diff --git a/src/renderer/inbox/api.ts b/src/renderer/inbox/api.ts
index 3a78192..aa42f7e 100644
--- a/src/renderer/inbox/api.ts
+++ b/src/renderer/inbox/api.ts
@@ -1,2 +1,3 @@
-import type { InboxApi } from '@shared/types';
+import type { InboxApi, NotebookApi } from '@shared/types';
 export const inboxApi: InboxApi = window.inkling.inbox;
+export const notebookApi: NotebookApi = window.inkling.notebook;
diff --git a/src/renderer/inbox/store.ts b/src/renderer/inbox/store.ts
index d2fda2e..8ab3eff 100644
--- a/src/renderer/inbox/store.ts
+++ b/src/renderer/inbox/store.ts
@@ -1,6 +1,6 @@
 import { create } from 'zustand';
-import type { Note, ReviewAggregate, WeeklyContinuity } from '@shared/types';
-import { inboxApi } from './api.js';
+import type { Note, Notebook, ReviewAggregate, WeeklyContinuity } from '@shared/types';
+import { inboxApi, notebookApi } from './api.js';
 import { nextKstMidnightMs } from '@shared/util/kstDate.js';
 
 export { selectFilteredNotes } from './selectFilteredNotes.js';
@@ -45,6 +45,11 @@ interface InboxState {
   searchQuery: string;
   searchResults: Note[] | null;  // null = 검색 안 한 상태
   reviewData: ReviewAggregate | null;
+  // v0.4 — Notebook sidebar state.
+  notebooks: Notebook[];
+  selectedNotebookId: string | null;
+  sidebarVisible: boolean;
+  sidebarWidth: number;
   loadInitial: () => Promise<void>;
   refreshMeta: () => Promise<void>;
   upsertNote: (note: Note) => void;
@@ -71,6 +76,15 @@ interface InboxState {
   searchNotes: (q: string) => Promise<void>;
   clearSearch: () => void;
   loadReview: (period: 'daily' | 'weekly' | 'monthly') => Promise<void>;
+  // v0.4 — Notebook actions.
+  loadNotebooks: () => Promise<void>;
+  selectNotebook: (id: string) => void;
+  createNotebook: (name: string, color?: string) => Promise<{ ok: boolean; reason?: string }>;
+  renameNotebook: (id: string, name: string) => Promise<{ ok: boolean; reason?: string }>;
+  setNotebookColor: (id: string, color: string | null) => Promise<void>;
+  deleteNotebook: (id: string) => Promise<{ ok: boolean; reason?: string }>;
+  moveNoteToNotebook: (noteId: string, notebookId: string) => Promise<void>;
+  toggleSidebar: () => void;
 }
 
 const emptyContinuity: WeeklyContinuity = {
@@ -101,6 +115,10 @@ export const useInbox = create<InboxState>((set, get) => ({
   searchQuery: '',
   searchResults: null,
   reviewData: null,
+  notebooks: [],
+  selectedNotebookId: null,
+  sidebarVisible: false,
+  sidebarWidth: 240,
   async loadInitial() {
     // v0.3.8 — IPC 실패 시 loading=true 영구 stuck 방지. catch 로 reset.
     set({ loading: true });
@@ -388,5 +406,58 @@ export const useInbox = create<InboxState>((set, get) => ({
       console.error('[inbox] loadReview failed', period, e);
       set({ reviewData: { totalCount: 0, tagCounts: [], dueProgress: { total: 0, passed: 0, pending: 0 }, recentNotes: [] } });
     }
+  },
+  // v0.4 — Notebook actions.
+  async loadNotebooks() {
+    const notebooks = await notebookApi.list();
+    const current = get().selectedNotebookId;
+    // selectedNotebookId 가 null 이면 첫 notebook (가장 오래된 = 기본) 으로 설정.
+    const selectedNotebookId = current === null && notebooks.length > 0
+      ? notebooks[0]!.id
+      : current;
+    set({ notebooks, selectedNotebookId });
+  },
+  selectNotebook(id) {
+    set({ selectedNotebookId: id });
+  },
+  async createNotebook(name, color) {
+    const r = await notebookApi.create({ name, color });
+    if (r.ok) {
+      set({ notebooks: [...get().notebooks, r.notebook] });
+      return { ok: true };
+    }
+    return { ok: false, reason: r.reason };
+  },
+  async renameNotebook(id, name) {
+    const r = await notebookApi.rename(id, name);
+    if (r.ok) {
+      set({ notebooks: get().notebooks.map((n) => n.id === id ? { ...n, name } : n) });
+      return { ok: true };
+    }
+    return { ok: false, reason: r.reason };
+  },
+  async setNotebookColor(id, color) {
+    await notebookApi.setColor(id, color);
+    set({ notebooks: get().notebooks.map((n) => n.id === id ? { ...n, color } : n) });
+  },
+  async deleteNotebook(id) {
+    const r = await notebookApi.delete(id);
+    if (r.ok) {
+      const remaining = get().notebooks.filter((n) => n.id !== id);
+      const wasSelected = get().selectedNotebookId === id;
+      set({
+        notebooks: remaining,
+        selectedNotebookId: wasSelected ? (remaining[0]?.id ?? null) : get().selectedNotebookId
+      });
+      return { ok: true };
+    }
+    return { ok: false, reason: r.reason };
+  },
+  async moveNoteToNotebook(noteId, notebookId) {
+    await notebookApi.moveNote(noteId, notebookId);
+    await get().refreshMeta();
+  },
+  toggleSidebar() {
+    set({ sidebarVisible: !get().sidebarVisible });
   }
 }));
diff --git a/tests/unit/store.notebook.test.ts b/tests/unit/store.notebook.test.ts
new file mode 100644
index 0000000..0903b1b
--- /dev/null
+++ b/tests/unit/store.notebook.test.ts
@@ -0,0 +1,77 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+vi.mock('../../src/renderer/inbox/api.js', () => ({
+  inboxApi: {
+    listNotes: vi.fn(async () => []),
+    listTrash: vi.fn(async () => []),
+    getTrashCount: vi.fn(async () => 0),
+    getContinuity: vi.fn(async () => ({ weekStart: '', weekCount: 0, weekTarget: 7, consecutiveCompleteWeeks: 0, showRecoveryToast: false, lastNoteAt: null })),
+    getPendingCount: vi.fn(async () => 0),
+    getOllamaStatus: vi.fn(async () => ({ ok: true })),
+    getTodayCount: vi.fn(async () => 0),
+    listExpired: vi.fn(async () => []),
+    getFailedCount: vi.fn(async () => 0),
+    listRecallCandidate: vi.fn(async () => null),
+    countsByStatus: vi.fn(async () => ({ active: 0, completed: 0, archived: 0, trashed: 0 })),
+    getSettings: vi.fn(async () => ({ ai_enabled: true })),
+    listByStatus: vi.fn(async () => [])
+  },
+  notebookApi: {
+    list: vi.fn(async () => [
+      { id: 'nb-1', name: '기본', color: null, createdAt: 't', updatedAt: 't', noteCount: 3 },
+      { id: 'nb-2', name: '회사', color: '#0a4b80', createdAt: 't', updatedAt: 't', noteCount: 1 }
+    ]),
+    create: vi.fn(async (i: { name: string; color?: string }) => ({ ok: true as const, notebook: { id: 'nb-new', name: i.name, color: i.color ?? null, createdAt: 't', updatedAt: 't', noteCount: 0 } })),
+    delete: vi.fn(async () => ({ ok: true as const })),
+    rename: vi.fn(async () => ({ ok: true as const })),
+    setColor: vi.fn(async () => ({ ok: true as const })),
+    moveNote: vi.fn(async () => ({ ok: true as const }))
+  }
+}));
+
+import { useInbox } from '../../src/renderer/inbox/store.js';
+
+describe('store notebooks', () => {
+  beforeEach(() => {
+    useInbox.setState({ notebooks: [], selectedNotebookId: null, sidebarVisible: false, sidebarWidth: 240 } as never);
+  });
+
+  it('loadNotebooks 가 notebookApi.list 결과 반영', async () => {
+    await useInbox.getState().loadNotebooks();
+    expect(useInbox.getState().notebooks).toHaveLength(2);
+  });
+
+  it('loadNotebooks: selectedNotebookId null 이면 첫 notebook 으로 자동 설정', async () => {
+    await useInbox.getState().loadNotebooks();
+    expect(useInbox.getState().selectedNotebookId).toBe('nb-1');
+  });
+
+  it('selectNotebook 가 selectedNotebookId 설정', () => {
+    useInbox.getState().selectNotebook('nb-X');
+    expect(useInbox.getState().selectedNotebookId).toBe('nb-X');
+  });
+
+  it('createNotebook 성공 시 notebooks 에 추가', async () => {
+    await useInbox.getState().createNotebook('학습', '#ccc');
+    expect(useInbox.getState().notebooks.some((n) => n.name === '학습')).toBe(true);
+  });
+
+  it('toggleSidebar 가 sidebarVisible 반전', () => {
+    expect(useInbox.getState().sidebarVisible).toBe(false);
+    useInbox.getState().toggleSidebar();
+    expect(useInbox.getState().sidebarVisible).toBe(true);
+  });
+
+  it('deleteNotebook 성공 시 notebooks 에서 제거 + selected 였으면 첫 notebook 으로', async () => {
+    useInbox.setState({
+      notebooks: [
+        { id: 'nb-1', name: '기본', color: null, createdAt: 't', updatedAt: 't', noteCount: 0 },
+        { id: 'nb-2', name: '회사', color: null, createdAt: 't', updatedAt: 't', noteCount: 0 }
+      ],
+      selectedNotebookId: 'nb-2'
+    } as never);
+    await useInbox.getState().deleteNotebook('nb-2');
+    expect(useInbox.getState().notebooks.map((n) => n.id)).toEqual(['nb-1']);
+    expect(useInbox.getState().selectedNotebookId).toBe('nb-1');
+  });
+});