diff --git a/tests/services/sync/test_sync_documents.py b/tests/services/sync/test_sync_documents.py
index a82aa738..dd7d7cfe 100644
--- a/tests/services/sync/test_sync_documents.py
+++ b/tests/services/sync/test_sync_documents.py
@@ -1,5 +1,5 @@
 """Test sync service."""
-
+import asyncio
 from pathlib import Path
 import pytest
 
@@ -39,3 +39,75 @@ async def test_sync_documents(
     paths = {d.path_id for d in documents}
     assert "new.md" in paths
     assert "modified.md" in paths
+
+
+@pytest.mark.asyncio
+async def test_sync_new_document_adds_frontmatter(
+        test_config: ProjectConfig,
+        sync_service: SyncService
+):
+    """Test that syncing a new document adds appropriate frontmatter."""
+
+    # Create document without frontmatter
+    doc_path = test_config.documents_dir / "test.md"
+    original_content = "# Test Document\n\nThis is a test."
+    doc_path.write_text(original_content)
+
+    # Sync
+    await sync_service.sync(test_config.home)
+
+    # Read updated file
+    content = doc_path.read_text()
+
+    # Verify frontmatter was added
+    assert "---" in content
+    assert "id: test.md" in content
+    assert "created:" in content
+    assert "modified:" in content
+
+    # Original content preserved
+    assert original_content in content
+
+    # Verify document in DB
+    doc = await sync_service.document_service.repository.find_by_path_id("test.md")
+    assert doc is not None
+    assert doc.checksum is not None
+    assert doc.created_at is not None
+    assert doc.updated_at is not None
+
+
+@pytest.mark.asyncio
+async def test_sync_modified_document_updates_frontmatter(
+        test_config: ProjectConfig,
+        sync_service: SyncService
+):
+    """Test that modifying a document updates frontmatter properly."""
+
+    # First create and sync a document
+    doc_path = test_config.documents_dir / "test.md"
+    original_content = "# Test Document\n\nOriginal content."
+    doc_path.write_text(original_content)
+    await sync_service.sync(test_config.home)
+
+    # Get original timestamps
+    doc = await sync_service.document_service.repository.find_by_path_id("test.md")
+    original_created = doc.created_at
+    original_modified = doc.updated_at
+
+    await asyncio.sleep(1)
+    
+    # Modify document
+    new_content = "# Test Document\n\nUpdated content."
+    doc_path.write_text(new_content)
+    await sync_service.sync(test_config.home)
+
+    # Verify document in DB
+    updated_doc = await sync_service.document_service.repository.find_by_path_id("test.md")
+    assert updated_doc.created_at == original_created  # Should not change
+    assert updated_doc.updated_at > original_modified  # Should be updated
+
+    # Check file content
+    content = doc_path.read_text()
+    assert "Updated content" in content
+    assert "created:" in content
+    assert "modified:" in content
\ No newline at end of file