Fix UUID non-determinism, null metadata NPE, and unbounded tool loop

T5: Replace UUID.randomUUID() with Workflow.randomUUID() in
LocalActivityToolCallbackWrapper to ensure deterministic replay.

T7: Convert recursive tool call loop in ActivityChatModel.call() to
iterative loop with MAX_TOOL_CALL_ITERATIONS (10) limit to prevent
infinite recursion from misbehaving models.

T14: Fix NPE when ChatResponse metadata is null by only calling
.metadata() on the builder when metadata is non-null.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: donald-pinckney

temporal-spring-ai/src/main/java/io/temporal/springai/model/ActivityChatModel.java

@@ -83,6 +83,9 @@ public class ActivityChatModel implements ChatModel {
   /** Default maximum retry attempts for chat model activity calls. */
   public static final int DEFAULT_MAX_ATTEMPTS = 3;
 
+  /** Maximum number of tool call iterations before aborting to prevent infinite loops. */
+  public static final int MAX_TOOL_CALL_ITERATIONS = 10;
+
   private final ChatModelActivity chatModelActivity;
   private final String modelName;
   private final ToolCallingManager toolCallingManager;
@@ -190,33 +193,41 @@ public ChatOptions getDefaultOptions() {
 
   @Override
   public ChatResponse call(Prompt prompt) {
-    // Convert prompt to activity input and call the activity
-    ChatModelTypes.ChatModelActivityInput input = createActivityInput(prompt);
-    ChatModelTypes.ChatModelActivityOutput output = chatModelActivity.callChatModel(input);
+    Prompt currentPrompt = prompt;
+
+    for (int iteration = 0; iteration < MAX_TOOL_CALL_ITERATIONS; iteration++) {
+      // Convert prompt to activity input and call the activity
+      ChatModelTypes.ChatModelActivityInput input = createActivityInput(currentPrompt);
+      ChatModelTypes.ChatModelActivityOutput output = chatModelActivity.callChatModel(input);
 
-    // Convert activity output to ChatResponse
-    ChatResponse response = toResponse(output);
+      // Convert activity output to ChatResponse
+      ChatResponse response = toResponse(output);
 
-    // Handle tool calls if the model requested them
-    if (prompt.getOptions() != null
-        && toolExecutionEligibilityPredicate.isToolExecutionRequired(
-            prompt.getOptions(), response)) {
+      // If no tool calls requested, return the response
+      if (currentPrompt.getOptions() == null
+          || !toolExecutionEligibilityPredicate.isToolExecutionRequired(
+              currentPrompt.getOptions(), response)) {
+        return response;
+      }
 
-      var toolExecutionResult = toolCallingManager.executeToolCalls(prompt, response);
+      var toolExecutionResult = toolCallingManager.executeToolCalls(currentPrompt, response);
 
       if (toolExecutionResult.returnDirect()) {
-        // Return tool execution result directly
         return ChatResponse.builder()
             .from(response)
             .generations(ToolExecutionResult.buildGenerations(toolExecutionResult))
             .build();
-      } else {
-        // Send tool results back to the model (recursive call)
-        return call(new Prompt(toolExecutionResult.conversationHistory(), prompt.getOptions()));
       }
+
+      // Continue loop with tool results sent back to the model
+      currentPrompt =
+          new Prompt(toolExecutionResult.conversationHistory(), currentPrompt.getOptions());
     }
 
-    return response;
+    throw new IllegalStateException(
+        "Chat model exceeded maximum tool call iterations ("
+            + MAX_TOOL_CALL_ITERATIONS
+            + "). This may indicate the model is stuck in a tool-calling loop.");
   }
 
   private ChatModelTypes.ChatModelActivityInput createActivityInput(Prompt prompt) {
@@ -341,12 +352,11 @@ private ChatResponse toResponse(ChatModelTypes.ChatModelActivityOutput output) {
             .map(gen -> new Generation(toAssistantMessage(gen.message())))
             .collect(Collectors.toList());
 
-    ChatResponseMetadata metadata = null;
+    var builder = ChatResponse.builder().generations(generations);
     if (output.metadata() != null) {
-      metadata = ChatResponseMetadata.builder().model(output.metadata().model()).build();
+      builder.metadata(ChatResponseMetadata.builder().model(output.metadata().model()).build());
     }
-
-    return ChatResponse.builder().generations(generations).metadata(metadata).build();
+    return builder.build();
   }
 
   private AssistantMessage toAssistantMessage(ChatModelTypes.Message message) {

temporal-spring-ai/src/main/java/io/temporal/springai/tool/LocalActivityToolCallbackWrapper.java

@@ -4,7 +4,6 @@
 import io.temporal.workflow.Workflow;
 import java.time.Duration;
 import java.util.Map;
-import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 import org.springframework.ai.chat.model.ToolContext;
 import org.springframework.ai.tool.ToolCallback;
@@ -87,7 +86,7 @@ public ToolMetadata getToolMetadata() {
 
   @Override
   public String call(String toolInput) {
-    String callbackId = UUID.randomUUID().toString();
+    String callbackId = Workflow.randomUUID().toString();
     try {
       CALLBACK_REGISTRY.put(callbackId, delegate);
       return stub.call(callbackId, toolInput);