diff --git a/tensormap-backend/app/services/data_process.py b/tensormap-backend/app/services/data_process.py
index cab7df0b..f36b3c24 100644
--- a/tensormap-backend/app/services/data_process.py
+++ b/tensormap-backend/app/services/data_process.py
@@ -42,6 +42,14 @@ def add_target_service(db: Session, file_id: uuid_pkg.UUID, target: str) -> tupl
         file = db.exec(select(DataFile).where(DataFile.id == file_id)).first()
         if not file:
             return _resp(400, False, "File doesn't exist in DB")
+        if file.file_type != "csv":
+            return _resp(400, False, "Only CSV files support target field assignment")
+        if file.columns is not None and target not in file.columns:
+            return _resp(
+                400,
+                False,
+                f"Target column '{target}' not found in dataset columns",
+            )
 
         data_process = DataProcess(file_id=file_id, target=target)
         db.add(data_process)
diff --git a/tensormap-backend/tests/test_data_process_service.py b/tensormap-backend/tests/test_data_process_service.py
index 93074962..b8771e2c 100644
--- a/tensormap-backend/tests/test_data_process_service.py
+++ b/tensormap-backend/tests/test_data_process_service.py
@@ -110,6 +110,45 @@ def test_file_not_found(self, mock_db, file_id):
         assert body["success"] is False
         assert "doesn't exist" in body["message"]
 
+    def test_rejects_non_csv_file(self, mock_db, file_id):
+        zip_file = MagicMock(spec=DataFile)
+        zip_file.id = file_id
+        zip_file.file_type = "zip"
+        mock_db.exec.return_value.first.return_value = zip_file
+
+        body, status = add_target_service(mock_db, file_id, "species")
+
+        assert status == 400
+        assert body["success"] is False
+        assert "CSV" in body["message"]
+
+    def test_rejects_column_not_in_dataset(self, mock_db, file_id):
+        csv_file = MagicMock(spec=DataFile)
+        csv_file.id = file_id
+        csv_file.file_type = "csv"
+        csv_file.columns = ["sepal_length", "sepal_width", "species"]
+        mock_db.exec.return_value.first.return_value = csv_file
+
+        body, status = add_target_service(mock_db, file_id, "nonexistent_column")
+
+        assert status == 400
+        assert body["success"] is False
+        assert "not found" in body["message"]
+
+    def test_accepts_column_in_dataset(self, mock_db, file_id):
+        csv_file = MagicMock(spec=DataFile)
+        csv_file.id = file_id
+        csv_file.file_type = "csv"
+        csv_file.columns = ["sepal_length", "sepal_width", "species"]
+        mock_db.exec.return_value.first.return_value = csv_file
+
+        body, status = add_target_service(mock_db, file_id, "species")
+
+        assert status == 201
+        assert body["success"] is True
+        mock_db.add.assert_called_once()
+        mock_db.commit.assert_called_once()
+
 
 # ---------------------------------------------------------------------------
 # get_one_target_by_id_service