fix(model): auto-generate ChatResponse.id when LLM doesn't provide it

agentscope-core/src/main/java/io/agentscope/core/model/ChatResponse.java

@@ -18,6 +18,7 @@
 import io.agentscope.core.message.ContentBlock;
 import java.util.List;
 import java.util.Map;
+import java.util.UUID;
 
 /**
  * Represents a chat completion response from a language model.
@@ -176,11 +177,20 @@ public Builder finishReason(String finishReason) {
 
         /**
          * Builds a new ChatResponse instance with the set values.
+         * <p>
+         * If no id was set (or is empty/blank), a random UUID will be generated
+         * automatically. This ensures compatibility with LLM providers (like Ollama)
+         * that don't return an id field in their API responses.
          *
          * @return a new ChatResponse instance
          */
         public ChatResponse build() {
-            return new ChatResponse(id, content, usage, metadata, finishReason);
+            // Auto-generate id if not set, empty, or blank (for providers like Ollama)
+            String responseId = this.id;
+            if (responseId == null || responseId.trim().isEmpty()) {
+                responseId = UUID.randomUUID().toString();
+            }
+            return new ChatResponse(responseId, content, usage, metadata, finishReason);
         }
     }
 }

agentscope-core/src/test/java/io/agentscope/core/formatter/anthropic/AnthropicResponseParserTest.java

@@ -16,6 +16,7 @@
 package io.agentscope.core.formatter.anthropic;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -324,7 +325,8 @@ void testParseStreamEventUnknownType() throws Exception {
         ChatResponse response = invokeParseStreamEvent(event, startTime);
 
         assertNotNull(response);
-        assertNull(response.getId());
+        assertNotNull(response.getId()); // Builder auto-generates UUID when id is null
+        assertFalse(response.getId().isEmpty());
         assertTrue(response.getContent().isEmpty());
         assertNull(response.getUsage());
     }