-08-21
tags: [architecture, security, contracts, platform, governance]
---

# ADR-0006: Harvest mechanisms from the parallel platform, keep our architecture

## Context

A second team built a competing platform monorepo — NestJS/Fastify API, PostgreSQL/Prisma, two Angular apps, Docker/Nginx infrastructure — sharing an older `dexarmarket` ancestor with this repo. On 2026-08-11 they received a snapshot of our code, audited it, and vendored it into their tree as `reference/parallel-frontend/`, classified as a UI/UX reference rather than production. Their handoff document ranks our work fifth of five priority sources.

Full comparison: [FORK-ANALYSIS-2026-08-21.md](../../FORK-ANALYSIS-2026-08-21.md).

The asymmetry is real and runs both ways. They have working server-side truth: tenancy resolved from a verified `Host`, RBAC enforced per endpoint, hashed server sessions with mandatory TOTP, encrypted per-tenant payment credentials, idempotent webhooks, immutable publish revisions, WAL archiving and a restore check. We have the deeper frontend — 530 `.ts` files against 189, 158 components, 30 spec files plus Playwright e2e against their 25 unit tests and no e2e at all, Angular 22 with a clean production audit against their 21.2.18 with open high findings, and architecture governance in CI that they have no equivalent of.

Three of their audit findings against us were still live when re-checked on 2026-08-21, and two of them were defects rather than posture: a plaintext `ip-api.com` call that mixed-content blocking had silently killed in production, and an unvalidated bank URL rendered into an iframe that most acquirers refuse to be framed in.

## Decision

Take the mechanisms. Do not take the architecture, and do not merge the codebases.

- **Harvest** specific, proven mechanisms into our backend contracts under a traceable `FH-*` tag: conditional-write stock reservation, idempotency as a unique constraint, hashed server sessions with per-contour cookies, an origin allowlist on cookie-authenticated mutations, an AES-256-GCM envelope for stored secrets, signed read-only preview, revision immutability and clone semantics, an append-only inventory journal, server-side content validation, and digital code pools.
- **Reject** anything that would regress us: their Angular version, their mock service still shipping in a backoffice, their test posture, their environment-pinned manager scope, their hardcoded server IP, and their narrower section schema.
- **Keep ours where ours is better** and say so explicitly, so it does not get relitigated: our marketplace lifecycle state machine is richer than theirs, our bulk-import preview/apply flow is equivalent, our editor validation engine is stronger — it simply needs a server-side counterpart to bind.
- **Record the nine invariants** from their handoff as the acceptance gate at the head of our own backend handoff, since they are more falsifiable than anything our delivery plan had.

## Consequences

The backend contracts gain normative mechanism text where they previously stated intent, which raises the bar a backend built against them must clear — at the cost of more prescription than these documents originally carried. That trade is deliberate: "the webhook must be idempotent" survives one refactor, `UNIQUE (provider, event_key)` survives every refactor.

Our repo stays frontend-only. Nothing harvested requires standing up Prisma or NestJS here; anything that would have becomes a contract line instead. Work splits across five lanes — frontend, contracts, the `@marketplaces/auth` package, infrastructure, and process — tracked in [FORK-HARVEST-TODO.md](../../FORK-HARVEST-TODO.md).

Adopting their invariants and their PR and release discipline as our own means our releases get slower and more evidenced. That is the intended direction.

The organizational question this ADR does not settle: whether the two implementations converge as their backend plus our frontend. Left unchallenged, their handoff document's ranking becomes the plan of record by default.