diff --git a/src/main/services/GitClient.ts b/src/main/services/GitClient.ts
index 49da9fb..e4db135 100644
--- a/src/main/services/GitClient.ts
+++ b/src/main/services/GitClient.ts
@@ -65,8 +65,21 @@ export class GitClient {
     throw new Error(`git commit failed: ${r.stderr || r.stdout}`);
   }
 
+  async hasUpstream(): Promise<boolean> {
+    const r = await this.run(['rev-parse', '--abbrev-ref', '--symbolic-full-name', '@{u}']);
+    return r.exitCode === 0;
+  }
+
   async push(remote: string = 'origin', branch?: string): Promise<void> {
-    const args = branch ? ['push', remote, branch] : ['push', remote];
+    // If no upstream is configured, set one with -u so subsequent `git push` works.
+    const upstream = await this.hasUpstream();
+    let args: string[];
+    if (!upstream) {
+      const targetBranch = branch ?? (await this.currentBranch());
+      args = ['push', '-u', remote, targetBranch];
+    } else {
+      args = branch ? ['push', remote, branch] : ['push', remote];
+    }
     const r = await this.run(args);
     if (r.exitCode !== 0) throw new Error(`git push failed: ${r.stderr}`);
   }
diff --git a/src/main/services/SyncService.ts b/src/main/services/SyncService.ts
new file mode 100644
index 0000000..0a790ab
--- /dev/null
+++ b/src/main/services/SyncService.ts
@@ -0,0 +1,63 @@
+import { join } from 'node:path';
+import { mkdir } from 'node:fs/promises';
+import type { ExportService } from './ExportService.js';
+import { GitClient } from './GitClient.js';
+
+export interface SyncStatus {
+  ok: boolean;
+  reason?: string;          // why the sync was skipped or failed
+  changed?: boolean;        // true if a new commit was created
+  sha?: string | null;
+  pushed?: boolean;
+}
+
+export class SyncService {
+  private syncDir: string;
+
+  constructor(
+    private profileDir: string,
+    private exportSvc: ExportService,
+    private now: () => Date = () => new Date()
+  ) {
+    this.syncDir = join(profileDir, 'sync');
+  }
+
+  getSyncDir(): string {
+    return this.syncDir;
+  }
+
+  async isConfigured(): Promise<boolean> {
+    const git = new GitClient(this.syncDir);
+    if (!(await git.isRepo())) return false;
+    if (!(await git.hasRemote())) return false;
+    return true;
+  }
+
+  async sync(): Promise<SyncStatus> {
+    if (!(await this.isConfigured())) {
+      return { ok: false, reason: 'not_configured' };
+    }
+    // 1. Re-export the full tree into syncDir (idempotent).
+    try {
+      await mkdir(this.syncDir, { recursive: true });
+      await this.exportSvc.export(this.syncDir, { includeMedia: true });
+    } catch (e) {
+      return { ok: false, reason: `export failed: ${(e as Error).message}` };
+    }
+    // 2. git add + commit + push
+    const git = new GitClient(this.syncDir);
+    try {
+      await git.addAll();
+      const ts = this.now().toISOString();
+      const message = `chore(notes): sync ${ts}`;
+      const commit = await git.commit(message);
+      if (!commit.changed) {
+        return { ok: true, changed: false, pushed: false };
+      }
+      await git.push();
+      return { ok: true, changed: true, sha: commit.sha, pushed: true };
+    } catch (e) {
+      return { ok: false, reason: (e as Error).message };
+    }
+  }
+}
diff --git a/tests/unit/SyncService.test.ts b/tests/unit/SyncService.test.ts
new file mode 100644
index 0000000..ea10c84
--- /dev/null
+++ b/tests/unit/SyncService.test.ts
@@ -0,0 +1,131 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import Database from 'better-sqlite3';
+import { mkdtempSync, rmSync, mkdirSync, existsSync, closeSync, openSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { execFile } from 'node:child_process';
+import { promisify } from 'node:util';
+import { runMigrations } from '@main/db/migrations/index.js';
+import { NoteRepository } from '@main/repository/NoteRepository.js';
+import { MediaStore } from '@main/services/MediaStore.js';
+import { ExportService } from '@main/services/ExportService.js';
+import { SyncService } from '@main/services/SyncService.js';
+
+const execFileAsync = promisify(execFile);
+
+let emptyConfigPath: string;
+let emptyConfigDir: string;
+
+function gitEnv(): NodeJS.ProcessEnv {
+  return {
+    ...process.env,
+    GIT_CONFIG_GLOBAL: emptyConfigPath,
+    GIT_CONFIG_SYSTEM: emptyConfigPath,
+    GIT_AUTHOR_NAME: 'Test',
+    GIT_AUTHOR_EMAIL: 'test@inkling.local',
+    GIT_COMMITTER_NAME: 'Test',
+    GIT_COMMITTER_EMAIL: 'test@inkling.local'
+  };
+}
+
+async function initRepoWithBareRemote(workDir: string): Promise<string> {
+  mkdirSync(workDir, { recursive: true });
+  const env = gitEnv();
+  await execFileAsync('git', ['init', '-b', 'main', workDir], { env });
+  await execFileAsync('git', ['-C', workDir, 'config', 'user.email', 'test@inkling.local'], { env });
+  await execFileAsync('git', ['-C', workDir, 'config', 'user.name', 'Test'], { env });
+  // Bare local remote so push works without network.
+  const remoteDir = `${workDir}-remote.git`;
+  await execFileAsync('git', ['init', '--bare', '-b', 'main', remoteDir], { env });
+  await execFileAsync('git', ['-C', workDir, 'remote', 'add', 'origin', remoteDir], { env });
+  return remoteDir;
+}
+
+describe('SyncService', () => {
+  let profileDir: string;
+  let db: Database.Database;
+  let repo: NoteRepository;
+  let mediaStore: MediaStore;
+  let exportSvc: ExportService;
+  let svc: SyncService;
+  let remoteDir: string | null = null;
+  let prevEnv: NodeJS.ProcessEnv;
+
+  beforeEach(() => {
+    emptyConfigDir = mkdtempSync(join(tmpdir(), 'inkling-sync-cfg-'));
+    emptyConfigPath = join(emptyConfigDir, 'empty.gitconfig');
+    closeSync(openSync(emptyConfigPath, 'w'));
+
+    prevEnv = { ...process.env };
+    Object.assign(process.env, {
+      GIT_CONFIG_GLOBAL: emptyConfigPath,
+      GIT_CONFIG_SYSTEM: emptyConfigPath,
+      GIT_AUTHOR_NAME: 'Test',
+      GIT_AUTHOR_EMAIL: 'test@inkling.local',
+      GIT_COMMITTER_NAME: 'Test',
+      GIT_COMMITTER_EMAIL: 'test@inkling.local'
+    });
+
+    profileDir = mkdtempSync(join(tmpdir(), 'inkling-sync-'));
+    mkdirSync(join(profileDir, 'media'), { recursive: true });
+    db = new Database(':memory:');
+    runMigrations(db);
+    repo = new NoteRepository(db);
+    mediaStore = new MediaStore(profileDir);
+    exportSvc = new ExportService(repo, mediaStore, () => new Date('2026-04-26T12:00:00Z'));
+    svc = new SyncService(profileDir, exportSvc, () => new Date('2026-04-26T12:00:00Z'));
+  });
+
+  afterEach(() => {
+    db.close();
+    rmSync(profileDir, { recursive: true, force: true });
+    if (remoteDir !== null) {
+      rmSync(remoteDir, { recursive: true, force: true });
+      remoteDir = null;
+    }
+    rmSync(emptyConfigDir, { recursive: true, force: true });
+    for (const k of Object.keys(process.env)) delete process.env[k];
+    Object.assign(process.env, prevEnv);
+  });
+
+  it('isConfigured returns false before sync dir is set up', async () => {
+    expect(await svc.isConfigured()).toBe(false);
+  });
+
+  it('sync returns not_configured when sync dir missing', async () => {
+    const r = await svc.sync();
+    expect(r.ok).toBe(false);
+    expect(r.reason).toBe('not_configured');
+  });
+
+  it('isConfigured returns true after init + remote', async () => {
+    remoteDir = await initRepoWithBareRemote(svc.getSyncDir());
+    expect(await svc.isConfigured()).toBe(true);
+  });
+
+  it('sync writes export tree, commits, pushes — first run', async () => {
+    remoteDir = await initRepoWithBareRemote(svc.getSyncDir());
+    repo.create({ rawText: 'first note' });
+    const r = await svc.sync();
+    expect(r.ok).toBe(true);
+    expect(r.changed).toBe(true);
+    expect(r.pushed).toBe(true);
+    expect(r.sha).toMatch(/^[0-9a-f]{40}$/);
+    expect(existsSync(join(svc.getSyncDir(), 'manifest.json'))).toBe(true);
+    expect(existsSync(join(svc.getSyncDir(), 'notes'))).toBe(true);
+    expect(existsSync(join(svc.getSyncDir(), 'index.jsonl'))).toBe(true);
+  });
+
+  it('sync returns changed=false when DB unchanged on second run', async () => {
+    remoteDir = await initRepoWithBareRemote(svc.getSyncDir());
+    repo.create({ rawText: 'first note' });
+    const first = await svc.sync();
+    expect(first.ok).toBe(true);
+    expect(first.changed).toBe(true);
+    // Re-sync without DB change. With fixed now() → identical files → git sees no change.
+    const second = await svc.sync();
+    expect(second.ok).toBe(true);
+    expect(second.changed).toBe(false);
+    expect(second.pushed).toBe(false);
+  });
+});