From 453fbab3d69aed3f5564683bf9b22591f76805d6 Mon Sep 17 00:00:00 2001
From: Nathalie Jonathan <nathhjo@amazon.com>
Date: Fri, 17 Oct 2025 15:01:38 -0700
Subject: [PATCH] Fix unsupported operation exception in execute tool API

Signed-off-by: Nathalie Jonathan <nathhjo@amazon.com>
---
 .../algorithms/tool/MLToolExecutor.java       |  7 +++--
 .../algorithms/tool/MLToolExecutorTest.java   | 28 ++++++++++++++++++-
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutor.java b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutor.java
index e92f722611..481e3b2dc2 100644
--- a/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutor.java
+++ b/ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutor.java
@@ -83,13 +83,14 @@ public void execute(Input input, ActionListener<Output> listener) {
         }
 
         try {
-            Tool tool = toolFactory.create(new HashMap<>(parameters));
-            if (!tool.validate(parameters)) {
+            Map<String, String> mutableParams = new HashMap<>(parameters);
+            Tool tool = toolFactory.create(mutableParams);
+            if (!tool.validate(mutableParams)) {
                 listener.onFailure(new IllegalArgumentException("Invalid parameters for tool: " + toolName));
                 return;
             }
 
-            tool.run(parameters, ActionListener.wrap(result -> {
+            tool.run(mutableParams, ActionListener.wrap(result -> {
                 List<ModelTensor> modelTensors = new ArrayList<>();
                 processOutput(result, modelTensors);
                 ModelTensors tensors = ModelTensors.builder().mlModelTensors(modelTensors).build();
diff --git a/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutorTest.java b/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutorTest.java
index 6c76a88991..58bd2199c8 100644
--- a/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutorTest.java
+++ b/ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/tool/MLToolExecutorTest.java
@@ -8,6 +8,7 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.when;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
@@ -41,7 +42,6 @@ public class MLToolExecutorTest {
     private Client client;
     @Mock
     private SdkClient sdkClient;
-    private Settings settings;
     @Mock
     private ClusterService clusterService;
     @Mock
@@ -176,4 +176,30 @@ public void test_EmptyInputData() {
             mlToolExecutor.execute(toolMLInput, actionListener);
         });
     }
+
+    @Test
+    public void test_ImmutableEmptyParametersMap() {
+        Map<String, String> immutableEmptyMap = Collections.emptyMap();
+
+        when(toolMLInput.getToolName()).thenReturn("TestTool");
+        when(toolMLInput.getInputDataset()).thenReturn(inputDataSet);
+        when(inputDataSet.getParameters()).thenReturn(immutableEmptyMap);
+        when(toolFactory.create(any())).thenReturn(tool);
+        when(tool.validate(any())).thenReturn(true);
+
+        Mockito.doAnswer(invocation -> {
+            Map<String, String> params = invocation.getArgument(0);
+            // Tool tries to modify parameters, should not throw exception
+            params.put("test_key", "test_value");
+            ActionListener<Object> listener = invocation.getArgument(1);
+            listener.onResponse("test result");
+            return null;
+        }).when(tool).run(any(), any());
+
+        mlToolExecutor.execute(toolMLInput, actionListener);
+
+        Mockito.verify(actionListener).onResponse(outputCaptor.capture());
+        Output output = outputCaptor.getValue();
+        Assert.assertTrue(output instanceof ModelTensorOutput);
+    }
 }