diff --git a/tunix/cli/base_config.yaml b/tunix/cli/base_config.yaml
index d949e0bf..1a9b2641 100644
--- a/tunix/cli/base_config.yaml
+++ b/tunix/cli/base_config.yaml
@@ -12,6 +12,22 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+
+################################# LoRa #################################
+_lora_config: &base_lora_config
+  module_path: ".*q_einsum|.*kv_einsum|.*gate_proj|.*down_proj|.*up_proj"
+  rank: 16
+  alpha: 2.0
+  weight_qtype: "nf4"
+  tile_size: 256
+
+################################## MESH ##################################
+_mesh: &base_mesh
+  shape: "(2,2)"
+  # "('fsdp',)"
+  axis_names: "('fsdp','tp')"
+
+
 ################################## LOAD MODEL ##################################
 model_config: &base_model_config
   # Specify model name in style of {model_version}-{model size}, this will use to invoke model config
@@ -45,28 +61,26 @@ model_config: &base_model_config
 
   # Directory used for NNX conversion if downloaded Gemma/Gemma2 from Kaggle source. 
   intermediate_ckpt_dir: "/tmp/intermediate_ckpt/"
-  ################################# LoRa #################################
-  lora_config:
-    module_path: ".*q_einsum|.*kv_einsum|.*gate_proj|.*down_proj|.*up_proj"
-    rank: 16
-    alpha: 2.0
-    weight_qtype: "nf4"
-    tile_size: 256
 
-  ################################## MESH ##################################
+  lora_config:
+    <<: *base_lora_config
   mesh:
-    shape: "(2,2)"
-    # "('fsdp',)"
-    axis_names: "('fsdp','tp')"
+    <<: *base_mesh
+
 
 actor_model_config:
-  <<: *base_model_config
+  lora_config:
+    <<: *base_lora_config
+  mesh:
+    <<: *base_mesh
 
 reference_model_config:
  <<: *base_model_config
 
 rollout_model_config:
- <<: *base_model_config
+  mesh:
+    <<: *base_mesh
+
 
 ################################## Tokenizer ##################################
 tokenizer_config:
diff --git a/tunix/cli/config.py b/tunix/cli/config.py
index 11a6dfc7..0ed093b8 100644
--- a/tunix/cli/config.py
+++ b/tunix/cli/config.py
@@ -174,6 +174,25 @@ def __init__(self, argv: list[str], **kwargs):
         keys_from_env_and_command_line,
     )
     self.config = raw_keys
+
+    # If no model_config related thing is overwritten, clone reference_model_config to model_config
+    model_config_overwritten = any(
+        k == "model_config" or k.startswith("model_config.")
+        for k in keys_from_env_and_command_line
+    )
+    if (
+        not model_config_overwritten
+        and "reference_model_config" in self.config
+        and self.config.get("reference_model_config")
+    ):
+      logging.info(
+          "No model_config overrides detected, cloning reference_model_config"
+          " to model_config"
+      )
+      self.config["model_config"] = copy.deepcopy(
+          self.config["reference_model_config"]
+      )
+
     self._validate_tokenizer()
     self._validate_model_source(raw_keys)
     self.check_supported_workflow()
@@ -776,6 +795,9 @@ def _load_config_from_yaml(self, config_path: str):
       config_oconf = omegaconf.OmegaConf.load(config_path)
     except FileNotFoundError as e:
       raise ValueError(f"Config {config_path} not found.") from e
+    for key in list(config_oconf.keys()):
+      if key.startswith("_"):
+        del config_oconf[key]
 
     return config_oconf