diff --git a/.gitignore b/.gitignore
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@@ -35,9 +35,14 @@ coverage
 
 .DS_Store
 
-# claude
-.claude
-CLAUDE.md
+# Claude Code - public files are committed (.claude/skills/, .claude/agents/, CLAUDE.md)
+# Private/personal files:
+.claude/settings.local.json
+.claude/memory/
+.claude/plans/
+.claude/skills/project-decisions/
+# Session notes (contain internal references)
+.claude/*.md
 
 # context files (session notes, etc.)
 context/
\ No newline at end of file
diff --git a/CLAUDE.md b/CLAUDE.md
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@@ -0,0 +1,209 @@
+# CLAUDE.md
+
+## Project Overview
+
+React utility hooks/components library. Monorepo with two packages:
+
+- `react-simplikit` (`packages/core`) — Platform-independent React hooks & components
+- `@react-simplikit/mobile` (`packages/mobile`) — Mobile web utilities (viewport, keyboard, layout)
+
+## Development Quick Start
+
+```bash
+yarn build          # Build all packages (tsup)
+yarn test           # Run tests (Vitest)
+yarn fix            # Auto-fix lint + format (ESLint + Prettier)
+yarn typecheck      # Type check (tsc --noEmit) - alias: yarn run test:type
+yarn changeset      # Create a changeset
+yarn changeset status  # Check pending changesets
+```
+
+## Architecture Rules
+
+Layer dependency is **unidirectional** — no upward or circular imports allowed:
+
+```
+components → hooks → utils → _internal
+```
+
+- Components may use hooks, utils, \_internal
+- Hooks may use utils, \_internal
+- Utils may use \_internal only
+- \_internal has no internal dependencies
+- Mobile may depend on core; core must NOT depend on mobile
+
+## File Structure Convention
+
+Each hook/component/util lives in its own folder with co-located docs:
+
+```
+src/
+├── hooks/
+│   └── useHookName/
+│       ├── index.ts               # Re-export
+│       ├── useHookName.ts         # Implementation
+│       ├── useHookName.spec.ts    # Tests (core)
+│       ├── useHookName.test.ts    # Tests (mobile)
+│       ├── useHookName.ssr.test.ts # SSR safety tests
+│       ├── useHookName.md         # English docs
+│       └── ko/
+│           └── useHookName.md     # Korean docs
+├── utils/
+│   └── utilName/
+│       ├── index.ts
+│       ├── utilName.ts
+│       └── utilName.test.ts
+└── index.ts                       # Public API exports (alphabetically sorted)
+```
+
+## Coding Standards
+
+- **`type` over `interface`** — Always use `type` for type aliases
+- **Named functions in useEffect** — Improves stack traces and readability
+  ```ts
+  useEffect(function handleResize() { ... }, []);  // ✅
+  useEffect(() => { ... }, []);                     // ❌
+  ```
+- **Strict boolean checks** — Use explicit comparisons (`value !== undefined`, not `if (value)`)
+- **Import extensions** — Include `.js` in relative imports for ESM compliance
+- **useEffect cleanup** — Always return cleanup to remove listeners/subscriptions
+- **`"use client"` banner** — tsup adds this for RSC compatibility
+- **Named exports only** — No default exports
+- **No `any` types** — Full TypeScript strict mode, no escape hatches
+- **Zero dependencies** — No runtime dependencies in production code
+
+### SSR-Safe Coding Pattern
+
+All hooks/utils accessing browser APIs must be SSR-safe:
+
+```ts
+// Pattern: Fixed initial value + useEffect sync
+const [state, setState] = useState(FIXED_INITIAL_VALUE);
+useEffect(function syncBrowserState() {
+  if (isServer()) return;
+  setState(getBrowserAPI());
+}, []);
+```
+
+Never initialize state with browser API calls (causes hydration mismatch).
+
+### Hook Return Value Convention
+
+- **Single value**: `useDebounce<T>(value, delay): T`
+- **Tuple** (state + action, 2 items): `useToggle(init): [boolean, () => void]`
+- **Object** (3+ items): `usePagination(): { page, nextPage, prevPage }`
+
+### Performance Patterns
+
+- **Throttle** subscriptions at ~16ms (60fps) for viewport/keyboard events
+- **Deduplicate** to skip updates when value hasn't changed
+- **`startTransition`** for non-urgent state updates (React 18+)
+
+## Testing
+
+- **100% coverage mandatory** — Enforced by Vitest coverage threshold, no exceptions
+- **SSR tests required** — All hooks accessing browser APIs must have `.ssr.test.ts`
+- **Core tests**: `.spec.ts` (legacy, will migrate to `.test.ts`)
+- **Mobile tests**: `.test.ts`
+- **SSR pattern**:
+  ```ts
+  import { renderHookSSR } from '../utils/renderHookSSR';
+  it('is safe on server side rendering', () => {
+    const result = renderHookSSR.serverOnly(() => useHookName());
+    expect(result.current).toBeDefined();
+  });
+  ```
+
+## Documentation
+
+- **Bilingual**: English + Korean (co-located in hook folders as `*.md` / `ko/*.md`)
+- **JSDoc required**: Every public API must have `@description` + `@example` + `@param` + `@returns`
+- **VitePress**: Used for documentation site; rewrites map source docs to clean URLs
+- **Co-location**: Docs live inside package source, not in separate docs/ tree
+- **Homepage**: `https://react-simplikit.slash.page`
+
+## Commit Convention
+
+Format: `<type>(<scope>): <description>`
+
+- **Types**: `feat`, `fix`, `docs`, `chore`, `refactor`, `test`
+- **Scope**: Package name (`core`, `mobile`) or area
+- Examples: `feat(mobile): add useKeyboardHeight hook`, `fix: correct SSR rendering logic`
+
+## PR Checklist
+
+- [ ] Tests pass (`yarn test`)
+- [ ] Lint/format pass (`yarn fix`)
+- [ ] 100% coverage maintained
+- [ ] JSDoc with `@description` + `@example`
+- [ ] Changeset added (if user-facing change)
+
+## Release Flow
+
+Uses **Changesets** + **GitHub Actions OIDC** for automated releases.
+
+```
+PR with changeset merged → release.yml triggers
+  → changesets/action detects changeset → creates "Version PR"
+  → Version PR merged → changesets/action: hasChangesets=false
+  → "Publish to npm" step → changeset publish (uses npm publish internally)
+```
+
+### Critical: publishConfig does NOT work with npm
+
+**npm does NOT support `publishConfig` overrides for manifest fields** (`main`, `types`, `module`, `exports`). Only `access`, `registry`, `tag` are supported. See [npm/cli#7586](https://github.com/npm/cli/issues/7586).
+
+- `yarn npm publish` DOES support publishConfig field overrides
+- `changeset publish` internally calls `npm publish` (not yarn)
+- Therefore: **always declare `main`/`types`/`module`/`exports` at the top level** of package.json
+- `publishConfig` should only contain `access: "public"`
+
+### OIDC Trusted Publishing
+
+- npm auth uses GitHub Actions OIDC (no secret tokens needed)
+- Requires `id-token: write` permission in workflow
+- Node 22 ships npm v10 which doesn't support OIDC → `npm install -g npm@latest` upgrades to npm 11+
+- `changesets/action` must NOT have `publish` option (it overwrites `.npmrc` and breaks OIDC)
+- Publish is done in a separate step after changesets/action
+
+### Snapshot/Canary Releases
+
+```bash
+GITHUB_TOKEN=$(gh auth token) yarn changeset version --snapshot canary
+yarn changeset publish --tag canary  # Requires npm login + OTP
+```
+
+## Package Structure
+
+```
+packages/
+├── core/          # react-simplikit
+│   ├── src/       # Source (hooks, components, utils)
+│   ├── dist/      # CJS build output
+│   ├── esm/       # ESM build output
+│   └── package.json
+└── mobile/        # @react-simplikit/mobile
+    ├── src/
+    ├── dist/      # CJS + ESM build output
+    └── package.json
+```
+
+## package.json Convention
+
+```jsonc
+{
+  "main": "./dist/index.cjs", // CJS entry (top level, NOT in publishConfig)
+  "module": "./esm/index.js", // ESM entry for bundlers
+  "types": "./dist/index.d.cts", // TypeScript types
+  "exports": {
+    // Modern Node.js/bundler resolution
+    ".": {
+      "import": { "types": "...", "default": "..." },
+      "require": { "types": "...", "default": "..." },
+    },
+  },
+  "publishConfig": {
+    "access": "public", // ONLY access here, nothing else
+  },
+}
+```