Frontend Feature Boundaries

Enforces feature isolation in apps/{app}/features/. Complements 01-nextjs-app-router.md §11.

Presentation code lives under features/{feature}/. Business rules and invariants live in docs/domain/ and the backend. Do not confuse the two.

Agent Quick Rules {#agent-quick-rules}

• MUST NOT import features/{a}/ from features/{b}/.
• Promote shared code to @/shared/ or components/ui/ per Strike 2 rule in principles.md.
• App Router shells MUST import feature entry components from features/{feature}/ only.
• MUST enable eslint-plugin-boundaries with feature isolation zones.
• UI strings MUST come from API fields, i18n keys, or page composition docs; do not invent copy.

Full convention: docs/conventions/frontend/feature-boundaries.md
When generating new files: Load and copy from docs/blueprints/frontend/feature-use-case.md.

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1. Import Rules

• Code under features/{feature}/ MUST NOT import from features/{otherFeature}/.
• Cross-feature reuse MUST follow the promotion rule in docs/conventions/principles.md: promote to shared/ (@/shared/...) or generic UI to components/ui/.
• app/ route shells MUST import feature entry components from features/{feature}/ only.

// GOOD
import { PostCard } from "@/features/posts/list/PostCard"

// BAD
import { AuthorAvatar } from "@/features/authors/shared/AuthorAvatar"

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2. ESLint Enforcement

Project repositories MUST enable eslint-plugin-boundaries (or equivalent) with zones:

Zone	Pattern	Allowed imports
features	features/*/**	Same feature area, shared, components/ui, lib
shared	shared/**	lib, other shared
app	app/**	features/* entry points only, lib, components

Example dependency rule (copy full file from docs/templates/config/eslint.config.ts):

{
  "settings": {
    "boundaries/elements": [
      { "type": "features", "pattern": "features/*", "mode": "folder" },
      { "type": "shared", "pattern": "shared/**" },
      { "type": "app", "pattern": "app/**" }
    ]
  }
}

CI MUST fail when a cross-feature import is introduced.

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3. Public Feature API

Each feature folder MAY expose a barrel features/{feature}/index.ts exporting only public entry components and hooks. Other features MUST NOT import deep paths from sibling features even if ESLint is misconfigured.

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4. Architecture Tests

There is no .NET-style architecture test for TypeScript. ESLint boundaries plus code review are REQUIRED. Playwright tests MUST live under apps/{app}/e2e/ and MUST NOT import feature internals across feature boundaries.