diff --git a/backend/tests/test_cloud.py b/backend/tests/test_cloud.py
index 1e765be..aea810f 100644
--- a/backend/tests/test_cloud.py
+++ b/backend/tests/test_cloud.py
@@ -563,3 +563,125 @@ async def test_cross_user_idor(
     )
 
     assert resp.status_code == 404
+
+
+# ── Plan 09 tests: PATCH /documents/{id} and cloud-aware re-analyze ──────────
+
+async def test_patch_document_filename(async_client, db_session):
+    """PATCH /api/documents/{id} with {filename} returns 200 with updated filename.
+
+    Covers T-05-09-01: ownership enforced via get_regular_user.
+    """
+    from db.models import Document
+
+    auth = await _create_user_and_token(db_session, role="user")
+
+    # Create a document owned by this user
+    doc_id = _uuid.uuid4()
+    doc = Document(
+        id=doc_id,
+        user_id=auth["user"].id,
+        filename="original.pdf",
+        content_type="application/pdf",
+        size_bytes=1024,
+        storage_backend="minio",
+        status="uploaded",
+        object_key=f"{auth['user'].id}/{doc_id}/some-uuid.pdf",
+    )
+    db_session.add(doc)
+    await db_session.commit()
+
+    resp = await async_client.patch(
+        f"/api/documents/{doc_id}",
+        json={"filename": "renamed.pdf"},
+        headers=auth["headers"],
+    )
+
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["filename"] == "renamed.pdf" or data.get("original_name") == "renamed.pdf"
+
+
+async def test_patch_document_wrong_owner(async_client, db_session):
+    """PATCH /api/documents/{id} by a non-owner returns 404 (IDOR protection).
+
+    Covers T-05-09-01: cross-user access returns 404, not 403, to avoid leaking
+    which document IDs exist for other users (D-16, T-03-11).
+    """
+    from db.models import Document
+
+    auth1 = await _create_user_and_token(db_session, role="user")
+    auth2 = await _create_user_and_token(db_session, role="user")
+
+    # Create a document owned by user1
+    doc_id = _uuid.uuid4()
+    doc = Document(
+        id=doc_id,
+        user_id=auth1["user"].id,
+        filename="private.pdf",
+        content_type="application/pdf",
+        size_bytes=512,
+        storage_backend="minio",
+        status="uploaded",
+        object_key=f"{auth1['user'].id}/{doc_id}/some-uuid.pdf",
+    )
+    db_session.add(doc)
+    await db_session.commit()
+
+    # User2 tries to rename user1's document
+    resp = await async_client.patch(
+        f"/api/documents/{doc_id}",
+        json={"filename": "hacked.pdf"},
+        headers=auth2["headers"],
+    )
+
+    assert resp.status_code == 404
+
+
+async def test_reanalyze_cloud_document_routes_to_cloud_backend(db_session):
+    """Re-analyze task calls get_storage_backend_for_document for cloud documents.
+
+    Verifies that doc.storage_backend != 'minio' causes _run() to use the cloud
+    backend path instead of the MinIO path (Plan 09, requirement CLOUD-07).
+    """
+    from db.models import Document
+    from tasks.document_tasks import _run
+    from unittest.mock import AsyncMock, patch, MagicMock
+
+    auth = await _create_user_and_token(db_session, role="user")
+
+    # Create a nextcloud document
+    doc_id = _uuid.uuid4()
+    doc = Document(
+        id=doc_id,
+        user_id=auth["user"].id,
+        filename="cloud.pdf",
+        content_type="application/pdf",
+        size_bytes=2048,
+        storage_backend="nextcloud",
+        status="uploaded",
+        object_key="nc_file_id_xyz",
+    )
+    db_session.add(doc)
+    await db_session.commit()
+
+    # Mock cloud backend: returns file bytes, enabling extraction to proceed
+    mock_cloud_backend = AsyncMock()
+    mock_cloud_backend.get_object = AsyncMock(return_value=b"%PDF-1.4 fake content")
+
+    # Mock MinIO backend to verify it is NOT called
+    mock_minio_backend = AsyncMock()
+    mock_minio_backend.get_object = AsyncMock(return_value=b"should not be called")
+
+    with patch("tasks.document_tasks.get_storage_backend_for_document", return_value=mock_cloud_backend) as mock_gsb_doc, \
+         patch("tasks.document_tasks.get_storage_backend", return_value=mock_minio_backend) as mock_gsb:
+        result = await _run(str(doc_id))
+
+    # Cloud backend's get_object must have been called
+    mock_cloud_backend.get_object.assert_called_once_with("nc_file_id_xyz")
+
+    # MinIO backend's get_object must NOT have been called
+    mock_minio_backend.get_object.assert_not_called()
+
+    # Result must not be an error from MinIO path
+    assert result.get("status") != "extract_failed" or "MinIO" not in result.get("error", "")