Backend Conventions

Postmill's backend follows a strict NestJS layering discipline. Every request passes through every layer — no shortcuts.

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NestJS layering

Controller → Service/Manager → Repository

When a manager is involved (orchestration/coordination across domains):

Controller → Manager → Service → Repository

What goes where

Layer	Responsibility	Must NOT
Controller	HTTP route wiring (@Get, @Post), @Body/@Query/@Param extraction, @UseGuards decorators, @CheckPolicies, @RequirePermission	Call Prisma, contain business logic
Service	Business logic, validation, cross-domain coordination	Call Prisma directly
Manager	Multi-step orchestration, transaction boundaries, workflow coordination	Call Prisma directly
Repository	Prisma queries ONLY — findMany, create, update, $queryRaw	Contain business logic

Cross-domain calls

When a service needs data from another domain, it calls that domain's service — never its repository:

// CORRECT — call the service
const post = await this._postsService.getPost(orgId, postId);

// WRONG — never reach into another domain's repository
const post = await this._postsRepository.findById(postId);

Thin backend app

apps/backend is kept intentionally thin — mostly controllers + module wiring. Real logic lives in libraries/nestjs-libraries. The backend imports and re-exports from shared libraries; it should not contain substantial business logic, database access, or provider integrations.

Sanctioned exceptions

Two situations are allowed to bypass the normal layering rule by design:

1. Seeders and migration steps under database/seeds/** — notably BackfillService and RbacSeeder — intentionally use PrismaService + $transaction directly for cross-table backfills and seeds.
2. Cross-domain leaf-reads where routing "up" through the owning service would create a Nest dependency-injection cycle. These are deliberate, behavior-neutral reads and must carry a // layering: sanctioned leaf-read comment:
   • PostsService → AnalyticsRepository / CampaignsRepository (the analytics/campaigns services depend on PostsService).
   • OrgMediaProviderSettingsService → @Optional() OrgAiSettingsRepository (the Qwen/Google universal-credential read; OrgAiSettingsService depends on this package's ProviderCredentialLinkService).
   • AiMediaService (ai/governance/media.service.ts) → @Optional() OrgAiSettingsRepository (universal-credential fallback; same DI-cycle rationale as above).
   • PaymentsService → PaymentEventRepository (narrow payment-webhook idempotency/grace reads, no service-level cycle).
   • PostActivity (Inngest) → CampaignsRepository (UTM utmEnabled flag) and PostsRepository (atomic publish claim).
   • OrgVpnConfigService → OrgProviderConfigRepository (OrgProviderConfigService depends back on this service; used to clear orphaned channel vpnSelection rows).
   • StorageService → subscription read via the repository (routing through SubscriptionService would close a DI cycle that crashes Nest at boot).
   • WebhooksService → IntegrationRepository (id-only ownership check, no token decrypt).
   • NotificationService → OrganizationRepository (OrganizationService depends on NotificationService).
   • PermissionsService → AiSettingsRepository (the video-export gate's in-flight AIMediaJob count; the repository has no service back-edge).

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DTO validation

The global ValidationPipe is configured with:

new ValidationPipe({
  transform: true,
  whitelist: true,
  forbidNonWhitelisted: true,
})

Setting	Effect
transform: true	Auto-casts query/param strings to their declared types
whitelist: true	Strips properties not declared in the DTO class
forbidNonWhitelisted	Returns a 400 error when unknown properties are sent

Rule: Every new optional field must be declared on its DTO class. Unknown fields are rejected.

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Two orthogonal access gates

Routes are gated by two independent guards. Do not merge them.

Gate	Decorator	Guard	Question	Failure
Billing/tier	@CheckPolicies([Action, Section])	PoliciesGuard	Has this org paid for this feature?	SubscriptionException → HTTP 402
RBAC	@RequirePermission(resource, action)	OrgRbacGuard	Is this member allowed to do this?	ForbiddenException → HTTP 403

@CheckPolicies([AuthorizationActions.Create, Sections.TEAM_MEMBERS]) // 402 if plan lacks it
@RequirePermission('settings', 'update')                             // 403 if role lacks it
@Post('/team')

Rules:

• @RequirePermission resolves the acting user's membership (UserOrganization.roleId → AppRole → permissions). manage on a resource implies every action on it.
• User.isSuperAdmin (the platform operator flag) bypasses RBAC — it does not bypass billing. It is a different axis from the org owner role.
• The seeded system roles are owner, admin, editor, member, viewer (see libraries/nestjs-libraries/src/database/seeds/rbac-seeder.ts for the exact catalog); orgs can define custom roles via /settings/roles.
• Guard sources: apps/backend/src/services/auth/rbac/org-rbac.guard.ts and require-permission.decorator.ts.

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CSRF protection

CSRF middleware is applied to all cookie-authenticated mutating routes (POST, PUT, PATCH, DELETE). The middleware checks for a matching x-csrf-token header on state-changing requests.

Exemptions:

• Routes authenticated via Authorization header (API keys, OAuth tokens).
• Routes authenticated via browser extension JWT (different session model).
• All routes when NOT_SECURED env var is set (dev/local only).

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Security invariants

safeFetch for outbound HTTP

Every outbound HTTP call that involves a user-influenced URL must go through safeFetch (libraries/nestjs-libraries/src/dtos/webhooks/safe.fetch.ts):

safeFetch lives in libraries/nestjs-libraries/src/dtos/webhooks/safe.fetch.ts and enforces:

• isSafePublicHttpsUrl validation — blocks private IPs, localhost, etc.
• ssrfSafeDispatcher — custom undici dispatcher.
• Manual per-hop redirect re-validation (prevents DNS rebinding attacks).

Areas covered: webhook dispatch, provider HTTP fetches, watchlist probes. Never use bare fetch(url) where url is user-influenced. DTO validation alone doesn't survive DNS rebinding or 30x redirects.

The SSRF_ALLOWED_PRIVATE_CIDRS env var allows self-hosted instances to whitelist internal network ranges.

EncryptionService for secrets

All at-rest secrets are encrypted with AES-256-GCM via EncryptionService. Encrypted values use the v2: prefix. The service reads ENCRYPTION_KEY or falls back to deriving a key from JWT_SECRET.

This is a single-key model: one deployment-wide key encrypts every secret, regardless of organization. There is no per-org crypto key — an organizationId column scopes storage, and cross-org isolation is enforced by query scoping, not by separate keys. EncryptionService (the per-org domain path) is a thin wrapper over AuthService.fixedEncryption/fixedDecryption (the global-row path); the split is an implementation detail — both derive the identical key and produce the identical v2: envelope, so never mix the two decrypt routes for the same row.

No secrets in logs

Use NestJS Logger.warn(message) / Logger.error(message) — never console.log(err). Raw API response bodies and full prompt bodies are stripped before logging. Error messages stored in Errors.body are redacted before persist.

JWT configuration

• Algorithm pinned to HS256.
• New tokens carry exp with sliding renewal.
• IDs and secrets generated with CSPRNG.

NOT_SECURED bypass

When NOT_SECURED=true (dev/local only):

• HSTS and CSP headers are skipped.
• CSRF middleware is disabled.
• CopilotKit policy gate is bypassed.

Response headers never expose JWTs, even under NOT_SECURED.

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Repository pattern

Base classes

// Typed access to a single Prisma model
export class PrismaRepository<T extends keyof PrismaService> {
  public model: Pick<PrismaService, T>;
  // ...
}

// Transaction wrapper
export class PrismaTransaction {
  public model: Pick<PrismaService, '$transaction'>;
  // ...
}

Both are in libraries/nestjs-libraries/src/database/prisma/prisma.service.ts.

Domain structure

Each domain has its own directory under database/prisma/<domain>/:

database/prisma/
├── ai-rag/            → ai-rag.repository.ts
├── ai-settings/       → ai-settings.repository.ts, org-ai-settings.repository.ts
├── analytics/         → analytics.repository.ts
├── announcements/     → announcements.repository.ts
├── api-keys/          → api-keys.repository.ts
├── audit/             → audit.repository.ts
├── auth-providers/    → auth-provider.repository.ts
├── autopost/          → autopost.repository.ts
├── brands/            → brands.repository.ts
├── campaigns/         → campaigns.repository.ts
├── emails/            → email-log.repository.ts
├── featured-providers/→ featured-provider.repository.ts
├── federation/        → federation.repository.ts
├── file/              → file.repository.ts
├── integrations/      → integration.repository.ts
├── media/             → multipart-upload.repository.ts
├── media-providers/   → org-media-provider-settings.repository.ts
├── notifications/     → notifications.repository.ts
├── oauth/             → oauth.repository.ts
├── organizations/     → organization.repository.ts
├── posts/             → posts.repository.ts
├── provider-configs/  → org-provider-config.repository.ts
├── roles/             → roles.repository.ts
├── sets/              → sets.repository.ts
├── short-links/       → org-shortlink-settings.repository.ts
├── signatures/        → signature.repository.ts
├── social-comments/   → social.comments.repository.ts
├── storage/           → storage.repository.ts
├── subscriptions/     → subscription.repository.ts, payment-event.repository.ts
├── users/             → users.repository.ts
├── watchlist/         → watchlist.repository.ts
└── webhooks/          → webhooks.repository.ts

Each repository typically has a companion service file in the same directory (e.g., posts.service.ts).

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Module wiring

All provider domains (AI, Media, Storage, Short-link, Social, VPN, Content Packs, Email, Auth, Comms, Payments) register through the shared ProviderKernel at module init. apps/backend/src/providers.generated.ts (hand-maintained despite the name) imports every provider package's modules into a single providerModules array; ProvidersBootstrap.onModuleInit (apps/backend/src/providers.bootstrap.ts) walks that array and calls kernel.register(mod) for each, honoring the DEV_DISABLE_* feature flags. Malformed manifests or duplicate registrations are fatal to boot. The kernel is the only registry — there is no fallback.

Resolution is through ProviderResolutionService — the kernel is the sole resolution path. Channel provider integrations resolve the same way: social adapters are wrapped in SocialProviderKernelAdapter and registered like every other domain; IntegrationManager resolves them by identifier.

See Architecture and Provider Framework.

Verified against v1.3.0