RomM Frontend v2 — Component Constitution

This governs work inside frontend/src/v2/. v1 is frozen (src/views/, src/components/, src/console/, src/layouts/) — never refactor it; it will be deleted wholesale in a final wave. v2 is gated by user.ui_settings.uiVersion.

Official language for all code, comments, identifiers, .md, and commit/PR messages: English.

Related skills: frontend-v2-theming (tokens/colors), frontend-v2-input (focus/gamepad/responsive), frontend-v2-patterns (errors/loading/forms/permissions/confirmations), frontend-i18n, review-polish.

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Premises (stable)

1. v1 is frozen. Don't touch src/views/, src/components/, src/console/, src/layouts/. When coexistence forces a v2 fork of a store/composable/util, annotate the v1 export with @deprecated pointing at the v2 replacement.
2. Three component tiers (below).
3. Shared resources are canonical. Pinia stores, API services, OpenAPI types (src/__generated__/), locales, utils — v2 imports them, never forks them. Additive changes to shared resources are allowed; changing a shared store API to work around a v2 call-site issue is not.
4. TypeScript strict. Zero any (justify with a comment if unavoidable). No as unknown as ...; fix the source or define an intermediate type.
5. Universal substitution. When an R* primitive exists, use it. If it doesn't, create or extend it. Never drop to raw HTML when a primitive applies.
6. Attribute forwarding contract. A primitive whose root is polymorphic (<component :is>) or that forwards to an inner element uses defineOptions({ inheritAttrs: false }) + v-bind="$attrs" + slot passthrough, so call-site attrs and listeners land on the intended node instead of vanishing silently.
7. Layout in scoped CSS against tokens. v2 uses no utility-class framework and no component library: no Tailwind, no Vuetify. Write display: flex / gap: var(--r-space-*) in the component's own <style scoped>. Recurring structure becomes a primitive (RList, RToolbar, RCollapsible, RVirtualScroller), not a repeated block of classes.
8. Accessibility & performance are requirements: semantic HTML, focus management, contrast, ARIA on icon-only controls; lazy-load heavy views, virtualize large lists, stable :key on every v-for.

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The three tiers

Tier	Path	Prefix	Stores/services/router/emitter/i18n	Story	Domain knowledge
Primitive	src/v2/lib/	R* mandatory	No	Mandatory	None
Shared composite	src/v2/components/shared/	no prefix	Yes	Optional	Cross-feature, no specific domain
Feature composite	src/v2/components/<feature>/	no prefix	Yes	Optional	Feature-specific

A component is a primitive only if all three hold

1. Does not depend on stores, services, router, or emitter.
2. No knowledge of a product domain (ROM, Platform, Collection, User…). RAvatar yes, UserAvatar no.
3. Its API can be described without naming features — generic props/slots/events.

If any fails: shared composite if generic across features, feature composite if owned by one feature. Edge cases get raised to the user, not auto-decided. Consumer count never demotes a primitive.

Primitive boundaries

• Can use: tokens, other primitives, Vue, generic composables (useInput*, useFocus*).
• Cannot use: Pinia stores, API services, emitter, router (a RouterLink may be accepted as a prop), i18n directly. No $t() in primitives — text comes via props or slots.

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File & folder conventions

• Primitive: one per folder — RFoo/RFoo.vue, RFoo/RFoo.stories.ts, RFoo/index.ts, optional RFoo/types.ts.
• Composite: flat .vue if one file suffices; a folder with the same internal structure (no story required) if it has sub-pieces.
• Barrel: src/v2/lib/index.ts re-exports every primitive — update it when a new primitive ships. Composites are imported directly by path; no barrel. No single-file index.ts that just re-exports to shorten a path.

SFC structure

• <script setup lang="ts"> always.
• defineOptions({ inheritAttrs: false }) on every wrapper, paired with v-bind="$attrs" and slot passthrough (without the bind, attrs vanish silently).
• Props via defineProps<Props>() (interface), never runtime declarations. Emits via defineEmits<{...}>(). Slots with payload via defineSlots<{}>().
• Order: <script setup> → <template> → <style scoped>. Unscoped <style> (teleport overrides only) goes after the scoped block.

Import order & aliases

// 1. External
// 2. v2 primitives
import { RBtn, RDialog } from "@v2/lib";
import { computed, ref } from "vue";
import type { SimpleRom } from "@/__generated__";
// 5. Canonical shared resources
import storeAuth from "@/stores/auth";
// 4. v2 feature siblings
import GameCard from "@/v2/components/GameCard.vue";
// 3. v2 composables / shared
import { useCan } from "@/v2/composables/useCan";

• @v2/lib — primitives barrel. @/v2/... — anything else under v2. @/... — canonical shared resources. Never relative paths (../../foo) when an alias exists.
• Shared v2 types live in src/v2/types/; backend types come from src/__generated__/; not src/types/ (legacy).

Composables

• use prefix; single named export from composables/useFoo/index.ts; fully typed args/return; no side effects on module load (init on first call). Creating a v2-only composable when a v1 equivalent exists is allowed.

Console logging

• console.error allowed for production-visible errors. console.log/console.warn must not ship. console.debug is dev-only — remove before PR.

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Storybook (mandatory for /lib)

• Every primitive ships at least one story with controls and at least one variant per theme.
• A new interactive primitive that warrants gamepad navigation ships a play() interaction.
• Modified primitive: existing story must still render and its interactions still pass.
• npm run test runs Vitest and every /lib story's play() via composeStories. Don't duplicate coverage between Vitest (pure logic) and Storybook play() (components).

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Anti-patterns (beyond what the premises already say)

1. Don't change shared store APIs to work around a v2 call-site issue. (Fix the call site; the Gallery lesson was calling romsStore.reset() from the view, not adding _fetchSeq to the store.)
2. Don't drop to inline role checks — always go through useCan (see frontend-v2-patterns).
3. Don't reinvent a surface — dialog/menu/popover/card all go through their primitive; special cases become a new prop, not a parallel surface.
4. Don't hand-roll a <form>; use RForm.
5. Don't add backwards-compat shims inside v2: delete removed code; no // removed, no renamed-but-unused exports, no deprecated wrappers that just call the new function.
6. Don't write redundant tests; don't touch v1; never --no-verify on commits.

Allowed (often misread): modifying shared stores/services/utils additively; creating v2-only composables; importing from src/__generated__/.

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Known debt (focused follow-ups)

• When v1 dies: move uiVersion into UI_SETTINGS_KEYS; drop .r-v2-* scope classes (tokens move to :root); simplify useUISettings sync; delete useGameAnimation; drop the color-string→tone collapser in NotificationHost; remove the Vuetify rule arrays in stores/users.ts.

Full reference: docs/FRONTEND_ARCHITECTURE.md.