feat: add internationalization message platform

merge: design system platform
feat: add design system platform
2026-07-26 16:17:39 +09:00 · 2026-07-26 15:49:13 +09:00 · 2026-07-26 15:49:07 +09:00 · 2026-07-26 15:22:58 +09:00
93 changed files with 5159 additions and 582 deletions
@@ -31,6 +31,16 @@ module.exports = {
        path: "^(src/(application|adapters|bootstrap)|src/presentation/adapters|@tanstack)",
      },
    },
+    {
+      name: "icon-vendor-is-facade-only",
+      severity: "error",
+      from: {
+        path: "^src",
+        pathNot:
+          "^src/presentation/design-system/icons/vendors/lucide\\.tsx$",
+      },
+      to: { path: "^lucide-react$" },
+    },
    {
      name: "adapters-do-not-know-presentation",
      severity: "error",
@@ -15,4 +15,4 @@ M5 Error association: pending
 M6 Color signal: pending
 M7 Reduced motion: pending
 Screen reader: pending
-Notes: Review the text-field error association and modal focus containment/restoration.
+Notes: Review form primitives, Menu/Tabs keyboard behavior, Toast announcements, Tooltip supplemental copy, text-field error association and modal focus containment/restoration.
@@ -81,7 +81,10 @@
        { "script": "check:types:fixture:application-input", "expect": "fail" },
        { "script": "check:types:fixture:async-overlay", "expect": "fail" },
        { "script": "check:types:fixture:route-runtime", "expect": "fail" },
-        { "script": "check:types:fixture:page-action", "expect": "fail" }
+        { "script": "check:types:fixture:page-action", "expect": "fail" },
+        { "script": "check:types:fixture:icon-button", "expect": "fail" },
+        { "script": "check:types:fixture:i18n-key", "expect": "fail" },
+        { "script": "check:types:fixture:i18n-params", "expect": "fail" }
      ],
      "logPath": "artifacts/quality/check-types.txt",
      "evidence": ["artifacts/quality/check-types.txt"],
@@ -151,6 +154,10 @@
      "name": "architecture",
      "steps": [
        { "script": "check:architecture", "expect": "pass" },
+        { "script": "check:design-system", "expect": "pass" },
+        { "script": "check:design-system:fixture", "expect": "fail" },
+        { "script": "check:i18n", "expect": "pass" },
+        { "script": "check:i18n:fixture", "expect": "fail" },
        { "script": "check:registries", "expect": "pass" },
        { "script": "check:registries:fixture", "expect": "fail" },
        { "script": "check:routes:fixture", "expect": "fail" }
@@ -158,6 +165,10 @@
      "logPath": "artifacts/quality/gates/FE-GATE-010.txt",
      "evidence": [
        "artifacts/quality/dependency-report.json",
+        "artifacts/quality/design-system.json",
+        "artifacts/quality/design-system-fixture.json",
+        "artifacts/quality/i18n.json",
+        "artifacts/quality/i18n-fixture.json",
        "artifacts/quality/registries.json",
        "artifacts/quality/registry-fixture.json",
        "artifacts/quality/route-registry-fixture.json"
@@ -0,0 +1,57 @@
+# VD-05: Semantic icon facade와 native-first interaction
+
+- 상태: Accepted
+- 결정일: 2026-07-26
+- 적용 브랜치: `feature-frontend-design-system-platform`
+- 재검토: native 계약으로 충족할 수 없는 widget 요구가 확인될 때
+
+## 배경
+
+앱 셸과 공통 UI는 문자 glyph, raw button/select와 페이지별 focus 처리를
+사용했다. 아이콘 공급자와 복합 interaction을 제품 코드에 직접 노출하면 번들,
+접근성, vendor type과 교체 비용이 모든 feature로 전파된다. 반대로 실제 요구가
+없는 두 개의 headless vendor를 기본 설치하면 skeleton 소비자가 제거해야 할
+의존성과 중복 interaction 모델이 생긴다.
+
+## 결정
+
+1. 아이콘 공급자는 lockfile 최소 게시 유예를 통과한 `lucide-react@1.25.0`으로
+   고정한다.
+2. `lucide-react`의 static named import는
+   `design-system/icons/vendors/lucide.tsx` 한 파일에서만 허용한다.
+3. public API는 `MenuIcon`, `CloseIcon`, `WarningIcon` 같은 의미 이름만
+   노출한다. vendor component type, icon name, stroke API와 dynamic icon
+   registry는 노출하지 않는다.
+4. 장식 아이콘은 accessibility tree에서 제외한다. 정보를 단독 전달하는
+   아이콘은 `label`, icon-only action은 필수 `accessibleName`을 사용한다.
+5. 현재 복합 control은 native `dialog`, form control, `details`와 local
+   TypeScript state model로 구현한다. Menu는 roving focus/typeahead/Escape,
+   Tabs는 manual/automatic activation, Drawer는 modal/background
+   비활성화/focus restore 계약을 가진다.
+6. React Aria와 Radix는 기본 dependency로 추가하지 않는다. native platform이
+   collision, nested overlay, virtualized collection 또는 복합 select 요구를
+   충족하지 못한다는 재현 가능한 요구가 생길 때 prototype과 ADR로 다시
+   평가한다.
+7. Storybook과 pinned visual baseline은 VD-08/RP-10에서 도입한다. RP-07의
+   runtime gallery와 browser interaction test는 해당 workshop을 대체한다고
+   주장하지 않는다.
+
+## 경계와 검증
+
+- 제품 코드는 `presentation/design-system/index`만 import한다.
+- design-system 검사기는 direct icon/headless import, deep import, raw palette,
+  undefined token과 tooltip-only required information fixture를 거절한다.
+- type negative fixture는 accessible name 없는 `IconButton`을 거절한다.
+- component test는 decorative icon, form control, Menu, Tabs, Drawer와 Toast를
+  검증한다.
+- Chromium/Firefox E2E는 compact Drawer의 native modal 상태, Escape, focus
+  restore, gallery keyboard interaction과 axe를 검증한다.
+- 로컬 WebKit 실행은 host `libevent-2.1.so.7` 부재로 환경 검증이 남아 있으며
+  공급자 선택이나 product behavior의 PASS로 숨기지 않는다.
+
+## Rollback
+
+기존 `presentation/components/ui/*` 경로는 canonical TypeScript primitive를
+재수출하므로 소비 코드를 즉시 되돌릴 수 있다. Lucide 제거 시 vendor facade와
+semantic icon 구현만 교체하고 제품 API는 유지한다. headless vendor를 나중에
+도입해도 public props와 interaction test를 유지한다.
@@ -0,0 +1,96 @@
+# VD-06: Intl과 typed local message catalog
+
+- 상태: Accepted
+- 결정일: 2026-07-26
+- 적용 브랜치: `feature-frontend-i18n-message-formatting-contract`
+- 재검토: 승인 locale·복수형 문법·번역 추출 workflow가 local catalog 범위를 넘을 때
+
+## 배경
+
+공통 셸, route surface, async/form 상태와 디자인 시스템 기본 문구가 JSX와
+JavaScript에 분산돼 있었다. 날짜는 일부 application mapper에서 고정 locale로
+가공되어 presentation이 locale을 바꿀 수 없었고, direction·누락 key·보간 실패
+정책도 없었다. 반면 현재 skeleton에는 번역 관리 서비스, 실제 번역 승인 절차,
+복잡한 ICU 문법이라는 제품 요구가 아직 없다. 이 단계에서 i18n vendor를 기본
+번들에 넣으면 소비 프로젝트가 제거하거나 다시 감싸야 할 의존성만 늘어난다.
+
+## 결정
+
+1. 표준 `Intl.DateTimeFormat`, `NumberFormat`, `RelativeTimeFormat`,
+   `ListFormat`, `PluralRules`와 typed local catalog를 기본 엔진으로 사용한다.
+2. `MessageKey`는 한국어 canonical catalog에서 도출하며 영어와 RTL smoke
+   catalog는 `satisfies Record<MessageKey, string>`으로 compile-time parity를
+   강제한다.
+3. 보간이 필요한 key는 `MessageParameters`에 key별 parameter object를
+   선언한다. 잘못된 key, 누락·초과 parameter는 TypeScript negative fixture가
+   거절한다.
+4. 기본 locale은 `ko-KR`, fallback locale도 `ko-KR`이다. 알려지지 않은 locale은
+   language fallback 후 `ko-KR`로 정규화한다. 알려지지 않은 key와 누락 보간은
+   raw key나 외부 값을 출력하지 않고 안전한 공통 fallback을 반환한다.
+5. `en-XA`는 영어 문구를 확장·accent 처리하는 pseudo locale이고 `ar-EG`는
+   RTL 동작 smoke locale이다. 이 두 locale은 실제 제품 번역 완료를 의미하지
+   않는다.
+6. 날짜 formatter의 기본 timezone은 테스트와 SSR/브라우저 결과가 흔들리지
+   않도록 `UTC`다. 제품 timezone이 필요하면 호출자가 명시한다. invalid
+   date/number/timezone은 `—`를 반환하고 throw하지 않는다.
+7. locale state는 React inbound concern이다. `LocaleProvider`가 copy,
+   formatter와 `<html lang/dir>`을 제공하며 application/domain은 미리 번역된
+   문자열 대신 의미 값과 timestamp를 반환한다.
+8. backend `message`, raw HTML, stack과 내부 key를 catalog 입력으로 신뢰하지
+   않는다. transport/application failure kind를 등록된 사용자 message key로
+   매핑한 뒤 presentation이 해석한다.
+9. key rename은 즉시 제거하지 않고 `MESSAGE_KEY_ALIASES`에 compatibility alias를
+   둔다. alias는 새 호출의 타입에 포함하지 않아 신규 코드는 canonical key만
+   사용한다.
+10. extraction, ICU rich message, 번역 SaaS 또는 framework adapter가 필요해지면
+    `presentation/i18n` public API 뒤에서 교체한다. vendor type은 feature와
+    design-system public prop으로 노출하지 않는다.
+
+## 실행 경계
+
+```text
+route/form/failure 의미 값
+  -> presentation message key
+  -> LocaleProvider
+  -> typed catalog / Intl formatter
+  -> text node와 accessible name
+```
+
+- canonical catalog: `src/presentation/i18n/catalog.ts`
+- feature contribution: `src/features/*/contracts/*-message-catalog.js`를
+  `src/features/installed-feature-messages.js`에서 조립
+- key/보간/fallback/alias: `message-contract.ts`
+- locale-safe value formatting: `formatters.ts`
+- React composition과 document metadata: `locale-provider.tsx`
+- public entry: `src/presentation/i18n/index.ts`
+
+## 검증
+
+- `check:i18n`은 catalog key와 placeholder parity, common UI의 한국어 literal,
+  backend message JSX 렌더링과 raw HTML 사용을 검사한다.
+- `check:i18n:fixture`는 세 금지 사례를 실제로 거절해야 성공으로 인정된다.
+- type negative fixture는 unknown key와 잘못된 parameter shape를 거절한다.
+- unit test는 fallback, alias, pseudo 확장, direction과 timezone/number/relative/
+  list/plural/select의 결정성을 검증한다.
+- component test는 document `lang/dir`, RTL Tabs와 direction-aware pagination,
+  Drawer semantics를 검증한다.
+- Playwright는 320px pseudo reflow와 RTL compact shell/Drawer/focus restore를
+  Chromium, Firefox, WebKit project에서 실행한다.
+
+## 한계와 재검토 조건
+
+현재 catalog는 실제 번역 승인, ICU rich text, locale별 plural 문장 전체 조합,
+메시지 추출/번역 메모리와 서버 locale negotiation을 제공하지 않는다. 다음 중
+하나가 확인되면 별도 ADR로 엔진을 재평가한다.
+
+- 세 개 이상의 실제 승인 locale과 번역 담당 workflow
+- 복수형·성별·select가 한 문장 안에서 중첩되는 제품 copy
+- server/client extraction, namespace lazy-loading 또는 번역 SaaS 연동
+- SSR locale negotiation과 hydration 일치가 필요한 rendering mode
+
+## Rollback
+
+`ko-KR` catalog가 기존 기본 문구를 보존하므로 provider를 고정 locale adapter로
+되돌려도 기본 UX를 유지한다. formatter/vendor 교체 시 public `message`,
+`date`, `number`, `relativeTime`, `list`, `plural`, `select` 계약과 negative
+fixture는 유지한다. alias는 migration window 종료 근거 없이 제거하지 않는다.
@@ -12,7 +12,7 @@
 - 기본 번들에 포함할 역량과 필요할 때 설치할 확장 역량을 구분한다.
 - 특정 벤더를 채택하더라도 제품 코드가 벤더 API에 직접 결합되지 않는지 확인한다.

-최초 검토 기준은 `develop`의 `cb195f8`이며, RP-01~RP-04 구현 결과를 이 문서에
+최초 검토 기준은 `develop`의 `cb195f8`이며, RP-01~RP-08 구현 결과를 이 문서에
 누적 반영했다. 이후 구현으로 경로나 세부 내용이 달라질 수 있으므로, 각 항목은
 문서의 경로뿐 아니라 해당 테스트와 아키텍처 게이트로 계속 검증해야 한다.

@@ -33,13 +33,14 @@

 특히 다음은 선행 해결이 필요하다.

-RP-01~RP-05에서 TypeScript 도구 안전망, application runtime 주입,
+RP-01~RP-08에서 TypeScript 도구 안전망, application runtime 주입,
 query/mutation inbound adapter, HTTP 실행 계약과 executable route/release
-recovery 계약, 제거 가능한 reference 수직 슬라이스는 구현됐다. 현재 선행 해결
+recovery 계약, 제거 가능한 reference 수직 슬라이스, form/page, design system과
+i18n 실행 경계는 구현됐다. 현재 선행 해결
 대상은 다음과 같다.

-1. 폼, 페이지 템플릿, 확장된 디자인 시스템과 컴포넌트 워크벤치
-2. 국제화, diagnostics, optional adapter recipe와 심화 품질 게이트
+1. diagnostics/telemetry 실제 producer 연결
+2. registry evidence, 공급망과 optional adapter recipe 심화 게이트

 따라서 현재 상태를 “프론트 공통부가 모두 구현됐다”고 표현하면 범위가 과장된다.
 더 정확한 표현은 다음과 같다.
@@ -73,13 +74,13 @@ recovery 계약, 제거 가능한 reference 수직 슬라이스는 구현됐다.
 | 클라이언트 상태 | 부분 준비 | local state, theme context, session external store | 상태 소유권 표와 typed external-store 예제 |
 | 범용 global store | 프로젝트 선택 | 별도 라이브러리 없음 | 필요 조건에 따라 Zustand/Redux Toolkit/state machine 선택 |
 | 라우팅 | 준비됨 | Data Router, typed runtime map, codec, metadata consumer, bounded chunk recovery | reference feature route와 release E2E로 사용 범위 확장 |
-| 앱 셸·반응형 | 부분 준비 | header/sidebar/content/theme 구현 | 접근 가능한 mobile drawer와 focus 복원 |
-| 페이지 템플릿 | 준비됨 | Standard/Collection/Detail/Form/Status slot 계약과 reference 소비 화면 | RP-07 public design-system entry로 이동 |
-| 디자인 토큰 | 부분 준비 | semantic color/theme 토큰 존재 | typography, spacing, motion, layer 등 3단계 토큰 |
-| 공통 UI | 부분 준비 | Button, TextField, Card, Alert, Badge, Dialog | form/navigation/overlay/data/layout primitives 확장 |
-| 아이콘 | 미제공 | 문자 기호를 직접 사용 | Lucide를 로컬 icon facade 뒤에서 사용 |
+| 앱 셸·반응형 | 준비됨 | native modal Drawer, compact/desktop layout, Escape/link dismiss/focus restore, pseudo reflow와 RTL direction | compact browser matrix 유지 |
+| 페이지 템플릿 | 준비됨 | Standard/Collection/Detail/Form/Status와 public design-system entry | feature별 slot 조합 유지 |
+| 디자인 토큰 | 준비됨 | primitive/semantic/component CSS, 48-token 자동 계약, dark/forced-colors/reduced-motion | 제품 brand token은 외부 프로젝트에서 확장 |
+| 공통 UI | 준비됨 | action/form/feedback/overlay/navigation primitive와 pattern, compatibility export | Storybook/visual은 RP-10 |
+| 아이콘 | 준비됨 | Lucide static vendor facade와 semantic icon/IconButton 접근성 계약 | 의미 icon 추가 시 bundle/접근성 기준 적용 |
 | 폼 | 준비됨 | Zod 기반 local facade, error summary/focus, 422 allowlist, dirty/pending/conflict 정책 | 복합 form 요구가 생기면 VD-04 조건으로 vendor adapter 평가 |
-| 국제화 | 미제공 | 한국어 문자열·locale이 하드코딩 | typed message/formatter/locale/RTL 경계 |
+| 국제화 | 준비됨 | 137-key typed catalog, locale provider, Intl formatter, safe fallback/alias, pseudo·RTL gate | 실제 locale·번역 승인은 프로젝트에서 연결 |
 | logging/diagnostics | 미제공 | telemetry port는 있으나 logger 없음 | redaction이 적용된 diagnostics/logging 경계 |
 | telemetry | 부분 준비 | registry, queue, redaction 존재 | HTTP·boot·cache·storage·route 사건에 실제 연결 |
 | 비동기 상태 불변식 | 준비됨 | 배타적 typed overlay, stale latch, 실제 retry/conflict action | reference 화면에서 전체 상태 전시 |
@@ -250,6 +251,24 @@ known vulnerability, license policy, SBOM/provenance를 pinned tool로 검사해
 - registry/compatibility의 실제 diff와 orphan reference 검사
 - transitive vulnerability, license, SBOM/provenance 공급망 gate

+#### RP-08에서 국제화 실행 경계 구현
+
+`src/presentation/i18n`은 shell, route, async/form error, page template와
+design-system 기본 copy의 canonical 경계다. `MessageKey`와 key별
+`MessageParameters`가 잘못된 key/보간을 compile time에 막고, runtime
+`resolveMessage`는 unknown locale/key와 누락 보간에서 raw 값 대신 안전한
+fallback을 반환한다. application mapper는 locale-formatted date를 반환하지
+않고 timestamp를 유지하며 presentation formatter가 `UTC` 또는 명시 timezone을
+적용한다.
+
+`LocaleProvider`는 `ko-KR`, `en-US`, `en-XA`, `ar-EG` smoke set과 document
+`lang/dir`을 동기화한다. `en-XA`는 긴 문구 reflow, `ar-EG`는 logical CSS,
+Drawer, Tabs arrow와 pagination 방향 icon을 검증하기 위한 개발 locale이다.
+실제 아랍어 번역 완료를 뜻하지 않는다. `check:i18n`과 negative fixture는 common
+UI literal, backend raw message render와 raw HTML interpolation을 거절한다.
+새 key rename은 canonical type에는 넣지 않고 runtime alias/migration window로
+호환한다.
+
 ### 5.3 P2: 경계와 recipe를 제공할 선택 항목

 다음 기능을 모든 앱의 초기 번들에 설치할 필요는 없다. 대신 port 또는 local
@@ -588,6 +588,22 @@ RP-07은 compatibility export로 기존 primitive import를 복구할 수 있어
 token rename은 alias/migration 기간을 두고, vendor adapter와 local API commit을
 분리한다.

+**구현 증거 (2026-07-26)**
+
+- VD-05에서 `lucide-react@1.25.0` static semantic facade와 native-first
+  interaction을 채택하고 headless vendor 재평가 조건을 닫았다.
+- `src/presentation/design-system`이 48개 필수 token, public TypeScript barrel,
+  action/form/feedback/overlay/navigation primitive와 공통 pattern을 제공한다.
+- 기존 `components/ui` 경로는 compatibility export로 유지하고 앱 셸, gallery와
+  reference feature는 public entry를 소비한다.
+- 모바일 navigation은 native modal Drawer로 전환되어 배경 비활성화, Escape,
+  route dismiss와 trigger focus restore를 제공한다.
+- source/negative fixture gate가 undefined token, raw palette, direct vendor,
+  deep import, tooltip-only 정보와 accessible name 누락을 거절한다.
+- component/browser test가 Menu typeahead, Tabs activation, Toast queue,
+  form controls, compact reflow와 open-dialog axe를 실행한다. 로컬 WebKit은 host
+  `libevent-2.1.so.7` 부재로 환경 검증 상태를 유지한다.
+
 ### 08. `feature-frontend-i18n-message-formatting-contract`

 **목표**
@@ -635,6 +651,26 @@ token rename은 alias/migration 기간을 두고, vendor adapter와 local API co
 RP-08은 기존 기본 언어 catalog를 fallback으로 유지한다. 번역 catalog를
 파괴적으로 덮어쓰지 않는다.

+**구현 증거 (2026-07-26)**
+
+- VD-06에서 dependency를 추가하지 않는 browser `Intl` + typed local catalog를
+  채택하고 vendor 재평가 조건, fallback과 key migration 정책을 문서화했다.
+- `src/presentation/i18n`이 137개 common key, key별 interpolation,
+  `ko-KR` fallback, compatibility alias, date/number/relative/list/plural/select
+  formatter와 `LocaleProvider`를 제공한다.
+- shell, route lifecycle/access/recovery, async/form error, page template와
+  design-system default copy가 catalog consumer로 연결됐다.
+- feature route copy는 feature-owned catalog contribution으로 분리되어 reference
+  feature 제거 시 source와 built artifact에 전용 message key가 남지 않는다.
+- reference application mapper는 locale-formatted date 대신 timestamp를
+  반환하고 presentation formatter가 UTC 또는 명시 timezone을 적용한다.
+- `check:i18n`과 type negative fixture가 catalog/placeholder 불일치,
+  hardcoded common literal, backend raw message render, unsafe HTML,
+  unknown key와 interpolation mismatch를 거절한다.
+- unit/component/browser test가 safe fallback, pseudo 320px reflow,
+  document `lang/dir`, RTL Drawer/Tabs/directional icon과 deterministic formatter를
+  검증한다.
+
 ### 09. `feature-frontend-diagnostics-telemetry-runtime`

 **목표**
@@ -171,6 +171,22 @@ query vendor import는 architecture gate가 거절한다. reference feature의
 list/detail/create/status route가 각각 Collection/Detail/Form/Status template의
 실제 consumer다.

+RP-07에서 React inbound adapter 안의 UI 공급자 경계도 닫혔다.
+`src/presentation/design-system/index.ts`는 token → primitive → pattern →
+template public API이며 feature와 shell은 이 entry만 소비한다. Lucide는
+`icons/vendors/lucide.tsx`에 격리된 inbound vendor facade이므로 application
+port가 아니다. native Dialog/Drawer/Menu/Tabs의 focus·keyboard 상태도
+presentation이 소유하고 use case나 outbound adapter로 올리지 않는다.
+
+RP-08에서 i18n은 application output port가 아니라 React inbound adapter의
+local facade로 확정됐다. domain/application은 locale이나 번역 문장을 알지 않고
+timestamp, number, failure kind 같은 의미 값만 반환한다.
+`src/presentation/i18n`이 typed message catalog, formatter, fallback,
+`<html lang/dir>`과 pseudo/RTL smoke를 소유한다. backend raw `message`는
+application failure registry를 우회해 렌더링할 수 없으며 `check:i18n` negative
+fixture가 이 경계를 집행한다. 번역 vendor를 나중에 선택해도 이 facade 뒤의
+adapter만 교체한다.
+
 이 문서의 목표 구조는 기존 기반을 폐기하는 것이 아니라 이러한
 불일치를 제거하는 것이다.

@@ -447,6 +447,13 @@ controller가 소유하지 않는 것:
 | Page Template | 반복 layout/state | 접근성과 반응형 구조 재사용 | data fetching을 template에 포함 |
 | Registry + Runtime Map | route/operation/event | 선언과 실행 완전성 | 모든 설정을 하나의 거대 전역 파일에 집중 |

+RP-08 이후 route contract의 `title`/`navigation` 필드는 fallback metadata이며
+실제 document title, navigation, loading/error/access surface는
+`route.<ROUTE_ID>.title|navigation` typed catalog key를 해석한다. route params,
+search, backend message를 translation key로 조립하지 않는다. locale 변경은
+현재 route를 재요청하거나 query key를 바꾸지 않고 document title과 화면 copy만
+다시 렌더링한다.
+
 패턴은 추상화 파일만 만든 것으로 완료되지 않는다. reference usage, negative
 architecture test, 실패 상태 test가 있어야 제공된 패턴으로 본다.

@@ -485,6 +485,32 @@ raw response body, stack, token, URL query, PII를 사용자 copy나 일반 log
 - logging failure가 제품 flow를 실패시키지 않음
 - consent가 필요한 analytics와 essential diagnostics를 분리

+### 7.4 locale, message와 표시 값
+
+RP-08부터 locale은 presentation-owned React context다. server/application
+state에 번역된 문자열을 저장하거나 query key에 locale을 넣는 것은 응답 자체가
+locale별 데이터인 경우에만 허용한다. 공통 UI copy 변경 때문에 query cache를
+복제하지 않는다.
+
+```text
+API timestamp/number/failure kind
+  -> schema + mapper (의미 값 유지)
+  -> application result
+  -> presentation controller
+  -> useLocale().date/number/message
+```
+
+- message key는 `MessageKey` union이며 interpolation은 key별 tuple type이다.
+- unknown external key는 `resolveMessage`에 전달해도 raw key가 표시되지 않는다.
+- backend `message`는 diagnostic input일 수 있지만 사용자 copy가 아니다.
+- form validation code는 `ParameterlessMessageKey` allowlist로 mapping한다.
+- date의 기본 timezone은 UTC이고 제품 timezone은 presentation 호출자가
+  명시한다.
+- pseudo/RTL locale state는 local interaction state이며 persistence와 server
+  synchronization을 기본 제공하지 않는다.
+- key rename은 typed canonical key를 먼저 이동하고 runtime alias에 migration
+  기간을 둔다.
+
 ## 8. 폼 표준

 VD-04에 따라 현재 기본 엔진은 React native form event와 controlled value이며
@@ -584,4 +610,5 @@ backend message와 알 수 없는 path는 field copy로 사용하지 않는다.
 - 상태 종류별 소유권이 테스트와 문서에서 확인된다.
 - token은 UI와 일반 storage/store에 노출되지 않는다.
 - failure와 validation의 각 계층이 typed mapper로 분리된다.
+- common UI copy, locale formatter와 direction이 typed i18n facade를 통과한다.
 - query/mutation/form recipe만으로 새 기능을 만들 수 있다.
@@ -47,23 +47,23 @@
  - Chromium, Firefox, WebKit
  - 등록 라우트의 자동 접근성 검사

-이 기반은 유효하지만 아직 디자인 시스템 플랫폼 전체는 아니다.
+RP-07 구현 이후 이 기반은 저장소 내부 디자인 시스템 플랫폼 계약을 충족한다.
+아래 목록은 구현 전 공백과 현재 해결 상태를 함께 보존한다.

-1. 토큰이 색상 중심이며 typography, elevation, motion, z-layer, control size,
-   breakpoint가 계약으로 닫혀 있지 않다.
+1. typography, elevation, motion, z-layer, control size와 breakpoint는
+   `design-system/tokens`의 3계층과 자동 gate로 닫혔다.
 2. RP-06 form/page foundation은 준비됐지만 TextArea, Select, Checkbox,
   RadioGroup 같은 form primitive 확장은 RP-07에 남아 있다.
-3. 앱 셸과 예제 화면에서 공용 primitive 대신 raw `button`, `select`, 링크
-   class를 다시 작성하는 곳이 있다.
-4. `☰`, `×` 같은 문자 glyph를 직접 사용하며 아이콘 공급자 경계가 없다.
-5. `theme.css` 하나가 token, layout, primitive, pattern 스타일을 모두 소유한다.
+3. 앱 셸, 예제와 reference feature는 public design-system barrel을 소비한다.
+4. 문자 glyph는 semantic Lucide facade로 교체됐다.
+5. token은 세 CSS 파일로 분리됐고 `theme.css`는 layout/component styling만
+   소유한다.
 6. runtime gallery는 있지만 격리된 story, interaction story, 시각 회귀 기준선이
   없다.
 7. 사용자 문구가 한국어 literal로 고정되어 locale과 RTL 계약이 없다.
-8. page template은 준비됐지만 RP-07 design-system public entry와 token/pattern
-   계층으로 정리해야 한다.
-9. 모바일 sidebar는 표시 전환은 되지만 modal drawer 수준의 focus 이동, focus
-   복원, 배경 비활성화 계약은 없다.
+8. page template, form과 pattern은 public barrel에서 제공된다.
+9. 모바일 navigation은 native modal Drawer로 focus 이동, 배경 비활성화,
+   Escape/link dismiss와 trigger focus restore를 제공한다.

 따라서 기존 구성요소는 폐기하지 않고 아래 목표 계층으로 이동·확장한다.

@@ -534,8 +534,9 @@ Radix는 overlay와 primitive composition을 중심으로 평가할 수 있다.

 ## 9. 국제화 계약

-디자인 시스템 primitive는 한국어 문구를 내부 기본값으로 숨기지 않는다.
-접근성 label이나 오류 문구가 필요하면 명시적인 prop 또는 message key를 받는다.
+RP-08에서 디자인 시스템 primitive의 닫기, alert, toast, 글자 수 같은 기본
+문구는 `useLocale()` typed catalog로 이동했다. 제품 의미를 가진 label은 여전히
+명시적인 prop으로 받으며 primitive가 feature message key를 소유하지 않는다.

 필수 국제화 기반:

@@ -551,6 +552,17 @@ Radix는 overlay와 primitive composition을 중심으로 평가할 수 있다.
 - pseudo-locale
 - RTL story와 E2E smoke

+현재 구현 위치와 실패 정책:
+
+- `presentation/i18n/catalog.ts`: 137개 canonical common key와 locale parity
+- `message-contract.ts`: key별 interpolation, fallback과 compatibility alias
+- `formatters.ts`: UTC-default date, number, relative time, list, plural/select
+- `locale-provider.tsx`: document `lang/dir`과 React consumer API
+- missing key/parameter와 formatter 예외: 빈 문자열이나 raw key 대신 안전한
+  fallback
+- `en-XA`: 긴 문자열/320px reflow, `ar-EG`: logical layout/RTL keyboard smoke
+- backend raw message와 translated HTML: 정적 negative gate에서 거절
+
 금지 패턴:

 - 번역 문장 중간에 JSX 문자열을 연결한다.
@@ -559,7 +571,7 @@ Radix는 overlay와 primitive composition을 중심으로 평가할 수 있다.
 - route title, navigation label, toast message를 JSX literal로 분산한다.
 - 번역 누락 시 빈 문자열을 렌더링한다.

-Storybook toolbar에서 최소한 다음 조합을 전환할 수 있어야 한다.
+RP-10의 Storybook toolbar에서 최소한 다음 조합을 전환할 수 있어야 한다.

 - `ko-KR`, light
 - `en-US`, light
@@ -562,6 +562,30 @@ client route guard는 UX이며 authorization이 아님을 test 이름과 문서

 공용 컴포넌트는 한 번의 결함이 모든 페이지로 전파되므로 위험도가 높다.

+RP-07의 실행 경로는 `check:design-system`,
+`check:design-system:fixture`, `check:types:fixture:icon-button`,
+`tests/component/design-system-platform.test.tsx`와
+`tests/e2e/design-system-interactions.spec.js`다. Story interaction/visual
+baseline은 VD-08/RP-10에서 추가하며 현재 runtime gallery를 isolated workshop
+완료 증거로 사용하지 않는다.
+
+RP-08의 국제화 실행 경로는 `check:i18n`, `check:i18n:fixture`,
+`check:types:fixture:i18n-key`, `check:types:fixture:i18n-params`,
+`tests/unit/i18n-contract.test.ts`, `tests/component/locale-platform.test.tsx`와
+`tests/e2e/i18n.spec.js`다.
+
+- unit: locale catalog/placeholder parity, safe fallback/alias, pseudo expansion,
+  direction과 UTC date/number/relative/list/plural/select
+- component: document `lang/dir`, RTL tab arrow semantics, direction-aware
+  pagination과 modal Drawer
+- E2E: 320px pseudo reflow와 compact RTL shell/Drawer/focus restore
+- negative: common UI locale literal, backend message JSX render, raw translated
+  HTML, unknown key와 잘못된 interpolation parameter
+
+`ar-EG` catalog가 영어 smoke copy를 재사용하는 것은 RTL behavior 검증용이며
+번역 품질 PASS가 아니다. 실제 locale catalog에는 언어 담당 승인 evidence가
+추가되어야 한다.
+
 ### 10.1 Component behavior

 - native role/name/value
@@ -76,6 +76,7 @@ export default [
      "artifacts/**",
      "tests/fixtures/typecheck/**",
      "tests/fixtures/architecture/forbidden/**",
+      "tests/fixtures/i18n/forbidden/**",
      "tests/fixtures/security/forbidden/**",
    ],
  },
@@ -15,6 +15,10 @@
    "preview": "vite preview",
    "lint": "eslint src scripts tests vite.config.js vitest.config.js playwright.config.js --max-warnings=0",
    "check:architecture": "node scripts/check-architecture.mjs",
+    "check:design-system": "node scripts/check-design-system.mjs",
+    "check:design-system:fixture": "node scripts/check-design-system.mjs --fixture",
+    "check:i18n": "node scripts/check-i18n.mjs",
+    "check:i18n:fixture": "node scripts/check-i18n.mjs --fixture",
    "check:types": "corepack pnpm check:types:app && corepack pnpm check:types:node && corepack pnpm check:types:test",
    "check:types:app": "tsc --project tsconfig.app.json",
    "check:types:node": "tsc --project tsconfig.node.json",
@@ -27,6 +31,9 @@
    "check:types:fixture:async-overlay": "tsc --ignoreConfig --allowJs --checkJs --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler tests/fixtures/typecheck/invalid-async-overlay.ts",
    "check:types:fixture:route-runtime": "tsc --ignoreConfig --allowJs --checkJs --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler tests/fixtures/typecheck/invalid-route-runtime.ts",
    "check:types:fixture:page-action": "tsc --ignoreConfig --allowJs --checkJs --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler --jsx react-jsx tests/fixtures/typecheck/invalid-page-action.tsx",
+    "check:types:fixture:icon-button": "tsc --ignoreConfig --allowJs --checkJs --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler --jsx react-jsx tests/fixtures/typecheck/invalid-icon-button.tsx",
+    "check:types:fixture:i18n-key": "tsc --ignoreConfig --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler tests/fixtures/typecheck/invalid-message-key.ts",
+    "check:types:fixture:i18n-params": "tsc --ignoreConfig --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler tests/fixtures/typecheck/invalid-message-params.ts",
    "test:runtime-schema": "vitest run tests/runtime-schema --reporter=default --reporter=junit --outputFile.junit=artifacts/tests/runtime-schema.xml --passWithNoTests",
    "test:unit": "vitest run tests/unit --reporter=default --reporter=junit --outputFile.junit=artifacts/tests/unit.xml",
    "test:component": "vitest run tests/component --reporter=default --reporter=junit --outputFile.junit=artifacts/tests/component.xml",
@@ -58,6 +65,7 @@
  },
  "dependencies": {
    "@tanstack/react-query": "5.101.4",
+    "lucide-react": "1.25.0",
    "react": "19.2.8",
    "react-dom": "19.2.8",
    "react-router-dom": "7.18.1",
@@ -11,6 +11,9 @@ importers:
      '@tanstack/react-query':
        specifier: 5.101.4
        version: 5.101.4(react@19.2.8)
+      lucide-react:
+        specifier: 1.25.0
+        version: 1.25.0(react@19.2.8)
      react:
        specifier: 19.2.8
        version: 19.2.8
@@ -1536,6 +1539,11 @@ packages:
  lru-cache@5.1.1:
    resolution: {integrity: sha512-KpNARQA3Iwv+jTA0utUVVbrh+Jlrr1Fv0e56GGzAFOXN7dk/FviaDW8LHmK52DlcH4WP2n6gI8vN1aesBFgo9w==}

+  lucide-react@1.25.0:
+    resolution: {integrity: sha512-/mdJTRbiwcLOQ1NZZK1amZF9rIZyvO18D6r9TngE6TG1NmqHgFuT4eE7Xrkm9UsXMbBJD1NlfwHVltCDWHrOTw==}
+    peerDependencies:
+      react: ^16.5.1 || ^17.0.0 || ^18.0.0 || ^19.0.0
+
  lz-string@1.5.0:
    resolution: {integrity: sha512-h5bgJWpxJNswbU7qCrV0tIKQCaS3blPDrqKWx+QxzuzL1zGUzij9XCWLrSLsJPu5t+eWA/ycetzYAO5IOMcWAQ==}
    hasBin: true
@@ -3314,6 +3322,10 @@ snapshots:
    dependencies:
      yallist: 3.1.1

+  lucide-react@1.25.0(react@19.2.8):
+    dependencies:
+      react: 19.2.8
+
  lz-string@1.5.0: {}

  magic-string@0.30.21:
@@ -0,0 +1,148 @@
+import { mkdir, readFile, readdir, writeFile } from "node:fs/promises";
+import path from "node:path";
+
+// @ts-expect-error Node 24 executes erasable TypeScript for this build-time gate.
+import { REQUIRED_COMPONENT_TOKENS, REQUIRED_PRIMITIVE_TOKENS, REQUIRED_SEMANTIC_TOKENS } from "../src/presentation/design-system/tokens/token-contract.ts";
+
+const fixtureMode = process.argv.includes("--fixture");
+const failures = [];
+const tokenFiles = {
+  primitive: "src/presentation/design-system/tokens/primitive.css",
+  semantic: "src/presentation/design-system/tokens/semantic.css",
+  component: "src/presentation/design-system/tokens/component.css",
+};
+/** @type {Array<readonly [string, string, readonly string[]]>} */
+const tokenLayers = [
+  ["primitive", tokenFiles.primitive, REQUIRED_PRIMITIVE_TOKENS],
+  ["semantic", tokenFiles.semantic, REQUIRED_SEMANTIC_TOKENS],
+  ["component", tokenFiles.component, REQUIRED_COMPONENT_TOKENS],
+];
+
+for (const [layer, file, tokens] of tokenLayers) {
+  const source = await readFile(file, "utf8");
+  for (const token of tokens) {
+    if (!source.includes(`${token}:`)) {
+      failures.push(`${layer} token is missing: ${token}`);
+    }
+  }
+}
+
+const cssSources = await Promise.all(
+  [...Object.values(tokenFiles), "src/presentation/styles/theme.css"].map(
+    async (file) => ({ file, source: await readFile(file, "utf8") }),
+  ),
+);
+const definitions = new Set(
+  cssSources.flatMap(({ source }) =>
+    [...source.matchAll(/(--[a-z0-9-]+)\s*:/g)].map((match) => match[1]),
+  ),
+);
+for (const { file, source } of cssSources) {
+  for (const match of source.matchAll(/var\((--[a-z0-9-]+)/g)) {
+    if (!definitions.has(match[1])) {
+      failures.push(`${file} uses undefined token ${match[1]}`);
+    }
+  }
+}
+
+const semanticSource = await readFile(tokenFiles.semantic, "utf8");
+const darkSource =
+  semanticSource.match(/:root\[data-theme="dark"\]\s*\{([\s\S]*?)\n\}/)?.[1] ??
+  "";
+for (const token of [
+  "--color-surface",
+  "--color-surface-muted",
+  "--color-surface-elevated",
+  "--color-content",
+  "--color-content-muted",
+  "--color-content-inverse",
+  "--color-border",
+  "--color-border-strong",
+  "--color-action",
+  "--color-action-hover",
+  "--color-action-pressed",
+  "--color-danger",
+  "--color-focus",
+  "--color-disabled-content",
+  "--color-disabled-surface",
+]) {
+  if (!darkSource.includes(`${token}:`)) {
+    failures.push(`dark theme token is missing: ${token}`);
+  }
+}
+const componentSource = await readFile(tokenFiles.component, "utf8");
+if (!componentSource.includes("@media (forced-colors: active)")) {
+  failures.push("forced-colors token fallback is missing");
+}
+
+/** @param {string} directory @returns {Promise<string[]>} */
+async function listSourceFiles(directory) {
+  const result = [];
+  for (const entry of await readdir(directory, { withFileTypes: true })) {
+    const target = path.join(directory, entry.name);
+    if (entry.isDirectory()) result.push(...(await listSourceFiles(target)));
+    else if (/\.(js|jsx|mjs|ts|tsx|mts)$/.test(entry.name)) result.push(target);
+  }
+  return result;
+}
+
+const sources = fixtureMode
+  ? await listSourceFiles("tests/fixtures/design-system/forbidden")
+  : await listSourceFiles("src");
+for (const file of sources) {
+  const source = await readFile(file, "utf8");
+  const vendorFacade =
+    file === "src/presentation/design-system/icons/vendors/lucide.tsx";
+  if (!vendorFacade && /from\s+["']lucide-react["']/.test(source)) {
+    failures.push(`direct icon vendor import in ${file}`);
+  }
+  if (
+    /from\s+["'](?:react-aria-components|@radix-ui\/[^"']+)["']/.test(source)
+  ) {
+    failures.push(`direct headless vendor import in ${file}`);
+  }
+  if (
+    !file.includes("src/presentation/design-system/") &&
+    /presentation\/design-system\/(?!index(?:\.js)?["'])/.test(source)
+  ) {
+    failures.push(`design-system deep import in ${file}`);
+  }
+  if (
+    !file.includes("src/presentation/design-system/tokens/") &&
+    /(?:#[0-9a-f]{3,8}\b|oklch\(|rgba?\()/i.test(source)
+  ) {
+    failures.push(`raw palette value in ${file}`);
+  }
+  if (
+    file.includes("tests/fixtures/design-system/forbidden") &&
+    source.includes("TOOLTIP_ONLY_REQUIRED_INFORMATION")
+  ) {
+    failures.push(`tooltip-only required information in ${file}`);
+  }
+}
+
+const report = {
+  schemaVersion: 1,
+  mode: fixtureMode ? "negative-fixture" : "source",
+  checkedTokenCount:
+    REQUIRED_PRIMITIVE_TOKENS.length +
+    REQUIRED_SEMANTIC_TOKENS.length +
+    REQUIRED_COMPONENT_TOKENS.length,
+  failures,
+  passed: failures.length === 0,
+};
+await mkdir("artifacts/quality", { recursive: true });
+await writeFile(
+  fixtureMode
+    ? "artifacts/quality/design-system-fixture.json"
+    : "artifacts/quality/design-system.json",
+  `${JSON.stringify(report, null, 2)}\n`,
+);
+
+if (failures.length > 0) {
+  process.stderr.write(`Design system contract failed:\n${failures.join("\n")}\n`);
+  process.exit(1);
+}
+process.stdout.write(
+  `Design system contract: ${report.checkedTokenCount} tokens and vendor boundaries PASS\n`,
+);
@@ -0,0 +1,108 @@
+import { mkdir, readFile, readdir, writeFile } from "node:fs/promises";
+import path from "node:path";
+
+// @ts-expect-error Node 24 executes erasable TypeScript for this build-time gate.
+import { EN_MESSAGES, KO_MESSAGES, MESSAGE_CATALOGS } from "../src/presentation/i18n/catalog.ts";
+
+const fixtureMode = process.argv.includes("--fixture");
+const failures = [];
+const sourceExtensions = /\.(?:js|jsx|mjs|ts|tsx|mts)$/;
+const koreanLiteral = /[가-힣]/;
+const rawFailureRender =
+  /(?<!\$)\{\s*(?:failure|error|response|backend)(?:\?\.|\.)[\w?.]*message\s*\}/;
+
+/** @param {string} directory @returns {Promise<string[]>} */
+async function listSourceFiles(directory) {
+  const result = [];
+  for (const entry of await readdir(directory, { withFileTypes: true })) {
+    const target = path.join(directory, entry.name);
+    if (entry.isDirectory()) result.push(...(await listSourceFiles(target)));
+    else if (sourceExtensions.test(entry.name)) result.push(target);
+  }
+  return result;
+}
+
+/** @param {string} template */
+function placeholders(template) {
+  return [...template.matchAll(/\{([a-zA-Z][a-zA-Z0-9]*)\}/g)]
+    .map((match) => match[1])
+    .sort();
+}
+
+if (!fixtureMode) {
+  const canonicalKeys = Object.keys(KO_MESSAGES).sort();
+  for (const [locale, catalog] of Object.entries(MESSAGE_CATALOGS)) {
+    const readableCatalog =
+      /** @type {Readonly<Record<string, string>>} */ (catalog);
+    const canonicalCatalog =
+      /** @type {Readonly<Record<string, string>>} */ (KO_MESSAGES);
+    const keys = Object.keys(catalog).sort();
+    if (JSON.stringify(keys) !== JSON.stringify(canonicalKeys)) {
+      failures.push(`${locale} catalog keys do not match ko-KR`);
+    }
+    for (const key of canonicalKeys) {
+      if (
+        JSON.stringify(placeholders(readableCatalog[key] ?? "")) !==
+        JSON.stringify(placeholders(canonicalCatalog[key] ?? ""))
+      ) {
+        failures.push(`${locale}:${key} interpolation parameters do not match`);
+      }
+    }
+  }
+  if (Object.keys(EN_MESSAGES).length !== canonicalKeys.length) {
+    failures.push("en-US catalog key count does not match ko-KR");
+  }
+}
+
+const commonDirectories = [
+  "src/presentation/boundaries",
+  "src/presentation/components",
+  "src/presentation/design-system",
+  "src/presentation/forms",
+  "src/presentation/layouts",
+  "src/presentation/routes",
+  "src/presentation/templates",
+];
+const sources = fixtureMode
+  ? await listSourceFiles("tests/fixtures/i18n/forbidden")
+  : (
+      await Promise.all(commonDirectories.map((directory) => listSourceFiles(directory)))
+    ).flat();
+
+for (const file of sources) {
+  const source = await readFile(file, "utf8");
+  if (koreanLiteral.test(source)) {
+    failures.push(`hardcoded common user-facing locale literal in ${file}`);
+  }
+  if (rawFailureRender.test(source)) {
+    failures.push(`raw backend/error message rendered in ${file}`);
+  }
+  if (source.includes("dangerouslySetInnerHTML")) {
+    failures.push(`untrusted HTML interpolation boundary in ${file}`);
+  }
+}
+
+const report = {
+  schemaVersion: 1,
+  mode: fixtureMode ? "negative-fixture" : "source",
+  localeCount: Object.keys(MESSAGE_CATALOGS).length + 1,
+  messageKeyCount: Object.keys(KO_MESSAGES).length,
+  checkedFiles: sources.length,
+  failures,
+  passed: failures.length === 0,
+};
+await mkdir("artifacts/quality", { recursive: true });
+await writeFile(
+  fixtureMode
+    ? "artifacts/quality/i18n-fixture.json"
+    : "artifacts/quality/i18n.json",
+  `${JSON.stringify(report, null, 2)}\n`,
+);
+
+if (failures.length > 0) {
+  process.stderr.write(`I18n contract failed:\n${failures.join("\n")}\n`);
+  process.exit(1);
+}
+process.stdout.write(
+  `I18n contract: ${report.messageKeyCount} keys across ${report.localeCount} locales PASS\n`,
+);
@@ -89,6 +89,12 @@ export function createInstalledFeatureInputs(_context: FeatureContext) {
 }
 `;

+const emptyMessages = `export const INSTALLED_MESSAGE_CATALOGS = Object.freeze({
+  "ko-KR": Object.freeze({}),
+  "en-US": Object.freeze({}),
+});
+`;
+
 /** @param {string} directory @returns {Promise<string[]>} */
 async function filesBelow(directory) {
  const entries = await readdir(directory, { withFileTypes: true });
@@ -135,6 +141,10 @@ await writeFile(
  path.join(fixtureRoot, "src/features/installed-feature-adapters.ts"),
  emptyAdapters,
 );
+await writeFile(
+  path.join(fixtureRoot, "src/features/installed-feature-messages.js"),
+  emptyMessages,
+);

 /** @type {string[]} */
 const residue = [];
@@ -0,0 +1,10 @@
+import { REFERENCE_MESSAGE_CATALOGS } from "./reference-feature/contracts/reference-message-catalog.js";
+
+export const INSTALLED_MESSAGE_CATALOGS = Object.freeze({
+  "ko-KR": Object.freeze({
+    ...REFERENCE_MESSAGE_CATALOGS["ko-KR"],
+  }),
+  "en-US": Object.freeze({
+    ...REFERENCE_MESSAGE_CATALOGS["en-US"],
+  }),
+});
@@ -6,7 +6,7 @@ import {
 export type ReferenceResourceView = Readonly<{
  resourceId: string;
  title: string;
-  createdAtLabel: string | null;
+  createdAt: string | null;
  optimistic?: boolean;
 }>;

@@ -44,14 +44,10 @@ export function mapReferenceOperation(

 export function toReferenceView(
  resource: ReferenceResource,
-  formatDate: (value: Date) => string = (value) =>
-    new Intl.DateTimeFormat("ko-KR").format(value),
 ): ReferenceResourceView {
  return Object.freeze({
    resourceId: resource.id,
    title: resource.displayName,
-    createdAtLabel: resource.createdAt
-      ? formatDate(new Date(resource.createdAt))
-      : null,
+    createdAt: resource.createdAt,
  });
 }
@@ -0,0 +1,22 @@
+export const REFERENCE_MESSAGE_CATALOGS = Object.freeze({
+  "ko-KR": Object.freeze({
+    "route.REFERENCE_RESOURCE_LIST.navigation": "Reference feature",
+    "route.REFERENCE_RESOURCE_LIST.title": "Reference resources",
+    "route.REFERENCE_RESOURCE_DETAIL.navigation": "Reference detail",
+    "route.REFERENCE_RESOURCE_DETAIL.title": "Reference resource detail",
+    "route.REFERENCE_RESOURCE_FORM.navigation": "Reference form",
+    "route.REFERENCE_RESOURCE_FORM.title": "Create reference resource",
+    "route.REFERENCE_RESOURCE_STATUS.navigation": "Reference status",
+    "route.REFERENCE_RESOURCE_STATUS.title": "Reference resource status",
+  }),
+  "en-US": Object.freeze({
+    "route.REFERENCE_RESOURCE_LIST.navigation": "Reference feature",
+    "route.REFERENCE_RESOURCE_LIST.title": "Reference resources",
+    "route.REFERENCE_RESOURCE_DETAIL.navigation": "Reference detail",
+    "route.REFERENCE_RESOURCE_DETAIL.title": "Reference resource detail",
+    "route.REFERENCE_RESOURCE_FORM.navigation": "Reference form",
+    "route.REFERENCE_RESOURCE_FORM.title": "Create reference resource",
+    "route.REFERENCE_RESOURCE_STATUS.navigation": "Reference status",
+    "route.REFERENCE_RESOURCE_STATUS.title": "Reference resource status",
+  }),
+});
@@ -1,11 +1,15 @@
 import { Link } from "react-router-dom";

-import { AsyncSurface } from "../../../presentation/components/async-surface.jsx";
-import { DetailPage } from "../../../presentation/templates/index.js";
+import {
+  AsyncSurface,
+  DetailPage,
+} from "../../../presentation/design-system/index.js";
 import { useRouteInput } from "../../../presentation/routes/app-router.js";
+import { useLocale } from "../../../presentation/i18n/index.js";
 import { useReferenceDetail } from "./use-reference-feature.js";

 export default function ReferenceResourceDetailPage() {
+  const { date, message } = useLocale();
  const route = useRouteInput();
  const resourceId = String(route.params.resourceId);
  const { query } = useReferenceDetail(resourceId);
@@ -28,7 +32,11 @@ export default function ReferenceResourceDetailPage() {
            <dt>Resource ID</dt>
            <dd>{resource.resourceId}</dd>
            <dt>Created</dt>
-            <dd>{resource.createdAtLabel ?? "표시 정보 없음"}</dd>
+            <dd>
+              {resource.createdAt
+                ? date(new Date(resource.createdAt))
+                : message("common.noDisplayValue")}
+            </dd>
          </dl>
        ) : (
          <p>요약 정보를 준비하고 있습니다.</p>
@@ -1,17 +1,17 @@
 import { useCallback } from "react";
 import { useNavigate } from "react-router-dom";

-import { Button } from "../../../presentation/components/ui/button.jsx";
 import {
+  Button,
  DirtyNavigationDialog,
  ErrorSummary,
  Form,
  FormActions,
+  FormPage,
  FormField,
  useAppForm,
  useDirtyNavigationGuard,
-} from "../../../presentation/forms/index.js";
-import { FormPage } from "../../../presentation/templates/index.js";
+} from "../../../presentation/design-system/index.js";
 import {
  REFERENCE_FORM_DEFAULTS,
  referenceResourceFormSchema,
@@ -1,8 +1,10 @@
 import { Link, useNavigate } from "react-router-dom";

-import { AsyncSurface } from "../../../presentation/components/async-surface.jsx";
-import { Button } from "../../../presentation/components/ui/button.jsx";
-import { CollectionPage } from "../../../presentation/templates/index.js";
+import {
+  AsyncSurface,
+  Button,
+  CollectionPage,
+} from "../../../presentation/design-system/index.js";
 import { useReferenceFeature } from "./use-reference-feature.js";

 export default function ReferenceResourcePage() {
@@ -1,6 +1,6 @@
 import { useNavigate } from "react-router-dom";

-import { StatusPage } from "../../../presentation/templates/index.js";
+import { StatusPage } from "../../../presentation/design-system/index.js";

 export default function ReferenceResourceStatusPage() {
  const navigate = useNavigate();
@@ -70,7 +70,7 @@ export function useReferenceFeature() {
          {
            resourceId: `optimistic:${command.name}`,
            title: command.name,
-            createdAtLabel: null,
+            createdAt: null,
            optimistic: true,
          },
        ];
@@ -1,3 +1,5 @@
+import { formatMessage } from "../i18n/index.js";
+
 /**
 * @param {{
 *   kind?: string,
@@ -18,32 +20,36 @@ export function BootErrorShell({
 }) {
  return (
    <main role="alert">
-      <h1>애플리케이션을 시작할 수 없습니다.</h1>
+      <h1>{formatMessage("ko-KR", "boot.failure.title")}</h1>
      <dl>
-        <dt>오류</dt>
+        <dt>{formatMessage("ko-KR", "boot.field.error")}</dt>
        <dd>{kind}</dd>
-        <dt>코드</dt>
+        <dt>{formatMessage("ko-KR", "boot.field.code")}</dt>
        <dd>{code}</dd>
        {buildId && (
          <>
-            <dt>빌드</dt>
+            <dt>{formatMessage("ko-KR", "boot.field.build")}</dt>
            <dd>{buildId}</dd>
          </>
        )}
        {configSchemaVersion && (
          <>
-            <dt>설정 스키마</dt>
+            <dt>{formatMessage("ko-KR", "boot.field.configSchema")}</dt>
            <dd>{configSchemaVersion}</dd>
          </>
        )}
        {releaseId && (
          <>
-            <dt>릴리스</dt>
+            <dt>{formatMessage("ko-KR", "boot.field.release")}</dt>
            <dd>{releaseId}</dd>
          </>
        )}
      </dl>
-      <p>지원 참조: {supportReference}</p>
+      <p>
+        {formatMessage("ko-KR", "boot.supportReference", {
+          reference: supportReference,
+        })}
+      </p>
    </main>
  );
 }
@@ -3,6 +3,7 @@ import {
  type ErrorInfo,
  type ReactNode,
 } from "react";
+import { useLocale } from "../i18n/index.js";

 type RecoveryResult =
  | Readonly<{ action: "reload-once"; releasePair: string }>
@@ -71,27 +72,44 @@ export class ChunkRecoveryBoundary extends Component<Props, State> {
    const { error, recovery, reason } = this.state;
    if (error && !isChunkLoadFailure(error)) throw error;
    if (error && recovery === "checking") {
-      return (
-        <section className="ui-page" aria-live="polite" aria-busy="true">
-          새 릴리스 정보를 확인하고 있습니다.
-        </section>
-      );
+      return <ChunkRecoverySurface recovery="checking" />;
    }
    if (error && recovery === "reload-requested") {
-      return (
-        <section className="ui-page" aria-live="polite">
-          새 버전으로 한 번만 전환합니다.
-        </section>
-      );
+      return <ChunkRecoverySurface recovery="reload-requested" />;
    }
    if (error && recovery === "support") {
-      return (
-        <section className="ui-page" role="alert" data-recovery-reason={reason}>
-          <h1>화면 자산을 복구하지 못했습니다.</h1>
-          <p>문제가 계속되면 배포 상태와 지원 참조 정보를 확인해 주세요.</p>
-        </section>
-      );
+      return <ChunkRecoverySurface recovery="support" reason={reason} />;
    }
    return this.props.children;
  }
 }
+
+function ChunkRecoverySurface({
+  recovery,
+  reason,
+}: Readonly<{
+  recovery: Exclude<State["recovery"], "idle">;
+  reason?: string;
+}>) {
+  const { message } = useLocale();
+  if (recovery === "checking") {
+    return (
+      <section className="ui-page" aria-live="polite" aria-busy="true">
+        {message("chunk.checking")}
+      </section>
+    );
+  }
+  if (recovery === "reload-requested") {
+    return (
+      <section className="ui-page" aria-live="polite">
+        {message("chunk.reloadOnce")}
+      </section>
+    );
+  }
+  return (
+    <section className="ui-page" role="alert" data-recovery-reason={reason}>
+      <h1>{message("chunk.failure.title")}</h1>
+      <p>{message("chunk.failure.description")}</p>
+    </section>
+  );
+}
@@ -1,4 +1,5 @@
 import { Component } from "react";
+import { formatMessage } from "../i18n/index.js";

 /**
 * @typedef {{
@@ -57,9 +58,9 @@ export class RenderErrorBoundary extends Component {
      return (
        this.props.fallback ?? (
          <section role="alert">
-            <p>error.render_failure</p>
+            <p>{formatMessage("ko-KR", "error.render_failure")}</p>
            <button type="button" onClick={this.reset}>
-              retry
+              {formatMessage("ko-KR", "action.retry")}
            </button>
          </section>
        )
@@ -2,19 +2,22 @@ import { useId } from "react";

 import { errorMessage } from "./error-copy.js";
 import { Button } from "./ui/button.jsx";
+import { useLocale } from "../i18n/index.js";

 /** @param {{ label?: string }} props */
-export function LoadingSurface({ label = "불러오는 중" }) {
+export function LoadingSurface({ label }) {
+  const { message } = useLocale();
+  const accessibleLabel = label ?? message("async.loading");
  return (
    <section
      className="state-surface state-surface--loading"
      aria-busy="true"
-      aria-label={label}
+      aria-label={accessibleLabel}
      aria-live="polite"
      aria-atomic="true"
    >
      <div className="ui-skeleton" aria-hidden="true" />
-      <span className="visually-hidden">{label}</span>
+      <span className="visually-hidden">{accessibleLabel}</span>
    </section>
  );
 }
@@ -27,13 +30,14 @@ export function LoadingSurface({ label = "불러오는 중" }) {
 * }} props
 */
 export function EmptySurface({
-  title = "표시할 항목이 없습니다.",
+  title,
  description,
  action,
 }) {
+  const { message } = useLocale();
  return (
    <section className="ui-empty state-surface" aria-live="polite">
-      <h2>{title}</h2>
+      <h2>{title ?? message("async.empty")}</h2>
      {description ? <p>{description}</p> : null}
      {action}
    </section>
@@ -49,13 +53,14 @@ export function EmptySurface({
 * }} props
 */
 export function TerminalErrorSurface({ userMessageKey, action, onAction }) {
+  const { locale, message } = useLocale();
  const messageId = useId();
  const actionLabels = Object.freeze({
-    retry: "다시 시도",
-    reauth: "로그인",
-    navigate: "안전한 화면으로 이동",
-    "reload-once": "한 번 새로고침",
-    "contact-support": "지원 정보 확인",
+    retry: message("action.retry"),
+    reauth: message("action.reauth"),
+    navigate: message("action.navigateSafe"),
+    "reload-once": message("action.reloadOnce"),
+    "contact-support": message("action.contactSupport"),
  });
  return (
    <section
@@ -64,7 +69,7 @@ export function TerminalErrorSurface({ userMessageKey, action, onAction }) {
      aria-labelledby={messageId}
      data-message-key={userMessageKey}
    >
-      <h2 id={messageId}>{errorMessage(userMessageKey)}</h2>
+      <h2 id={messageId}>{errorMessage(userMessageKey, locale)}</h2>
      {action !== "none" && onAction && (
        <Button onClick={onAction}>{actionLabels[action]}</Button>
      )}
@@ -88,6 +93,7 @@ export function AsyncSurface({
  onRetry,
  onResolveConflict,
 }) {
+  const { message } = useLocale();
  if (state.base === "initial-loading") return <LoadingSurface />;
  if (state.base === "empty") return <EmptySurface />;
  if (state.base === "terminal-error" && state.failure) {
@@ -104,12 +110,24 @@ export function AsyncSurface({
    <section aria-busy={state.overlay.refreshing || state.overlay.mutationPending}>
      {state.indicator ? (
        <div role="status" aria-live="polite">
-          <span>{state.indicator}</span>
+          <span>
+            {message(
+              state.indicator === "stale-degraded"
+                ? "async.staleDegraded"
+                : state.indicator === "mutation-conflict"
+                  ? "async.mutationConflict"
+                  : state.indicator === "mutation-pending"
+                    ? "async.mutationPending"
+                    : "async.refreshing",
+            )}
+          </span>
          {state.indicator === "stale-degraded" && onRetry ? (
-            <Button onClick={onRetry}>다시 시도</Button>
+            <Button onClick={onRetry}>{message("action.retry")}</Button>
          ) : null}
          {state.indicator === "mutation-conflict" && onResolveConflict ? (
-            <Button onClick={onResolveConflict}>충돌 해결</Button>
+            <Button onClick={onResolveConflict}>
+              {message("action.resolveConflict")}
+            </Button>
          ) : null}
        </div>
      ) : null}
@@ -1,26 +1,6 @@
-const ERROR_MESSAGES = Object.freeze({
-  "error.network_unreachable": "네트워크에 연결할 수 없습니다.",
-  "error.request_timeout": "요청 시간이 초과되었습니다.",
-  "error.auth_required": "계속하려면 로그인이 필요합니다.",
-  "error.auth_integration_failure": "로그인 연동을 사용할 수 없습니다.",
-  "error.forbidden": "이 작업을 수행할 권한이 없습니다.",
-  "error.not_found": "요청한 항목을 찾을 수 없습니다.",
-  "error.rate_limited": "요청이 많습니다. 잠시 후 다시 시도해 주세요.",
-  "error.server_failure": "요청을 완료하지 못했습니다.",
-  "error.chunk_load_failure": "새 화면 파일을 불러오지 못했습니다.",
-  "error.build_mismatch": "현재 화면과 활성 빌드가 일치하지 않습니다.",
-  "error.config_mismatch": "런타임 설정 버전이 현재 화면과 일치하지 않습니다.",
-  "error.api_contract_mismatch": "API 계약 버전이 현재 화면과 일치하지 않습니다.",
-  "error.release_mismatch": "현재 화면과 활성 릴리스가 일치하지 않습니다.",
-  "error.asset_mismatch": "화면 자산 구성이 현재 릴리스와 일치하지 않습니다.",
-  "error.render_failure": "화면을 표시하지 못했습니다.",
-  "error.unknown_failure": "예상하지 못한 문제가 발생했습니다.",
-});
+import { resolveMessage } from "../i18n/index.js";

-/** @param {string} messageKey */
-export function errorMessage(messageKey) {
-  const messages = /** @type {Readonly<Record<string, string>>} */ (
-    ERROR_MESSAGES
-  );
-  return messages[messageKey] ?? "요청을 완료하지 못했습니다.";
+/** @param {string} messageKey @param {string} [locale] */
+export function errorMessage(messageKey, locale = "ko-KR") {
+  return resolveMessage(locale, messageKey);
 }
@@ -1,4 +1,5 @@
 import { Button } from "./ui/button.jsx";
+import { useLocale } from "../i18n/index.js";

 /**
 * @param {{
@@ -30,12 +31,13 @@ function StateSurface({

 /** @param {{ onSignIn?: () => void }} props */
 export function AuthRequiredSurface({ onSignIn }) {
+  const { message } = useLocale();
  return (
    <StateSurface
-      eyebrow="401 · 인증 필요"
-      title="로그인이 필요합니다."
-      description="세션을 시작한 뒤 이전 작업을 안전하게 계속할 수 있습니다."
-      actionLabel="로그인 시작"
+      eyebrow={message("access.auth.eyebrow")}
+      title={message("access.auth.title")}
+      description={message("access.auth.description")}
+      actionLabel={message("action.signIn")}
      onAction={onSignIn}
    />
  );
@@ -43,12 +45,13 @@ export function AuthRequiredSurface({ onSignIn }) {

 /** @param {{ onNavigate?: () => void }} props */
 export function ForbiddenSurface({ onNavigate }) {
+  const { message } = useLocale();
  return (
    <StateSurface
-      eyebrow="403 · 권한 없음"
-      title="접근할 수 없습니다."
-      description="권한을 확인하거나 접근 가능한 화면으로 이동하세요."
-      actionLabel="안전한 화면으로 이동"
+      eyebrow={message("access.forbidden.eyebrow")}
+      title={message("access.forbidden.title")}
+      description={message("access.forbidden.description")}
+      actionLabel={message("action.navigateSafe")}
      onAction={onNavigate}
      tone="warning"
    />
@@ -57,12 +60,13 @@ export function ForbiddenSurface({ onNavigate }) {

 /** @param {{ onNavigate?: () => void }} props */
 export function NotFoundSurface({ onNavigate }) {
+  const { message } = useLocale();
  return (
    <StateSurface
-      eyebrow="404 · 찾을 수 없음"
-      title="요청한 화면이 없습니다."
-      description="주소를 확인하거나 시작 화면으로 돌아가세요."
-      actionLabel="시작 화면으로 이동"
+      eyebrow={message("access.notFound.eyebrow")}
+      title={message("access.notFound.title")}
+      description={message("access.notFound.description")}
+      actionLabel={message("action.goHome")}
      onAction={onNavigate}
    />
  );
@@ -1,36 +1 @@
-/**
- * @param {{
- *   title: string,
- *   children?: React.ReactNode,
- *   variant?: "info" | "success" | "warning" | "danger",
- *   onDismiss?: () => void
- * }} props
- */
-export function Alert({
-  title,
-  children,
-  variant = "info",
-  onDismiss,
-}) {
-  return (
-    <section
-      className={`ui-alert ui-alert--${variant}`}
-      role={variant === "danger" ? "alert" : "status"}
-    >
-      <div>
-        <strong>{title}</strong>
-        {children ? <div className="ui-alert__content">{children}</div> : null}
-      </div>
-      {onDismiss ? (
-        <button
-          className="ui-alert__dismiss"
-          type="button"
-          aria-label={`${title} 알림 닫기`}
-          onClick={onDismiss}
-        >
-          ×
-        </button>
-      ) : null}
-    </section>
-  );
-}
+export { Alert } from "../../design-system/primitives/core.js";
@@ -1,9 +1 @@
-/**
- * @param {{
- *   children: React.ReactNode,
- *   variant?: "neutral" | "info" | "success" | "warning" | "danger"
- * }} props
- */
-export function Badge({ children, variant = "neutral" }) {
-  return <span className={`ui-badge ui-badge--${variant}`}>{children}</span>;
-}
+export { Badge } from "../../design-system/primitives/core.js";
@@ -1,24 +1 @@
-/**
- * @param {React.ButtonHTMLAttributes<HTMLButtonElement> & {
- *   variant?: "primary" | "secondary" | "danger" | "ghost",
- *   size?: "default" | "compact"
- * }} props
- */
-export function Button({
-  variant = "primary",
-  size = "default",
-  className = "",
-  type = "button",
-  ...props
-}) {
-  const classes = [
-    "ui-button",
-    `ui-button--${variant}`,
-    size === "compact" ? "ui-button--compact" : "",
-    className,
-  ]
-    .filter(Boolean)
-    .join(" ");
-
-  return <button {...props} className={classes} type={type} />;
-}
+export { Button } from "../../design-system/primitives/core.js";
@@ -1,28 +1 @@
-import { useId } from "react";
-
-/**
- * @param {{
- *   title: string,
- *   description?: string,
- *   children?: React.ReactNode,
- *   footer?: React.ReactNode,
- *   className?: string
- * }} props
- */
-export function Card({ title, description, children, footer, className = "" }) {
-  const titleId = useId();
-
-  return (
-    <article
-      className={`ui-card ${className}`.trim()}
-      aria-labelledby={titleId}
-    >
-      <div className="ui-card__header">
-        <h3 id={titleId}>{title}</h3>
-        {description ? <p>{description}</p> : null}
-      </div>
-      {children ? <div className="ui-card__content">{children}</div> : null}
-      {footer ? <footer className="ui-card__footer">{footer}</footer> : null}
-    </article>
-  );
-}
+export { Card } from "../../design-system/primitives/core.js";
@@ -1,88 +1 @@
-import { useEffect, useId, useRef } from "react";
-
-/**
- * @param {{
- *   open: boolean,
- *   onClose: () => void,
- *   title: string,
- *   description?: string,
- *   children?: React.ReactNode,
- *   actions?: React.ReactNode
- * }} props
- */
-export function Dialog({
-  open,
-  onClose,
-  title,
-  description,
-  children,
-  actions,
-}) {
-  const dialogRef = useRef(/** @type {HTMLDialogElement | null} */ (null));
-  const previousFocusRef = useRef(/** @type {HTMLElement | null} */ (null));
-  const titleId = useId();
-  const descriptionId = useId();
-
-  useEffect(() => {
-    const dialog = dialogRef.current;
-    if (!dialog) return;
-
-    if (open) {
-      previousFocusRef.current =
-        document.activeElement instanceof HTMLElement
-          ? document.activeElement
-          : null;
-      if (!dialog.open) {
-        if (typeof dialog.showModal === "function") dialog.showModal();
-        else dialog.setAttribute("open", "");
-      }
-      const firstFocusable = dialog.querySelector(
-        "[autofocus], button, [href], input, select, textarea, [tabindex]:not([tabindex='-1'])",
-      );
-      if (firstFocusable instanceof HTMLElement) firstFocusable.focus();
-      return;
-    }
-
-    if (dialog.open) {
-      if (typeof dialog.close === "function") dialog.close();
-      else dialog.removeAttribute("open");
-    }
-    previousFocusRef.current?.focus();
-    previousFocusRef.current = null;
-  }, [open]);
-
-  return (
-    <dialog
-      className="ui-dialog"
-      ref={dialogRef}
-      aria-labelledby={titleId}
-      aria-describedby={description ? descriptionId : undefined}
-      onCancel={(event) => {
-        event.preventDefault();
-        onClose();
-      }}
-      onClick={(event) => {
-        if (event.target === event.currentTarget) onClose();
-      }}
-    >
-      <div className="ui-dialog__surface">
-        <header className="ui-dialog__header">
-          <div>
-            <h2 id={titleId}>{title}</h2>
-            {description ? <p id={descriptionId}>{description}</p> : null}
-          </div>
-          <button
-            className="ui-dialog__close"
-            type="button"
-            aria-label={`${title} 닫기`}
-            onClick={onClose}
-          >
-            ×
-          </button>
-        </header>
-        {children ? <div className="ui-dialog__content">{children}</div> : null}
-        {actions ? <footer className="ui-dialog__actions">{actions}</footer> : null}
-      </div>
-    </dialog>
-  );
-}
+export { Dialog } from "../../design-system/primitives/core.js";
@@ -1,52 +1 @@
-import { useId } from "react";
-
-/**
- * @param {Omit<React.InputHTMLAttributes<HTMLInputElement>, "id"> & {
- *   id?: string,
- *   label: string,
- *   description?: string,
- *   error?: string
- * }} props
- */
-export function TextField({
-  id,
-  label,
-  description,
-  error,
-  className = "",
-  required,
-  ...inputProps
-}) {
-  const generatedId = useId();
-  const inputId = id ?? `field-${generatedId}`;
-  const descriptionId = description ? `${inputId}-description` : undefined;
-  const errorId = error ? `${inputId}-error` : undefined;
-  const describedBy = [descriptionId, errorId].filter(Boolean).join(" ");
-
-  return (
-    <div className={`ui-field ${className}`.trim()}>
-      <label className="ui-field__label" htmlFor={inputId}>
-        {label}
-        {required ? <span aria-hidden="true"> *</span> : null}
-      </label>
-      {description ? (
-        <p className="ui-field__description" id={descriptionId}>
-          {description}
-        </p>
-      ) : null}
-      <input
-        {...inputProps}
-        className="ui-field__input"
-        id={inputId}
-        required={required}
-        aria-describedby={describedBy || undefined}
-        aria-invalid={error ? "true" : undefined}
-      />
-      {error ? (
-        <p className="ui-field__error" id={errorId}>
-          {error}
-        </p>
-      ) : null}
-    </div>
-  );
-}
+export { TextField } from "../../design-system/primitives/core.js";
@@ -0,0 +1,47 @@
+import type { ComponentType, SVGProps } from "react";
+
+import {
+  CloseGlyph,
+  ErrorGlyph,
+  InfoGlyph,
+  MenuGlyph,
+  NextGlyph,
+  PreviousGlyph,
+  SearchGlyph,
+  SuccessGlyph,
+  WarningGlyph,
+} from "./vendors/lucide.js";
+
+export type SemanticIconProps = Readonly<{
+  label?: string;
+  size?: "small" | "medium" | "large";
+}>;
+
+function createSemanticIcon(
+  Glyph: ComponentType<SVGProps<SVGSVGElement>>,
+) {
+  return function SemanticIcon({
+    label,
+    size = "medium",
+  }: SemanticIconProps) {
+    return (
+      <Glyph
+        aria-hidden={label ? undefined : "true"}
+        aria-label={label}
+        className={`ui-icon ui-icon--${size}`}
+        focusable="false"
+        role={label ? "img" : undefined}
+      />
+    );
+  };
+}
+
+export const MenuIcon = createSemanticIcon(MenuGlyph);
+export const CloseIcon = createSemanticIcon(CloseGlyph);
+export const WarningIcon = createSemanticIcon(WarningGlyph);
+export const SuccessIcon = createSemanticIcon(SuccessGlyph);
+export const ErrorIcon = createSemanticIcon(ErrorGlyph);
+export const InfoIcon = createSemanticIcon(InfoGlyph);
+export const SearchIcon = createSemanticIcon(SearchGlyph);
+export const PreviousIcon = createSemanticIcon(PreviousGlyph);
+export const NextIcon = createSemanticIcon(NextGlyph);
@@ -0,0 +1,21 @@
+import {
+  AlertTriangle,
+  Check,
+  ChevronLeft,
+  ChevronRight,
+  CircleX,
+  Info,
+  Menu,
+  Search,
+  X,
+} from "lucide-react";
+
+export const MenuGlyph = Menu;
+export const CloseGlyph = X;
+export const WarningGlyph = AlertTriangle;
+export const SuccessGlyph = Check;
+export const ErrorGlyph = CircleX;
+export const InfoGlyph = Info;
+export const SearchGlyph = Search;
+export const PreviousGlyph = ChevronLeft;
+export const NextGlyph = ChevronRight;
@@ -0,0 +1,146 @@
+export {
+  Alert,
+  Badge,
+  Button,
+  Card,
+  Dialog,
+  Field,
+  FocusRing,
+  IconButton,
+  LinkButton,
+  Portal,
+  Spinner,
+  TextField,
+  VisuallyHidden,
+} from "./primitives/core.js";
+export type {
+  AlertProps,
+  BadgeProps,
+  ButtonProps,
+  ButtonSize,
+  ButtonVariant,
+  CardProps,
+  DialogProps,
+  IconButtonProps,
+  LinkButtonProps,
+  SpinnerProps,
+  TextFieldProps,
+} from "./primitives/core.js";
+export {
+  Checkbox,
+  RadioGroup,
+  SearchField,
+  Select,
+  Switch,
+  TextArea,
+} from "./primitives/forms.js";
+export type {
+  CheckboxProps,
+  RadioGroupProps,
+  RadioOption,
+  SearchFieldProps,
+  SelectOption,
+  SelectProps,
+  SwitchProps,
+  TextAreaProps,
+} from "./primitives/forms.js";
+export {
+  ProgressBar,
+  Separator,
+  Skeleton,
+} from "./primitives/feedback.js";
+export type {
+  ProgressBarProps,
+  SkeletonProps,
+} from "./primitives/feedback.js";
+export {
+  ConfirmationDialog,
+  Drawer,
+  Menu,
+  Popover,
+  ToastProvider,
+  Tooltip,
+  useToast,
+} from "./primitives/overlays.js";
+export type {
+  DrawerProps,
+  MenuItemDefinition,
+  MenuProps,
+  PopoverProps,
+  TooltipProps,
+} from "./primitives/overlays.js";
+export {
+  Breadcrumbs,
+  Pagination,
+  Tabs,
+} from "./primitives/navigation.js";
+export type {
+  BreadcrumbItem,
+  TabDefinition,
+} from "./primitives/navigation.js";
+export {
+  CloseIcon,
+  ErrorIcon,
+  InfoIcon,
+  MenuIcon,
+  NextIcon,
+  PreviousIcon,
+  SearchIcon,
+  SuccessIcon,
+  WarningIcon,
+} from "./icons/semantic-icons.js";
+export type {
+  SemanticIconProps,
+} from "./icons/semantic-icons.js";
+export {
+  DESIGN_TOKEN_CONTRACT,
+  REQUIRED_COMPONENT_TOKENS,
+  REQUIRED_PRIMITIVE_TOKENS,
+  REQUIRED_SEMANTIC_TOKENS,
+} from "./tokens/token-contract.js";
+export {
+  AccessSurface,
+  DataTable,
+  DisclosureGroup,
+  PaginationBar,
+  SearchFilterToolbar,
+} from "./patterns/common-patterns.js";
+export type {
+  AccessSurfaceProps,
+  DataTableColumn,
+  DisclosureDefinition,
+} from "./patterns/common-patterns.js";
+
+export {
+  AsyncSurface,
+  EmptySurface,
+  LoadingSurface,
+  TerminalErrorSurface,
+} from "../components/async-surface.jsx";
+export { PageHeader } from "../components/page-header.jsx";
+export {
+  AuthRequiredSurface,
+  ForbiddenSurface,
+  NotFoundSurface,
+} from "../components/state-surfaces.jsx";
+export {
+  DetailPage,
+  CollectionPage,
+  FormPage,
+  StandardPage,
+  StatusPage,
+} from "../templates/index.js";
+export {
+  DirtyNavigationDialog,
+  ErrorSummary,
+  Form,
+  FormActions,
+  FormField,
+  useAppForm,
+  useDirtyNavigationGuard,
+} from "../forms/index.js";
+export type {
+  PageActionDefinition,
+  PageHeading,
+} from "../templates/page-templates.js";
+export type { FormResult } from "../forms/form-contracts.js";
@@ -0,0 +1,139 @@
+import { useId } from "react";
+
+import {
+  AuthRequiredSurface,
+  ForbiddenSurface,
+  NotFoundSurface,
+} from "../../components/state-surfaces.jsx";
+import { Button } from "../primitives/core.js";
+import { Pagination } from "../primitives/navigation.js";
+
+export type DataTableColumn<Row> = Readonly<{
+  id: string;
+  header: string;
+  cell(row: Row): React.ReactNode;
+}>;
+
+export function DataTable<Row>({
+  caption,
+  columns,
+  rows,
+  rowKey,
+  empty,
+}: Readonly<{
+  caption: string;
+  columns: readonly DataTableColumn<Row>[];
+  rows: readonly Row[];
+  rowKey(row: Row): string;
+  empty: React.ReactNode;
+}>) {
+  if (rows.length === 0) return <>{empty}</>;
+  return (
+    <div className="ui-data-table__scroll" tabIndex={0}>
+      <table className="ui-data-table">
+        <caption>{caption}</caption>
+        <thead>
+          <tr>
+            {columns.map((column) => (
+              <th key={column.id} scope="col">
+                {column.header}
+              </th>
+            ))}
+          </tr>
+        </thead>
+        <tbody>
+          {rows.map((row) => (
+            <tr key={rowKey(row)}>
+              {columns.map((column) => (
+                <td key={column.id}>{column.cell(row)}</td>
+              ))}
+            </tr>
+          ))}
+        </tbody>
+      </table>
+    </div>
+  );
+}
+
+export function SearchFilterToolbar({
+  label,
+  search,
+  filters,
+  resetLabel,
+  onReset,
+  resultCount,
+}: Readonly<{
+  label: string;
+  search: React.ReactNode;
+  filters?: React.ReactNode;
+  resetLabel: string;
+  onReset(): void;
+  resultCount: React.ReactNode;
+}>) {
+  return (
+    <section aria-label={label} className="ui-search-filter-toolbar">
+      <div>{search}</div>
+      {filters ? <div>{filters}</div> : null}
+      <Button onClick={onReset} variant="ghost">
+        {resetLabel}
+      </Button>
+      <output>{resultCount}</output>
+    </section>
+  );
+}
+
+export function PaginationBar({
+  range,
+  ...pagination
+}: React.ComponentProps<typeof Pagination> & Readonly<{ range: string }>) {
+  return (
+    <div className="ui-pagination-bar">
+      <p>{range}</p>
+      <Pagination {...pagination} />
+    </div>
+  );
+}
+
+export type DisclosureDefinition = Readonly<{
+  id: string;
+  title: string;
+  content: React.ReactNode;
+}>;
+
+export function DisclosureGroup({
+  label,
+  items,
+}: Readonly<{
+  label: string;
+  items: readonly DisclosureDefinition[];
+}>) {
+  const groupId = useId();
+  return (
+    <section aria-labelledby={groupId} className="ui-disclosure-group">
+      <h2 className="visually-hidden" id={groupId}>
+        {label}
+      </h2>
+      {items.map((item) => (
+        <details key={item.id}>
+          <summary>{item.title}</summary>
+          <div>{item.content}</div>
+        </details>
+      ))}
+    </section>
+  );
+}
+
+export type AccessSurfaceProps =
+  | Readonly<{ kind: "auth-required"; onAction(): void }>
+  | Readonly<{ kind: "forbidden"; onAction(): void }>
+  | Readonly<{ kind: "not-found"; onAction(): void }>;
+
+export function AccessSurface(props: AccessSurfaceProps) {
+  if (props.kind === "auth-required") {
+    return <AuthRequiredSurface onSignIn={props.onAction} />;
+  }
+  if (props.kind === "forbidden") {
+    return <ForbiddenSurface onNavigate={props.onAction} />;
+  }
+  return <NotFoundSurface onNavigate={props.onAction} />;
+}
@@ -0,0 +1,456 @@
+import {
+  forwardRef,
+  useEffect,
+  useId,
+  useImperativeHandle,
+  useRef,
+} from "react";
+import { createPortal } from "react-dom";
+
+import { CloseIcon } from "../icons/semantic-icons.js";
+import { useLocale } from "../../i18n/index.js";
+
+export type ButtonVariant = "primary" | "secondary" | "danger" | "ghost";
+export type ButtonSize = "default" | "compact";
+
+export type ButtonProps = React.ButtonHTMLAttributes<HTMLButtonElement> &
+  Readonly<{
+    variant?: ButtonVariant;
+    size?: ButtonSize;
+    pending?: boolean;
+    pendingLabel?: string;
+  }>;
+
+export const Button = forwardRef<HTMLButtonElement, ButtonProps>(
+  function Button(
+    {
+      variant = "primary",
+      size = "default",
+      pending = false,
+      pendingLabel,
+      className = "",
+      type = "button",
+      children,
+      disabled,
+      ...props
+    },
+    ref,
+  ) {
+    const classes = [
+      "ui-button",
+      `ui-button--${variant}`,
+      size === "compact" ? "ui-button--compact" : "",
+      pending ? "ui-button--pending" : "",
+      className,
+    ]
+      .filter(Boolean)
+      .join(" ");
+
+    return (
+      <button
+        {...props}
+        aria-busy={pending || undefined}
+        className={classes}
+        disabled={disabled}
+        ref={ref}
+        type={type}
+      >
+        {pending ? (
+          <>
+            <Spinner decorative />
+            {pendingLabel ?? children}
+          </>
+        ) : (
+          children
+        )}
+      </button>
+    );
+  },
+);
+
+export type LinkButtonProps = React.AnchorHTMLAttributes<HTMLAnchorElement> &
+  Readonly<{
+    href: string;
+    variant?: ButtonVariant;
+    size?: ButtonSize;
+  }>;
+
+export const LinkButton = forwardRef<HTMLAnchorElement, LinkButtonProps>(
+  function LinkButton(
+    {
+      href,
+      variant = "primary",
+      size = "default",
+      className = "",
+      ...props
+    },
+    ref,
+  ) {
+    return (
+      <a
+        {...props}
+        className={[
+          "ui-button",
+          `ui-button--${variant}`,
+          size === "compact" ? "ui-button--compact" : "",
+          className,
+        ]
+          .filter(Boolean)
+          .join(" ")}
+        href={href}
+        ref={ref}
+      />
+    );
+  },
+);
+
+export type IconButtonProps = Omit<ButtonProps, "aria-label" | "children"> &
+  Readonly<{
+    accessibleName: string;
+    children: React.ReactElement;
+  }>;
+
+export const IconButton = forwardRef<HTMLButtonElement, IconButtonProps>(
+  function IconButton({ accessibleName, className = "", ...props }, ref) {
+    return (
+      <Button
+        {...props}
+        aria-label={accessibleName}
+        className={`ui-icon-button ${className}`.trim()}
+        ref={ref}
+      />
+    );
+  },
+);
+
+type FieldFrameProps = Readonly<{
+  id?: string;
+  label: string;
+  description?: string;
+  error?: string;
+  required?: boolean;
+  className?: string;
+  children(
+    contract: Readonly<{
+      controlId: string;
+      describedBy: string | undefined;
+      invalid: boolean;
+    }>,
+  ): React.ReactNode;
+}>;
+
+export function Field({
+  id,
+  label,
+  description,
+  error,
+  required,
+  className = "",
+  children,
+}: FieldFrameProps) {
+  const generatedId = useId();
+  const controlId = id ?? `field-${generatedId}`;
+  const descriptionId = description ? `${controlId}-description` : undefined;
+  const errorId = error ? `${controlId}-error` : undefined;
+  const describedBy = [descriptionId, errorId].filter(Boolean).join(" ");
+
+  return (
+    <div className={`ui-field ${className}`.trim()}>
+      <label className="ui-field__label" htmlFor={controlId}>
+        {label}
+        {required ? <span aria-hidden="true"> *</span> : null}
+      </label>
+      {description ? (
+        <p className="ui-field__description" id={descriptionId}>
+          {description}
+        </p>
+      ) : null}
+      {children({
+        controlId,
+        describedBy: describedBy || undefined,
+        invalid: Boolean(error),
+      })}
+      {error ? (
+        <p className="ui-field__error" id={errorId}>
+          {error}
+        </p>
+      ) : null}
+    </div>
+  );
+}
+
+export type TextFieldProps = Omit<
+  React.InputHTMLAttributes<HTMLInputElement>,
+  "id"
+> &
+  Readonly<{
+    id?: string;
+    label: string;
+    description?: string;
+    error?: string;
+  }>;
+
+export const TextField = forwardRef<HTMLInputElement, TextFieldProps>(
+  function TextField(
+    {
+      id,
+      label,
+      description,
+      error,
+      className = "",
+      required,
+      ...inputProps
+    },
+    ref,
+  ) {
+    return (
+      <Field
+        className={className}
+        description={description}
+        error={error}
+        id={id}
+        label={label}
+        required={required}
+      >
+        {({ controlId, describedBy, invalid }) => (
+          <input
+            {...inputProps}
+            aria-describedby={describedBy}
+            aria-invalid={invalid || undefined}
+            className="ui-field__input"
+            id={controlId}
+            ref={ref}
+            required={required}
+          />
+        )}
+      </Field>
+    );
+  },
+);
+
+export type CardProps = Readonly<{
+  title: string;
+  headingLevel?: 2 | 3 | 4;
+  description?: string;
+  children?: React.ReactNode;
+  footer?: React.ReactNode;
+  className?: string;
+}>;
+
+export function Card({
+  title,
+  headingLevel = 3,
+  description,
+  children,
+  footer,
+  className = "",
+}: CardProps) {
+  const titleId = useId();
+  const Heading = `h${headingLevel}` as "h2" | "h3" | "h4";
+
+  return (
+    <article
+      aria-labelledby={titleId}
+      className={`ui-card ${className}`.trim()}
+    >
+      <div className="ui-card__header">
+        <Heading id={titleId}>{title}</Heading>
+        {description ? <p>{description}</p> : null}
+      </div>
+      {children ? <div className="ui-card__content">{children}</div> : null}
+      {footer ? <footer className="ui-card__footer">{footer}</footer> : null}
+    </article>
+  );
+}
+
+export type AlertProps = Readonly<{
+  title: string;
+  children?: React.ReactNode;
+  variant?: "info" | "success" | "warning" | "danger";
+  dismissLabel?: string;
+  onDismiss?: () => void;
+}>;
+
+export function Alert({
+  title,
+  children,
+  variant = "info",
+  dismissLabel,
+  onDismiss,
+}: AlertProps) {
+  const { message } = useLocale();
+  return (
+    <section
+      className={`ui-alert ui-alert--${variant}`}
+      role={variant === "danger" ? "alert" : "status"}
+    >
+      <div>
+        <strong>{title}</strong>
+        {children ? <div className="ui-alert__content">{children}</div> : null}
+      </div>
+      {onDismiss ? (
+        <IconButton
+          accessibleName={
+            dismissLabel ?? message("action.alertCloseNamed", { title })
+          }
+          className="ui-alert__dismiss"
+          onClick={onDismiss}
+          variant="ghost"
+        >
+          <CloseIcon />
+        </IconButton>
+      ) : null}
+    </section>
+  );
+}
+
+export type BadgeProps = Readonly<{
+  children: React.ReactNode;
+  variant?: "neutral" | "info" | "success" | "warning" | "danger";
+}>;
+
+export function Badge({ children, variant = "neutral" }: BadgeProps) {
+  return <span className={`ui-badge ui-badge--${variant}`}>{children}</span>;
+}
+
+export type DialogProps = Readonly<{
+  open: boolean;
+  onClose(): void;
+  title: string;
+  description?: string;
+  closeLabel?: string;
+  children?: React.ReactNode;
+  actions?: React.ReactNode;
+  className?: string;
+}>;
+
+export const Dialog = forwardRef<HTMLDialogElement, DialogProps>(
+  function Dialog(
+    {
+      open,
+      onClose,
+      title,
+      description,
+      closeLabel,
+      children,
+      actions,
+      className = "",
+    },
+    forwardedRef,
+  ) {
+    const { message } = useLocale();
+    const dialogRef = useRef<HTMLDialogElement | null>(null);
+    const previousFocusRef = useRef<HTMLElement | null>(null);
+    const titleId = useId();
+    const descriptionId = useId();
+    useImperativeHandle(forwardedRef, () => dialogRef.current!, []);
+
+    useEffect(() => {
+      const dialog = dialogRef.current;
+      if (!dialog) return;
+
+      if (open) {
+        previousFocusRef.current =
+          document.activeElement instanceof HTMLElement
+            ? document.activeElement
+            : null;
+        if (!dialog.open) {
+          if (typeof dialog.showModal === "function") dialog.showModal();
+          else dialog.setAttribute("open", "");
+        }
+        const firstFocusable = dialog.querySelector<HTMLElement>(
+          "[autofocus], button, [href], input, select, textarea, [tabindex]:not([tabindex='-1'])",
+        );
+        firstFocusable?.focus();
+        return;
+      }
+
+      if (dialog.open) {
+        if (typeof dialog.close === "function") dialog.close();
+        else dialog.removeAttribute("open");
+      }
+      const previousFocus = previousFocusRef.current;
+      previousFocusRef.current = null;
+      queueMicrotask(() => {
+        if (previousFocus?.isConnected) previousFocus.focus();
+      });
+    }, [open]);
+
+    return (
+      <dialog
+        aria-describedby={description ? descriptionId : undefined}
+        aria-labelledby={titleId}
+        className={`ui-dialog ${className}`.trim()}
+        onCancel={(event) => {
+          event.preventDefault();
+          onClose();
+        }}
+        onClick={(event) => {
+          if (event.target === event.currentTarget) onClose();
+        }}
+        onKeyDown={(event) => {
+          if (event.key === "Escape") {
+            event.preventDefault();
+            onClose();
+          }
+        }}
+        ref={dialogRef}
+      >
+        <div className="ui-dialog__surface">
+          <header className="ui-dialog__header">
+            <div>
+              <h2 id={titleId}>{title}</h2>
+              {description ? <p id={descriptionId}>{description}</p> : null}
+            </div>
+            <IconButton
+              accessibleName={
+                closeLabel ?? message("action.closeNamed", { title })
+              }
+              className="ui-dialog__close"
+              onClick={onClose}
+              variant="ghost"
+            >
+              <CloseIcon />
+            </IconButton>
+          </header>
+          {children ? (
+            <div className="ui-dialog__content">{children}</div>
+          ) : null}
+          {actions ? (
+            <footer className="ui-dialog__actions">{actions}</footer>
+          ) : null}
+        </div>
+      </dialog>
+    );
+  },
+);
+
+export type SpinnerProps =
+  | Readonly<{ decorative: true; label?: never }>
+  | Readonly<{ decorative?: false; label: string }>;
+
+export function Spinner(props: SpinnerProps) {
+  const accessibility = props.decorative
+    ? { "aria-hidden": true as const }
+    : { "aria-label": props.label, role: "status" };
+  return <span {...accessibility} className="ui-spinner" />;
+}
+
+export function VisuallyHidden({
+  children,
+}: Readonly<{ children: React.ReactNode }>) {
+  return <span className="visually-hidden">{children}</span>;
+}
+
+export function Portal({
+  children,
+}: Readonly<{ children: React.ReactNode }>) {
+  if (typeof document === "undefined") return <>{children}</>;
+  return createPortal(children, document.body);
+}
+
+export function FocusRing({
+  children,
+}: Readonly<{ children: React.ReactNode }>) {
+  return <span className="ui-focus-ring">{children}</span>;
+}
@@ -0,0 +1,55 @@
+export type ProgressBarProps = Readonly<{
+  label: string;
+  value?: number;
+  max?: number;
+}>;
+
+export function ProgressBar({ label, value, max = 100 }: ProgressBarProps) {
+  const determinate = typeof value === "number";
+  return (
+    <div className="ui-progress">
+      <div className="ui-progress__label">
+        <span>{label}</span>
+        {determinate ? <span>{Math.round((value / max) * 100)}%</span> : null}
+      </div>
+      <progress
+        aria-label={label}
+        className="ui-progress__bar"
+        max={max}
+        value={determinate ? Math.min(Math.max(value, 0), max) : undefined}
+      />
+    </div>
+  );
+}
+
+export type SkeletonProps = Readonly<{
+  label?: string;
+  height?: "text" | "control" | "surface";
+}>;
+
+export function Skeleton({
+  label,
+  height = "surface",
+}: SkeletonProps) {
+  return (
+    <span
+      aria-label={label}
+      aria-hidden={label ? undefined : true}
+      className={`ui-skeleton ui-skeleton--${height}`}
+      role={label ? "status" : undefined}
+    />
+  );
+}
+
+export function Separator({
+  label,
+  decorative = true,
+}: Readonly<{ label?: string; decorative?: boolean }>) {
+  return (
+    <hr
+      aria-label={decorative ? undefined : label}
+      aria-hidden={decorative || undefined}
+      className="ui-separator"
+    />
+  );
+}
@@ -0,0 +1,411 @@
+import {
+  forwardRef,
+  useEffect,
+  useId,
+  useRef,
+  useState,
+} from "react";
+
+import { CloseIcon, SearchIcon } from "../icons/semantic-icons.js";
+import { Field, IconButton } from "./core.js";
+import type { TextFieldProps } from "./core.js";
+import { useLocale } from "../../i18n/index.js";
+
+type FieldCopy = Readonly<{
+  id?: string;
+  label: string;
+  description?: string;
+  error?: string;
+}>;
+
+export type TextAreaProps = Omit<
+  React.TextareaHTMLAttributes<HTMLTextAreaElement>,
+  "id"
+> &
+  FieldCopy &
+  Readonly<{ maxLengthMessage?: (remaining: number) => string }>;
+
+export const TextArea = forwardRef<HTMLTextAreaElement, TextAreaProps>(
+  function TextArea(
+    {
+      id,
+      label,
+      description,
+      error,
+      required,
+      className = "",
+      maxLength,
+      maxLengthMessage,
+      value,
+      defaultValue,
+      ...props
+    },
+    ref,
+  ) {
+    const { message } = useLocale();
+    const [uncontrolledValue, setUncontrolledValue] = useState(
+      String(defaultValue ?? ""),
+    );
+    const currentValue =
+      value === undefined ? uncontrolledValue : String(value ?? "");
+    const remaining =
+      typeof maxLength === "number" ? maxLength - currentValue.length : null;
+
+    return (
+      <Field
+        className={className}
+        description={description}
+        error={error}
+        id={id}
+        label={label}
+        required={required}
+      >
+        {({ controlId, describedBy, invalid }) => (
+          <>
+            <textarea
+              {...props}
+              aria-describedby={describedBy}
+              aria-invalid={invalid || undefined}
+              className="ui-field__input ui-field__textarea"
+              defaultValue={value === undefined ? defaultValue : undefined}
+              id={controlId}
+              maxLength={maxLength}
+              onChange={(event) => {
+                if (value === undefined) setUncontrolledValue(event.currentTarget.value);
+                props.onChange?.(event);
+              }}
+              ref={ref}
+              required={required}
+              value={value}
+            />
+            {remaining !== null ? (
+              <output className="ui-field__counter">
+                {maxLengthMessage
+                  ? maxLengthMessage(remaining)
+                  : message("form.remaining", { count: remaining })}
+              </output>
+            ) : null}
+          </>
+        )}
+      </Field>
+    );
+  },
+);
+
+export type SelectOption = Readonly<{
+  value: string;
+  label: string;
+  disabled?: boolean;
+}>;
+
+export type SelectProps = Omit<
+  React.SelectHTMLAttributes<HTMLSelectElement>,
+  "id" | "children"
+> &
+  FieldCopy &
+  Readonly<{
+    options: readonly SelectOption[];
+    placeholder?: string;
+  }>;
+
+export const Select = forwardRef<HTMLSelectElement, SelectProps>(
+  function Select(
+    {
+      id,
+      label,
+      description,
+      error,
+      options,
+      placeholder,
+      required,
+      className = "",
+      ...props
+    },
+    ref,
+  ) {
+    return (
+      <Field
+        className={className}
+        description={description}
+        error={error}
+        id={id}
+        label={label}
+        required={required}
+      >
+        {({ controlId, describedBy, invalid }) => (
+          <select
+            {...props}
+            aria-describedby={describedBy}
+            aria-invalid={invalid || undefined}
+            className="ui-field__input ui-field__select"
+            id={controlId}
+            ref={ref}
+            required={required}
+          >
+            {placeholder ? (
+              <option disabled value="">
+                {placeholder}
+              </option>
+            ) : null}
+            {options.map((option) => (
+              <option
+                disabled={option.disabled}
+                key={option.value}
+                value={option.value}
+              >
+                {option.label}
+              </option>
+            ))}
+          </select>
+        )}
+      </Field>
+    );
+  },
+);
+
+export type CheckboxProps = Omit<
+  React.InputHTMLAttributes<HTMLInputElement>,
+  "type"
+> &
+  Readonly<{
+    label: string;
+    description?: string;
+    error?: string;
+    indeterminate?: boolean;
+  }>;
+
+export const Checkbox = forwardRef<HTMLInputElement, CheckboxProps>(
+  function Checkbox(
+    { label, description, error, indeterminate = false, id, ...props },
+    forwardedRef,
+  ) {
+    const generatedId = useId();
+    const controlId = id ?? `checkbox-${generatedId}`;
+    const inputRef = useRef<HTMLInputElement | null>(null);
+    const descriptionId = description ? `${controlId}-description` : undefined;
+    const errorId = error ? `${controlId}-error` : undefined;
+    useEffect(() => {
+      if (inputRef.current) inputRef.current.indeterminate = indeterminate;
+    }, [indeterminate]);
+
+    return (
+      <div className="ui-choice-field">
+        <label className="ui-choice-field__control" htmlFor={controlId}>
+          <input
+            {...props}
+            aria-describedby={
+              [descriptionId, errorId].filter(Boolean).join(" ") || undefined
+            }
+            aria-invalid={error ? true : undefined}
+            id={controlId}
+            ref={(node) => {
+              inputRef.current = node;
+              if (typeof forwardedRef === "function") forwardedRef(node);
+              else if (forwardedRef) forwardedRef.current = node;
+            }}
+            type="checkbox"
+          />
+          <span>{label}</span>
+        </label>
+        {description ? (
+          <p className="ui-field__description" id={descriptionId}>
+            {description}
+          </p>
+        ) : null}
+        {error ? (
+          <p className="ui-field__error" id={errorId}>
+            {error}
+          </p>
+        ) : null}
+      </div>
+    );
+  },
+);
+
+export type RadioOption = Readonly<{
+  value: string;
+  label: string;
+  description?: string;
+  disabled?: boolean;
+}>;
+
+export type RadioGroupProps = Readonly<{
+  name: string;
+  label: string;
+  options: readonly RadioOption[];
+  value?: string;
+  defaultValue?: string;
+  onChange?(value: string): void;
+  disabled?: boolean;
+  error?: string;
+}>;
+
+export function RadioGroup({
+  name,
+  label,
+  options,
+  value,
+  defaultValue,
+  onChange,
+  disabled,
+  error,
+}: RadioGroupProps) {
+  const [internalValue, setInternalValue] = useState(defaultValue ?? "");
+  const selected = value ?? internalValue;
+  const errorId = useId();
+  const refs = useRef<Array<HTMLInputElement | null>>([]);
+
+  function choose(nextValue: string) {
+    if (value === undefined) setInternalValue(nextValue);
+    onChange?.(nextValue);
+  }
+
+  return (
+    <fieldset
+      aria-describedby={error ? errorId : undefined}
+      className="ui-radio-group"
+      disabled={disabled}
+    >
+      <legend>{label}</legend>
+      {options.map((option, index) => (
+        <label className="ui-choice-field__control" key={option.value}>
+          <input
+            checked={selected === option.value}
+            disabled={option.disabled}
+            name={name}
+            onChange={() => choose(option.value)}
+            onKeyDown={(event) => {
+              if (!["ArrowDown", "ArrowRight", "ArrowUp", "ArrowLeft"].includes(event.key)) {
+                return;
+              }
+              event.preventDefault();
+              const direction =
+                event.key === "ArrowDown" || event.key === "ArrowRight" ? 1 : -1;
+              let next = index;
+              do {
+                next = (next + direction + options.length) % options.length;
+              } while (options[next]?.disabled && next !== index);
+              const nextOption = options[next];
+              if (nextOption && !nextOption.disabled) {
+                choose(nextOption.value);
+                refs.current[next]?.focus();
+              }
+            }}
+            ref={(node) => {
+              refs.current[index] = node;
+            }}
+            type="radio"
+            value={option.value}
+          />
+          <span>
+            {option.label}
+            {option.description ? <small>{option.description}</small> : null}
+          </span>
+        </label>
+      ))}
+      {error ? (
+        <p className="ui-field__error" id={errorId}>
+          {error}
+        </p>
+      ) : null}
+    </fieldset>
+  );
+}
+
+export type SwitchProps = Readonly<{
+  label: string;
+  checked: boolean;
+  onChange(checked: boolean): void;
+  disabled?: boolean;
+  description?: string;
+}>;
+
+export function Switch({
+  label,
+  checked,
+  onChange,
+  disabled,
+  description,
+}: SwitchProps) {
+  const descriptionId = useId();
+  return (
+    <div className="ui-switch-field">
+      <button
+        aria-checked={checked}
+        aria-describedby={description ? descriptionId : undefined}
+        className="ui-switch"
+        disabled={disabled}
+        onClick={() => onChange(!checked)}
+        role="switch"
+        type="button"
+      >
+        <span aria-hidden="true" className="ui-switch__thumb" />
+        <span>{label}</span>
+      </button>
+      {description ? (
+        <p className="ui-field__description" id={descriptionId}>
+          {description}
+        </p>
+      ) : null}
+    </div>
+  );
+}
+
+export type SearchFieldProps = Omit<TextFieldProps, "type"> &
+  Readonly<{
+    clearLabel: string;
+    onClear(): void;
+  }>;
+
+export const SearchField = forwardRef<HTMLInputElement, SearchFieldProps>(
+  function SearchField(
+    {
+      clearLabel,
+      onClear,
+      value,
+      className = "",
+      id,
+      label,
+      description,
+      error,
+      required,
+      ...inputProps
+    },
+    ref,
+  ) {
+    return (
+      <div className={`ui-search-field ${className}`.trim()}>
+        <SearchIcon />
+        <Field
+          description={description}
+          error={error}
+          id={id}
+          label={label}
+          required={required}
+        >
+          {({ controlId, describedBy, invalid }) => (
+            <input
+              {...inputProps}
+              aria-describedby={describedBy}
+              aria-invalid={invalid || undefined}
+              className="ui-field__input"
+              id={controlId}
+              ref={ref}
+              type="search"
+              value={value}
+            />
+          )}
+        </Field>
+        {String(value ?? "").length > 0 ? (
+          <IconButton
+            accessibleName={clearLabel}
+            onClick={onClear}
+            variant="ghost"
+          >
+            <CloseIcon />
+          </IconButton>
+        ) : null}
+      </div>
+    );
+  },
+);
@@ -0,0 +1,199 @@
+import { useId, useRef, useState } from "react";
+
+import { useLocale } from "../../i18n/index.js";
+import { NextIcon, PreviousIcon } from "../icons/semantic-icons.js";
+import { IconButton, LinkButton } from "./core.js";
+
+export type BreadcrumbItem = Readonly<{
+  label: string;
+  href?: string;
+}>;
+
+export function Breadcrumbs({
+  label,
+  items,
+}: Readonly<{ label: string; items: readonly BreadcrumbItem[] }>) {
+  return (
+    <nav aria-label={label} className="ui-breadcrumbs">
+      <ol>
+        {items.map((item, index) => {
+          const current = index === items.length - 1;
+          return (
+            <li key={`${item.label}-${index}`}>
+              {item.href && !current ? (
+                <a href={item.href}>{item.label}</a>
+              ) : (
+                <span aria-current={current ? "page" : undefined}>
+                  {item.label}
+                </span>
+              )}
+            </li>
+          );
+        })}
+      </ol>
+    </nav>
+  );
+}
+
+export type TabDefinition = Readonly<{
+  id: string;
+  label: string;
+  panel: React.ReactNode;
+  disabled?: boolean;
+}>;
+
+export function Tabs({
+  label,
+  tabs,
+  value,
+  defaultValue,
+  activation = "automatic",
+  onChange,
+}: Readonly<{
+  label: string;
+  tabs: readonly TabDefinition[];
+  value?: string;
+  defaultValue?: string;
+  activation?: "automatic" | "manual";
+  onChange?(id: string): void;
+}>) {
+  const fallback = tabs.find((tab) => !tab.disabled)?.id ?? "";
+  const [internalValue, setInternalValue] = useState(defaultValue ?? fallback);
+  const [focusValue, setFocusValue] = useState(value ?? internalValue);
+  const selected = value ?? internalValue;
+  const tabRefs = useRef<Array<HTMLButtonElement | null>>([]);
+  const baseId = useId();
+  const { direction } = useLocale();
+
+  function select(id: string) {
+    if (value === undefined) setInternalValue(id);
+    onChange?.(id);
+  }
+
+  function move(currentIndex: number, direction: 1 | -1) {
+    let next = currentIndex;
+    do {
+      next = (next + direction + tabs.length) % tabs.length;
+    } while (tabs[next]?.disabled && next !== currentIndex);
+    const nextTab = tabs[next];
+    if (!nextTab || nextTab.disabled) return;
+    setFocusValue(nextTab.id);
+    if (activation === "automatic") select(nextTab.id);
+    tabRefs.current[next]?.focus();
+  }
+
+  return (
+    <div className="ui-tabs">
+      <div aria-label={label} className="ui-tabs__list" role="tablist">
+        {tabs.map((tab, index) => (
+          <button
+            aria-controls={`${baseId}-${tab.id}-panel`}
+            aria-selected={selected === tab.id}
+            className="ui-tabs__tab"
+            disabled={tab.disabled}
+            id={`${baseId}-${tab.id}-tab`}
+            key={tab.id}
+            onClick={() => {
+              setFocusValue(tab.id);
+              select(tab.id);
+            }}
+            onKeyDown={(event) => {
+              if (event.key === "ArrowRight") {
+                event.preventDefault();
+                move(index, direction === "rtl" ? -1 : 1);
+              } else if (event.key === "ArrowLeft") {
+                event.preventDefault();
+                move(index, direction === "rtl" ? 1 : -1);
+              } else if (
+                activation === "manual" &&
+                (event.key === "Enter" || event.key === " ")
+              ) {
+                event.preventDefault();
+                select(tab.id);
+              }
+            }}
+            ref={(node) => {
+              tabRefs.current[index] = node;
+            }}
+            role="tab"
+            tabIndex={focusValue === tab.id ? 0 : -1}
+            type="button"
+          >
+            {tab.label}
+          </button>
+        ))}
+      </div>
+      {tabs.map((tab) => (
+        <div
+          aria-labelledby={`${baseId}-${tab.id}-tab`}
+          className="ui-tabs__panel"
+          hidden={selected !== tab.id}
+          id={`${baseId}-${tab.id}-panel`}
+          key={tab.id}
+          role="tabpanel"
+          tabIndex={0}
+        >
+          {tab.panel}
+        </div>
+      ))}
+    </div>
+  );
+}
+
+export function Pagination({
+  label,
+  page,
+  pageCount,
+  previousLabel,
+  nextLabel,
+  pageLabel,
+  onChange,
+}: Readonly<{
+  label: string;
+  page: number;
+  pageCount: number;
+  previousLabel: string;
+  nextLabel: string;
+  pageLabel(page: number): string;
+  onChange(page: number): void;
+}>) {
+  const pages = Array.from({ length: pageCount }, (_, index) => index + 1);
+  const { direction } = useLocale();
+  const PreviousDirectionalIcon =
+    direction === "rtl" ? NextIcon : PreviousIcon;
+  const NextDirectionalIcon = direction === "rtl" ? PreviousIcon : NextIcon;
+  return (
+    <nav aria-label={label} className="ui-pagination">
+      <IconButton
+        accessibleName={previousLabel}
+        disabled={page <= 1}
+        onClick={() => onChange(page - 1)}
+        variant="secondary"
+      >
+        <PreviousDirectionalIcon />
+      </IconButton>
+      {pages.map((candidate) => (
+        <LinkButton
+          aria-current={candidate === page ? "page" : undefined}
+          href={`?page=${candidate}`}
+          key={candidate}
+          onClick={(event) => {
+            event.preventDefault();
+            onChange(candidate);
+          }}
+          variant={candidate === page ? "primary" : "ghost"}
+        >
+          {pageLabel(candidate)}
+        </LinkButton>
+      ))}
+      <IconButton
+        accessibleName={nextLabel}
+        disabled={page >= pageCount}
+        onClick={() => onChange(page + 1)}
+        variant="secondary"
+      >
+        <NextDirectionalIcon />
+      </IconButton>
+    </nav>
+  );
+}
@@ -0,0 +1,444 @@
+import {
+  createContext,
+  useCallback,
+  useContext,
+  useEffect,
+  useId,
+  useMemo,
+  useRef,
+  useState,
+} from "react";
+
+import { CloseIcon } from "../icons/semantic-icons.js";
+import { Button, Dialog, IconButton } from "./core.js";
+import { useLocale } from "../../i18n/index.js";
+
+export type DrawerProps = Readonly<{
+  open: boolean;
+  onClose(): void;
+  title: string;
+  closeLabel?: string;
+  placement?: "start" | "end";
+  children: React.ReactNode;
+}>;
+
+export function Drawer({
+  open,
+  onClose,
+  title,
+  closeLabel,
+  placement = "start",
+  children,
+}: DrawerProps) {
+  return (
+    <Dialog
+      className={`ui-drawer ui-drawer--${placement}`}
+      closeLabel={closeLabel}
+      onClose={onClose}
+      open={open}
+      title={title}
+    >
+      {children}
+    </Dialog>
+  );
+}
+
+export type PopoverProps = Readonly<{
+  triggerLabel: string;
+  children: React.ReactNode;
+}>;
+
+export function Popover({ triggerLabel, children }: PopoverProps) {
+  const [open, setOpen] = useState(false);
+  const rootRef = useRef<HTMLDivElement | null>(null);
+  const triggerRef = useRef<HTMLButtonElement | null>(null);
+  const contentId = useId();
+
+  useEffect(() => {
+    if (!open) return;
+    function closeOutside(event: PointerEvent) {
+      if (
+        event.target instanceof Node &&
+        !rootRef.current?.contains(event.target)
+      ) {
+        setOpen(false);
+        triggerRef.current?.focus();
+      }
+    }
+    function closeOnEscape(event: KeyboardEvent) {
+      if (event.key === "Escape") {
+        setOpen(false);
+        triggerRef.current?.focus();
+      }
+    }
+    document.addEventListener("pointerdown", closeOutside);
+    document.addEventListener("keydown", closeOnEscape);
+    return () => {
+      document.removeEventListener("pointerdown", closeOutside);
+      document.removeEventListener("keydown", closeOnEscape);
+    };
+  }, [open]);
+
+  return (
+    <div className="ui-popover" ref={rootRef}>
+      <Button
+        aria-controls={contentId}
+        aria-expanded={open}
+        onClick={() => setOpen((current) => !current)}
+        ref={triggerRef}
+        variant="secondary"
+      >
+        {triggerLabel}
+      </Button>
+      {open ? (
+        <div className="ui-popover__content" id={contentId} role="dialog">
+          {children}
+        </div>
+      ) : null}
+    </div>
+  );
+}
+
+export type TooltipProps = Readonly<{
+  content: string;
+  children: React.ReactElement;
+}>;
+
+export function Tooltip({ content, children }: TooltipProps) {
+  const tooltipId = useId();
+  return (
+    <span className="ui-tooltip">
+      <span aria-describedby={tooltipId} className="ui-tooltip__trigger">
+        {children}
+      </span>
+      <span className="ui-tooltip__content" id={tooltipId} role="tooltip">
+        {content}
+      </span>
+    </span>
+  );
+}
+
+export type MenuItemDefinition = Readonly<{
+  id: string;
+  label: string;
+  disabled?: boolean;
+  onSelect(): void;
+}>;
+
+export type MenuProps = Readonly<{
+  triggerLabel: string;
+  items: readonly MenuItemDefinition[];
+}>;
+
+export function Menu({ triggerLabel, items }: MenuProps) {
+  const [open, setOpen] = useState(false);
+  const [activeIndex, setActiveIndex] = useState(0);
+  const triggerRef = useRef<HTMLButtonElement | null>(null);
+  const rootRef = useRef<HTMLDivElement | null>(null);
+  const itemRefs = useRef<Array<HTMLButtonElement | null>>([]);
+  const searchRef = useRef("");
+  const resetSearchRef = useRef<number | undefined>(undefined);
+
+  const enabledIndexes = useMemo(
+    () => items.flatMap((item, index) => (item.disabled ? [] : [index])),
+    [items],
+  );
+
+  const focusIndex = useCallback(
+    (index: number) => {
+      setActiveIndex(index);
+      queueMicrotask(() => itemRefs.current[index]?.focus());
+    },
+    [],
+  );
+
+  function openAt(index: number) {
+    setOpen(true);
+    focusIndex(index);
+  }
+
+  function dismiss() {
+    setOpen(false);
+    queueMicrotask(() => triggerRef.current?.focus());
+  }
+
+  function move(direction: 1 | -1) {
+    const currentPosition = Math.max(enabledIndexes.indexOf(activeIndex), 0);
+    const nextPosition =
+      (currentPosition + direction + enabledIndexes.length) %
+      enabledIndexes.length;
+    const nextIndex = enabledIndexes[nextPosition];
+    if (nextIndex !== undefined) focusIndex(nextIndex);
+  }
+
+  useEffect(() => {
+    if (!open) return;
+    function closeOutside(event: PointerEvent) {
+      if (
+        event.target instanceof Node &&
+        !rootRef.current?.contains(event.target)
+      ) {
+        setOpen(false);
+        queueMicrotask(() => triggerRef.current?.focus());
+      }
+    }
+    document.addEventListener("pointerdown", closeOutside);
+    return () => document.removeEventListener("pointerdown", closeOutside);
+  }, [open]);
+
+  return (
+    <div className="ui-menu" ref={rootRef}>
+      <Button
+        aria-expanded={open}
+        aria-haspopup="menu"
+        onClick={() => {
+          if (open) dismiss();
+          else openAt(enabledIndexes[0] ?? 0);
+        }}
+        onKeyDown={(event) => {
+          if (event.key === "ArrowDown") {
+            event.preventDefault();
+            openAt(enabledIndexes[0] ?? 0);
+          }
+          if (event.key === "ArrowUp") {
+            event.preventDefault();
+            openAt(enabledIndexes.at(-1) ?? 0);
+          }
+        }}
+        ref={triggerRef}
+        variant="secondary"
+      >
+        {triggerLabel}
+      </Button>
+      {open ? (
+        <div
+          className="ui-menu__content"
+          onKeyDown={(event) => {
+            if (event.key === "Escape") {
+              event.preventDefault();
+              dismiss();
+            } else if (event.key === "ArrowDown") {
+              event.preventDefault();
+              move(1);
+            } else if (event.key === "ArrowUp") {
+              event.preventDefault();
+              move(-1);
+            } else if (event.key === "Home") {
+              event.preventDefault();
+              focusIndex(enabledIndexes[0] ?? 0);
+            } else if (event.key === "End") {
+              event.preventDefault();
+              focusIndex(enabledIndexes.at(-1) ?? 0);
+            } else if (
+              event.key.length === 1 &&
+              !event.ctrlKey &&
+              !event.metaKey &&
+              !event.altKey
+            ) {
+              searchRef.current += event.key.toLocaleLowerCase();
+              window.clearTimeout(resetSearchRef.current);
+              resetSearchRef.current = window.setTimeout(() => {
+                searchRef.current = "";
+              }, 500);
+              const match = items.findIndex(
+                (item) =>
+                  !item.disabled &&
+                  item.label
+                    .toLocaleLowerCase()
+                    .startsWith(searchRef.current),
+              );
+              if (match >= 0) focusIndex(match);
+            }
+          }}
+          role="menu"
+        >
+          {items.map((item, index) => (
+            <button
+              className="ui-menu__item"
+              disabled={item.disabled}
+              key={item.id}
+              onClick={() => {
+                item.onSelect();
+                dismiss();
+              }}
+              ref={(node) => {
+                itemRefs.current[index] = node;
+              }}
+              role="menuitem"
+              tabIndex={index === activeIndex ? 0 : -1}
+              type="button"
+            >
+              {item.label}
+            </button>
+          ))}
+        </div>
+      ) : null}
+    </div>
+  );
+}
+
+type ToastTone = "info" | "success" | "warning" | "danger";
+type ToastInput = Readonly<{
+  id: string;
+  title: string;
+  description?: string;
+  tone?: ToastTone;
+  durationMs?: number;
+}>;
+type ToastEntry = ToastInput & Readonly<{ count: number }>;
+type ToastContextValue = Readonly<{
+  push(toast: ToastInput): void;
+  dismiss(id: string): void;
+}>;
+
+const ToastContext = createContext<ToastContextValue | null>(null);
+
+export function ToastProvider({
+  children,
+  limit = 3,
+}: Readonly<{ children: React.ReactNode; limit?: number }>) {
+  const [toasts, setToasts] = useState<readonly ToastEntry[]>([]);
+
+  const dismiss = useCallback((id: string) => {
+    setToasts((current) => current.filter((toast) => toast.id !== id));
+  }, []);
+
+  const push = useCallback(
+    (toast: ToastInput) => {
+      setToasts((current) => {
+        const existing = current.find((entry) => entry.id === toast.id);
+        if (existing) {
+          return current.map((entry) =>
+            entry.id === toast.id
+              ? { ...entry, ...toast, count: entry.count + 1 }
+              : entry,
+          );
+        }
+        return [...current, { ...toast, count: 1 }].slice(-limit);
+      });
+    },
+    [limit],
+  );
+
+  const value = useMemo(() => ({ push, dismiss }), [dismiss, push]);
+  return (
+    <ToastContext.Provider value={value}>
+      {children}
+      <ToastRegion dismiss={dismiss} toasts={toasts} />
+    </ToastContext.Provider>
+  );
+}
+
+export function useToast() {
+  const context = useContext(ToastContext);
+  if (!context) {
+    throw new Error("ToastProvider is required.");
+  }
+  return context;
+}
+
+function ToastRegion({
+  toasts,
+  dismiss,
+}: Readonly<{
+  toasts: readonly ToastEntry[];
+  dismiss(id: string): void;
+}>) {
+  const { message } = useLocale();
+  return (
+    <section
+      aria-label={message("toast.region")}
+      aria-live="polite"
+      className="ui-toast-region"
+    >
+      {toasts.map((toast) => (
+        <ToastItem dismiss={dismiss} key={toast.id} toast={toast} />
+      ))}
+    </section>
+  );
+}
+
+function ToastItem({
+  toast,
+  dismiss,
+}: Readonly<{
+  toast: ToastEntry;
+  dismiss(id: string): void;
+}>) {
+  const { message } = useLocale();
+  const [paused, setPaused] = useState(false);
+  useEffect(() => {
+    if (paused) return;
+    const timeout = window.setTimeout(
+      () => dismiss(toast.id),
+      toast.durationMs ?? 5000,
+    );
+    return () => window.clearTimeout(timeout);
+  }, [dismiss, paused, toast.durationMs, toast.id, toast.count]);
+
+  return (
+    <article
+      className={`ui-toast ui-toast--${toast.tone ?? "info"}`}
+      onBlur={(event) => {
+        if (!event.currentTarget.contains(event.relatedTarget)) setPaused(false);
+      }}
+      onFocus={() => setPaused(true)}
+      onMouseEnter={() => setPaused(true)}
+      onMouseLeave={() => setPaused(false)}
+    >
+      <div>
+        <strong>{toast.title}</strong>
+        {toast.count > 1 ? (
+          <span className="ui-toast__count"> ×{toast.count}</span>
+        ) : null}
+        {toast.description ? <p>{toast.description}</p> : null}
+      </div>
+      <IconButton
+        accessibleName={message("action.closeNamed", { title: toast.title })}
+        onClick={() => dismiss(toast.id)}
+        variant="ghost"
+      >
+        <CloseIcon />
+      </IconButton>
+    </article>
+  );
+}
+
+export function ConfirmationDialog({
+  open,
+  title,
+  description,
+  confirmLabel,
+  cancelLabel,
+  danger = false,
+  onConfirm,
+  onCancel,
+}: Readonly<{
+  open: boolean;
+  title: string;
+  description: string;
+  confirmLabel: string;
+  cancelLabel: string;
+  danger?: boolean;
+  onConfirm(): void;
+  onCancel(): void;
+}>) {
+  return (
+    <Dialog
+      actions={
+        <>
+          <Button onClick={onCancel} variant="secondary">
+            {cancelLabel}
+          </Button>
+          <Button onClick={onConfirm} variant={danger ? "danger" : "primary"}>
+            {confirmLabel}
+          </Button>
+        </>
+      }
+      description={description}
+      onClose={onCancel}
+      open={open}
+      title={title}
+    />
+  );
+}
@@ -0,0 +1,26 @@
+@theme {
+  --button-primary-background: var(--color-action);
+  --button-primary-content: var(--color-on-action);
+  --button-primary-hover: var(--color-action-hover);
+  --field-border: var(--color-border-strong);
+  --field-border-invalid: var(--color-danger);
+  --dialog-elevation: var(--elevation-dialog);
+  --navigation-active-background: color-mix(
+    in oklch,
+    var(--color-action) 14%,
+    var(--color-panel)
+  );
+  --drawer-width: min(20rem, 88vw);
+  --toast-width: min(24rem, calc(100vw - 2rem));
+}
+
+@media (forced-colors: active) {
+  :root {
+    --color-border: CanvasText;
+    --color-border-strong: CanvasText;
+    --color-focus: Highlight;
+    --color-action: LinkText;
+    --color-danger: MarkText;
+    --color-danger-surface: Mark;
+  }
+}
@@ -0,0 +1,63 @@
+@theme {
+  --palette-white: oklch(1 0 0);
+  --palette-slate-50: oklch(0.985 0.003 247);
+  --palette-slate-100: oklch(0.94 0.01 247);
+  --palette-slate-300: oklch(0.87 0.015 247);
+  --palette-slate-500: oklch(0.48 0.025 247);
+  --palette-slate-800: oklch(0.25 0.025 247);
+  --palette-slate-950: oklch(0.16 0.02 255);
+  --palette-blue-500: oklch(0.7 0.14 250);
+  --palette-blue-600: oklch(0.55 0.18 255);
+  --palette-blue-700: oklch(0.48 0.2 255);
+  --palette-red-500: oklch(0.68 0.19 25);
+  --palette-red-600: oklch(0.55 0.2 25);
+  --palette-red-700: oklch(0.47 0.2 25);
+
+  --space-1: 0.25rem;
+  --space-2: 0.5rem;
+  --space-3: 0.75rem;
+  --space-4: 1rem;
+  --space-5: 1.25rem;
+  --space-6: 1.5rem;
+  --space-8: 2rem;
+  --space-12: 3rem;
+
+  --font-size-xs: 0.75rem;
+  --font-size-sm: 0.875rem;
+  --font-size-md: 1rem;
+  --font-size-lg: 1.125rem;
+  --line-height-tight: 1.25;
+  --line-height-normal: 1.5;
+  --line-height-relaxed: 1.7;
+  --font-weight-regular: 400;
+  --font-weight-semibold: 650;
+  --font-weight-bold: 750;
+
+  --radius-xs: 0.25rem;
+  --radius-sm: 0.5rem;
+  --radius-md: 0.75rem;
+  --radius-full: 999px;
+
+  --shadow-panel: 0 8px 28px rgb(15 23 42 / 8%);
+  --shadow-popover: 0 14px 40px rgb(15 23 42 / 16%);
+  --shadow-dialog: 0 24px 70px rgb(15 23 42 / 25%);
+
+  --duration-fast: 100ms;
+  --duration-normal: 180ms;
+  --duration-slow: 300ms;
+  --easing-standard: cubic-bezier(0.2, 0, 0, 1);
+  --easing-emphasized: cubic-bezier(0.2, 0, 0, 1.2);
+
+  --size-control-sm: 2.25rem;
+  --size-control-md: 2.75rem;
+  --size-touch-target: 2.75rem;
+  --size-icon-sm: 1rem;
+  --size-icon-md: 1.25rem;
+  --size-icon-lg: 1.5rem;
+  --icon-stroke-default: 2;
+
+  --breakpoint-compact: 48rem;
+  --breakpoint-medium: 64rem;
+  --breakpoint-wide: 80rem;
+  --container-content: 72rem;
+}
@@ -0,0 +1,83 @@
+@theme {
+  --color-surface: var(--palette-slate-50);
+  --color-surface-muted: var(--palette-slate-100);
+  --color-panel: var(--palette-white);
+  --color-surface-elevated: var(--palette-white);
+  --color-border: var(--palette-slate-300);
+  --color-border-strong: var(--palette-slate-500);
+  --color-content: var(--palette-slate-800);
+  --color-content-muted: var(--palette-slate-500);
+  --color-content-inverse: var(--palette-white);
+  --color-action: var(--palette-blue-600);
+  --color-action-hover: var(--palette-blue-700);
+  --color-action-pressed: var(--palette-blue-700);
+  --color-danger: var(--palette-red-600);
+  --color-danger-hover: var(--palette-red-700);
+  --color-on-action: var(--palette-white);
+  --color-focus: oklch(0.72 0.16 225);
+  --color-disabled-content: color-mix(in oklch, var(--color-content) 55%, transparent);
+  --color-disabled-surface: var(--color-surface-muted);
+  --color-info-content: oklch(0.38 0.16 255);
+  --color-info-surface: oklch(0.95 0.03 255);
+  --color-info-border: oklch(0.75 0.08 250);
+  --color-success-content: oklch(0.35 0.12 155);
+  --color-success-surface: oklch(0.95 0.04 155);
+  --color-success-border: oklch(0.72 0.1 155);
+  --color-warning-content: oklch(0.38 0.12 70);
+  --color-warning-surface: oklch(0.96 0.05 80);
+  --color-warning-border: oklch(0.75 0.12 80);
+  --color-danger-content: oklch(0.42 0.18 25);
+  --color-danger-surface: oklch(0.96 0.035 25);
+  --color-danger-border: oklch(0.72 0.12 25);
+
+  --font-sans: Inter, ui-sans-serif, system-ui, sans-serif;
+  --spacing-page: var(--space-6);
+  --radius-control: var(--radius-sm);
+  --radius-surface: var(--radius-md);
+  --radius-modal: var(--radius-md);
+  --elevation-panel: var(--shadow-panel);
+  --elevation-popover: var(--shadow-popover);
+  --elevation-dialog: var(--shadow-dialog);
+  --layer-base: 0;
+  --layer-sticky: 30;
+  --layer-navigation: 50;
+  --layer-popover: 60;
+  --layer-modal: 70;
+  --layer-toast: 80;
+  --opacity-disabled: 0.55;
+  --opacity-scrim: 0.55;
+  --opacity-skeleton: 0.7;
+}
+
+:root[data-theme="dark"] {
+  --color-surface: var(--palette-slate-950);
+  --color-surface-muted: oklch(0.25 0.025 255);
+  --color-panel: oklch(0.205 0.022 255);
+  --color-surface-elevated: oklch(0.235 0.025 255);
+  --color-border: oklch(0.36 0.025 255);
+  --color-border-strong: oklch(0.58 0.025 255);
+  --color-content: oklch(0.94 0.012 255);
+  --color-content-muted: oklch(0.74 0.025 255);
+  --color-content-inverse: var(--palette-slate-950);
+  --color-action: var(--palette-blue-500);
+  --color-action-hover: oklch(0.79 0.12 245);
+  --color-action-pressed: oklch(0.83 0.1 245);
+  --color-danger: var(--palette-red-500);
+  --color-danger-hover: oklch(0.76 0.16 25);
+  --color-on-action: var(--palette-slate-950);
+  --color-focus: oklch(0.82 0.15 220);
+  --color-disabled-content: color-mix(in oklch, var(--color-content) 55%, transparent);
+  --color-disabled-surface: var(--color-surface-muted);
+  --color-info-content: oklch(0.83 0.09 250);
+  --color-info-surface: oklch(0.27 0.045 255);
+  --color-info-border: oklch(0.55 0.09 250);
+  --color-success-content: oklch(0.83 0.1 155);
+  --color-success-surface: oklch(0.27 0.045 155);
+  --color-success-border: oklch(0.53 0.1 155);
+  --color-warning-content: oklch(0.88 0.1 80);
+  --color-warning-surface: oklch(0.29 0.045 80);
+  --color-warning-border: oklch(0.58 0.11 80);
+  --color-danger-content: oklch(0.84 0.11 25);
+  --color-danger-surface: oklch(0.28 0.055 25);
+  --color-danger-border: oklch(0.56 0.13 25);
+}
@@ -0,0 +1,62 @@
+export const REQUIRED_PRIMITIVE_TOKENS = Object.freeze([
+  "--space-1",
+  "--space-2",
+  "--space-4",
+  "--font-size-sm",
+  "--line-height-normal",
+  "--radius-sm",
+  "--shadow-dialog",
+  "--duration-fast",
+  "--easing-standard",
+  "--size-control-md",
+  "--size-touch-target",
+  "--size-icon-md",
+  "--breakpoint-compact",
+] as const);
+
+export const REQUIRED_SEMANTIC_TOKENS = Object.freeze([
+  "--color-surface",
+  "--color-surface-muted",
+  "--color-surface-elevated",
+  "--color-content",
+  "--color-content-muted",
+  "--color-content-inverse",
+  "--color-border",
+  "--color-border-strong",
+  "--color-action",
+  "--color-action-hover",
+  "--color-action-pressed",
+  "--color-danger",
+  "--color-warning-content",
+  "--color-success-content",
+  "--color-info-content",
+  "--color-focus",
+  "--color-disabled-content",
+  "--color-disabled-surface",
+  "--elevation-panel",
+  "--layer-navigation",
+  "--layer-popover",
+  "--layer-modal",
+  "--layer-toast",
+  "--opacity-disabled",
+  "--opacity-scrim",
+  "--opacity-skeleton",
+] as const);
+
+export const REQUIRED_COMPONENT_TOKENS = Object.freeze([
+  "--button-primary-background",
+  "--button-primary-content",
+  "--button-primary-hover",
+  "--field-border",
+  "--field-border-invalid",
+  "--dialog-elevation",
+  "--navigation-active-background",
+  "--drawer-width",
+  "--toast-width",
+] as const);
+
+export const DESIGN_TOKEN_CONTRACT = Object.freeze({
+  primitive: REQUIRED_PRIMITIVE_TOKENS,
+  semantic: REQUIRED_SEMANTIC_TOKENS,
+  component: REQUIRED_COMPONENT_TOKENS,
+});
@@ -1,7 +1,7 @@
 import { useState } from "react";
 import { useLocation } from "react-router-dom";

-import { PageHeader } from "../components/page-header.jsx";
+import { PageHeader } from "../design-system/index.js";
 import { useSession } from "../providers/session-provider.jsx";

 export default function AuthExamplePage() {
@@ -7,15 +7,13 @@ import {
  EmptySurface,
  LoadingSurface,
  TerminalErrorSurface,
-} from "../components/async-surface.jsx";
-import { PageHeader } from "../components/page-header.jsx";
-import {
  AuthRequiredSurface,
  ForbiddenSurface,
  NotFoundSurface,
-} from "../components/state-surfaces.jsx";
-import { Button } from "../components/ui/button.jsx";
-import { Card } from "../components/ui/card.jsx";
+  Button,
+  Card,
+  PageHeader,
+} from "../design-system/index.js";

 export default function StateGalleryPage() {
  const [lastAction, setLastAction] = useState(
@@ -1,12 +1,25 @@
 import { useState } from "react";

-import { PageHeader } from "../components/page-header.jsx";
-import { Alert } from "../components/ui/alert.jsx";
-import { Badge } from "../components/ui/badge.jsx";
-import { Button } from "../components/ui/button.jsx";
-import { Card } from "../components/ui/card.jsx";
-import { Dialog } from "../components/ui/dialog.jsx";
-import { TextField } from "../components/ui/text-field.jsx";
+import {
+  Alert,
+  Badge,
+  Button,
+  Card,
+  Checkbox,
+  Dialog,
+  Menu,
+  PageHeader,
+  ProgressBar,
+  RadioGroup,
+  Select,
+  Switch,
+  Tabs,
+  TextArea,
+  TextField,
+  ToastProvider,
+  Tooltip,
+  useToast,
+} from "../design-system/index.js";

 const COLOR_TOKENS = Object.freeze([
  ["Surface", "--color-surface"],
@@ -19,7 +32,21 @@ const COLOR_TOKENS = Object.freeze([
 ]);

 export default function UiGalleryPage() {
+  return (
+    <ToastProvider>
+      <UiGalleryContent />
+    </ToastProvider>
+  );
+}
+
+function UiGalleryContent() {
+  const toast = useToast();
  const [projectName, setProjectName] = useState("");
+  const [description, setDescription] = useState("");
+  const [template, setTemplate] = useState("application");
+  const [reviewed, setReviewed] = useState(false);
+  const [notifications, setNotifications] = useState(true);
+  const [density, setDensity] = useState("comfortable");
  const [fieldTouched, setFieldTouched] = useState(false);
  const [dialogOpen, setDialogOpen] = useState(false);
  const [notice, setNotice] = useState(
@@ -92,6 +119,60 @@ export default function UiGalleryPage() {
        </div>
      </section>

+      <section className="gallery-section" aria-labelledby="form-controls-title">
+        <header className="gallery-section__header">
+          <h2 id="form-controls-title">폼과 선택 컨트롤</h2>
+          <p>native semantics, 설명·오류 연결과 controlled 상태를 제공합니다.</p>
+        </header>
+        <div className="component-grid component-grid--two">
+          <Card title="긴 입력과 선택">
+            <div className="component-stack">
+              <TextArea
+                label="설명"
+                maxLength={120}
+                value={description}
+                onChange={(event) => setDescription(event.currentTarget.value)}
+              />
+              <Select
+                label="시작 템플릿"
+                options={[
+                  { value: "application", label: "Application" },
+                  { value: "library", label: "Library" },
+                ]}
+                value={template}
+                onChange={(event) => setTemplate(event.currentTarget.value)}
+              />
+              <Checkbox
+                checked={reviewed}
+                label="접근성 계약을 확인했습니다."
+                onChange={(event) => setReviewed(event.currentTarget.checked)}
+              />
+            </div>
+          </Card>
+          <Card title="단일 선택과 설정">
+            <div className="component-stack">
+              <RadioGroup
+                label="화면 밀도"
+                name="density"
+                onChange={setDensity}
+                options={[
+                  { value: "comfortable", label: "여유롭게" },
+                  { value: "compact", label: "조밀하게" },
+                ]}
+                value={density}
+              />
+              <Switch
+                checked={notifications}
+                description="boolean 설정에만 switch를 사용합니다."
+                label="알림 사용"
+                onChange={setNotifications}
+              />
+              <ProgressBar label="설정 준비도" max={4} value={3} />
+            </div>
+          </Card>
+        </div>
+      </section>
+
      <section className="gallery-section" aria-labelledby="feedback-title">
        <header className="gallery-section__header">
          <h2 id="feedback-title">피드백과 모달</h2>
@@ -126,7 +207,32 @@ export default function UiGalleryPage() {
            </div>
          </Card>
          <Card title="모달" description="배경과 키보드 Esc로 닫고 포커스를 복원합니다.">
+            <div className="button-row">
              <Button onClick={() => setDialogOpen(true)}>모달 열기</Button>
+              <Menu
+                items={[
+                  {
+                    id: "inspect",
+                    label: "상태 확인",
+                    onSelect: () => setNotice("메뉴 작업을 실행했습니다."),
+                  },
+                  {
+                    id: "notify",
+                    label: "Toast 표시",
+                    onSelect: () =>
+                      toast.push({
+                        id: "gallery-saved",
+                        title: "예제가 저장되었습니다.",
+                        tone: "success",
+                      }),
+                  },
+                ]}
+                triggerLabel="작업 메뉴"
+              />
+              <Tooltip content="이 설명은 필수 정보가 아닙니다.">
+                <Button variant="ghost">도움말</Button>
+              </Tooltip>
+            </div>
            <Dialog
              open={dialogOpen}
              onClose={() => setDialogOpen(false)}
@@ -157,6 +263,34 @@ export default function UiGalleryPage() {
        </div>
      </section>

+      <section className="gallery-section" aria-labelledby="navigation-title">
+        <header className="gallery-section__header">
+          <h2 id="navigation-title">탐색 패턴</h2>
+          <p>화살표 키와 명시적인 활성화 정책을 갖는 탭 예제입니다.</p>
+        </header>
+        <Tabs
+          activation="manual"
+          label="디자인 시스템 계층"
+          tabs={[
+            {
+              id: "tokens",
+              label: "토큰",
+              panel: <p>원시 값에서 의미와 컴포넌트 토큰을 파생합니다.</p>,
+            },
+            {
+              id: "primitives",
+              label: "프리미티브",
+              panel: <p>native semantics와 interaction을 닫습니다.</p>,
+            },
+            {
+              id: "patterns",
+              label: "패턴",
+              panel: <p>반복되는 사용자 문제를 조합으로 해결합니다.</p>,
+            },
+          ]}
+        />
+      </section>
+
      <section className="gallery-section" aria-labelledby="tokens-title">
        <header className="gallery-section__header">
          <h2 id="tokens-title">디자인 토큰</h2>
@@ -1,6 +1,7 @@
 import { useId, type FormHTMLAttributes, type ReactNode } from "react";

 import { TextField } from "../components/ui/text-field.jsx";
+import { useLocale } from "../i18n/index.js";
 import type {
  FieldErrors,
  FieldName,
@@ -31,6 +32,7 @@ export function ErrorSummary<Values extends FormValues>(props: Readonly<{
  fieldId(name: FieldName<Values>): string;
  onFocusField?(name: FieldName<Values>): void;
 }>) {
+  const { message } = useLocale();
  const {
    fieldErrors,
    formErrors = [],
@@ -50,7 +52,7 @@ export function ErrorSummary<Values extends FormValues>(props: Readonly<{
      role="alert"
      aria-labelledby={headingId}
    >
-      <h2 id={headingId}>입력 내용을 확인해 주세요.</h2>
+      <h2 id={headingId}>{message("form.errorSummary")}</h2>
      {entries.length > 0 ? (
        <ul>
          {entries.map(([name, message]) => (
@@ -1,4 +1,8 @@
 import type { ApiFailure } from "../../contracts/errors.js";
+import {
+  formatMessage,
+  type ParameterlessMessageKey,
+} from "../i18n/index.js";

 export type FormValues = Readonly<Record<string, unknown>>;
 export type FieldName<Values extends FormValues> = Extract<keyof Values, string>;
@@ -23,24 +27,32 @@ export type MappedValidationFailure<Values extends FormValues> = Readonly<{
 }>;

 const VALIDATION_COPY = Object.freeze({
-  REQUIRED: "필수 입력값입니다.",
-  too_small: "입력값이 너무 짧습니다.",
-  too_big: "입력값이 너무 깁니다.",
-  invalid_type: "입력 형식을 확인해 주세요.",
-  invalid_format: "입력 형식을 확인해 주세요.",
-  invalid_value: "허용된 값을 선택해 주세요.",
+  REQUIRED: "form.validation.required",
+  too_small: "form.validation.tooSmall",
+  too_big: "form.validation.tooBig",
+  invalid_type: "form.validation.invalidType",
+  invalid_format: "form.validation.invalidFormat",
+  invalid_value: "form.validation.invalidValue",
 });

-export function validationMessage(code: string): string {
-  return (
+type MessageResolver = (key: ParameterlessMessageKey) => string;
+
+const defaultMessage: MessageResolver = (key) => formatMessage("ko-KR", key);
+
+export function validationMessage(
+  code: string,
+  message: MessageResolver = defaultMessage,
+): string {
+  return message(
    VALIDATION_COPY[code as keyof typeof VALIDATION_COPY] ??
-    "입력값을 확인해 주세요."
+      "form.validation.unknown",
  );
 }

 export function mapValidationFailureToFields<Values extends FormValues>(
  failure: ApiFailure,
  allowedFields: readonly FieldName<Values>[],
+  message: MessageResolver = defaultMessage,
 ): MappedValidationFailure<Values> {
  if (failure.kind !== "VALIDATION_REJECTED") {
    return Object.freeze({ fieldErrors: Object.freeze({}), formErrors: [] });
@@ -51,15 +63,15 @@ export function mapValidationFailureToFields<Values extends FormValues>(
  const issues = failure.validationIssues ?? [];

  if (issues.length === 0) {
-    formErrors.push("입력값을 다시 확인해 주세요.");
+    formErrors.push(message("form.validation.retry"));
  }
  for (const issue of issues) {
    const field = issue.path.split(".").at(0) ?? "";
    if (allowed.has(field)) {
      const name = field as FieldName<Values>;
-      fieldErrors[name] ??= validationMessage(issue.code);
+      fieldErrors[name] ??= validationMessage(issue.code, message);
    } else {
-      formErrors.push("서버가 확인하지 못한 입력 항목이 있습니다.");
+      formErrors.push(message("form.validation.unknownField"));
    }
  }
  return Object.freeze({
@@ -8,6 +8,10 @@ import {
  type FormEvent,
 } from "react";
 import type { ZodType, ZodIssue } from "zod";
+import {
+  useLocale,
+  type ParameterlessMessageKey,
+} from "../i18n/index.js";

 import {
  mapValidationFailureToFields,
@@ -37,6 +41,7 @@ export function useAppForm<
  Command,
  Output,
 >(options: AppFormOptions<Values, Command, Output>) {
+  const { message } = useLocale();
  const {
    schema,
    defaultValues,
@@ -142,13 +147,14 @@ export function useAppForm<
        const errors = issuesToFieldErrors<Values>(
          parsed.error.issues,
          allowedServerFields,
+          message,
        );
        setFieldErrors(errors);
        setFormErrors(
          parsed.error.issues.some(
            (issue) => !allowedServerFields.includes(issue.path[0] as FieldName<Values>),
          )
-            ? ["입력 구성을 다시 확인해 주세요."]
+            ? [message("form.validation.configuration")]
            : [],
        );
        setTouched(new Set(allowedServerFields));
@@ -178,6 +184,7 @@ export function useAppForm<
          const mapped = mapValidationFailureToFields<Values>(
            outcome.error,
            allowedServerFields,
+            message,
          );
          setFieldErrors(mapped.fieldErrors);
          setFormErrors(mapped.formErrors);
@@ -185,11 +192,11 @@ export function useAppForm<
          focusFirstError(mapped.fieldErrors);
        } else if (outcome.error.kind === "CONFLICT") {
          setFormErrors([
-            "다른 변경과 충돌했습니다. 입력은 유지되었으니 최신 상태를 확인해 주세요.",
+            message("form.conflict"),
          ]);
          setResult("conflict");
        } else {
-          setFormErrors(["저장하지 못했습니다. 잠시 후 다시 시도해 주세요."]);
+          setFormErrors([message("form.unavailable")]);
          setResult("unavailable");
        }
        return outcome;
@@ -203,6 +210,7 @@ export function useAppForm<
      defaultValues,
      focusFirstError,
      mapToCommand,
+      message,
      resetOnSuccess,
      schema,
      submit,
@@ -231,6 +239,7 @@ export function useAppForm<
 function issuesToFieldErrors<Values extends FormValues>(
  issues: readonly ZodIssue[],
  allowedFields: readonly FieldName<Values>[],
+  message: (key: ParameterlessMessageKey) => string,
 ): FieldErrors<Values> {
  const allowed = new Set<PropertyKey>(allowedFields);
  const errors: Partial<Record<FieldName<Values>, string>> = {};
@@ -238,7 +247,7 @@ function issuesToFieldErrors<Values extends FormValues>(
    const field = issue.path[0];
    if (!allowed.has(field)) continue;
    const name = field as FieldName<Values>;
-    errors[name] ??= validationMessage(issue.code);
+    errors[name] ??= validationMessage(issue.code, message);
  }
  return Object.freeze(errors);
 }
@@ -3,6 +3,7 @@ import { useBeforeUnload, useBlocker } from "react-router-dom";

 import { Button } from "../components/ui/button.jsx";
 import { Dialog } from "../components/ui/dialog.jsx";
+import { useLocale } from "../i18n/index.js";

 export function useDirtyNavigationGuard(when: boolean) {
  const blocker = useBlocker(when);
@@ -33,19 +34,20 @@ export function useDirtyNavigationGuard(when: boolean) {
 export function DirtyNavigationDialog(props: Readonly<{
  guard: ReturnType<typeof useDirtyNavigationGuard>;
 }>) {
+  const { message } = useLocale();
  return (
    <Dialog
      open={props.guard.blocked}
      onClose={props.guard.stay}
-      title="저장하지 않은 변경이 있습니다."
-      description="이 화면을 떠나면 입력한 내용이 사라집니다."
+      title={message("form.unsaved.title")}
+      description={message("form.unsaved.description")}
      actions={
        <>
          <Button variant="secondary" onClick={props.guard.stay}>
-            계속 작성
+            {message("action.continueEditing")}
          </Button>
          <Button variant="danger" onClick={props.guard.leave}>
-            변경 버리고 이동
+            {message("action.discardAndLeave")}
          </Button>
        </>
      }
@@ -0,0 +1,304 @@
+import { INSTALLED_MESSAGE_CATALOGS } from "../../features/installed-feature-messages.js";
+
+const PLATFORM_KO_MESSAGES = {
+  "common.unavailable": "요청한 문구를 표시할 수 없습니다.",
+  "common.processing": "처리 중…",
+  "common.appName": "Frontend Skeleton",
+  "common.noDisplayValue": "표시 정보 없음",
+  "action.retry": "다시 시도",
+  "action.reauth": "로그인",
+  "action.navigateSafe": "안전한 화면으로 이동",
+  "action.reloadOnce": "한 번 새로고침",
+  "action.contactSupport": "지원 정보 확인",
+  "action.resolveConflict": "충돌 해결",
+  "action.continueEditing": "계속 작성",
+  "action.discardAndLeave": "변경 버리고 이동",
+  "action.signIn": "로그인 시작",
+  "action.recoverSession": "세션 복구",
+  "action.signOut": "로그아웃",
+  "action.goHome": "홈으로 이동",
+  "action.closeNamed": "{title} 닫기",
+  "action.alertCloseNamed": "{title} 알림 닫기",
+  "shell.skipToContent": "본문으로 건너뛰기",
+  "shell.menu": "메뉴",
+  "shell.closeMenu": "메뉴 닫기",
+  "shell.sidebar": "사이드바",
+  "shell.primaryNavigation": "주요 탐색",
+  "shell.theme": "색상 테마",
+  "shell.theme.system": "시스템 테마",
+  "shell.theme.light": "라이트 테마",
+  "shell.theme.dark": "다크 테마",
+  "shell.locale": "언어",
+  "shell.locale.ko": "한국어",
+  "shell.locale.en": "English",
+  "shell.locale.pseudo": "Pseudo",
+  "shell.locale.rtl": "RTL smoke",
+  "shell.session.authenticated": "인증됨",
+  "shell.session.unauthenticated": "로그인 전",
+  "shell.session.recoveryPending": "복구 대기",
+  "shell.session.integrationFailed": "연동 필요",
+  "shell.session.actionFailed": "세션 작업을 완료하지 못했습니다.",
+  "route.APP_HOME.navigation": "홈",
+  "route.APP_HOME.title": "Clean Architecture Frontend",
+  "route.EXAMPLES_UI.navigation": "UI 구성요소",
+  "route.EXAMPLES_UI.title": "UI 구성요소",
+  "route.EXAMPLES_STATES.navigation": "화면 상태",
+  "route.EXAMPLES_STATES.title": "화면 상태",
+  "route.EXAMPLES_AUTH.navigation": "인증 연동",
+  "route.EXAMPLES_AUTH.title": "인증 연동",
+  "route.NOT_FOUND.navigation": "찾을 수 없음",
+  "route.NOT_FOUND.title": "페이지를 찾을 수 없습니다.",
+  "async.loading": "불러오는 중",
+  "async.empty": "표시할 항목이 없습니다.",
+  "async.refreshing": "최신 정보를 확인하고 있습니다.",
+  "async.staleDegraded": "기존 정보를 표시하고 있습니다.",
+  "async.mutationPending": "변경 사항을 저장하고 있습니다.",
+  "async.mutationConflict": "다른 변경과 충돌했습니다.",
+  "access.auth.eyebrow": "401 · 인증 필요",
+  "access.auth.title": "로그인이 필요합니다.",
+  "access.auth.description":
+    "세션을 시작한 뒤 이전 작업을 안전하게 계속할 수 있습니다.",
+  "access.forbidden.eyebrow": "403 · 권한 없음",
+  "access.forbidden.title": "접근할 수 없습니다.",
+  "access.forbidden.description":
+    "권한을 확인하거나 접근 가능한 화면으로 이동하세요.",
+  "access.notFound.eyebrow": "404 · 찾을 수 없음",
+  "access.notFound.title": "요청한 화면이 없습니다.",
+  "access.notFound.description":
+    "주소를 확인하거나 시작 화면으로 돌아가세요.",
+  "route.loading": "화면을 준비하고 있습니다.",
+  "route.loadingNamed": "{title} 로딩 중",
+  "route.failure.title": "화면을 표시하지 못했습니다.",
+  "route.failure.description":
+    "잠시 후 다시 시도해 주세요. 문제가 계속되면 운영 지원 참조 정보를 확인하세요.",
+  "route.invalid.title": "올바르지 않은 주소입니다.",
+  "route.invalid.description": "주소의 경로 또는 검색 조건을 확인해 주세요.",
+  "route.invalid.action": "안전한 탐색 링크를 사용해 주세요.",
+  "route.auth.integration.title": "로그인 연동이 필요합니다.",
+  "route.auth.integration.description":
+    "외부 인증 소유자가 연결되면 이 보호 라우트를 사용할 수 있습니다.",
+  "route.auth.recovering.title": "세션을 복구하고 있습니다.",
+  "route.auth.required.title": "세션이 필요합니다.",
+  "route.auth.recovering.description":
+    "기존 세션 확인을 계속하려면 복구를 실행하세요.",
+  "route.auth.required.description":
+    "이 화면은 인증 연동 지점을 확인하기 위한 보호 라우트입니다.",
+  "route.documentTitle": "{title} · {appName}",
+  "chunk.checking": "새 릴리스 정보를 확인하고 있습니다.",
+  "chunk.reloadOnce": "새 버전으로 한 번만 전환합니다.",
+  "chunk.failure.title": "화면 자산을 복구하지 못했습니다.",
+  "chunk.failure.description":
+    "문제가 계속되면 배포 상태와 지원 참조 정보를 확인해 주세요.",
+  "page.notFound.title": "페이지를 찾을 수 없습니다.",
+  "page.notFound.description":
+    "주소를 확인하거나 준비된 시작 화면으로 돌아가세요.",
+  "template.breadcrumb": "현재 위치",
+  "template.relatedInformation": "관련 정보",
+  "template.searchAndFilter": "검색과 필터",
+  "template.pagination": "페이지 탐색",
+  "template.summary": "요약 정보",
+  "template.dangerActions": "위험 작업",
+  "template.supportReference": "지원 참조: {reference}",
+  "form.errorSummary": "입력 내용을 확인해 주세요.",
+  "form.unsaved.title": "저장하지 않은 변경이 있습니다.",
+  "form.unsaved.description": "이 화면을 떠나면 입력한 내용이 사라집니다.",
+  "form.validation.required": "필수 입력값입니다.",
+  "form.validation.tooSmall": "입력값이 너무 짧습니다.",
+  "form.validation.tooBig": "입력값이 너무 깁니다.",
+  "form.validation.invalidType": "입력 형식을 확인해 주세요.",
+  "form.validation.invalidFormat": "입력 형식을 확인해 주세요.",
+  "form.validation.invalidValue": "허용된 값을 선택해 주세요.",
+  "form.validation.unknown": "입력값을 확인해 주세요.",
+  "form.validation.retry": "입력값을 다시 확인해 주세요.",
+  "form.validation.unknownField":
+    "서버가 확인하지 못한 입력 항목이 있습니다.",
+  "form.validation.configuration": "입력 구성을 다시 확인해 주세요.",
+  "form.conflict":
+    "다른 변경과 충돌했습니다. 입력은 유지되었으니 최신 상태를 확인해 주세요.",
+  "form.unavailable": "저장하지 못했습니다. 잠시 후 다시 시도해 주세요.",
+  "form.remaining": "{count}자 남음",
+  "toast.region": "알림",
+  "error.network_unreachable": "네트워크에 연결할 수 없습니다.",
+  "error.request_timeout": "요청 시간이 초과되었습니다.",
+  "error.auth_required": "계속하려면 로그인이 필요합니다.",
+  "error.auth_integration_failure": "로그인 연동을 사용할 수 없습니다.",
+  "error.forbidden": "이 작업을 수행할 권한이 없습니다.",
+  "error.not_found": "요청한 항목을 찾을 수 없습니다.",
+  "error.rate_limited": "요청이 많습니다. 잠시 후 다시 시도해 주세요.",
+  "error.server_failure": "요청을 완료하지 못했습니다.",
+  "error.chunk_load_failure": "새 화면 파일을 불러오지 못했습니다.",
+  "error.build_mismatch": "현재 화면과 활성 빌드가 일치하지 않습니다.",
+  "error.config_mismatch": "런타임 설정 버전이 현재 화면과 일치하지 않습니다.",
+  "error.api_contract_mismatch": "API 계약 버전이 현재 화면과 일치하지 않습니다.",
+  "error.release_mismatch": "현재 화면과 활성 릴리스가 일치하지 않습니다.",
+  "error.asset_mismatch": "화면 자산 구성이 현재 릴리스와 일치하지 않습니다.",
+  "error.render_failure": "화면을 표시하지 못했습니다.",
+  "error.unknown_failure": "예상하지 못한 문제가 발생했습니다.",
+  "boot.failure.title": "애플리케이션을 시작할 수 없습니다.",
+  "boot.field.error": "오류",
+  "boot.field.code": "코드",
+  "boot.field.build": "빌드",
+  "boot.field.configSchema": "설정 스키마",
+  "boot.field.release": "릴리스",
+  "boot.supportReference": "지원 참조: {reference}",
+} as const;
+
+export const KO_MESSAGES = {
+  ...PLATFORM_KO_MESSAGES,
+  ...INSTALLED_MESSAGE_CATALOGS["ko-KR"],
+} as const;
+
+export type MessageKey = keyof typeof KO_MESSAGES;
+
+const PLATFORM_EN_MESSAGES = {
+  "common.unavailable": "This message is unavailable.",
+  "common.processing": "Processing…",
+  "common.appName": "Frontend Skeleton",
+  "common.noDisplayValue": "No display value",
+  "action.retry": "Try again",
+  "action.reauth": "Sign in",
+  "action.navigateSafe": "Go to an available page",
+  "action.reloadOnce": "Reload once",
+  "action.contactSupport": "View support information",
+  "action.resolveConflict": "Resolve conflict",
+  "action.continueEditing": "Continue editing",
+  "action.discardAndLeave": "Discard and leave",
+  "action.signIn": "Start sign-in",
+  "action.recoverSession": "Recover session",
+  "action.signOut": "Sign out",
+  "action.goHome": "Go home",
+  "action.closeNamed": "Close {title}",
+  "action.alertCloseNamed": "Dismiss {title} alert",
+  "shell.skipToContent": "Skip to content",
+  "shell.menu": "Menu",
+  "shell.closeMenu": "Close menu",
+  "shell.sidebar": "Sidebar",
+  "shell.primaryNavigation": "Primary navigation",
+  "shell.theme": "Color theme",
+  "shell.theme.system": "System theme",
+  "shell.theme.light": "Light theme",
+  "shell.theme.dark": "Dark theme",
+  "shell.locale": "Language",
+  "shell.locale.ko": "한국어",
+  "shell.locale.en": "English",
+  "shell.locale.pseudo": "Pseudo",
+  "shell.locale.rtl": "RTL smoke",
+  "shell.session.authenticated": "Authenticated",
+  "shell.session.unauthenticated": "Signed out",
+  "shell.session.recoveryPending": "Recovery pending",
+  "shell.session.integrationFailed": "Integration required",
+  "shell.session.actionFailed": "The session action could not be completed.",
+  "route.APP_HOME.navigation": "Home",
+  "route.APP_HOME.title": "Clean Architecture Frontend",
+  "route.EXAMPLES_UI.navigation": "UI components",
+  "route.EXAMPLES_UI.title": "UI components",
+  "route.EXAMPLES_STATES.navigation": "Screen states",
+  "route.EXAMPLES_STATES.title": "Screen states",
+  "route.EXAMPLES_AUTH.navigation": "Authentication",
+  "route.EXAMPLES_AUTH.title": "Authentication",
+  "route.NOT_FOUND.navigation": "Not found",
+  "route.NOT_FOUND.title": "Page not found",
+  "async.loading": "Loading",
+  "async.empty": "There are no items to display.",
+  "async.refreshing": "Checking for the latest information.",
+  "async.staleDegraded": "Showing previously loaded information.",
+  "async.mutationPending": "Saving changes.",
+  "async.mutationConflict": "The change conflicts with another update.",
+  "access.auth.eyebrow": "401 · Authentication required",
+  "access.auth.title": "Sign-in is required.",
+  "access.auth.description":
+    "Start a session to safely continue the previous task.",
+  "access.forbidden.eyebrow": "403 · Access denied",
+  "access.forbidden.title": "You cannot access this page.",
+  "access.forbidden.description":
+    "Check your permissions or go to an available page.",
+  "access.notFound.eyebrow": "404 · Not found",
+  "access.notFound.title": "The requested page does not exist.",
+  "access.notFound.description": "Check the address or return to the start page.",
+  "route.loading": "Preparing the page.",
+  "route.loadingNamed": "Loading {title}",
+  "route.failure.title": "The page could not be displayed.",
+  "route.failure.description":
+    "Try again shortly. If the problem continues, check the support reference.",
+  "route.invalid.title": "This address is invalid.",
+  "route.invalid.description": "Check the path and search parameters.",
+  "route.invalid.action": "Use a safe navigation link.",
+  "route.auth.integration.title": "Sign-in integration is required.",
+  "route.auth.integration.description":
+    "This protected route is available after an external authentication owner is connected.",
+  "route.auth.recovering.title": "Recovering the session.",
+  "route.auth.required.title": "A session is required.",
+  "route.auth.recovering.description":
+    "Run recovery to continue checking the existing session.",
+  "route.auth.required.description":
+    "This protected route demonstrates the authentication integration seam.",
+  "route.documentTitle": "{title} · {appName}",
+  "chunk.checking": "Checking the new release information.",
+  "chunk.reloadOnce": "Switching to the new version once.",
+  "chunk.failure.title": "The page assets could not be recovered.",
+  "chunk.failure.description":
+    "If the problem continues, check deployment status and support information.",
+  "page.notFound.title": "Page not found.",
+  "page.notFound.description": "Check the address or return to the start page.",
+  "template.breadcrumb": "Current location",
+  "template.relatedInformation": "Related information",
+  "template.searchAndFilter": "Search and filters",
+  "template.pagination": "Pagination",
+  "template.summary": "Summary information",
+  "template.dangerActions": "Dangerous actions",
+  "template.supportReference": "Support reference: {reference}",
+  "form.errorSummary": "Review the entered information.",
+  "form.unsaved.title": "You have unsaved changes.",
+  "form.unsaved.description":
+    "The entered information will be lost if you leave this page.",
+  "form.validation.required": "This field is required.",
+  "form.validation.tooSmall": "This value is too short.",
+  "form.validation.tooBig": "This value is too long.",
+  "form.validation.invalidType": "Check the input type.",
+  "form.validation.invalidFormat": "Check the input format.",
+  "form.validation.invalidValue": "Choose an allowed value.",
+  "form.validation.unknown": "Check the entered value.",
+  "form.validation.retry": "Review the entered values.",
+  "form.validation.unknownField":
+    "The server reported an unrecognized input field.",
+  "form.validation.configuration": "Review the input configuration.",
+  "form.conflict":
+    "Another update conflicts with this change. Your input has been preserved.",
+  "form.unavailable": "The change could not be saved. Try again shortly.",
+  "form.remaining": "{count} characters remaining",
+  "toast.region": "Notifications",
+  "error.network_unreachable": "The network is unavailable.",
+  "error.request_timeout": "The request timed out.",
+  "error.auth_required": "Sign in to continue.",
+  "error.auth_integration_failure": "Sign-in integration is unavailable.",
+  "error.forbidden": "You are not allowed to perform this action.",
+  "error.not_found": "The requested item could not be found.",
+  "error.rate_limited": "Too many requests were made. Try again shortly.",
+  "error.server_failure": "The request could not be completed.",
+  "error.chunk_load_failure": "The new page assets could not be loaded.",
+  "error.build_mismatch": "The active build does not match this page.",
+  "error.config_mismatch": "The runtime configuration does not match this page.",
+  "error.api_contract_mismatch": "The API contract does not match this page.",
+  "error.release_mismatch": "The active release does not match this page.",
+  "error.asset_mismatch": "The page assets do not match this release.",
+  "error.render_failure": "The page could not be displayed.",
+  "error.unknown_failure": "An unexpected problem occurred.",
+  "boot.failure.title": "The application could not start.",
+  "boot.field.error": "Error",
+  "boot.field.code": "Code",
+  "boot.field.build": "Build",
+  "boot.field.configSchema": "Configuration schema",
+  "boot.field.release": "Release",
+  "boot.supportReference": "Support reference: {reference}",
+} as const satisfies Record<keyof typeof PLATFORM_KO_MESSAGES, string>;
+
+export const EN_MESSAGES = {
+  ...PLATFORM_EN_MESSAGES,
+  ...INSTALLED_MESSAGE_CATALOGS["en-US"],
+} as const satisfies Record<MessageKey, string>;
+
+export const MESSAGE_CATALOGS = Object.freeze({
+  "ko-KR": KO_MESSAGES,
+  "en-US": EN_MESSAGES,
+  "ar-EG": EN_MESSAGES,
+});
@@ -0,0 +1,96 @@
+import { normalizeLocale, type SupportedLocale } from "./message-contract.js";
+
+const FORMAT_FALLBACK = "—";
+
+export type DateFormatStyle = "short" | "medium" | "long";
+
+export function formatDate(
+  locale: SupportedLocale,
+  value: Date | number,
+  options: Readonly<{
+    dateStyle?: DateFormatStyle;
+    timeZone?: string;
+  }> = {},
+): string {
+  try {
+    const date = value instanceof Date ? value : new Date(value);
+    if (Number.isNaN(date.getTime())) return FORMAT_FALLBACK;
+    return new Intl.DateTimeFormat(normalizeLocale(locale), {
+      dateStyle: options.dateStyle ?? "medium",
+      timeZone: options.timeZone ?? "UTC",
+    }).format(date);
+  } catch {
+    return FORMAT_FALLBACK;
+  }
+}
+
+export function formatNumber(
+  locale: SupportedLocale,
+  value: number,
+  options: Readonly<{
+    style?: "decimal" | "percent";
+    maximumFractionDigits?: number;
+  }> = {},
+): string {
+  try {
+    if (!Number.isFinite(value)) return FORMAT_FALLBACK;
+    return new Intl.NumberFormat(normalizeLocale(locale), options).format(value);
+  } catch {
+    return FORMAT_FALLBACK;
+  }
+}
+
+export function formatRelativeTime(
+  locale: SupportedLocale,
+  value: number,
+  unit: Intl.RelativeTimeFormatUnit,
+): string {
+  try {
+    if (!Number.isFinite(value)) return FORMAT_FALLBACK;
+    return new Intl.RelativeTimeFormat(normalizeLocale(locale), {
+      numeric: "auto",
+    }).format(value, unit);
+  } catch {
+    return FORMAT_FALLBACK;
+  }
+}
+
+export function formatList(
+  locale: SupportedLocale,
+  values: readonly string[],
+): string {
+  try {
+    return new Intl.ListFormat(normalizeLocale(locale), {
+      style: "long",
+      type: "conjunction",
+    }).format(values);
+  } catch {
+    return values.join(", ");
+  }
+}
+
+export function selectPlural(
+  locale: SupportedLocale,
+  value: number,
+  choices: Readonly<
+    Partial<Record<Intl.LDMLPluralRule, string>> & { other: string }
+  >,
+): string {
+  try {
+    if (!Number.isFinite(value)) return choices.other;
+    return choices[
+      new Intl.PluralRules(normalizeLocale(locale)).select(value)
+    ] ?? choices.other;
+  } catch {
+    return choices.other;
+  }
+}
+
+export function selectMessage(
+  value: string,
+  choices: Readonly<Record<string, string> & { other: string }>,
+): string {
+  return choices[value] ?? choices.other;
+}
+
+export { FORMAT_FALLBACK };
@@ -0,0 +1,29 @@
+export { LocaleProvider, useLocale } from "./locale-provider.js";
+export {
+  catalogKeys,
+  fallbackMessage,
+  formatMessage,
+  localeDirection,
+  MESSAGE_KEY_ALIASES,
+  messagePlaceholders,
+  normalizeLocale,
+  resolveMessage,
+  SUPPORTED_LOCALES,
+} from "./message-contract.js";
+export type {
+  MessageArguments,
+  MessageParameters,
+  ParameterlessMessageKey,
+  SupportedLocale,
+  TextDirection,
+} from "./message-contract.js";
+export type { MessageKey } from "./catalog.js";
+export {
+  FORMAT_FALLBACK,
+  formatDate,
+  formatList,
+  formatNumber,
+  formatRelativeTime,
+  selectMessage,
+  selectPlural,
+} from "./formatters.js";
@@ -0,0 +1,118 @@
+import {
+  createContext,
+  useContext,
+  useEffect,
+  useMemo,
+  useState,
+} from "react";
+
+import {
+  formatDate,
+  formatList,
+  formatNumber,
+  formatRelativeTime,
+  selectMessage,
+  selectPlural,
+} from "./formatters.js";
+import {
+  formatMessage,
+  localeDirection,
+  normalizeLocale,
+  resolveMessage,
+  type MessageArguments,
+  type SupportedLocale,
+  type TextDirection,
+} from "./message-contract.js";
+import type { MessageKey } from "./catalog.js";
+
+type LocaleContextValue = Readonly<{
+  locale: SupportedLocale;
+  direction: TextDirection;
+  setLocale(locale: SupportedLocale): void;
+  message<Key extends MessageKey>(
+    key: Key,
+    ...args: MessageArguments<Key>
+  ): string;
+  resolve(key: string): string;
+  date(
+    value: Date | number,
+    options?: Parameters<typeof formatDate>[2],
+  ): string;
+  number(value: number, options?: Parameters<typeof formatNumber>[2]): string;
+  relativeTime(
+    value: number,
+    unit: Intl.RelativeTimeFormatUnit,
+  ): string;
+  list(values: readonly string[]): string;
+  plural(
+    value: number,
+    choices: Parameters<typeof selectPlural>[2],
+  ): string;
+  select(
+    value: string,
+    choices: Readonly<Record<string, string> & { other: string }>,
+  ): string;
+}>;
+
+const DEFAULT_LOCALE = "ko-KR" as const;
+const DEFAULT_CONTEXT: LocaleContextValue = Object.freeze({
+  locale: DEFAULT_LOCALE,
+  direction: "ltr",
+  setLocale() {},
+  message: (key, ...args) => formatMessage(DEFAULT_LOCALE, key, ...args),
+  resolve: (key) => resolveMessage(DEFAULT_LOCALE, key),
+  date: (value, options) => formatDate(DEFAULT_LOCALE, value, options),
+  number: (value, options) => formatNumber(DEFAULT_LOCALE, value, options),
+  relativeTime: (value, unit) =>
+    formatRelativeTime(DEFAULT_LOCALE, value, unit),
+  list: (values) => formatList(DEFAULT_LOCALE, values),
+  plural: (value, choices) => selectPlural(DEFAULT_LOCALE, value, choices),
+  select: (value, choices) => selectMessage(value, choices),
+});
+const LocaleContext = createContext<LocaleContextValue>(DEFAULT_CONTEXT);
+
+export function LocaleProvider({
+  children,
+  initialLocale = "ko-KR",
+}: Readonly<{
+  children: React.ReactNode;
+  initialLocale?: SupportedLocale;
+}>) {
+  const [locale, setLocaleState] = useState<SupportedLocale>(() =>
+    normalizeLocale(initialLocale),
+  );
+  const direction = localeDirection(locale);
+
+  useEffect(() => {
+    document.documentElement.lang = locale;
+    document.documentElement.dir = direction;
+  }, [direction, locale]);
+
+  const value = useMemo<LocaleContextValue>(
+    () => ({
+      locale,
+      direction,
+      setLocale: setLocaleState,
+      message: (key, ...args) => formatMessage(locale, key, ...args),
+      resolve: (key) => resolveMessage(locale, key),
+      date: (dateValue, options) => formatDate(locale, dateValue, options),
+      number: (numberValue, options) =>
+        formatNumber(locale, numberValue, options),
+      relativeTime: (relativeValue, unit) =>
+        formatRelativeTime(locale, relativeValue, unit),
+      list: (values) => formatList(locale, values),
+      plural: (pluralValue, choices) =>
+        selectPlural(locale, pluralValue, choices),
+      select: (selectValue, choices) => selectMessage(selectValue, choices),
+    }),
+    [direction, locale],
+  );
+
+  return (
+    <LocaleContext.Provider value={value}>{children}</LocaleContext.Provider>
+  );
+}
+
+export function useLocale(): LocaleContextValue {
+  return useContext(LocaleContext);
+}
@@ -0,0 +1,135 @@
+import {
+  EN_MESSAGES,
+  KO_MESSAGES,
+  MESSAGE_CATALOGS,
+  type MessageKey,
+} from "./catalog.js";
+
+export const SUPPORTED_LOCALES = Object.freeze([
+  "ko-KR",
+  "en-US",
+  "en-XA",
+  "ar-EG",
+] as const);
+export type SupportedLocale = (typeof SUPPORTED_LOCALES)[number];
+export type TextDirection = "ltr" | "rtl";
+
+export type MessageParameters = Readonly<{
+  "action.closeNamed": { title: string };
+  "action.alertCloseNamed": { title: string };
+  "route.loadingNamed": { title: string };
+  "route.documentTitle": { title: string; appName: string };
+  "template.supportReference": { reference: string };
+  "form.remaining": { count: number };
+  "boot.supportReference": { reference: string };
+}>;
+export type ParameterlessMessageKey = Exclude<
+  MessageKey,
+  keyof MessageParameters
+>;
+
+export type MessageArguments<Key extends MessageKey> =
+  Key extends keyof MessageParameters
+    ? [parameters: MessageParameters[Key]]
+    : [parameters?: never];
+
+const PLACEHOLDER_PATTERN = /\{([a-zA-Z][a-zA-Z0-9]*)\}/g;
+const FALLBACK_LOCALE = "ko-KR" as const;
+export const MESSAGE_KEY_ALIASES = Object.freeze({
+  "action.login": "action.reauth",
+  "async.pending": "common.processing",
+} as const satisfies Readonly<Record<string, MessageKey>>);
+
+export function normalizeLocale(locale: string): SupportedLocale {
+  if ((SUPPORTED_LOCALES as readonly string[]).includes(locale)) {
+    return locale as SupportedLocale;
+  }
+  const language = locale.split("-")[0]?.toLowerCase();
+  if (language === "ko") return "ko-KR";
+  if (language === "ar") return "ar-EG";
+  if (language === "en") return "en-US";
+  return FALLBACK_LOCALE;
+}
+
+export function localeDirection(locale: SupportedLocale): TextDirection {
+  return locale === "ar-EG" ? "rtl" : "ltr";
+}
+
+export function messagePlaceholders(template: string): readonly string[] {
+  return Object.freeze(
+    [...template.matchAll(PLACEHOLDER_PATTERN)].map((match) => match[1] ?? ""),
+  );
+}
+
+export function resolveMessage(
+  locale: string,
+  key: string,
+  parameters?: Readonly<Record<string, string | number>>,
+): string {
+  const normalized = normalizeLocale(locale);
+  const sourceLocale: keyof typeof MESSAGE_CATALOGS =
+    normalized === "en-XA" ? "en-US" : normalized;
+  const catalog =
+    MESSAGE_CATALOGS[sourceLocale] ??
+    MESSAGE_CATALOGS[FALLBACK_LOCALE];
+  const fallback = KO_MESSAGES["common.unavailable"];
+  const canonicalKey =
+    MESSAGE_KEY_ALIASES[key as keyof typeof MESSAGE_KEY_ALIASES] ?? key;
+  const template = catalog[canonicalKey as MessageKey] ?? fallback;
+  const placeholders = messagePlaceholders(template);
+  if (
+    placeholders.some(
+      (placeholder) =>
+        parameters?.[placeholder] === undefined ||
+        parameters?.[placeholder] === null,
+    )
+  ) {
+    return fallback;
+  }
+  const formatted = template.replace(
+    PLACEHOLDER_PATTERN,
+    (_, placeholder: string) => String(parameters?.[placeholder] ?? ""),
+  );
+  return normalized === "en-XA" ? pseudoLocalize(formatted) : formatted;
+}
+
+export function formatMessage<Key extends MessageKey>(
+  locale: string,
+  key: Key,
+  ...args: MessageArguments<Key>
+): string {
+  return resolveMessage(
+    locale,
+    key,
+    args[0] as Readonly<Record<string, string | number>> | undefined,
+  );
+}
+
+function pseudoLocalize(value: string): string {
+  const expanded = value.replace(/[A-Za-z]/g, (character) => {
+    const replacements: Readonly<Record<string, string>> = {
+      a: "á",
+      e: "é",
+      i: "í",
+      o: "ó",
+      u: "ú",
+      A: "Á",
+      E: "É",
+      I: "Í",
+      O: "Ó",
+      U: "Ú",
+    };
+    return replacements[character] ?? character;
+  });
+  return `［${expanded} ···］`;
+}
+
+export function catalogKeys(
+  locale: "ko-KR" | "en-US" | "ar-EG",
+): MessageKey[] {
+  return Object.keys(MESSAGE_CATALOGS[locale]).sort() as MessageKey[];
+}
+
+export function fallbackMessage() {
+  return EN_MESSAGES["common.unavailable"];
+}
@@ -5,20 +5,29 @@ import {
  NAVIGATION_ROUTES,
  routePath,
 } from "../../features/installed-feature-contracts.js";
+import {
+  Button,
+  Drawer,
+  IconButton,
+  MenuIcon,
+  Select,
+} from "../design-system/index.js";
+import { useLocale } from "../i18n/index.js";
 import { useSession } from "../providers/session-provider.jsx";
 import { useTheme } from "../providers/theme-provider.jsx";

-const SESSION_LABELS = Object.freeze({
-  authenticated: "인증됨",
-  unauthenticated: "로그인 전",
-  "recovery-pending": "복구 대기",
-  "integration-failed": "연동 필요",
+const SESSION_MESSAGE_KEYS = Object.freeze({
+  authenticated: "shell.session.authenticated",
+  unauthenticated: "shell.session.unauthenticated",
+  "recovery-pending": "shell.session.recoveryPending",
+  "integration-failed": "shell.session.integrationFailed",
 });

 export function AppShell() {
  const location = useLocation();
  const { sessionState, beginSignIn, signOut, recover } = useSession();
  const { preference, setPreference } = useTheme();
+  const { locale, setLocale, message } = useLocale();
  const [navigationOpen, setNavigationOpen] = useState(false);
  const [sessionActionPending, setSessionActionPending] = useState(false);
  const [sessionActionFailed, setSessionActionFailed] = useState(false);
@@ -27,16 +36,6 @@ export function AppShell() {
    setNavigationOpen(false);
  }, [location.pathname]);

-  useEffect(() => {
-    if (!navigationOpen) return undefined;
-    /** @param {KeyboardEvent} event */
-    const closeOnEscape = (event) => {
-      if (event.key === "Escape") setNavigationOpen(false);
-    };
-    window.addEventListener("keydown", closeOnEscape);
-    return () => window.removeEventListener("keydown", closeOnEscape);
-  }, [navigationOpen]);
-
  async function runSessionAction() {
    setSessionActionPending(true);
    setSessionActionFailed(false);
@@ -59,38 +58,41 @@ export function AppShell() {

  const sessionActionLabel =
    sessionState === "authenticated"
-      ? "로그아웃"
+      ? message("action.signOut")
      : sessionState === "recovery-pending"
-        ? "세션 복구"
-        : "로그인";
+        ? message("action.recoverSession")
+        : message("action.reauth");
  const integrationAvailable = sessionState !== "integration-failed";

  return (
    <div className="app-shell">
      <a className="skip-link" href="#main-content">
-        본문으로 건너뛰기
+        {message("shell.skipToContent")}
      </a>
      <header className="app-shell__header">
-        <button
+        <IconButton
+          accessibleName={message("shell.menu")}
          className="app-shell__menu-button"
-          type="button"
-          aria-controls="primary-navigation"
+          aria-controls="mobile-primary-navigation"
          aria-expanded={navigationOpen}
          onClick={() => setNavigationOpen((open) => !open)}
+          variant="secondary"
        >
-          <span aria-hidden="true">☰</span>
-          <span>메뉴</span>
-        </button>
+          <MenuIcon />
+        </IconButton>
        <NavLink className="app-shell__brand" to={routePath("APP_HOME")}>
-          Frontend Skeleton
+          {message("common.appName")}
        </NavLink>
        <div className="app-shell__session">
-          <label className="visually-hidden" htmlFor="theme-preference">
-            색상 테마
-          </label>
-          <select
+          <Select
            className="theme-selector"
            id="theme-preference"
+            label={message("shell.theme")}
+            options={[
+              { value: "system", label: message("shell.theme.system") },
+              { value: "light", label: message("shell.theme.light") },
+              { value: "dark", label: message("shell.theme.dark") },
+            ]}
            value={preference}
            onChange={(event) =>
              setPreference(
@@ -99,37 +101,75 @@ export function AppShell() {
                ),
              )
            }
-          >
-            <option value="system">시스템 테마</option>
-            <option value="light">라이트 테마</option>
-            <option value="dark">다크 테마</option>
-          </select>
+          />
+          <Select
+            className="locale-selector"
+            id="locale-preference"
+            label={message("shell.locale")}
+            options={[
+              { value: "ko-KR", label: message("shell.locale.ko") },
+              { value: "en-US", label: message("shell.locale.en") },
+              { value: "en-XA", label: message("shell.locale.pseudo") },
+              { value: "ar-EG", label: message("shell.locale.rtl") },
+            ]}
+            value={locale}
+            onChange={(event) =>
+              setLocale(
+                /** @type {import("../i18n/index.js").SupportedLocale} */ (
+                  event.currentTarget.value
+                ),
+              )
+            }
+          />
          <span className="session-status" data-state={sessionState}>
-            {SESSION_LABELS[sessionState]}
+            {message(SESSION_MESSAGE_KEYS[sessionState])}
          </span>
          {integrationAvailable ? (
-            <button
-              className="ui-button ui-button--compact"
-              type="button"
+            <Button
              disabled={sessionActionPending}
              onClick={() => void runSessionAction()}
+              size="compact"
            >
-              {sessionActionPending ? "처리 중…" : sessionActionLabel}
-            </button>
+              {sessionActionPending
+                ? message("common.processing")
+                : sessionActionLabel}
+            </Button>
          ) : null}
        </div>
        {sessionActionFailed ? (
          <p className="app-shell__session-error" role="alert">
-            세션 작업을 완료하지 못했습니다.
+            {message("shell.session.actionFailed")}
          </p>
        ) : null}
      </header>
      <aside
        className="app-shell__sidebar"
-        data-open={navigationOpen}
-        aria-label="사이드바"
+        aria-label={message("shell.sidebar")}
      >
-        <nav id="primary-navigation" aria-label="주요 탐색">
+        <PrimaryNavigation id="primary-navigation" />
+      </aside>
+      <Drawer
+        closeLabel={message("shell.closeMenu")}
+        onClose={() => setNavigationOpen(false)}
+        open={navigationOpen}
+        title={message("shell.menu")}
+      >
+        <PrimaryNavigation id="mobile-primary-navigation" />
+      </Drawer>
+      <main className="app-shell__content" id="main-content" tabIndex={-1}>
+        <Outlet />
+      </main>
+    </div>
+  );
+}
+
+/**
+ * @param {{ id: string }} props
+ */
+function PrimaryNavigation({ id }) {
+  const { resolve, message } = useLocale();
+  return (
+    <nav id={id} aria-label={message("shell.primaryNavigation")}>
      <ul className="app-navigation">
        {NAVIGATION_ROUTES.map((definition) => (
          <li key={definition.routeId}>
@@ -140,24 +180,11 @@ export function AppShell() {
              end={definition.path === "/"}
              to={definition.path}
            >
-                  {definition.navigationLabel}
+              {resolve(`route.${definition.routeId}.navigation`)}
            </NavLink>
          </li>
        ))}
      </ul>
    </nav>
-      </aside>
-      {navigationOpen ? (
-        <button
-          className="app-shell__scrim"
-          type="button"
-          aria-label="메뉴 닫기"
-          onClick={() => setNavigationOpen(false)}
-        />
-      ) : null}
-      <main className="app-shell__content" id="main-content" tabIndex={-1}>
-        <Outlet />
-      </main>
-    </div>
  );
 }
@@ -2,7 +2,7 @@ import { useEffect, useState } from "react";
 import { Link } from "react-router-dom";

 import { routePath } from "../../features/installed-feature-contracts.js";
-import { PageHeader } from "../components/page-header.jsx";
+import { PageHeader } from "../design-system/index.js";
 import { useApplication } from "../providers/application-provider.js";

 const READINESS_ITEMS = Object.freeze([
@@ -1,18 +1,20 @@
 import { Link } from "react-router-dom";

 import { routePath } from "../../features/installed-feature-contracts.js";
-import { PageHeader } from "../components/page-header.jsx";
+import { PageHeader } from "../design-system/index.js";
+import { useLocale } from "../i18n/index.js";

 export default function NotFoundPage() {
+  const { message } = useLocale();
  return (
    <section className="ui-page">
      <PageHeader
-        title="페이지를 찾을 수 없습니다."
-        description="주소를 확인하거나 준비된 시작 화면으로 돌아가세요."
+        title={message("page.notFound.title")}
+        description={message("page.notFound.description")}
      />
      <div>
        <Link className="ui-button" to={routePath("APP_HOME")}>
-          홈으로 이동
+          {message("action.goHome")}
        </Link>
      </div>
    </section>
@@ -28,7 +28,8 @@ import {
  RouteBoundary,
 } from "../boundaries/render-error-boundary.jsx";
 import { ChunkRecoveryBoundary } from "../boundaries/chunk-recovery-boundary.js";
-import { PageHeader } from "../components/page-header.jsx";
+import { Button, PageHeader } from "../design-system/index.js";
+import { LocaleProvider, useLocale } from "../i18n/index.js";
 import { AppShell } from "../layouts/app-shell.jsx";
 import { useApplication } from "../providers/application-provider.js";
 import { SessionProvider, useSession } from "../providers/session-provider.jsx";
@@ -54,6 +55,8 @@ export function useRouteInput(): ParsedRouteInput {
 }

 function RouteLoadingSurface({ definition }: { definition: RouteDefinition }) {
+  const { message, resolve } = useLocale();
+  const title = resolve(`route.${definition.routeId}.title`);
  return (
    <section
      className="ui-page route-loading"
@@ -62,8 +65,10 @@ function RouteLoadingSurface({ definition }: { definition: RouteDefinition }) {
      data-surface={definition.loadingSurface}
    >
      <div className="ui-skeleton" aria-hidden="true" />
-      <p>화면을 준비하고 있습니다.</p>
-      <span className="visually-hidden">{definition.title} 로딩 중</span>
+      <p>{message("route.loading")}</p>
+      <span className="visually-hidden">
+        {message("route.loadingNamed", { title })}
+      </span>
    </section>
  );
 }
@@ -73,35 +78,41 @@ function RouteFailureSurface({
 }: {
  definition?: RouteDefinition;
 }) {
+  const { message } = useLocale();
  return (
    <section
      className="ui-page"
      data-surface={definition?.errorSurface ?? "route-boundary"}
    >
      <PageHeader
-        title="화면을 표시하지 못했습니다."
-        description="잠시 후 다시 시도해 주세요. 문제가 계속되면 운영 지원 참조 정보를 확인하세요."
+        title={message("route.failure.title")}
+        description={message("route.failure.description")}
      />
    </section>
  );
 }

 function InvalidRouteSurface({ code }: { code: string }) {
+  const { message } = useLocale();
  return (
    <section className="ui-page" data-surface="invalid-route">
      <PageHeader
-        title="올바르지 않은 주소입니다."
-        description="주소의 경로 또는 검색 조건을 확인해 주세요."
+        title={message("route.invalid.title")}
+        description={message("route.invalid.description")}
      />
-      <p data-route-error={code}>안전한 탐색 링크를 사용해 주세요.</p>
+      <p data-route-error={code}>{message("route.invalid.action")}</p>
    </section>
  );
 }

 function RouteLifecycle({ definition }: { definition: RouteDefinition }) {
  const location = useLocation();
+  const { message, resolve } = useLocale();
  useEffect(() => {
-    document.title = `${definition.title} · Frontend Skeleton`;
+    document.title = message("route.documentTitle", {
+      title: resolve(`route.${definition.routeId}.title`),
+      appName: message("common.appName"),
+    });
    const main = document.getElementById("main-content");
    main?.focus({ preventScroll: true });
    try {
@@ -111,7 +122,7 @@ function RouteLifecycle({ definition }: { definition: RouteDefinition }) {
    } catch {
      // Non-browser test hosts may not implement scrolling.
    }
-  }, [definition, location.key, location.pathname]);
+  }, [definition, location.key, location.pathname, message, resolve]);
  return null;
 }

@@ -146,6 +157,7 @@ function ProtectedRoute({
 }) {
  const location = useLocation();
  const { sessionState, beginSignIn, recover } = useSession();
+  const { message } = useLocale();
  const [pending, setPending] = useState(false);
  const [failed, setFailed] = useState(false);
  const decision = decideRouteAccess(routeId, sessionState);
@@ -173,8 +185,8 @@ function ProtectedRoute({
    return (
      <section className="ui-page" data-surface="auth-integration-required">
        <PageHeader
-          title="로그인 연동이 필요합니다."
-          description="외부 인증 소유자가 연결되면 이 보호 라우트를 사용할 수 있습니다."
+          title={message("route.auth.integration.title")}
+          description={message("route.auth.integration.description")}
        />
      </section>
    );
@@ -183,24 +195,30 @@ function ProtectedRoute({
  return (
    <section className="ui-page" data-surface="authentication-required">
      <PageHeader
-        title={recovering ? "세션을 복구하고 있습니다." : "세션이 필요합니다."}
+        title={
+          recovering
+            ? message("route.auth.recovering.title")
+            : message("route.auth.required.title")
+        }
        description={
          recovering
-            ? "기존 세션 확인을 계속하려면 복구를 실행하세요."
-            : "이 화면은 인증 연동 지점을 확인하기 위한 보호 라우트입니다."
+            ? message("route.auth.recovering.description")
+            : message("route.auth.required.description")
        }
      />
-      <button
-        className="ui-button"
-        type="button"
+      <Button
        disabled={pending}
        onClick={() => void continueSession()}
      >
-        {pending ? "처리 중…" : recovering ? "세션 복구" : "로그인 시작"}
-      </button>
+        {pending
+          ? message("common.processing")
+          : recovering
+            ? message("action.recoverSession")
+            : message("action.signIn")}
+      </Button>
      {failed ? (
        <p className="ui-terminal-error" role="alert">
-          세션 작업을 완료하지 못했습니다.
+          {message("shell.session.actionFailed")}
        </p>
      ) : null}
    </section>
@@ -300,10 +318,12 @@ export function AppRouter({
    [basename, buildId],
  );
  return (
+    <LocaleProvider>
      <ThemeProvider>
        <SessionProvider>
          <RouterProvider router={router} />
        </SessionProvider>
      </ThemeProvider>
+    </LocaleProvider>
  );
 }
@@ -1,35 +1,7 @@
@import "tailwindcss";
-
-@theme {
-  --color-surface: oklch(0.985 0.003 247);
-  --color-surface-muted: oklch(0.94 0.01 247);
-  --color-panel: oklch(1 0 0);
-  --color-border: oklch(0.87 0.015 247);
-  --color-content: oklch(0.25 0.025 247);
-  --color-content-muted: oklch(0.48 0.025 247);
-  --color-action: oklch(0.55 0.18 255);
-  --color-action-hover: oklch(0.48 0.2 255);
-  --color-danger: oklch(0.55 0.2 25);
-  --color-danger-hover: oklch(0.47 0.2 25);
-  --color-on-action: oklch(1 0 0);
-  --color-focus: oklch(0.72 0.16 225);
-  --color-info-content: oklch(0.38 0.16 255);
-  --color-info-surface: oklch(0.95 0.03 255);
-  --color-info-border: oklch(0.75 0.08 250);
-  --color-success-content: oklch(0.35 0.12 155);
-  --color-success-surface: oklch(0.95 0.04 155);
-  --color-success-border: oklch(0.72 0.1 155);
-  --color-warning-content: oklch(0.38 0.12 70);
-  --color-warning-surface: oklch(0.96 0.05 80);
-  --color-warning-border: oklch(0.75 0.12 80);
-  --color-danger-content: oklch(0.42 0.18 25);
-  --color-danger-surface: oklch(0.96 0.035 25);
-  --color-danger-border: oklch(0.72 0.12 25);
-  --radius-control: 0.5rem;
-  --radius-surface: 0.75rem;
-  --spacing-page: 1.5rem;
-  --font-sans: Inter, ui-sans-serif, system-ui, sans-serif;
-}
+@import "../design-system/tokens/primitive.css";
+@import "../design-system/tokens/semantic.css";
+@import "../design-system/tokens/component.css";

@layer base {
  :root {
@@ -38,33 +10,6 @@
    font-family: var(--font-sans);
  }

-  :root[data-theme="dark"] {
-    --color-surface: oklch(0.16 0.02 255);
-    --color-surface-muted: oklch(0.25 0.025 255);
-    --color-panel: oklch(0.205 0.022 255);
-    --color-border: oklch(0.36 0.025 255);
-    --color-content: oklch(0.94 0.012 255);
-    --color-content-muted: oklch(0.74 0.025 255);
-    --color-action: oklch(0.7 0.14 250);
-    --color-action-hover: oklch(0.79 0.12 245);
-    --color-danger: oklch(0.68 0.19 25);
-    --color-danger-hover: oklch(0.76 0.16 25);
-    --color-on-action: oklch(0.16 0.02 255);
-    --color-focus: oklch(0.82 0.15 220);
-    --color-info-content: oklch(0.83 0.09 250);
-    --color-info-surface: oklch(0.27 0.045 255);
-    --color-info-border: oklch(0.55 0.09 250);
-    --color-success-content: oklch(0.83 0.1 155);
-    --color-success-surface: oklch(0.27 0.045 155);
-    --color-success-border: oklch(0.53 0.1 155);
-    --color-warning-content: oklch(0.88 0.1 80);
-    --color-warning-surface: oklch(0.29 0.045 80);
-    --color-warning-border: oklch(0.58 0.11 80);
-    --color-danger-content: oklch(0.84 0.11 25);
-    --color-danger-surface: oklch(0.28 0.055 25);
-    --color-danger-border: oklch(0.56 0.13 25);
-  }
-
  body {
    margin: 0;
    min-width: 20rem;
@@ -186,17 +131,36 @@
    margin-inline-start: auto;
  }

-  .theme-selector {
-    min-height: 2.25rem;
+  .theme-selector,
+  .locale-selector {
+    display: block;
+  }
+
+  .theme-selector .ui-field__label,
+  .locale-selector .ui-field__label {
+    position: absolute;
+    width: 1px;
+    height: 1px;
+    padding: 0;
+    margin: -1px;
+    overflow: hidden;
+    clip: rect(0, 0, 0, 0);
+    white-space: nowrap;
+    border: 0;
+  }
+
+  .theme-selector .ui-field__input,
+  .locale-selector .ui-field__input {
+    min-height: var(--size-control-sm);
    max-width: 8.5rem;
-    border: 1px solid var(--color-border);
-    border-radius: var(--radius-control);
    padding: 0.35rem 2rem 0.35rem 0.65rem;
-    color: var(--color-content);
-    background: var(--color-panel);
    cursor: pointer;
  }

+  .locale-selector .ui-field__input {
+    max-width: 7rem;
+  }
+
  .app-shell__session-error {
    position: absolute;
    top: calc(100% + 0.25rem);
@@ -305,7 +269,12 @@

  .ui-button:disabled {
    cursor: not-allowed;
-    opacity: 0.55;
+    opacity: var(--opacity-disabled);
+  }
+
+  .ui-button--pending {
+    gap: var(--space-2);
+    cursor: progress;
  }

  .ui-button--secondary {
@@ -339,11 +308,59 @@
  }

  .ui-button--compact {
-    min-height: 2.25rem;
+    min-height: var(--size-control-sm);
    padding: 0.4rem 0.75rem;
    font-size: 0.85rem;
  }

+  .ui-icon-button {
+    width: var(--size-touch-target);
+    min-width: var(--size-touch-target);
+    padding: 0;
+  }
+
+  .app-shell__menu-button.ui-icon-button {
+    display: none;
+  }
+
+  .ui-icon {
+    display: inline-block;
+    flex: 0 0 auto;
+    stroke-width: var(--icon-stroke-default);
+  }
+
+  .ui-icon--small {
+    width: var(--size-icon-sm);
+    height: var(--size-icon-sm);
+  }
+
+  .ui-icon--medium {
+    width: var(--size-icon-md);
+    height: var(--size-icon-md);
+  }
+
+  .ui-icon--large {
+    width: var(--size-icon-lg);
+    height: var(--size-icon-lg);
+  }
+
+  .ui-spinner {
+    display: inline-block;
+    width: var(--size-icon-sm);
+    height: var(--size-icon-sm);
+    box-sizing: border-box;
+    border: 2px solid currentColor;
+    border-inline-end-color: transparent;
+    border-radius: var(--radius-full);
+    animation: ui-spin var(--duration-slow) linear infinite;
+  }
+
+  @keyframes ui-spin {
+    to {
+      transform: rotate(360deg);
+    }
+  }
+
  .ui-skeleton {
    @apply h-24 animate-pulse rounded-surface bg-surface-muted;
  }
@@ -391,7 +408,110 @@
  }

  .ui-field__input[aria-invalid="true"] {
-    border-color: var(--color-danger);
+    border-color: var(--field-border-invalid);
+  }
+
+  .ui-field__textarea {
+    min-height: 7rem;
+    resize: vertical;
+  }
+
+  .ui-field__counter {
+    justify-self: end;
+    color: var(--color-content-muted);
+    font-size: var(--font-size-sm);
+  }
+
+  .ui-choice-field,
+  .ui-radio-group,
+  .ui-switch-field {
+    display: grid;
+    gap: var(--space-2);
+  }
+
+  .ui-choice-field__control {
+    display: flex;
+    min-height: var(--size-touch-target);
+    align-items: center;
+    gap: var(--space-2);
+    cursor: pointer;
+  }
+
+  .ui-choice-field__control input {
+    width: 1.15rem;
+    height: 1.15rem;
+    accent-color: var(--color-action);
+  }
+
+  .ui-choice-field__control small {
+    display: block;
+    color: var(--color-content-muted);
+  }
+
+  .ui-radio-group {
+    min-width: 0;
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius-control);
+    padding: var(--space-3);
+  }
+
+  .ui-radio-group legend {
+    padding-inline: var(--space-1);
+    font-weight: var(--font-weight-bold);
+  }
+
+  .ui-switch {
+    display: inline-flex;
+    width: fit-content;
+    min-height: var(--size-touch-target);
+    align-items: center;
+    gap: var(--space-2);
+    border: 0;
+    color: var(--color-content);
+    background: transparent;
+    cursor: pointer;
+  }
+
+  .ui-switch__thumb {
+    display: inline-block;
+    width: 2.5rem;
+    height: 1.5rem;
+    border: 1px solid var(--color-border-strong);
+    border-radius: var(--radius-full);
+    background: var(--color-disabled-surface);
+  }
+
+  .ui-switch__thumb::after {
+    display: block;
+    width: 1rem;
+    height: 1rem;
+    margin: 0.2rem;
+    border-radius: var(--radius-full);
+    background: var(--color-content-muted);
+    content: "";
+    transition: transform var(--duration-normal) var(--easing-standard);
+  }
+
+  .ui-switch[aria-checked="true"] .ui-switch__thumb {
+    border-color: var(--color-action);
+    background: var(--color-action);
+  }
+
+  .ui-switch[aria-checked="true"] .ui-switch__thumb::after {
+    background: var(--color-on-action);
+    transform: translateX(1rem);
+  }
+
+  [dir="rtl"] .ui-switch[aria-checked="true"] .ui-switch__thumb::after {
+    transform: translateX(-1rem);
+  }
+
+  .ui-search-field {
+    position: relative;
+    display: grid;
+    grid-template-columns: auto minmax(0, 1fr) auto;
+    align-items: end;
+    gap: var(--space-2);
  }

  .ui-card {
@@ -406,7 +526,7 @@
    box-shadow: 0 8px 28px color-mix(in oklch, var(--color-content) 6%, transparent);
  }

-  .ui-card__header h3,
+  .ui-card__header :is(h2, h3, h4),
  .ui-card__header p {
    margin-block-end: 0;
  }
@@ -478,6 +598,13 @@
    cursor: pointer;
  }

+  .ui-alert__dismiss.ui-icon-button,
+  .ui-dialog__close.ui-icon-button {
+    min-width: 2rem;
+    min-height: 2rem;
+    padding: 0;
+  }
+
  .ui-alert__dismiss:hover,
  .ui-dialog__close:hover {
    background: color-mix(in oklch, var(--color-content) 8%, transparent);
@@ -523,7 +650,7 @@
    padding: 0;
    color: var(--color-content);
    background: var(--color-panel);
-    box-shadow: 0 24px 70px color-mix(in oklch, var(--color-content) 25%, transparent);
+    box-shadow: var(--dialog-elevation);
  }

  .ui-dialog::backdrop {
@@ -531,6 +658,271 @@
    backdrop-filter: blur(2px);
  }

+  .ui-drawer {
+    width: var(--drawer-width);
+    max-width: none;
+    height: 100dvh;
+    max-height: none;
+    margin-block: 0;
+    border-radius: 0;
+  }
+
+  .ui-drawer--start {
+    margin-inline: 0 auto;
+  }
+
+  .ui-drawer--end {
+    margin-inline: auto 0;
+  }
+
+  .ui-drawer .ui-dialog__surface {
+    min-height: 100%;
+    box-sizing: border-box;
+  }
+
+  .ui-popover,
+  .ui-menu,
+  .ui-tooltip {
+    position: relative;
+    display: inline-block;
+  }
+
+  .ui-popover__content,
+  .ui-menu__content {
+    position: absolute;
+    z-index: var(--layer-popover);
+    top: calc(100% + var(--space-2));
+    inset-inline-start: 0;
+    min-width: 12rem;
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius-control);
+    padding: var(--space-2);
+    background: var(--color-surface-elevated);
+    box-shadow: var(--elevation-popover);
+  }
+
+  .ui-menu__content {
+    display: grid;
+    gap: var(--space-1);
+  }
+
+  .ui-menu__item {
+    min-height: var(--size-control-sm);
+    border: 0;
+    border-radius: var(--radius-control);
+    padding: var(--space-2) var(--space-3);
+    color: var(--color-content);
+    background: transparent;
+    text-align: start;
+    cursor: pointer;
+  }
+
+  .ui-menu__item:hover,
+  .ui-menu__item:focus-visible {
+    background: var(--color-surface-muted);
+  }
+
+  .ui-tooltip__content {
+    position: absolute;
+    z-index: var(--layer-popover);
+    inset-block-end: calc(100% + var(--space-2));
+    inset-inline-start: 50%;
+    width: max-content;
+    max-width: 16rem;
+    padding: var(--space-2);
+    border-radius: var(--radius-control);
+    color: var(--color-content-inverse);
+    background: var(--color-content);
+    opacity: 0;
+    pointer-events: none;
+    transform: translateX(-50%);
+    transition: opacity var(--duration-fast) var(--easing-standard);
+  }
+
+  .ui-tooltip:focus-within .ui-tooltip__content,
+  .ui-tooltip:hover .ui-tooltip__content {
+    opacity: 1;
+  }
+
+  .ui-progress,
+  .ui-progress__label {
+    display: grid;
+    gap: var(--space-2);
+  }
+
+  .ui-progress__label {
+    grid-template-columns: 1fr auto;
+  }
+
+  .ui-progress__bar {
+    width: 100%;
+    accent-color: var(--color-action);
+  }
+
+  .ui-skeleton--text {
+    height: 1em;
+  }
+
+  .ui-skeleton--control {
+    height: var(--size-control-md);
+  }
+
+  .ui-skeleton--surface {
+    height: 6rem;
+  }
+
+  .ui-separator {
+    width: 100%;
+    border: 0;
+    border-block-start: 1px solid var(--color-border);
+  }
+
+  .ui-breadcrumbs ol,
+  .ui-pagination,
+  .ui-tabs__list {
+    display: flex;
+    flex-wrap: wrap;
+    align-items: center;
+    gap: var(--space-2);
+    margin: 0;
+    padding: 0;
+    list-style: none;
+  }
+
+  .ui-breadcrumbs li:not(:last-child)::after {
+    margin-inline-start: var(--space-2);
+    color: var(--color-content-muted);
+    content: "/";
+  }
+
+  .ui-tabs {
+    display: grid;
+    gap: var(--space-3);
+  }
+
+  .ui-tabs__list {
+    border-block-end: 1px solid var(--color-border);
+  }
+
+  .ui-tabs__tab {
+    min-height: var(--size-touch-target);
+    border: 0;
+    border-block-end: 0.2rem solid transparent;
+    padding: var(--space-2) var(--space-3);
+    color: var(--color-content-muted);
+    background: transparent;
+    cursor: pointer;
+  }
+
+  .ui-tabs__tab[aria-selected="true"] {
+    border-block-end-color: var(--color-action);
+    color: var(--color-content);
+    font-weight: var(--font-weight-bold);
+  }
+
+  .ui-tabs__panel {
+    padding: var(--space-3);
+  }
+
+  .ui-toast-region {
+    position: fixed;
+    z-index: var(--layer-toast);
+    inset-block-end: var(--space-4);
+    inset-inline-end: var(--space-4);
+    display: grid;
+    width: var(--toast-width);
+    gap: var(--space-2);
+  }
+
+  .ui-toast {
+    display: flex;
+    align-items: flex-start;
+    justify-content: space-between;
+    gap: var(--space-3);
+    border: 1px solid var(--color-border);
+    border-inline-start: 0.25rem solid var(--color-info-border);
+    border-radius: var(--radius-control);
+    padding: var(--space-3);
+    background: var(--color-surface-elevated);
+    box-shadow: var(--elevation-popover);
+  }
+
+  .ui-toast--success {
+    border-inline-start-color: var(--color-success-border);
+  }
+
+  .ui-toast--warning {
+    border-inline-start-color: var(--color-warning-border);
+  }
+
+  .ui-toast--danger {
+    border-inline-start-color: var(--color-danger-border);
+  }
+
+  .ui-toast p {
+    margin: var(--space-1) 0 0;
+    color: var(--color-content-muted);
+  }
+
+  .ui-data-table__scroll {
+    max-width: 100%;
+    overflow-x: auto;
+  }
+
+  .ui-data-table {
+    width: 100%;
+    border-collapse: collapse;
+  }
+
+  .ui-data-table caption {
+    margin-block-end: var(--space-2);
+    font-weight: var(--font-weight-bold);
+    text-align: start;
+  }
+
+  .ui-data-table th,
+  .ui-data-table td {
+    border-block-end: 1px solid var(--color-border);
+    padding: var(--space-3);
+    text-align: start;
+  }
+
+  .ui-search-filter-toolbar,
+  .ui-pagination-bar {
+    display: flex;
+    flex-wrap: wrap;
+    align-items: end;
+    justify-content: space-between;
+    gap: var(--space-3);
+  }
+
+  .ui-disclosure-group {
+    display: grid;
+    gap: var(--space-2);
+  }
+
+  .ui-disclosure-group details {
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius-control);
+    padding: var(--space-3);
+  }
+
+  .ui-disclosure-group summary {
+    min-height: var(--size-control-sm);
+    cursor: pointer;
+    font-weight: var(--font-weight-bold);
+  }
+
+  .ui-focus-ring {
+    display: inline-flex;
+    border-radius: var(--radius-control);
+  }
+
+  .ui-focus-ring:focus-within {
+    outline: 0.1875rem solid var(--color-focus);
+    outline-offset: 0.1875rem;
+  }
+
  .ui-dialog__surface {
    padding: 1.5rem;
  }
@@ -920,7 +1312,7 @@
    padding-inline: 0.75rem;
  }

-  .app-shell__menu-button {
+  .app-shell__menu-button.ui-icon-button {
    display: inline-flex;
  }

@@ -955,6 +1347,10 @@
    display: none;
  }

+  .app-shell__session .theme-selector {
+    display: none;
+  }
+
  .app-shell__brand {
    display: none;
  }
@@ -2,6 +2,7 @@ import type { ReactNode } from "react";

 import { PageHeader } from "../components/page-header.jsx";
 import { Button } from "../components/ui/button.jsx";
+import { useLocale } from "../i18n/index.js";

 export type PageHeading = Readonly<{
  title: string;
@@ -36,10 +37,14 @@ export type PageTemplateSlots = Readonly<{
 }>;

 export function StandardPage(props: PageTemplateSlots) {
+  const { message } = useLocale();
  return (
    <article className="ui-page page-template page-template--standard">
      {props.breadcrumb ? (
-        <nav className="page-template__breadcrumb" aria-label="현재 위치">
+        <nav
+          className="page-template__breadcrumb"
+          aria-label={message("template.breadcrumb")}
+        >
          {props.breadcrumb}
        </nav>
      ) : null}
@@ -64,7 +69,10 @@ export function StandardPage(props: PageTemplateSlots) {
      >
        <div className="page-template__content">{props.children}</div>
        {props.aside ? (
-          <aside className="page-template__aside" aria-label="관련 정보">
+          <aside
+            className="page-template__aside"
+            aria-label={message("template.relatedInformation")}
+          >
            {props.aside}
          </aside>
        ) : null}
@@ -83,6 +91,7 @@ export function CollectionPage(
      pagination?: ReactNode;
    }>,
 ) {
+  const { message } = useLocale();
  return (
    <StandardPage
      {...props}
@@ -92,7 +101,7 @@ export function CollectionPage(
          {props.toolbar ? (
            <section
              className="collection-page__toolbar"
-              aria-label="검색과 필터"
+              aria-label={message("template.searchAndFilter")}
            >
              {props.toolbar}
            </section>
@@ -117,7 +126,10 @@ export function CollectionPage(
    >
      <div className="collection-page__results">{props.children}</div>
      {props.pagination ? (
-        <nav className="collection-page__pagination" aria-label="페이지 탐색">
+        <nav
+          className="collection-page__pagination"
+          aria-label={message("template.pagination")}
+        >
          {props.pagination}
        </nav>
      ) : null}
@@ -132,16 +144,23 @@ export function DetailPage(
      destructiveAction?: ReactNode;
    }>,
 ) {
+  const { message } = useLocale();
  return (
    <StandardPage {...props}>
      {props.metadata ? (
-        <section className="detail-page__metadata" aria-label="요약 정보">
+        <section
+          className="detail-page__metadata"
+          aria-label={message("template.summary")}
+        >
          {props.metadata}
        </section>
      ) : null}
      <div className="detail-page__sections">{props.children}</div>
      {props.destructiveAction ? (
-        <section className="detail-page__danger" aria-label="위험 작업">
+        <section
+          className="detail-page__danger"
+          aria-label={message("template.dangerActions")}
+        >
          {props.destructiveAction}
        </section>
      ) : null}
@@ -190,6 +209,7 @@ export function StatusPage(
    supportReference?: string;
  }>,
 ) {
+  const { message } = useLocale();
  return (
    <section
      className={`ui-page page-template status-page status-page--${props.variant}`}
@@ -208,7 +228,9 @@ export function StatusPage(
      ) : null}
      {props.supportReference ? (
        <p className="status-page__support">
-          지원 참조: <code>{props.supportReference}</code>
+          {message("template.supportReference", {
+            reference: props.supportReference,
+          })}
        </p>
      ) : null}
    </section>
@@ -50,7 +50,9 @@ describe("async UI state matrix", () => {
    render(<AsyncSurface state={state}>existing content</AsyncSurface>);

    expect(screen.getByText("existing content")).toBeVisible();
-    expect(screen.getByRole("status")).toHaveTextContent("refreshing");
+    expect(screen.getByRole("status")).toHaveTextContent(
+      "최신 정보를 확인하고 있습니다.",
+    );
  });

  it("connects stale retry and conflict resolution to real callbacks", async () => {
@@ -60,7 +60,9 @@ describe("chunk recovery boundary classification", () => {
      </FeatureBoundary>,
    );

-    expect(screen.getByRole("alert")).toHaveTextContent("error.render_failure");
+    expect(screen.getByRole("alert")).toHaveTextContent(
+      "화면을 표시하지 못했습니다.",
+    );
    expect(recover).not.toHaveBeenCalled();
  });
 });
@@ -0,0 +1,269 @@
+// @vitest-environment jsdom
+
+import {
+  act,
+  fireEvent,
+  render,
+  screen,
+  waitFor,
+  within,
+} from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { useState } from "react";
+import { describe, expect, it, vi } from "vitest";
+
+import {
+  Button,
+  Checkbox,
+  DataTable,
+  Drawer,
+  IconButton,
+  Menu,
+  MenuIcon,
+  Pagination,
+  Popover,
+  RadioGroup,
+  Switch,
+  Tabs,
+  ToastProvider,
+  useToast,
+} from "../../src/presentation/design-system/index.js";
+
+describe("design-system platform interactions", () => {
+  it("keeps decorative icons out of the accessibility tree and names icon actions", () => {
+    render(
+      <>
+        <MenuIcon />
+        <IconButton accessibleName="탐색 열기">
+          <MenuIcon />
+        </IconButton>
+      </>,
+    );
+
+    expect(screen.getByRole("button", { name: "탐색 열기" })).toBeVisible();
+    expect(screen.queryByRole("img")).not.toBeInTheDocument();
+  });
+
+  it("supports native choices, indeterminate state, radio arrows and switches", async () => {
+    const user = userEvent.setup();
+    const onRadio = vi.fn();
+    const onSwitch = vi.fn();
+    render(
+      <>
+        <Checkbox indeterminate label="일부 선택" />
+        <RadioGroup
+          label="밀도"
+          name="density"
+          onChange={onRadio}
+          options={[
+            { value: "normal", label: "보통" },
+            { value: "compact", label: "조밀" },
+          ]}
+          value="normal"
+        />
+        <Switch
+          checked={false}
+          label="알림"
+          onChange={onSwitch}
+        />
+      </>,
+    );
+
+    const checkbox = screen.getByRole("checkbox", { name: "일부 선택" });
+    expect(checkbox).toBePartiallyChecked();
+    const normal = screen.getByRole("radio", { name: "보통" });
+    normal.focus();
+    await user.keyboard("{ArrowRight}");
+    expect(onRadio).toHaveBeenCalledWith("compact");
+    await user.click(screen.getByRole("switch", { name: "알림" }));
+    expect(onSwitch).toHaveBeenCalledWith(true);
+  });
+
+  it("moves through a menu, executes once, dismisses and restores focus", async () => {
+    const user = userEvent.setup();
+    const inspect = vi.fn();
+    render(
+      <Menu
+        items={[
+          { id: "open", label: "열기", onSelect: vi.fn() },
+          { id: "inspect", label: "검사", onSelect: inspect },
+        ]}
+        triggerLabel="작업"
+      />,
+    );
+
+    const trigger = screen.getByRole("button", { name: "작업" });
+    trigger.focus();
+    await user.keyboard("{ArrowDown}");
+    expect(screen.getByRole("menuitem", { name: "열기" })).toHaveFocus();
+    await user.keyboard("{ArrowDown}{Enter}");
+    expect(inspect).toHaveBeenCalledOnce();
+    await waitFor(() => expect(trigger).toHaveFocus());
+    expect(screen.queryByRole("menu")).not.toBeInTheDocument();
+  });
+
+  it("supports manual tab activation with arrow-key roving focus", async () => {
+    const user = userEvent.setup();
+    render(
+      <Tabs
+        activation="manual"
+        label="계층"
+        tabs={[
+          { id: "tokens", label: "토큰", panel: "토큰 내용" },
+          { id: "patterns", label: "패턴", panel: "패턴 내용" },
+        ]}
+      />,
+    );
+
+    const tokenTab = screen.getByRole("tab", { name: "토큰" });
+    tokenTab.focus();
+    await user.keyboard("{ArrowRight}");
+    const patternTab = screen.getByRole("tab", { name: "패턴" });
+    expect(patternTab).toHaveFocus();
+    expect(patternTab).toHaveAttribute("aria-selected", "false");
+    await user.keyboard("{Enter}");
+    expect(patternTab).toHaveAttribute("aria-selected", "true");
+    expect(screen.getByRole("tabpanel", { name: "패턴" })).toHaveTextContent(
+      "패턴 내용",
+    );
+  });
+
+  it("uses a modal drawer and restores focus after Escape", async () => {
+    const user = userEvent.setup();
+    function Harness() {
+      const [open, setOpen] = useState(false);
+      return (
+        <>
+          <Button onClick={() => setOpen(true)}>탐색 열기</Button>
+          <Drawer onClose={() => setOpen(false)} open={open} title="탐색">
+            <a href="/target">대상</a>
+          </Drawer>
+        </>
+      );
+    }
+    render(<Harness />);
+
+    const trigger = screen.getByRole("button", { name: "탐색 열기" });
+    await user.click(trigger);
+    expect(screen.getByRole("dialog", { name: "탐색" })).toHaveAttribute("open");
+    await user.keyboard("{Escape}");
+    await waitFor(() => expect(trigger).toHaveFocus());
+  });
+
+  it("bounds the toast queue and collapses duplicate IDs", async () => {
+    const user = userEvent.setup();
+    function Harness() {
+      const toast = useToast();
+      return (
+        <>
+          <Button
+            onClick={() =>
+              toast.push({ id: "same", title: "저장됨", durationMs: 60_000 })
+            }
+          >
+            중복
+          </Button>
+          <Button
+            onClick={() => {
+              for (let index = 0; index < 5; index += 1) {
+                toast.push({
+                  id: `toast-${index}`,
+                  title: `알림 ${index}`,
+                  durationMs: 60_000,
+                });
+              }
+            }}
+          >
+            다섯 개
+          </Button>
+        </>
+      );
+    }
+    render(
+      <ToastProvider limit={3}>
+        <Harness />
+      </ToastProvider>,
+    );
+
+    await user.click(screen.getByRole("button", { name: "중복" }));
+    await user.click(screen.getByRole("button", { name: "중복" }));
+    expect(screen.getByText("×2")).toBeVisible();
+    await user.click(screen.getByRole("button", { name: "다섯 개" }));
+    const region = screen.getByRole("region", { name: "알림" });
+    expect(within(region).getAllByRole("article")).toHaveLength(3);
+    expect(within(region).queryByText("알림 0")).not.toBeInTheDocument();
+    expect(within(region).getByText("알림 4")).toBeVisible();
+  });
+
+  it("pauses toast timeout while the user is interacting", () => {
+    vi.useFakeTimers();
+    function Harness() {
+      const toast = useToast();
+      return (
+        <Button
+          onClick={() =>
+            toast.push({ id: "timed", title: "시간 제한", durationMs: 1000 })
+          }
+        >
+          표시
+        </Button>
+      );
+    }
+    render(
+      <ToastProvider>
+        <Harness />
+      </ToastProvider>,
+    );
+    fireEvent.click(screen.getByRole("button", { name: "표시" }));
+    const item = screen.getByRole("article");
+    fireEvent.mouseEnter(item);
+    act(() => vi.advanceTimersByTime(2000));
+    expect(item).toBeVisible();
+    fireEvent.mouseLeave(item);
+    act(() => vi.advanceTimersByTime(1000));
+    expect(screen.queryByText("시간 제한")).not.toBeInTheDocument();
+    vi.useRealTimers();
+  });
+
+  it("provides dismissible popover and data/navigation patterns", async () => {
+    const user = userEvent.setup();
+    const onPage = vi.fn();
+    render(
+      <>
+        <Popover triggerLabel="설명 열기">
+          <Button>내부 작업</Button>
+        </Popover>
+        <DataTable
+          caption="결과"
+          columns={[
+            { id: "name", header: "이름", cell: (row) => row.name },
+          ]}
+          empty="비어 있음"
+          rowKey={(row) => row.id}
+          rows={[{ id: "one", name: "첫 항목" }]}
+        />
+        <Pagination
+          label="페이지"
+          nextLabel="다음"
+          onChange={onPage}
+          page={1}
+          pageCount={2}
+          pageLabel={(page) => `${page}페이지`}
+          previousLabel="이전"
+        />
+      </>,
+    );
+
+    const popoverTrigger = screen.getByRole("button", { name: "설명 열기" });
+    await user.click(popoverTrigger);
+    expect(screen.getByRole("dialog")).toHaveTextContent("내부 작업");
+    await user.keyboard("{Escape}");
+    expect(screen.queryByRole("dialog")).not.toBeInTheDocument();
+    expect(popoverTrigger).toHaveFocus();
+    expect(screen.getByRole("table", { name: "결과" })).toHaveTextContent(
+      "첫 항목",
+    );
+    await user.click(screen.getByRole("link", { name: "2페이지" }));
+    expect(onPage).toHaveBeenCalledWith(2);
+  });
+});
@@ -0,0 +1,120 @@
+// @vitest-environment jsdom
+
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { useState } from "react";
+import { describe, expect, it } from "vitest";
+
+import {
+  Button,
+  Drawer,
+  Pagination,
+  Tabs,
+} from "../../src/presentation/design-system/index.js";
+import {
+  LocaleProvider,
+  useLocale,
+  type SupportedLocale,
+} from "../../src/presentation/i18n/index.js";
+
+function LocaleHarness() {
+  const { direction, locale, message, setLocale } = useLocale();
+  const [drawerOpen, setDrawerOpen] = useState(false);
+  return (
+    <>
+      <label htmlFor="test-locale">{message("shell.locale")}</label>
+      <select
+        id="test-locale"
+        onChange={(event) =>
+          setLocale(event.currentTarget.value as SupportedLocale)
+        }
+        value={locale}
+      >
+        <option value="ko-KR">한국어</option>
+        <option value="en-US">English</option>
+        <option value="ar-EG">RTL</option>
+      </select>
+      <output>{`${locale}:${direction}`}</output>
+      <Button onClick={() => setDrawerOpen(true)}>
+        {message("shell.menu")}
+      </Button>
+      <Drawer
+        closeLabel={message("shell.closeMenu")}
+        onClose={() => setDrawerOpen(false)}
+        open={drawerOpen}
+        title={message("shell.menu")}
+      >
+        content
+      </Drawer>
+    </>
+  );
+}
+
+describe("locale provider runtime", () => {
+  it("switches copy and synchronizes the document language and direction", async () => {
+    const user = userEvent.setup();
+    render(
+      <LocaleProvider>
+        <LocaleHarness />
+      </LocaleProvider>,
+    );
+
+    expect(document.documentElement).toHaveAttribute("lang", "ko-KR");
+    await user.selectOptions(screen.getByLabelText("언어"), "en-US");
+    expect(screen.getByLabelText("Language")).toHaveValue("en-US");
+    expect(document.documentElement).toHaveAttribute("lang", "en-US");
+    expect(document.documentElement).toHaveAttribute("dir", "ltr");
+
+    await user.selectOptions(screen.getByLabelText("Language"), "ar-EG");
+    expect(document.documentElement).toHaveAttribute("lang", "ar-EG");
+    expect(document.documentElement).toHaveAttribute("dir", "rtl");
+    await user.click(screen.getByRole("button", { name: "Menu" }));
+    expect(screen.getByRole("dialog", { name: "Menu" })).toHaveAttribute(
+      "open",
+    );
+  });
+
+  it("reverses horizontal tab focus semantics in RTL", async () => {
+    const user = userEvent.setup();
+    render(
+      <LocaleProvider initialLocale="ar-EG">
+        <Tabs
+          activation="manual"
+          label="sections"
+          tabs={[
+            { id: "one", label: "One", panel: "One panel" },
+            { id: "two", label: "Two", panel: "Two panel" },
+            { id: "three", label: "Three", panel: "Three panel" },
+          ]}
+        />
+      </LocaleProvider>,
+    );
+    const first = screen.getByRole("tab", { name: "One" });
+    first.focus();
+    await user.keyboard("{ArrowRight}");
+    expect(screen.getByRole("tab", { name: "Three" })).toHaveFocus();
+    await user.keyboard("{ArrowLeft}");
+    expect(first).toHaveFocus();
+  });
+
+  it("keeps pagination semantics while direction-aware icons remain decorative", () => {
+    render(
+      <LocaleProvider initialLocale="ar-EG">
+        <Pagination
+          label="pages"
+          nextLabel="Next page"
+          onChange={() => {}}
+          page={2}
+          pageCount={3}
+          pageLabel={(page) => `Page ${page}`}
+          previousLabel="Previous page"
+        />
+      </LocaleProvider>,
+    );
+    expect(
+      screen.getByRole("button", { name: "Previous page" }),
+    ).toBeEnabled();
+    expect(screen.getByRole("button", { name: "Next page" })).toBeEnabled();
+    expect(screen.queryByRole("img")).not.toBeInTheDocument();
+  });
+});
@@ -86,7 +86,7 @@ describe("page template slot contracts", () => {
      />,
    );
    expect(screen.getByRole("heading", { level: 1, name: "Offline" })).toBeVisible();
-    expect(screen.getByText("SAFE-123")).toBeVisible();
+    expect(screen.getByText(/SAFE-123/)).toBeVisible();
    expect(document.body).not.toHaveTextContent("stack");
  });
 });
@@ -28,7 +28,9 @@ describe("render recovery boundaries", () => {
      </FeatureBoundary>,
    );

-    expect(screen.getByRole("alert")).toHaveTextContent("error.render_failure");
+    expect(screen.getByRole("alert")).toHaveTextContent(
+      "화면을 표시하지 못했습니다.",
+    );
    expect(onRenderFailure).toHaveBeenCalledWith({
      routeId: "APP_HOME",
      buildId: "build-a",
@@ -83,7 +85,7 @@ describe("render recovery boundaries", () => {
      </FeatureBoundary>,
    );
    shouldThrow = false;
-    await user.click(screen.getByRole("button", { name: "retry" }));
+    await user.click(screen.getByRole("button", { name: "다시 시도" }));
    view.rerender(
      <FeatureBoundary routeId="APP_HOME" buildId="build-a">
        <Recoverable />
@@ -40,3 +40,19 @@ test("@a11y reduced-motion policy disables long animation", async ({ page }) =>
    .evaluate((body) => getComputedStyle(body).animationDuration);
  expect(["0s", "0.00001s", "1e-05s"]).toContain(duration);
 });
+
+test("@a11y opened design-system dialog has no blocking violations", async ({
+  page,
+}) => {
+  await page.goto("/examples/ui");
+  await page.getByRole("button", { name: "모달 열기" }).click();
+  const results = await new AxeBuilder({ page })
+    .include(".ui-dialog")
+    .withTags(["wcag2a", "wcag2aa", "wcag21a", "wcag21aa"])
+    .analyze();
+  expect(
+    results.violations.filter((violation) =>
+      ["critical", "serious"].includes(violation.impact ?? ""),
+    ),
+  ).toEqual([]);
+});
@@ -53,8 +53,13 @@ test("provides an escape-dismissible mobile navigation", async ({ page }) => {
  await menu.click();
  await expect(menu).toHaveAttribute("aria-expanded", "true");
  await expect(page.getByRole("navigation", { name: "주요 탐색" })).toBeVisible();
+  await expect(page.locator(".ui-drawer")).toHaveJSProperty("open", true);
+  expect(
+    await page.locator(".ui-drawer").evaluate((drawer) => drawer.matches(":modal")),
+  ).toBe(true);

  await page.keyboard.press("Escape");
  await expect(menu).toHaveAttribute("aria-expanded", "false");
  await expect(page.getByRole("navigation", { name: "주요 탐색" })).toBeHidden();
+  await expect(menu).toBeFocused();
 });
@@ -0,0 +1,29 @@
+import { expect, test } from "@playwright/test";
+
+test("runs menu typeahead, tabs and duplicate toast interactions", async ({
+  page,
+}) => {
+  await page.goto("/examples/ui");
+
+  const menuTrigger = page.getByRole("button", { name: "작업 메뉴" });
+  await menuTrigger.focus();
+  await page.keyboard.press("ArrowDown");
+  await page.keyboard.type("toast");
+  const toastItem = page.getByRole("menuitem", { name: "Toast 표시" });
+  await expect(toastItem).toBeFocused();
+  await page.keyboard.press("Enter");
+  await expect(page.getByText("예제가 저장되었습니다.")).toBeVisible();
+  await expect(menuTrigger).toBeFocused();
+
+  const tokenTab = page.getByRole("tab", { name: "토큰" });
+  await tokenTab.focus();
+  await page.keyboard.press("ArrowRight");
+  const primitiveTab = page.getByRole("tab", { name: "프리미티브" });
+  await expect(primitiveTab).toBeFocused();
+  await expect(primitiveTab).toHaveAttribute("aria-selected", "false");
+  await page.keyboard.press("Enter");
+  await expect(primitiveTab).toHaveAttribute("aria-selected", "true");
+  await expect(
+    page.getByRole("tabpanel", { name: "프리미티브" }),
+  ).toContainText("native semantics");
+});
@@ -0,0 +1,41 @@
+import { expect, test } from "@playwright/test";
+
+test("switches the shell locale and keeps pseudo-locale copy within compact layout", async ({
+  page,
+}) => {
+  await page.setViewportSize({ width: 320, height: 720 });
+  await page.goto("/");
+
+  const locale = page.getByRole("combobox", { name: "언어" });
+  await locale.selectOption("en-US");
+  await expect(page.locator("html")).toHaveAttribute("lang", "en-US");
+  await expect(page.locator("html")).toHaveAttribute("dir", "ltr");
+  await expect(page.getByRole("button", { name: "Menu" })).toBeVisible();
+
+  await page.getByRole("combobox", { name: "Language" }).selectOption("en-XA");
+  await expect(page.locator("html")).toHaveAttribute("lang", "en-XA");
+  const dimensions = await page.evaluate(() => ({
+    clientWidth: document.documentElement.clientWidth,
+    scrollWidth: document.documentElement.scrollWidth,
+  }));
+  expect(dimensions.scrollWidth).toBeLessThanOrEqual(dimensions.clientWidth);
+  await expect(page.getByRole("button", { name: /Ménú/ })).toBeVisible();
+});
+
+test("applies RTL to the shell and modal navigation without changing action semantics", async ({
+  page,
+}) => {
+  await page.setViewportSize({ width: 390, height: 844 });
+  await page.goto("/");
+  await page.getByRole("combobox", { name: "언어" }).selectOption("ar-EG");
+
+  await expect(page.locator("html")).toHaveAttribute("lang", "ar-EG");
+  await expect(page.locator("html")).toHaveAttribute("dir", "rtl");
+  const trigger = page.getByRole("button", { name: "Menu" });
+  await trigger.click();
+  await expect(page.getByRole("dialog", { name: "Menu" })).toBeVisible();
+  await expect(page.getByRole("navigation", { name: "Primary navigation" }))
+    .toHaveCount(1);
+  await page.keyboard.press("Escape");
+  await expect(trigger).toBeFocused();
+});
@@ -72,10 +72,10 @@ describe("reference feature boundary contracts", () => {
      createdAt: "2026-07-26T00:00:00.000Z",
    });
    if (!("id" in model)) throw new Error("expected one model");
-    expect(toReferenceView(model, () => "formatted")).toEqual({
+    expect(toReferenceView(model)).toEqual({
      resourceId: "reference-1",
      title: "Example",
-      createdAtLabel: "formatted",
+      createdAt: "2026-07-26T00:00:00.000Z",
    });
  });

@@ -55,7 +55,7 @@ function inputWith(
      value: {
        resourceId: "created",
        title: name,
-        createdAtLabel: null,
+        createdAt: null,
      },
    }),
    getResource: async (resourceId) => ({
@@ -63,7 +63,7 @@ function inputWith(
      value: {
        resourceId,
        title: "Detail",
-        createdAtLabel: null,
+        createdAt: null,
      },
    }),
    ...overrides,
@@ -90,7 +90,7 @@ describe("reference feature page states", () => {
        {
          resourceId: "reference-1",
          title: "Loaded",
-          createdAtLabel: null,
+          createdAt: null,
        },
      ],
    });
@@ -191,7 +191,7 @@ describe("reference feature page states", () => {
          {
            resourceId: "existing",
            title: "Existing",
-            createdAtLabel: null,
+            createdAt: null,
          },
        ],
      })
@@ -209,7 +209,7 @@ describe("reference feature page states", () => {
          {
            resourceId: "recovered",
            title: "Recovered",
-            createdAtLabel: null,
+            createdAt: null,
          },
        ],
      });
@@ -217,7 +217,9 @@ describe("reference feature page states", () => {
    await screen.findByText("Existing");
    await user.click(screen.getByRole("button", { name: "새로고침" }));

-    expect(await screen.findByText("stale-degraded")).toBeVisible();
+    expect(
+      await screen.findByText("기존 정보를 표시하고 있습니다."),
+    ).toBeVisible();
    expect(screen.getByText("Existing")).toBeVisible();
    await user.click(screen.getByRole("button", { name: "다시 시도" }));
    expect(await screen.findByText("Recovered")).toBeVisible();
@@ -0,0 +1,3 @@
+import { Button } from "../../../../src/presentation/design-system/primitives/core.js";
+
+export const DeepImport = Button;
@@ -0,0 +1,3 @@
+import { Menu } from "lucide-react";
+
+export const DirectIcon = Menu;
@@ -0,0 +1,3 @@
+export function RawPalette() {
+  return <div style={{ color: "#ff0000" }}>raw palette</div>;
+}
@@ -0,0 +1 @@
+export const TOOLTIP_ONLY_REQUIRED_INFORMATION = "Required approval details";
@@ -0,0 +1,5 @@
+export function UnsafeBackendFailure({
+  failure,
+}: Readonly<{ failure: { message: string } }>) {
+  return <p>{failure.message}</p>;
+}
@@ -0,0 +1,3 @@
+export function HardcodedCommonAction() {
+  return <button type="button">다시 시도</button>;
+}
@@ -0,0 +1,3 @@
+export function UnsafeTranslatedMarkup({ value }: Readonly<{ value: string }>) {
+  return <p dangerouslySetInnerHTML={{ __html: value }} />;
+}
@@ -0,0 +1,3 @@
+import { IconButton, MenuIcon } from "../../../src/presentation/design-system/index.js";
+
+export const InvalidIconButton = <IconButton><MenuIcon /></IconButton>;
@@ -0,0 +1,3 @@
+import { formatMessage } from "../../../src/presentation/i18n/index.js";
+
+formatMessage("ko-KR", "unknown.translation.key");
@@ -0,0 +1,5 @@
+import { formatMessage } from "../../../src/presentation/i18n/index.js";
+
+formatMessage("en-US", "route.documentTitle");
+formatMessage("en-US", "route.documentTitle", { title: "Missing app name" });
+formatMessage("en-US", "action.retry", { unexpected: "value" });
@@ -0,0 +1,48 @@
+import { readFile } from "node:fs/promises";
+
+import { describe, expect, it } from "vitest";
+
+import {
+  REQUIRED_COMPONENT_TOKENS,
+  REQUIRED_PRIMITIVE_TOKENS,
+  REQUIRED_SEMANTIC_TOKENS,
+} from "../../src/presentation/design-system/index.js";
+
+describe("design token contract", () => {
+  it("defines every registered token in its owning layer", async () => {
+    const layers = [
+      [
+        REQUIRED_PRIMITIVE_TOKENS,
+        "src/presentation/design-system/tokens/primitive.css",
+      ],
+      [
+        REQUIRED_SEMANTIC_TOKENS,
+        "src/presentation/design-system/tokens/semantic.css",
+      ],
+      [
+        REQUIRED_COMPONENT_TOKENS,
+        "src/presentation/design-system/tokens/component.css",
+      ],
+    ] as const;
+
+    for (const [tokens, file] of layers) {
+      const source = await readFile(file, "utf8");
+      for (const token of tokens) expect(source).toContain(`${token}:`);
+    }
+  });
+
+  it("provides dark and forced-color contracts", async () => {
+    const semantic = await readFile(
+      "src/presentation/design-system/tokens/semantic.css",
+      "utf8",
+    );
+    const component = await readFile(
+      "src/presentation/design-system/tokens/component.css",
+      "utf8",
+    );
+
+    expect(semantic).toContain(':root[data-theme="dark"]');
+    expect(component).toContain("@media (forced-colors: active)");
+    expect(component).toContain("--color-focus: Highlight");
+  });
+});
@@ -0,0 +1,115 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  catalogKeys,
+  FORMAT_FALLBACK,
+  formatDate,
+  formatList,
+  formatMessage,
+  formatNumber,
+  formatRelativeTime,
+  localeDirection,
+  messagePlaceholders,
+  normalizeLocale,
+  resolveMessage,
+  selectMessage,
+  selectPlural,
+} from "../../src/presentation/i18n/index.js";
+import {
+  EN_MESSAGES,
+  KO_MESSAGES,
+  MESSAGE_CATALOGS,
+} from "../../src/presentation/i18n/catalog.js";
+
+describe("internationalization message contract", () => {
+  it("keeps every registered catalog and interpolation contract in parity", () => {
+    expect(catalogKeys("en-US")).toEqual(catalogKeys("ko-KR"));
+    expect(catalogKeys("ar-EG")).toEqual(catalogKeys("ko-KR"));
+
+    for (const key of catalogKeys("ko-KR")) {
+      expect(messagePlaceholders(EN_MESSAGES[key])).toEqual(
+        messagePlaceholders(KO_MESSAGES[key]),
+      );
+    }
+    expect(MESSAGE_CATALOGS["ar-EG"]).toBe(EN_MESSAGES);
+  });
+
+  it("formats typed parameters and expands the pseudo locale", () => {
+    expect(
+      formatMessage("en-US", "route.documentTitle", {
+        title: "Settings",
+        appName: "Skeleton",
+      }),
+    ).toBe("Settings · Skeleton");
+    const pseudo = formatMessage("en-XA", "action.closeNamed", {
+      title: "Account",
+    });
+    expect(pseudo).toMatch(/^［.+ ···］$/);
+    expect(pseudo.length).toBeGreaterThan("Close Account".length);
+  });
+
+  it("falls back safely for unknown locale, key and missing interpolation", () => {
+    expect(normalizeLocale("fr-FR")).toBe("ko-KR");
+    expect(resolveMessage("fr-FR", "action.retry")).toBe("다시 시도");
+    expect(resolveMessage("en-US", "action.login")).toBe("Sign in");
+    expect(resolveMessage("en-US", "backend.stack.trace")).toBe(
+      "요청한 문구를 표시할 수 없습니다.",
+    );
+    expect(resolveMessage("en-US", "action.closeNamed")).toBe(
+      "요청한 문구를 표시할 수 없습니다.",
+    );
+    expect(resolveMessage("en-US", "backend.stack.trace")).not.toContain(
+      "backend.stack.trace",
+    );
+  });
+
+  it("defines direction without inferring it in components", () => {
+    expect(localeDirection("ko-KR")).toBe("ltr");
+    expect(localeDirection("en-XA")).toBe("ltr");
+    expect(localeDirection("ar-EG")).toBe("rtl");
+  });
+});
+
+describe("internationalization formatter contract", () => {
+  const instant = new Date("2026-07-26T23:30:00.000Z");
+
+  it("uses an explicit UTC default and deterministic locale formatting", () => {
+    expect(formatDate("en-US", instant, { dateStyle: "short" })).toBe(
+      "7/26/26",
+    );
+    expect(
+      formatDate("en-US", instant, {
+        dateStyle: "short",
+        timeZone: "Asia/Seoul",
+      }),
+    ).toBe("7/27/26");
+    expect(formatNumber("en-US", 1234.5)).toBe("1,234.5");
+    expect(formatRelativeTime("en-US", -1, "day")).toBe("yesterday");
+    expect(formatList("en-US", ["one", "two", "three"])).toBe(
+      "one, two, and three",
+    );
+    expect(selectPlural("en-US", 1, { one: "item", other: "items" })).toBe(
+      "item",
+    );
+    expect(
+      selectPlural("en-US", 3, { one: "item", other: "items" }),
+    ).toBe("items");
+    expect(
+      selectMessage("pending", {
+        ready: "Ready",
+        pending: "Pending",
+        other: "Unknown",
+      }),
+    ).toBe("Pending");
+  });
+
+  it("does not throw or expose invalid formatter input", () => {
+    expect(formatDate("en-US", Number.NaN)).toBe(FORMAT_FALLBACK);
+    expect(formatNumber("en-US", Number.POSITIVE_INFINITY)).toBe(
+      FORMAT_FALLBACK,
+    );
+    expect(
+      formatDate("en-US", instant, { timeZone: "not/a-time-zone" }),
+    ).toBe(FORMAT_FALLBACK);
+  });
+});
Author	SHA1	Message	Date
donghyeon-ka	668bf05b48	feat: add internationalization message platform	2026-07-26 16:17:39 +09:00
donghyeon-ka	b8c0444217	merge: design system platform	2026-07-26 15:49:13 +09:00
donghyeon-ka	13f28ef811	feat: add design system platform	2026-07-26 15:49:07 +09:00
donghyeon-ka	e49d90f713	merge: form and page platform	2026-07-26 15:22:58 +09:00
				`@@ -0,0 +1 @@`
				`export const TOOLTIP_ONLY_REQUIRED_INFORMATION = "Required approval details";`