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 3992b9f341..5809101be4 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
@@ -36,6 +36,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 
+import org.apache.commons.lang3.StringUtils;
 import org.apache.commons.text.StringSubstitutor;
 import org.opensearch.action.ActionRequest;
 import org.opensearch.action.StepListener;
@@ -121,12 +122,17 @@ public MLChatAgentRunner(
 
     @Override
     public void run(MLAgent mlAgent, Map<String, String> params, ActionListener<Object> listener) {
-        String memoryType = mlAgent.getMemory().getType();
+        String memoryType = mlAgent.getMemory() == null ? null : mlAgent.getMemory().getType();
         String memoryId = params.get(MLAgentExecutor.MEMORY_ID);
         String appType = mlAgent.getAppType();
         String title = params.get(MLAgentExecutor.QUESTION);
         int messageHistoryLimit = getMessageHistoryLimit(params);
 
+        if (StringUtils.isEmpty(memoryType)) {
+            runAgent(mlAgent, params, listener, null, null);
+            return;
+        }
+
         ConversationIndexMemory.Factory conversationIndexMemoryFactory = (ConversationIndexMemory.Factory) memoryFactoryMap.get(memoryType);
         conversationIndexMemoryFactory.create(title, memoryId, appType, ActionListener.<ConversationIndexMemory>wrap(memory -> {
             // TODO: call runAgent directly if messageHistoryLimit == 0
@@ -151,8 +157,8 @@ public void run(MLAgent mlAgent, Map<String, String> params, ActionListener<Obje
                         );
                 }
 
-                StringBuilder chatHistoryBuilder = new StringBuilder();
                 if (!messageList.isEmpty()) {
+                    StringBuilder chatHistoryBuilder = new StringBuilder();
                     String chatHistoryPrefix = params.getOrDefault(PROMPT_CHAT_HISTORY_PREFIX, CHAT_HISTORY_PREFIX);
                     chatHistoryBuilder.append(chatHistoryPrefix);
                     for (Message message : messageList) {
@@ -220,7 +226,9 @@ private void runReAct(
         AtomicReference<String> newPrompt = new AtomicReference<>(tmpSubstitutor.replace(prompt));
         tmpParameters.put(PROMPT, newPrompt.get());
 
-        List<ModelTensors> traceTensors = createModelTensors(sessionId, parentInteractionId);
+        List<ModelTensors> traceTensors = (conversationIndexMemory == null)
+            ? new ArrayList<>()
+            : createModelTensors(sessionId, parentInteractionId);
         int maxIterations = Integer.parseInt(tmpParameters.getOrDefault(MAX_ITERATION, "3")) * 2;
         for (int i = 0; i < maxIterations; i++) {
             int finalI = i;
@@ -401,8 +409,8 @@ private void runReAct(
         client.execute(MLPredictionTaskAction.INSTANCE, request, firstListener);
     }
 
-    private static List<ModelTensors> createFinalAnswerTensors(List<ModelTensors> sessionId, List<ModelTensor> lastThought) {
-        List<ModelTensors> finalModelTensors = sessionId;
+    private static List<ModelTensors> createFinalAnswerTensors(List<ModelTensors> modelTensorsList, List<ModelTensor> lastThought) {
+        List<ModelTensors> finalModelTensors = modelTensorsList;
         finalModelTensors.add(ModelTensors.builder().mlModelTensors(lastThought).build());
         return finalModelTensors;
     }
@@ -572,19 +580,21 @@ private void sendFinalAnswer(
     private static List<ModelTensors> createModelTensors(String sessionId, String parentInteractionId) {
         List<ModelTensors> cotModelTensors = new ArrayList<>();
 
-        cotModelTensors
-            .add(
-                ModelTensors
-                    .builder()
-                    .mlModelTensors(
-                        List
-                            .of(
-                                ModelTensor.builder().name(MLAgentExecutor.MEMORY_ID).result(sessionId).build(),
-                                ModelTensor.builder().name(MLAgentExecutor.PARENT_INTERACTION_ID).result(parentInteractionId).build()
-                            )
-                    )
-                    .build()
-            );
+        if (!StringUtils.isEmpty(sessionId)) {
+            cotModelTensors
+                .add(
+                    ModelTensors
+                        .builder()
+                        .mlModelTensors(
+                            List
+                                .of(
+                                    ModelTensor.builder().name(MLAgentExecutor.MEMORY_ID).result(sessionId).build(),
+                                    ModelTensor.builder().name(MLAgentExecutor.PARENT_INTERACTION_ID).result(parentInteractionId).build()
+                                )
+                        )
+                        .build()
+                );
+        }
         return cotModelTensors;
     }
 
diff --git a/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunnerTest.java b/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunnerTest.java
index 0fb416f0bf..9f9d881019 100644
--- a/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunnerTest.java
+++ b/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunnerTest.java
@@ -879,6 +879,42 @@ public void testToolExecutionWithChatHistoryParameter() {
         Assert.assertTrue(toolParamsCapture.getValue().containsKey(MLChatAgentRunner.CHAT_HISTORY));
     }
 
+    @Test
+    public void testParsingJsonBlockFromResponseNoMemory() {
+        // Prepare the response with JSON block
+        String jsonBlock = "{\"thought\":\"parsed thought\", \"action\":\"parsed action\", "
+            + "\"action_input\":\"parsed action input\", \"final_answer\":\"parsed final answer\"}";
+        String responseWithJsonBlock = "Some text```json" + jsonBlock + "```More text";
+
+        // Mock LLM response to not contain "thought" but contain "response" with JSON block
+        Map<String, String> llmResponse = new HashMap<>();
+        llmResponse.put("response", responseWithJsonBlock);
+        doAnswer(getLLMAnswer(llmResponse))
+            .when(client)
+            .execute(any(ActionType.class), any(ActionRequest.class), isA(ActionListener.class));
+
+        // Create an MLAgent and run the MLChatAgentRunner
+        MLAgent mlAgent = createMLAgentNoMemory();
+        Map<String, String> params = new HashMap<>();
+        params.put("verbose", "true");
+        mlChatAgentRunner.run(mlAgent, params, agentActionListener);
+
+        // Capture the response passed to the listener
+        ArgumentCaptor<Object> responseCaptor = ArgumentCaptor.forClass(Object.class);
+        verify(agentActionListener).onResponse(responseCaptor.capture());
+
+        // Extract the captured response
+        Object capturedResponse = responseCaptor.getValue();
+        assertTrue(capturedResponse instanceof ModelTensorOutput);
+        ModelTensorOutput modelTensorOutput = (ModelTensorOutput) capturedResponse;
+
+        ModelTensor modelTensor = modelTensorOutput.getMlModelOutputs().get(0).getMlModelTensors().get(0);
+
+        assertEquals(1, modelTensorOutput.getMlModelOutputs().size());
+        assertEquals(1, modelTensorOutput.getMlModelOutputs().get(0).getMlModelTensors().size());
+        assertEquals("parsed final answer", modelTensor.getResult());
+    }
+
     // Helper methods to create MLAgent and parameters
     private MLAgent createMLAgentWithTools() {
         LLMSpec llmSpec = LLMSpec.builder().modelId("MODEL_ID").build();
@@ -917,6 +953,23 @@ private MLAgent createMLAgentWithToolsConfig(Map<String, String> configMap) {
             .build();
     }
 
+    private MLAgent createMLAgentNoMemory() {
+        LLMSpec llmSpec = LLMSpec.builder().modelId("MODEL_ID").build();
+        MLToolSpec firstToolSpec = MLToolSpec
+            .builder()
+            .name(FIRST_TOOL)
+            .type(FIRST_TOOL)
+            .parameters(ImmutableMap.of("key1", "value1", "key2", "value2"))
+            .build();
+        return MLAgent
+            .builder()
+            .name("TestAgent")
+            .type(MLAgentType.CONVERSATIONAL.name())
+            .tools(Arrays.asList(firstToolSpec))
+            .llm(llmSpec)
+            .build();
+    }
+
     private Map<String, String> createAgentParamsWithAction(String action, String actionInput) {
         Map<String, String> params = new HashMap<>();
         params.put("action", action);