diff --git a/src/main/ipc/settingsApi.ts b/src/main/ipc/settingsApi.ts
index 2aa7ad0..b27fcaa 100644
--- a/src/main/ipc/settingsApi.ts
+++ b/src/main/ipc/settingsApi.ts
@@ -7,6 +7,7 @@ import type { BackupService } from '../services/BackupService.js';
 import type { ExportService } from '../services/ExportService.js';
 import type { ImportService } from '../services/ImportService.js';
 import type { SyncService } from '../services/SyncService.js';
+import { GitClient } from '../services/GitClient.js';
 import type { TelemetryService } from '../services/TelemetryService.js';
 import type { SettingsService } from '../services/SettingsService.js';
 import { collectAutostartState } from '../services/AutostartDiagnostic.js';
@@ -281,4 +282,78 @@ export function registerSettingsApi(deps?: SettingsIpcDeps): void {
     }
     return { ok: true } as const;
   });
+
+  // v0.3.0 Cut E — sync IPC.
+
+  // settings:configure-sync — URL 저장 + git init + remote add (없으면).
+  // null URL → 저장만 (init 안 함). 빈 문자열도 null 처리.
+  ipcMain.handle('settings:configure-sync', async (_e, url: string | null) => {
+    const trimmed = typeof url === 'string' ? url.trim() : '';
+    const finalUrl = trimmed.length === 0 ? null : trimmed;
+
+    try {
+      await deps.settings.setSyncRepoUrl(finalUrl);
+    } catch (e) {
+      return { ok: false as const, reason: `persist failed: ${(e as Error).message}` };
+    }
+
+    if (finalUrl === null) return { ok: true as const };
+
+    // git init + remote add origin
+    const syncDir = deps.syncSvc.getSyncDir();
+    const git = new GitClient(syncDir);
+
+    if (!(await git.isRepo())) {
+      const init = await git.run(['init']);
+      if (init.exitCode !== 0) {
+        return { ok: false as const, reason: `git init failed: ${init.stderr}` };
+      }
+    }
+    if (!(await git.hasRemote())) {
+      const add = await git.run(['remote', 'add', 'origin', finalUrl]);
+      if (add.exitCode !== 0) {
+        return { ok: false as const, reason: `remote add failed: ${add.stderr}` };
+      }
+    } else {
+      // remote exists — update URL
+      const set = await git.run(['remote', 'set-url', 'origin', finalUrl]);
+      if (set.exitCode !== 0) {
+        return { ok: false as const, reason: `remote set-url failed: ${set.stderr}` };
+      }
+    }
+    return { ok: true as const };
+  });
+
+  // settings:test-sync-connection — git ls-remote 결과
+  ipcMain.handle('settings:test-sync-connection', async () => {
+    const syncDir = deps.syncSvc.getSyncDir();
+    const git = new GitClient(syncDir);
+    if (!(await git.isRepo())) return { ok: false as const, reason: 'not_initialized' };
+    const r = await git.run(['ls-remote', 'origin']);
+    if (r.exitCode !== 0) return { ok: false as const, reason: r.stderr || 'connection failed' };
+    return { ok: true as const };
+  });
+
+  // sync:list-conflicts — SyncService 캐시 결과
+  ipcMain.handle('sync:list-conflicts', () => deps.syncSvc.listConflicts());
+
+  // sync:resolve-conflict — local/remote 2 choice
+  ipcMain.handle('sync:resolve-conflict', async (_e, noteId: string, choice: 'local' | 'remote') => {
+    if (choice !== 'local' && choice !== 'remote') {
+      return { ok: false as const, reason: 'invalid choice' };
+    }
+    return deps.syncSvc.resolveConflict(noteId, choice);
+  });
+
+  // sync:get-status — lastAt + lastResult + nextAt 계산
+  ipcMain.handle('sync:get-status', async () => {
+    const last = deps.syncSvc.getLastStatus();
+    let nextAt: string | null = null;
+    if (await deps.settings.isAutoSyncEnabled()) {
+      const intervalMin = await deps.settings.getSyncIntervalMin();
+      const baseMs = last.lastAt ? new Date(last.lastAt).getTime() : Date.now();
+      nextAt = new Date(baseMs + intervalMin * 60 * 1000).toISOString();
+    }
+    return { lastAt: last.lastAt, lastResult: last.lastResult, nextAt };
+  });
 }
diff --git a/src/preload/index.ts b/src/preload/index.ts
index f59ffe2..3db9c04 100644
--- a/src/preload/index.ts
+++ b/src/preload/index.ts
@@ -88,6 +88,13 @@ const api: InklingApi = {
     // v0.2.11 Cut D — search + 회고 aggregate.
     search: (query, opts) => ipcRenderer.invoke('inbox:search', query, opts ?? {}),
     reviewAggregate: (period) => ipcRenderer.invoke('inbox:review-aggregate', period),
+    // v0.3.0 Cut E — 양방향 sync.
+    configureSync: (url: string | null) => ipcRenderer.invoke('settings:configure-sync', url),
+    testSyncConnection: () => ipcRenderer.invoke('settings:test-sync-connection'),
+    listConflicts: () => ipcRenderer.invoke('sync:list-conflicts'),
+    resolveConflict: (noteId: string, choice: 'local' | 'remote') =>
+      ipcRenderer.invoke('sync:resolve-conflict', noteId, choice),
+    getSyncStatus: () => ipcRenderer.invoke('sync:get-status'),
   }
 };
 
diff --git a/src/shared/types.ts b/src/shared/types.ts
index cc625bf..217cc91 100644
--- a/src/shared/types.ts
+++ b/src/shared/types.ts
@@ -40,6 +40,29 @@ export interface ReviewAggregate {
   dueProgress: { total: number; passed: number; pending: number };
 }
 
+// v0.3.0 Cut E — 양방향 sync 결과 + conflict.
+export interface SyncConflict {
+  noteId: string;
+  localText: string;
+  remoteText: string;
+}
+
+export interface SyncStatus {
+  ok: boolean;
+  reason?: string;
+  changed?: boolean;
+  localSha?: string | null;
+  pushed?: boolean;
+  importedCount?: number;
+  conflicts?: SyncConflict[];
+}
+
+export interface SyncStatusSnapshot {
+  lastAt: string | null;
+  lastResult: SyncStatus | null;
+  nextAt: string | null;
+}
+
 export interface Note {
   id: string;
   rawText: string;
@@ -182,6 +205,12 @@ export interface InboxApi {
   // v0.2.11 Cut D — FTS5 search + 회고 aggregate.
   search(query: string, opts?: { limit?: number; status?: NoteStatus }): Promise<Note[]>;
   reviewAggregate(period: ReviewPeriod): Promise<ReviewAggregate>;
+  // v0.3.0 Cut E — 양방향 sync.
+  configureSync(url: string | null): Promise<{ ok: true } | { ok: false; reason: string }>;
+  testSyncConnection(): Promise<{ ok: true } | { ok: false; reason: string }>;
+  listConflicts(): Promise<SyncConflict[]>;
+  resolveConflict(noteId: string, choice: 'local' | 'remote'): Promise<{ ok: true } | { ok: false; reason: string }>;
+  getSyncStatus(): Promise<SyncStatusSnapshot>;
 }
 
 export interface InklingApi {
diff --git a/tests/unit/sync-ipc.test.ts b/tests/unit/sync-ipc.test.ts
new file mode 100644
index 0000000..d2f459a
--- /dev/null
+++ b/tests/unit/sync-ipc.test.ts
@@ -0,0 +1,250 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+
+vi.mock('electron', () => ({ default: { ipcMain: { handle: vi.fn() }, dialog: {}, shell: {} } }));
+vi.mock('../../src/main/services/GitClient.js');
+
+import electron from 'electron';
+import { GitClient } from '../../src/main/services/GitClient.js';
+import { registerSettingsApi } from '../../src/main/ipc/settingsApi.js';
+import type { SettingsIpcDeps } from '../../src/main/ipc/settingsApi.js';
+
+function getHandler(channel: string): (...args: unknown[]) => unknown {
+  const handle = (electron.ipcMain as unknown as { handle: ReturnType<typeof vi.fn> }).handle;
+  const call = handle.mock.calls.find((c) => c[0] === channel);
+  if (!call) throw new Error(`channel ${channel} not registered`);
+  return call[1] as (...args: unknown[]) => unknown;
+}
+
+function makeDeps() {
+  const gitInstance = {
+    isRepo: vi.fn(async () => false),
+    hasRemote: vi.fn(async () => false),
+    run: vi.fn(async () => ({ stdout: '', stderr: '', exitCode: 0 }))
+  };
+  (GitClient as unknown as ReturnType<typeof vi.fn>).mockImplementation(function () { return gitInstance; });
+
+  const syncSvc = {
+    getSyncDir: vi.fn(() => '/tmp/sync'),
+    listConflicts: vi.fn(() => [] as { noteId: string; localText: string; remoteText: string }[]),
+    resolveConflict: vi.fn(async () => ({ ok: true as const })),
+    getLastStatus: vi.fn(() => ({ lastAt: null as string | null, lastResult: null as { ok: boolean } | null }))
+  };
+  const settings = {
+    getSyncRepoUrl: vi.fn(async () => 'git@host:u/r.git'),
+    setSyncRepoUrl: vi.fn(async () => {}),
+    isAutoSyncEnabled: vi.fn(async () => false),
+    getSyncIntervalMin: vi.fn(async () => 30),
+    getAll: vi.fn(async () => ({})),
+    setAiEnabled: vi.fn(async () => {}),
+    setOnboardingCompleted: vi.fn(async () => {}),
+    isAiEnabled: vi.fn(async () => true)
+  };
+
+  const deps: Partial<SettingsIpcDeps> = {
+    backup: { runDaily: vi.fn(async () => ({ snapshotted: false })) } as never,
+    exportSvc: {} as never,
+    importSvc: {} as never,
+    syncSvc: syncSvc as never,
+    telemetry: { exportTo: vi.fn(async () => ({ eventCount: 0 })) } as never,
+    settings: settings as never,
+    getInboxWindow: () => null
+  };
+
+  return { gitInstance, syncSvc, settings, deps };
+}
+
+describe('sync IPC channels', () => {
+  beforeEach(() => {
+    (electron.ipcMain as unknown as { handle: ReturnType<typeof vi.fn> }).handle.mockClear();
+    vi.clearAllMocks();
+  });
+
+  it('5 sync channels registered', () => {
+    const { deps } = makeDeps();
+    registerSettingsApi(deps as SettingsIpcDeps);
+
+    const handle = (electron.ipcMain as unknown as { handle: ReturnType<typeof vi.fn> }).handle;
+    const channels = handle.mock.calls.map((c) => c[0]);
+    expect(channels).toContain('settings:configure-sync');
+    expect(channels).toContain('settings:test-sync-connection');
+    expect(channels).toContain('sync:list-conflicts');
+    expect(channels).toContain('sync:resolve-conflict');
+    expect(channels).toContain('sync:get-status');
+  });
+
+  describe('settings:configure-sync', () => {
+    it('null URL → setSyncRepoUrl(null), no git init', async () => {
+      const { deps, settings, gitInstance } = makeDeps();
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:configure-sync');
+      const r = await h({}, null);
+      expect(settings.setSyncRepoUrl).toHaveBeenCalledWith(null);
+      expect(gitInstance.run).not.toHaveBeenCalled();
+      expect(r).toEqual({ ok: true });
+    });
+
+    it('empty string URL → treated as null', async () => {
+      const { deps, settings, gitInstance } = makeDeps();
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:configure-sync');
+      const r = await h({}, '   ');
+      expect(settings.setSyncRepoUrl).toHaveBeenCalledWith(null);
+      expect(gitInstance.run).not.toHaveBeenCalled();
+      expect(r).toEqual({ ok: true });
+    });
+
+    it('valid URL → isRepo=false → git init + remote add', async () => {
+      const { deps, gitInstance } = makeDeps();
+      gitInstance.isRepo.mockResolvedValue(false);
+      gitInstance.hasRemote.mockResolvedValue(false);
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:configure-sync');
+      const r = await h({}, 'git@github.com:user/repo.git');
+      expect(gitInstance.run).toHaveBeenCalledWith(['init']);
+      expect(gitInstance.run).toHaveBeenCalledWith(['remote', 'add', 'origin', 'git@github.com:user/repo.git']);
+      expect(r).toEqual({ ok: true });
+    });
+
+    it('valid URL → isRepo=true, hasRemote=true → remote set-url', async () => {
+      const { deps, gitInstance } = makeDeps();
+      gitInstance.isRepo.mockResolvedValue(true);
+      gitInstance.hasRemote.mockResolvedValue(true);
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:configure-sync');
+      const r = await h({}, 'git@github.com:user/new-repo.git');
+      expect(gitInstance.run).toHaveBeenCalledWith(['remote', 'set-url', 'origin', 'git@github.com:user/new-repo.git']);
+      expect(r).toEqual({ ok: true });
+    });
+
+    it('git init failure → ok: false', async () => {
+      const { deps, gitInstance } = makeDeps();
+      gitInstance.isRepo.mockResolvedValue(false);
+      gitInstance.run.mockResolvedValue({ stdout: '', stderr: 'permission denied', exitCode: 1 });
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:configure-sync');
+      const r = await h({}, 'git@github.com:user/repo.git');
+      expect(r).toMatchObject({ ok: false, reason: expect.stringContaining('git init failed') });
+    });
+
+    it('setSyncRepoUrl throws → ok: false', async () => {
+      const { deps, settings } = makeDeps();
+      settings.setSyncRepoUrl.mockRejectedValue(new Error('disk full'));
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:configure-sync');
+      const r = await h({}, 'git@github.com:user/repo.git');
+      expect(r).toMatchObject({ ok: false, reason: expect.stringContaining('persist failed') });
+    });
+  });
+
+  describe('settings:test-sync-connection', () => {
+    it('not initialized → ok: false, reason: not_initialized', async () => {
+      const { deps, gitInstance } = makeDeps();
+      gitInstance.isRepo.mockResolvedValue(false);
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:test-sync-connection');
+      const r = await h({});
+      expect(r).toEqual({ ok: false, reason: 'not_initialized' });
+    });
+
+    it('ls-remote success → ok: true', async () => {
+      const { deps, gitInstance } = makeDeps();
+      gitInstance.isRepo.mockResolvedValue(true);
+      gitInstance.run.mockResolvedValue({ stdout: 'abc123\trefs/heads/main', stderr: '', exitCode: 0 });
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:test-sync-connection');
+      const r = await h({});
+      expect(gitInstance.run).toHaveBeenCalledWith(['ls-remote', 'origin']);
+      expect(r).toEqual({ ok: true });
+    });
+
+    it('ls-remote failure → ok: false', async () => {
+      const { deps, gitInstance } = makeDeps();
+      gitInstance.isRepo.mockResolvedValue(true);
+      gitInstance.run.mockResolvedValue({ stdout: '', stderr: 'connection refused', exitCode: 128 });
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('settings:test-sync-connection');
+      const r = await h({});
+      expect(r).toMatchObject({ ok: false, reason: 'connection refused' });
+    });
+  });
+
+  describe('sync:list-conflicts', () => {
+    it('returns syncSvc.listConflicts() result', () => {
+      const { deps, syncSvc } = makeDeps();
+      const conflicts = [{ noteId: 'abc', localText: 'local', remoteText: 'remote' }];
+      syncSvc.listConflicts.mockReturnValue(conflicts);
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('sync:list-conflicts');
+      const r = h({});
+      expect(r).toEqual(conflicts);
+    });
+  });
+
+  describe('sync:resolve-conflict', () => {
+    it('valid choice "local" → delegates to syncSvc.resolveConflict', async () => {
+      const { deps, syncSvc } = makeDeps();
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('sync:resolve-conflict');
+      const r = await h({}, 'note-1', 'local');
+      expect(syncSvc.resolveConflict).toHaveBeenCalledWith('note-1', 'local');
+      expect(r).toEqual({ ok: true });
+    });
+
+    it('valid choice "remote" → delegates to syncSvc.resolveConflict', async () => {
+      const { deps, syncSvc } = makeDeps();
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('sync:resolve-conflict');
+      await h({}, 'note-2', 'remote');
+      expect(syncSvc.resolveConflict).toHaveBeenCalledWith('note-2', 'remote');
+    });
+
+    it('invalid choice → ok: false, reason: invalid choice', async () => {
+      const { deps, syncSvc } = makeDeps();
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('sync:resolve-conflict');
+      const r = await h({}, 'note-1', 'both');
+      expect(syncSvc.resolveConflict).not.toHaveBeenCalled();
+      expect(r).toEqual({ ok: false, reason: 'invalid choice' });
+    });
+  });
+
+  describe('sync:get-status', () => {
+    it('auto-sync disabled → nextAt: null', async () => {
+      const { deps, syncSvc, settings } = makeDeps();
+      settings.isAutoSyncEnabled.mockResolvedValue(false);
+      syncSvc.getLastStatus.mockReturnValue({ lastAt: '2026-05-09T10:00:00.000Z', lastResult: { ok: true } });
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('sync:get-status');
+      const r = await h({});
+      expect(r).toMatchObject({ lastAt: '2026-05-09T10:00:00.000Z', lastResult: { ok: true }, nextAt: null });
+    });
+
+    it('auto-sync enabled → nextAt computed from lastAt + interval', async () => {
+      const { deps, syncSvc, settings } = makeDeps();
+      settings.isAutoSyncEnabled.mockResolvedValue(true);
+      settings.getSyncIntervalMin.mockResolvedValue(30);
+      syncSvc.getLastStatus.mockReturnValue({ lastAt: '2026-05-09T10:00:00.000Z', lastResult: { ok: true } });
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('sync:get-status');
+      const r = (await h({})) as { lastAt: string; nextAt: string };
+      const expectedNextAt = new Date(new Date('2026-05-09T10:00:00.000Z').getTime() + 30 * 60 * 1000).toISOString();
+      expect(r.nextAt).toBe(expectedNextAt);
+    });
+
+    it('no previous sync + auto-sync enabled → nextAt based on Date.now()', async () => {
+      const { deps, syncSvc, settings } = makeDeps();
+      settings.isAutoSyncEnabled.mockResolvedValue(true);
+      settings.getSyncIntervalMin.mockResolvedValue(15);
+      syncSvc.getLastStatus.mockReturnValue({ lastAt: null, lastResult: null });
+      registerSettingsApi(deps as SettingsIpcDeps);
+      const h = getHandler('sync:get-status');
+      const before = Date.now();
+      const r = (await h({})) as { lastAt: null; nextAt: string };
+      const after = Date.now();
+      const nextAtMs = new Date(r.nextAt).getTime();
+      expect(nextAtMs).toBeGreaterThanOrEqual(before + 15 * 60 * 1000);
+      expect(nextAtMs).toBeLessThanOrEqual(after + 15 * 60 * 1000);
+      expect(r.lastAt).toBeNull();
+    });
+  });
+});