diff --git a/src/google/adk/agents/base_agent_config.py b/src/google/adk/agents/base_agent_config.py
index 178587b8..57979f0e 100644
--- a/src/google/adk/agents/base_agent_config.py
+++ b/src/google/adk/agents/base_agent_config.py
@@ -79,12 +79,3 @@ Example:
       default=None,
       description='Optional. The after_agent_callbacks of the agent.',
   )
-
-  def to_agent_config(
-      self, custom_agent_config_cls: Type[TBaseAgentConfig]
-  ) -> TBaseAgentConfig:
-    """Converts this config to the concrete agent config type.
-
-    NOTE: this is for ADK framework use only.
-    """
-    return custom_agent_config_cls.model_validate(self.model_dump())
diff --git a/tests/unittests/agents/test_agent_config.py b/tests/unittests/agents/test_agent_config.py
index d7c3f078..ffe190e1 100644
--- a/tests/unittests/agents/test_agent_config.py
+++ b/tests/unittests/agents/test_agent_config.py
@@ -1,3 +1,17 @@
+# Copyright 2025 Google LLC
+#
+# 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.
+
 from typing import Literal
 
 from google.adk.agents.agent_config import AgentConfig
@@ -115,9 +129,12 @@ other_field: other value
 
   config = AgentConfig.model_validate(config_data)
 
-  assert isinstance(config.root, BaseAgentConfig)
+  # pylint: disable=unidiomatic-typecheck Needs exact class matching.
+  assert type(config.root) is BaseAgentConfig
   assert config.root.agent_class == "mylib.agents.MyCustomAgent"
   assert config.root.model_extra == {"other_field": "other value"}
 
-  my_custom_config = config.root.to_agent_config(MyCustomAgentConfig)
+  my_custom_config = MyCustomAgentConfig.model_validate(
+      config.root.model_dump()
+  )
   assert my_custom_config.other_field == "other value"