diff --git a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/AgentUtils.java b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/AgentUtils.java
index 02d9e3d96d..df6bd3ab20 100644
--- a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/AgentUtils.java
+++ b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/AgentUtils.java
@@ -40,6 +40,7 @@ public class AgentUtils {
     public static final String PROMPT_SUFFIX = "prompt.suffix";
     public static final String RESPONSE_FORMAT_INSTRUCTION = "prompt.format_instruction";
     public static final String TOOL_RESPONSE = "prompt.tool_response";
+    public static final String PROMPT_CHAT_HISTORY_PREFIX = "prompt.chat_history_prefix";
     public static final String DISABLE_TRACE = "disable_trace";
     public static final String VERBOSE = "verbose";
 
@@ -182,8 +183,8 @@ public static String extractModelResponseJson(String text, List<String> llmRespo
         }
     }
 
-    public static String findMatchedPart(String text, List<String> llmResponsePatterns) {
-        for (String p : llmResponsePatterns) {
+    public static String findMatchedPart(String text, List<String> patternList) {
+        for (String p : patternList) {
             Pattern pattern = Pattern.compile(p);
             Matcher matcher = pattern.matcher(text);
             if (matcher.find()) {
diff --git a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunner.java b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunner.java
index 8b95a8f78c..621b9884ae 100644
--- a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunner.java
+++ b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunner.java
@@ -12,6 +12,7 @@
 import static org.opensearch.ml.common.utils.StringUtils.isJson;
 import static org.opensearch.ml.common.utils.StringUtils.toJson;
 import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.DISABLE_TRACE;
+import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.PROMPT_CHAT_HISTORY_PREFIX;
 import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.PROMPT_PREFIX;
 import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.PROMPT_SUFFIX;
 import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.RESPONSE_FORMAT_INSTRUCTION;
@@ -23,6 +24,7 @@
 import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.getMlToolSpecs;
 import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.getToolNames;
 import static org.opensearch.ml.engine.algorithms.agent.AgentUtils.outputToOutputString;
+import static org.opensearch.ml.engine.algorithms.agent.PromptTemplate.CHAT_HISTORY_PREFIX;
 
 import java.security.PrivilegedActionException;
 import java.util.ArrayList;
@@ -145,7 +147,8 @@ public void run(MLAgent mlAgent, Map<String, String> params, ActionListener<Obje
 
                 StringBuilder chatHistoryBuilder = new StringBuilder();
                 if (messageList.size() > 0) {
-                    chatHistoryBuilder.append("Human:CONVERSATION HISTORY WITH AI ASSISTANT\n----------------------------\nBelow is Chat History between Human and AI which sorted by time with asc order:\n");
+                    String chatHistoryPrefix = params.getOrDefault(PROMPT_CHAT_HISTORY_PREFIX, CHAT_HISTORY_PREFIX);
+                    chatHistoryBuilder.append(chatHistoryPrefix);
                     for (Message message : messageList) {
                         chatHistoryBuilder.append(message.toString()).append("\n");
                     }
@@ -203,7 +206,6 @@ private void runReAct(
         AtomicInteger traceNumber = new AtomicInteger(0);
 
         AtomicReference<StepListener<MLTaskResponse>> lastLlmListener = new AtomicReference<>();
-//        AtomicBoolean getFinalAnswer = new AtomicBoolean(false);
         AtomicReference<String> lastThought = new AtomicReference<>();
         AtomicReference<String> lastAction = new AtomicReference<>();
         AtomicReference<String> lastActionInput = new AtomicReference<>();
diff --git a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/PromptTemplate.java b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/PromptTemplate.java
index d32d2b3edd..23ff6f9781 100644
--- a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/PromptTemplate.java
+++ b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/PromptTemplate.java
@@ -11,4 +11,5 @@ public class PromptTemplate {
     public static final String PROMPT_TEMPLATE = "\n\nHuman:${parameters.prompt.prefix}\n\n${parameters.prompt.suffix}\n\nHuman: follow RESPONSE FORMAT INSTRUCTIONS\n\nAssistant:";
     public static final String PROMPT_TEMPLATE_TOOL_RESPONSE =
         "Assistant:\n---------------------\n${parameters.llm_tool_selection_response}\n\nHuman: TOOL RESPONSE of ${parameters.tool_name}: \n---------------------\nTool input:\n${parameters.tool_input}\n\nTool output:\n${parameters.observation}\n\n";
+    public static final String CHAT_HISTORY_PREFIX = "Human:CONVERSATION HISTORY WITH AI ASSISTANT\n----------------------------\nBelow is Chat History between Human and AI which sorted by time with asc order:\n";
 }
diff --git a/ml-algorithms/src/main/java/org/opensearch/ml/engine/memory/ConversationIndexMessage.java b/ml-algorithms/src/main/java/org/opensearch/ml/engine/memory/ConversationIndexMessage.java
index 2a084ee9b9..8436d98059 100644
--- a/ml-algorithms/src/main/java/org/opensearch/ml/engine/memory/ConversationIndexMessage.java
+++ b/ml-algorithms/src/main/java/org/opensearch/ml/engine/memory/ConversationIndexMessage.java
@@ -34,7 +34,7 @@ public ConversationIndexMessage(String type, String sessionId, String question,
 
     @Override
     public String toString() {
-        return "Human:" + question + "\nAI:" + response;
+        return "Human:" + question + "\nAssistant:" + response;
     }
 
     @Override