diff --git a/src/google/adk/models/lite_llm.py b/src/google/adk/models/lite_llm.py
index 1eb902630f..ca04c4d71d 100644
--- a/src/google/adk/models/lite_llm.py
+++ b/src/google/adk/models/lite_llm.py
@@ -149,6 +149,7 @@
 # https://ai.google.dev/gemini-api/docs/thought-signatures
 _THOUGHT_SIGNATURE_SEPARATOR = "__thought__"
 
+
 _LITELLM_IMPORTED = False
 _LITELLM_GLOBAL_SYMBOLS = (
     "ChatCompletionAssistantMessage",
diff --git a/tests/unittests/models/test_litellm.py b/tests/unittests/models/test_litellm.py
index 8fda3d98d4..0ac38e5ece 100644
--- a/tests/unittests/models/test_litellm.py
+++ b/tests/unittests/models/test_litellm.py
@@ -2223,6 +2223,64 @@ def test_message_to_generate_content_response_tool_call():
   assert response.content.parts[0].function_call.id == "test_tool_call_id"
 
 
+def test_message_to_generate_content_response_tool_call_with_thought_signature():
+  signature = b"gemini_signature"
+  encoded_signature = base64.b64encode(signature).decode("utf-8")
+  message = ChatCompletionAssistantMessage(
+      role="assistant",
+      content=None,
+      tool_calls=[
+          ChatCompletionMessageToolCall(
+              type="function",
+              id="test_tool_call_id",
+              function=Function(
+                  name="test_function",
+                  arguments='{"test_arg": "test_value"}',
+              ),
+              provider_specific_fields={"thought_signature": encoded_signature},
+              extra_content={"google": {"thought_signature": encoded_signature}},
+          )
+      ],
+  )
+
+  response = _message_to_generate_content_response(message)
+  assert response.content.role == "model"
+  assert response.content.parts[0].function_call.name == "test_function"
+  assert response.content.parts[0].function_call.args == {
+      "test_arg": "test_value"
+  }
+  assert response.content.parts[0].function_call.id == "test_tool_call_id"
+  assert response.content.parts[0].thought_signature == signature
+
+
+@pytest.mark.asyncio
+async def test_content_to_message_param_embeds_thought_signature_in_tool_call():
+  part = types.Part.from_function_call(
+      name="test_function",
+      args={"test_arg": "test_value"},
+  )
+  part.function_call.id = "test_tool_call_id"
+  part.thought_signature = b"gemini_signature"
+  content = types.Content(role="model", parts=[part])
+
+  message = await _content_to_message_param(content)
+
+  tool_calls = message["tool_calls"]
+  assert tool_calls is not None
+  assert len(tool_calls) == 1
+  assert tool_calls[0]["id"] == "test_tool_call_id"
+  assert tool_calls[0]["provider_specific_fields"] == {
+      "thought_signature": base64.b64encode(b"gemini_signature").decode("utf-8")
+  }
+  assert tool_calls[0]["extra_content"] == {
+      "google": {
+          "thought_signature": base64.b64encode(b"gemini_signature").decode(
+              "utf-8"
+          )
+      }
+  }
+
+
 def test_message_to_generate_content_response_inline_tool_call_text():
   message = ChatCompletionAssistantMessage(
       role="assistant",