diff --git a/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/main/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPlugin.java b/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/main/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPlugin.java
index b46b56b83dd2..9e380027489c 100644
--- a/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/main/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPlugin.java
+++ b/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/main/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPlugin.java
@@ -111,7 +111,7 @@ private String decorateBody(final String originalBody, final AiPromptConfig aiPr
             prependMap.put(Constants.ROLE, aiPromptConfig.getPreRole());
             decoratedMessages.add(prependMap);
         }
-        decoratedMessages.add(messages.get(0));
+        decoratedMessages.addAll(messages);
         // If append in aiPromptConfig is not empty, add append to the end of message body
         if (Objects.nonNull(aiPromptConfig.getAppend()) && Objects.nonNull(aiPromptConfig.getPostRole())) {
             // Assemble append content role
diff --git a/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/test/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPluginTest.java b/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/test/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPluginTest.java
index b2aeb29b32dc..f4b57e69c469 100644
--- a/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/test/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPluginTest.java
+++ b/shenyu-plugin/shenyu-plugin-ai/shenyu-plugin-ai-prompt/src/test/java/org/apache/shenyu/plugin/ai/prompt/AiPromptPluginTest.java
@@ -17,12 +17,16 @@
 
 package org.apache.shenyu.plugin.ai.prompt;
 
+import org.apache.shenyu.common.dto.convert.plugin.AiPromptConfig;
 import org.apache.shenyu.common.enums.PluginEnum;
+import org.apache.shenyu.common.utils.GsonUtils;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.http.codec.HttpMessageReader;
 
+import java.lang.reflect.Method;
 import java.util.List;
+import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.mock;
@@ -50,4 +54,146 @@ void testGetOrder() {
 
         assertEquals(PluginEnum.AI_PROMPT.getCode(), plugin.getOrder());
     }
+
+    @Test
+    void testDecorateBodyReturnsOriginalWhenNoMessages() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+        String body = "{\"model\":\"gpt-4\"}";
+        String result = invokeDecorateBody(body, config);
+        assertEquals(body, result);
+    }
+
+    @Test
+    void testDecorateBodyReturnsOriginalWhenMessagesEmpty() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+        String body = "{\"messages\":[]}";
+        String result = invokeDecorateBody(body, config);
+        assertEquals(body, result);
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    void testDecorateBodyWithPrependAndAppend() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+        config.setPrepend("system instruction");
+        config.setPreRole("system");
+        config.setAppend("post instruction");
+        config.setPostRole("assistant");
+
+        String body = "{\"messages\":[{\"role\":\"user\",\"content\":\"hello\"}]}";
+        String result = invokeDecorateBody(body, config);
+
+        Map<String, Object> resultMap = GsonUtils.getInstance().convertToMap(result);
+        List<Map<String, Object>> messages = (List<Map<String, Object>>) resultMap.get("messages");
+
+        assertEquals(3, messages.size());
+        assertEquals("system instruction", messages.get(0).get("content"));
+        assertEquals("system", messages.get(0).get("role"));
+        assertEquals("hello", messages.get(1).get("content"));
+        assertEquals("user", messages.get(1).get("role"));
+        assertEquals("post instruction", messages.get(2).get("content"));
+        assertEquals("assistant", messages.get(2).get("role"));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    void testDecorateBodyWithOnlyPrepend() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+        config.setPrepend("system instruction");
+        config.setPreRole("system");
+
+        String body = "{\"messages\":[{\"role\":\"user\",\"content\":\"hello\"}]}";
+        String result = invokeDecorateBody(body, config);
+
+        Map<String, Object> resultMap = GsonUtils.getInstance().convertToMap(result);
+        List<Map<String, Object>> messages = (List<Map<String, Object>>) resultMap.get("messages");
+
+        assertEquals(2, messages.size());
+        assertEquals("system instruction", messages.get(0).get("content"));
+        assertEquals("hello", messages.get(1).get("content"));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    void testDecorateBodyPreservesAllOriginalMessages() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+        config.setPrepend("system prompt");
+        config.setPreRole("system");
+        config.setAppend("footer");
+        config.setPostRole("assistant");
+
+        String body = "{\"messages\":["
+                + "{\"role\":\"system\",\"content\":\"sys\"},"
+                + "{\"role\":\"user\",\"content\":\"hi\"},"
+                + "{\"role\":\"assistant\",\"content\":\"hello\"},"
+                + "{\"role\":\"user\",\"content\":\"how are you\"}"
+                + "]}";
+        String result = invokeDecorateBody(body, config);
+
+        Map<String, Object> resultMap = GsonUtils.getInstance().convertToMap(result);
+        List<Map<String, Object>> messages = (List<Map<String, Object>>) resultMap.get("messages");
+
+        assertEquals(6, messages.size());
+        assertEquals("system prompt", messages.get(0).get("content"));
+        assertEquals("sys", messages.get(1).get("content"));
+        assertEquals("hi", messages.get(2).get("content"));
+        assertEquals("hello", messages.get(3).get("content"));
+        assertEquals("how are you", messages.get(4).get("content"));
+        assertEquals("footer", messages.get(5).get("content"));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    void testDecorateBodyNoPrependOrAppend() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+
+        String body = "{\"messages\":[{\"role\":\"user\",\"content\":\"hello\"}]}";
+        String result = invokeDecorateBody(body, config);
+
+        Map<String, Object> resultMap = GsonUtils.getInstance().convertToMap(result);
+        List<Map<String, Object>> messages = (List<Map<String, Object>>) resultMap.get("messages");
+
+        assertEquals(1, messages.size());
+        assertEquals("hello", messages.get(0).get("content"));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    void testDecorateBodyPrependWithoutRoleIgnored() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+        config.setPrepend("system instruction");
+
+        String body = "{\"messages\":[{\"role\":\"user\",\"content\":\"hello\"}]}";
+        String result = invokeDecorateBody(body, config);
+
+        Map<String, Object> resultMap = GsonUtils.getInstance().convertToMap(result);
+        List<Map<String, Object>> messages = (List<Map<String, Object>>) resultMap.get("messages");
+
+        assertEquals(1, messages.size());
+        assertEquals("hello", messages.get(0).get("content"));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    void testDecorateBodyPreservesOtherFields() throws Exception {
+        AiPromptConfig config = new AiPromptConfig();
+        config.setPrepend("prefix");
+        config.setPreRole("system");
+
+        String body = "{\"model\":\"gpt-4\",\"temperature\":0.7,\"messages\":[{\"role\":\"user\",\"content\":\"hi\"}]}";
+        String result = invokeDecorateBody(body, config);
+
+        Map<String, Object> resultMap = GsonUtils.getInstance().convertToMap(result);
+        assertEquals("gpt-4", resultMap.get("model"));
+        assertEquals(0.7, ((Number) resultMap.get("temperature")).doubleValue(), 0.001);
+
+        List<Map<String, Object>> messages = (List<Map<String, Object>>) resultMap.get("messages");
+        assertEquals(2, messages.size());
+    }
+
+    private String invokeDecorateBody(final String body, final AiPromptConfig config) throws Exception {
+        Method method = AiPromptPlugin.class.getDeclaredMethod("decorateBody", String.class, AiPromptConfig.class);
+        method.setAccessible(true);
+        return (String) method.invoke(plugin, body, config);
+    }
 }