From bf629cc37ca4df1395657ae556cc89678c550b1e Mon Sep 17 00:00:00 2001
From: Sahil Kumar Singh <60318530+SahilKumar75@users.noreply.github.com>
Date: Sat, 22 Aug 2026 18:04:18 +0530
Subject: [PATCH] fix(trainer): unpack train_func_parameters as kwargs in
 localprocess backend

The LocalProcess backend embedded train_func_parameters as a single
positional dict argument instead of unpacking it as keyword arguments,
unlike the Kubernetes backend which already does this correctly. Any
CustomTrainer using func_args with LocalProcessBackend would fail with
a TypeError since the training function receives one dict positional
argument instead of its named parameters.

Signed-off-by: Sahil Kumar Singh <60318530+SahilKumar75@users.noreply.github.com>
---
 .../trainer/backends/localprocess/utils.py    |  2 +-
 .../backends/localprocess/utils_test.py       | 86 +++++++++++++++++++
 2 files changed, 87 insertions(+), 1 deletion(-)
 create mode 100644 kubeflow/trainer/backends/localprocess/utils_test.py

diff --git a/kubeflow/trainer/backends/localprocess/utils.py b/kubeflow/trainer/backends/localprocess/utils.py
index ef01fb501..9d61b25d3 100644
--- a/kubeflow/trainer/backends/localprocess/utils.py
+++ b/kubeflow/trainer/backends/localprocess/utils.py
@@ -216,7 +216,7 @@ def get_command_using_train_func(
     if train_func_parameters is None:
         func_code = f"{func_code}\n{train_func.__name__}()\n"
     else:
-        func_code = f"{func_code}\n{train_func.__name__}({train_func_parameters})\n"
+        func_code = f"{func_code}\n{train_func.__name__}(**{train_func_parameters})\n"
 
     with open(func_file, "w") as f:
         f.write(func_code)
diff --git a/kubeflow/trainer/backends/localprocess/utils_test.py b/kubeflow/trainer/backends/localprocess/utils_test.py
new file mode 100644
index 000000000..853a65582
--- /dev/null
+++ b/kubeflow/trainer/backends/localprocess/utils_test.py
@@ -0,0 +1,86 @@
+# Copyright 2025 The Kubeflow Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+from kubeflow.trainer.backends.localprocess import utils
+from kubeflow.trainer.backends.localprocess.constants import LOCAL_RUNTIME_IMAGE
+from kubeflow.trainer.backends.localprocess.types import LocalRuntimeTrainer
+from kubeflow.trainer.test.common import SUCCESS, TestCase
+from kubeflow.trainer.types import types
+
+
+def _build_runtime() -> types.Runtime:
+    return types.Runtime(
+        name="test-runtime",
+        trainer=LocalRuntimeTrainer(
+            trainer_type=types.TrainerType.CUSTOM_TRAINER,
+            framework="torch",
+            image=LOCAL_RUNTIME_IMAGE,
+        ),
+        kind=types.RuntimeKind.TRAINING_RUNTIME,
+    )
+
+
+def train_with_kwargs(lr: float, num_epochs: int):
+    print(f"Training with lr={lr}, num_epochs={num_epochs}")
+
+
+def train_with_no_args():
+    print("Training with no arguments")
+
+
+@pytest.mark.parametrize(
+    "test_case",
+    [
+        TestCase(
+            name="train func with parameters is called with kwargs unpacking",
+            expected_status=SUCCESS,
+            config={
+                "train_func": train_with_kwargs,
+                "train_func_parameters": {"lr": 0.01, "num_epochs": 5},
+            },
+            expected_output=f"{train_with_kwargs.__name__}(**{{'lr': 0.01, 'num_epochs': 5}})",
+        ),
+        TestCase(
+            name="train func without parameters is called with no arguments",
+            expected_status=SUCCESS,
+            config={
+                "train_func": train_with_no_args,
+                "train_func_parameters": None,
+            },
+            expected_output=f"{train_with_no_args.__name__}()",
+        ),
+    ],
+)
+def test_get_command_using_train_func_generates_valid_call(test_case, tmp_path):
+    runtime = _build_runtime()
+
+    utils.get_command_using_train_func(
+        runtime=runtime,
+        train_func=test_case.config["train_func"],
+        train_func_parameters=test_case.config["train_func_parameters"],
+        venv_dir=str(tmp_path),
+        train_job_name="test-job",
+    )
+
+    func_file = tmp_path / "train_test-job.py"
+    generated_code = func_file.read_text()
+
+    assert test_case.expected_output in generated_code
+    # The generated call must be valid Python that we can actually compile and execute,
+    # proving the training function receives its arguments as named parameters rather
+    # than as a single positional dict.
+    namespace: dict = {}
+    exec(generated_code, namespace)