diff --git a/app/src/chat_engine.py b/app/src/chat_engine.py
index 2dfbda4e..41403545 100644
--- a/app/src/chat_engine.py
+++ b/app/src/chat_engine.py
@@ -86,7 +86,9 @@ def __init__(self) -> None:
         super().__init__()
 
     @abstractmethod
-    def on_message(self, question: str, chat_history: Optional[ChatHistory]) -> OnMessageResult:
+    def on_message(
+        self, question: str, chat_history: Optional[ChatHistory] = None
+    ) -> OnMessageResult:
         pass
 
 
@@ -131,7 +133,9 @@ class BaseEngine(ChatEngineInterface):
 
     formatting_config = FormattingConfig()
 
-    def on_message(self, question: str, chat_history: Optional[ChatHistory]) -> OnMessageResult:
+    def on_message(
+        self, question: str, chat_history: Optional[ChatHistory] = None
+    ) -> OnMessageResult:
         attributes = analyze_message(self.llm, self.system_prompt_1, question, MessageAttributes)
 
         if attributes.needs_context:
@@ -299,7 +303,7 @@ class ImagineLaEngine(BaseEngine):
 - LGBTQ resources: https://dpss.lacounty.gov/en/rights/rights/sogie.html
 
 If the user's question is related to any of the following policy updates listed below, set canned_response to empty string and \
-set alert_message to one or more of the following text based on the user's question: 
+set alert_message to one or more of the following text based on the user's question:
 - Benefits application website: "YourBenefitsNow(YBN) no longer exists. Instead people use [benefitscal.com](https://benefitscal.com/) to apply for and manage \
 CalWorks, CalFresh, General Relief and Medi-Cal applications and documents. People can also apply for Medi-Cal and health insurance at coveredca.com."
 - Medicaid for immigrants: "Since January 1, 2024, a new law in California will allow adults ages 26 through 49 to qualify for full-scope Medi-Cal, \
@@ -331,7 +335,9 @@ class ImagineLaEngine(BaseEngine):
 
 {PROMPT}"""
 
-    def on_message(self, question: str, chat_history: Optional[ChatHistory]) -> OnMessageResult:
+    def on_message(
+        self, question: str, chat_history: Optional[ChatHistory] = None
+    ) -> OnMessageResult:
         attributes = analyze_message(
             self.llm, self.system_prompt_1, question, response_format=ImagineLA_MessageAttributes
         )
diff --git a/app/tests/src/test_chat_engine.py b/app/tests/src/test_chat_engine.py
index 3f91c35d..10938a33 100644
--- a/app/tests/src/test_chat_engine.py
+++ b/app/tests/src/test_chat_engine.py
@@ -1,5 +1,5 @@
 from src import chat_engine
-from src.chat_engine import CaEddWebEngine, ImagineLaEngine
+from src.chat_engine import CaEddWebEngine, ImagineLA_MessageAttributes, ImagineLaEngine
 
 
 def test_available_engines():
@@ -33,3 +33,58 @@ def test_create_engine_Imagine_LA():
         "WIC",
         "Covered California",
     ]
+
+
+def test_on_message_Imagine_LA_canned_response(monkeypatch):
+    def mock_analyze_message(llm: str, system_prompt: str, message: str, response_format):
+        return ImagineLA_MessageAttributes(
+            needs_context=True,
+            translated_message="",
+            canned_response="This is a canned response",
+            alert_message="",
+        )
+
+    monkeypatch.setattr(chat_engine, "analyze_message", mock_analyze_message)
+
+    engine = chat_engine.create_engine("imagine-la")
+    result = engine.on_message("What is AI?")
+    assert result.response == "This is a canned response"
+    assert result.attributes.alert_message == ""
+
+
+def test_on_message_Imagine_LA_alert_message(monkeypatch):
+    def mock_analyze_message(llm: str, system_prompt: str, message: str, response_format):
+        return ImagineLA_MessageAttributes(
+            needs_context=True,
+            translated_message="",
+            canned_response="",
+            alert_message="Some alert message",
+        )
+
+    monkeypatch.setattr(chat_engine, "analyze_message", mock_analyze_message)
+
+    def mock_generate(
+        llm: str,
+        system_prompt: str,
+        query: str,
+        context_text = None,
+        chat_history = None,
+    ) -> str:
+        return "This is a generated response"
+
+    monkeypatch.setattr(chat_engine, "generate", mock_generate)
+
+    def mock_retrieve_with_scores(
+        query: str,
+        retrieval_k: int,
+        retrieval_k_min_score: float,
+        **filters,
+    ):
+        return []
+
+    monkeypatch.setattr(chat_engine, "retrieve_with_scores", mock_retrieve_with_scores)
+
+    engine = chat_engine.create_engine("imagine-la")
+    result = engine.on_message("What is AI?")
+    assert result.attributes.alert_message.startswith("**Policy update**: ")
+    assert result.attributes.alert_message.endswith("\n\nThe rest of this answer may be outdated.")