diff --git a/src/main/ipc/inboxApi.ts b/src/main/ipc/inboxApi.ts
index 51c8c67..f830c2d 100644
--- a/src/main/ipc/inboxApi.ts
+++ b/src/main/ipc/inboxApi.ts
@@ -190,6 +190,31 @@ export function registerInboxApi(deps: InboxIpcDeps): void {
     trashed: deps.repo.countByStatus('trashed')
   }));
 
+  // v0.2.9 Cut B Task 8 — status 4분기 직접 전이 (사유 포함).
+  // Modal 의 "완료/보관/휴지통" 버튼 path. backward compat 동기화는
+  // NoteRepository.setStatus 내부에서 처리 (deleted_at sync).
+  ipcMain.handle(
+    'inbox:set-status',
+    async (_e, id: string, status: NoteStatus, reason: string | null) => {
+      const VALID: readonly NoteStatus[] = ['active', 'completed', 'archived', 'trashed'];
+      if (!VALID.includes(status)) {
+        return { ok: false as const, reason: 'invalid status' as const };
+      }
+      deps.repo.setStatus(id, status, reason);
+      return { ok: true as const };
+    }
+  );
+
+  // v0.2.9 Cut B Task 8 — AI 자동 분류 stub. Task 9 에서 본격 구현
+  // (Ollama provider 호출 + structured 출력). 본 task 는 Modal 의
+  // 호출 path 만 working state 로 만들기 위한 안전 default.
+  ipcMain.handle('ai:classify-status', async (_e, _id: string, _reason: string) => {
+    return {
+      recommended: 'archived' as const,
+      rationale: '본 task 는 stub. Task 9 에서 정식 구현.'
+    };
+  });
+
   ipcMain.handle('inbox:saveOllamaSettings', async (_e, value: { endpoint: string; model: string }) => {
     // 검증: 새 인스턴스로 healthCheck
     const trial = new LocalOllamaProvider({ endpoint: value.endpoint, model: value.model });
diff --git a/src/preload/index.ts b/src/preload/index.ts
index e93fdea..38c17b7 100644
--- a/src/preload/index.ts
+++ b/src/preload/index.ts
@@ -71,6 +71,9 @@ const api: InklingApi = {
     // v0.2.9 Cut B Task 4 — status 별 list + counts.
     listByStatus: (status, opts) => ipcRenderer.invoke('inbox:list-by-status', status, opts ?? {}),
     countsByStatus: () => ipcRenderer.invoke('inbox:counts-by-status'),
+    // v0.2.9 Cut B Task 8 — 4분기 status 전이 + AI 자동 분류 추천.
+    setStatus: (id, status, reason) => ipcRenderer.invoke('inbox:set-status', id, status, reason),
+    classifyStatus: (id, reason) => ipcRenderer.invoke('ai:classify-status', id, reason),
   }
 };
 
diff --git a/src/shared/types.ts b/src/shared/types.ts
index cad1cba..d8a2b63 100644
--- a/src/shared/types.ts
+++ b/src/shared/types.ts
@@ -138,6 +138,13 @@ export interface InboxApi {
   // v0.2.9 Cut B Task 4 — status 별 노트 목록 + status 별 count.
   listByStatus(status: NoteStatus, opts?: { limit?: number }): Promise<Note[]>;
   countsByStatus(): Promise<{ active: number; completed: number; archived: number; trashed: number }>;
+  // v0.2.9 Cut B Task 8 — 4분기 status 전이 + AI 자동 분류 추천.
+  setStatus(
+    id: string,
+    status: NoteStatus,
+    reason: string | null
+  ): Promise<{ ok: true } | { ok: false; reason: string }>;
+  classifyStatus(id: string, reason: string): Promise<{ recommended: NoteStatus; rationale: string }>;
 }
 
 export interface InklingApi {
diff --git a/tests/unit/inboxApi-setStatus.test.ts b/tests/unit/inboxApi-setStatus.test.ts
new file mode 100644
index 0000000..045652f
--- /dev/null
+++ b/tests/unit/inboxApi-setStatus.test.ts
@@ -0,0 +1,95 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+const { handlers, mockSetStatus } = vi.hoisted(() => ({
+  handlers: {} as Record<string, (...args: unknown[]) => unknown>,
+  mockSetStatus: vi.fn()
+}));
+
+vi.mock('electron', () => ({
+  default: {
+    ipcMain: {
+      handle: (ch: string, fn: (...args: unknown[]) => unknown) => {
+        handlers[ch] = fn;
+      }
+    },
+    dialog: {},
+    shell: {}
+  }
+}));
+
+import { registerInboxApi } from '../../src/main/ipc/inboxApi';
+
+function makeDeps(): Parameters<typeof registerInboxApi>[0] {
+  // Minimal stub — `inbox:set-status` 핸들러는 deps.repo.setStatus 만 참조.
+  return {
+    repo: {
+      setStatus: mockSetStatus,
+      list: vi.fn(),
+      listByStatus: vi.fn(),
+      countByStatus: vi.fn(() => 0)
+    } as never,
+    continuity: {} as never,
+    capture: {} as never,
+    health: {} as never,
+    intent: {} as never,
+    getInboxWindow: () => null,
+    settings: {} as never,
+    providerHolder: {} as never,
+    paths: { profileDir: '/profile' }
+  };
+}
+
+describe('inbox:set-status IPC', () => {
+  beforeEach(() => {
+    Object.keys(handlers).forEach((k) => delete handlers[k]);
+    mockSetStatus.mockReset();
+  });
+
+  it('forwards valid status + reason to repo.setStatus', async () => {
+    registerInboxApi(makeDeps());
+    const handler = handlers['inbox:set-status'];
+    if (handler === undefined) throw new Error('handler not registered');
+    const r = await handler(null, 'n1', 'completed', '결재 끝');
+    expect(r).toEqual({ ok: true });
+    expect(mockSetStatus).toHaveBeenCalledWith('n1', 'completed', '결재 끝');
+  });
+
+  it('forwards null reason as-is', async () => {
+    registerInboxApi(makeDeps());
+    const handler = handlers['inbox:set-status'];
+    if (handler === undefined) throw new Error('handler not registered');
+    const r = await handler(null, 'n1', 'archived', null);
+    expect(r).toEqual({ ok: true });
+    expect(mockSetStatus).toHaveBeenCalledWith('n1', 'archived', null);
+  });
+
+  it('rejects invalid status without calling repo', async () => {
+    registerInboxApi(makeDeps());
+    const handler = handlers['inbox:set-status'];
+    if (handler === undefined) throw new Error('handler not registered');
+    const r = (await handler(null, 'n1', 'invalid', null)) as { ok: boolean; reason?: string };
+    expect(r.ok).toBe(false);
+    expect(r.reason).toBe('invalid status');
+    expect(mockSetStatus).not.toHaveBeenCalled();
+  });
+});
+
+describe('ai:classify-status IPC (stub)', () => {
+  beforeEach(() => {
+    Object.keys(handlers).forEach((k) => delete handlers[k]);
+  });
+
+  it('returns recommendation shape (stub default)', async () => {
+    registerInboxApi(makeDeps());
+    const handler = handlers['ai:classify-status'];
+    if (handler === undefined) throw new Error('handler not registered');
+    const r = (await handler(null, 'n1', '결재 끝')) as {
+      recommended: string;
+      rationale: string;
+    };
+    expect(typeof r.recommended).toBe('string');
+    expect(['active', 'completed', 'archived', 'trashed']).toContain(r.recommended);
+    expect(typeof r.rationale).toBe('string');
+    expect(r.rationale.length).toBeGreaterThan(0);
+  });
+});