diff --git a/fiddle/_src/validation/baseline_style.py b/fiddle/_src/validation/baseline_style.py
new file mode 100644
index 00000000..748d8204
--- /dev/null
+++ b/fiddle/_src/validation/baseline_style.py
@@ -0,0 +1,61 @@
+# coding=utf-8
+# Copyright 2022 The Fiddle-Config 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.
+
+"""Programmatic checks for the style of a baseline configuration.
+
+"Baseline configurations" are configurations for baseline or flagship models.
+They will be read by a large number of people, so keeping them simple and
+readable is important.
+"""
+
+from typing import Any
+
+from fiddle._src import config as config_lib
+from fiddle._src import daglish
+from fiddle._src import history
+
+
+def check_baseline_style(
+    config: Any,
+    *,
+    max_files_writing_attributes: int = 3,
+) -> None:
+  """Checks that a configuration is style-conformant."""
+
+  # filename --> sample path.
+  sample_paths_by_file = {}
+
+  for value, path in daglish.iterate(config):
+    if isinstance(value, config_lib.Buildable):
+      for attr_name in config_lib.ordered_arguments(value).keys():
+        path_str = daglish.path_str((*path, daglish.Attr(attr_name)))
+        attr_history = value.__argument_history__[attr_name]
+        for history_entry in attr_history:
+          location: history.Location = history_entry.location
+          sample_paths_by_file.setdefault(location.filename, path_str)
+      pass
+
+  if len(sample_paths_by_file) > max_files_writing_attributes:
+    debug_str = ", ".join(
+        f"{filename} (example: wrote to <config>{path})"
+        for filename, path in sample_paths_by_file.items()
+    )
+    raise ValueError(
+        f"More than {max_files_writing_attributes} file(s) produced this"
+        " config. For baseline configurations, please ensure that you don't"
+        " have a big hierarchy of files each overriding values in a config,"
+        " because this is harder to read for new users. The files which have"
+        f" written to this config are: {debug_str}."
+    )
diff --git a/fiddle/_src/validation/baseline_style_test.py b/fiddle/_src/validation/baseline_style_test.py
new file mode 100644
index 00000000..4a950855
--- /dev/null
+++ b/fiddle/_src/validation/baseline_style_test.py
@@ -0,0 +1,47 @@
+# coding=utf-8
+# Copyright 2022 The Fiddle-Config 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.
+
+"""Tests for baseline_style."""
+
+
+from absl.testing import absltest
+from fiddle._src.testing.example import fake_encoder_decoder
+from fiddle._src.validation import fake_experiment
+from fiddle.validation import baseline_style
+
+
+class BaselineStyleTest(absltest.TestCase):
+
+  def test_check_baseline_style_okay(self):
+    config = fake_encoder_decoder.fixture.as_buildable()
+    baseline_style.check_baseline_style(
+        config=config, max_files_writing_attributes=1
+    )
+
+  def test_check_baseline_style_too_many_files(self):
+    config = fake_experiment.fake_experiment()
+    with self.assertRaisesRegex(
+        ValueError,
+        r"More than 1 file\(s\) produced this config.*files which have"
+        r" written.*fake_encoder_decoder.*\.encoder.*"
+        r"fake_experiment.*encoder\.attention\.dtype",
+    ):
+      baseline_style.check_baseline_style(
+          config=config, max_files_writing_attributes=1
+      )
+
+
+if __name__ == "__main__":
+  absltest.main()
diff --git a/fiddle/_src/validation/fake_experiment.py b/fiddle/_src/validation/fake_experiment.py
new file mode 100644
index 00000000..ae315af6
--- /dev/null
+++ b/fiddle/_src/validation/fake_experiment.py
@@ -0,0 +1,24 @@
+# coding=utf-8
+# Copyright 2022 The Fiddle-Config 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.
+
+"""Fake experiment overrides for the encoder-decoder."""
+
+from fiddle._src.testing.example import fake_encoder_decoder
+
+
+def fake_experiment():
+  config = fake_encoder_decoder.fixture.as_buildable()
+  config.encoder.attention.dtype = "float64"
+  return config
diff --git a/fiddle/validation/baseline_style.py b/fiddle/validation/baseline_style.py
new file mode 100644
index 00000000..8f44b440
--- /dev/null
+++ b/fiddle/validation/baseline_style.py
@@ -0,0 +1,24 @@
+# coding=utf-8
+# Copyright 2022 The Fiddle-Config 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.
+
+"""Programmatic checks for the style of a baseline configuration.
+
+"Baseline configurations" are configurations for baseline or flagship models.
+They will be read by a large number of people, so keeping them simple and
+readable is important.
+"""
+
+# pylint: disable=unused-import
+from fiddle._src.validation.baseline_style import check_baseline_style