feat: 支持配置 system 消息内容格式

- 为 OpenAI 兼容模型增加字符串与文本数组两种 system content 策略

- 在 AgentScope 模型工厂统一安装兼容 formatter 并补充测试

easy-agents-agent-runtime/src/main/java/com/easyagents/agent/runtime/agentscope/AgentOpenAIChatFormatter.java

@@ -0,0 +1,31 @@
+package com.easyagents.agent.runtime.agentscope;
+
+import io.agentscope.core.formatter.openai.OpenAIChatFormatter;
+import io.agentscope.core.formatter.openai.dto.OpenAIContentPart;
+import io.agentscope.core.formatter.openai.dto.OpenAIMessage;
+import io.agentscope.core.message.Msg;
+
+import java.util.List;
+
+/**
+ * 为 OpenAI-compatible 模型补充 system content 内容块数组兼容能力。
+ */
+public final class AgentOpenAIChatFormatter extends OpenAIChatFormatter {
+
+    /**
+     * 将 AgentScope 消息转换为 OpenAI 消息，并规范 system 文本的 content 格式。
+     *
+     * @param messages AgentScope 消息
+     * @return OpenAI 请求消息
+     */
+    @Override
+    protected List<OpenAIMessage> doFormat(List<Msg> messages) {
+        List<OpenAIMessage> formattedMessages = super.doFormat(messages);
+        for (OpenAIMessage message : formattedMessages) {
+            if ("system".equals(message.getRole()) && message.getContent() instanceof String text) {
+                message.setContent(List.of(OpenAIContentPart.text(text)));
+            }
+        }
+        return formattedMessages;
+    }
+}

easy-agents-agent-runtime/src/main/java/com/easyagents/agent/runtime/agentscope/AgentScopeModelFactory.java

@@ -6,6 +6,7 @@ import com.easyagents.agent.runtime.model.AgentHttpVersionPolicy;
 import com.easyagents.agent.runtime.model.AgentModelFactory;
 import com.easyagents.agent.runtime.model.AgentModelProviderType;
 import com.easyagents.agent.runtime.model.AgentModelSpec;
+import com.easyagents.agent.runtime.model.AgentSystemContentFormat;
 import io.agentscope.core.formatter.openai.DeepSeekFormatter;
 import io.agentscope.core.formatter.openai.GLMFormatter;
 import io.agentscope.core.model.*;
@@ -153,6 +154,9 @@ public class AgentScopeModelFactory implements AgentModelFactory<Model> {
                 .stream(Boolean.TRUE.equals(options.getStream()))
                 .httpTransport(httpTransportProvider.getTransport(modelSpec.getHttpVersionPolicy(), baseUrl))
                 .generateOptions(options);
+        if (modelSpec.getSystemContentFormat() == AgentSystemContentFormat.TEXT_PARTS) {
+            builder.formatter(new AgentOpenAIChatFormatter());
+        }
         return builder.build();
     }
 

easy-agents-agent-runtime/src/main/java/com/easyagents/agent/runtime/model/AgentModelSpec.java

@@ -16,6 +16,7 @@ public class AgentModelSpec {
     private boolean supportImage;
     private boolean supportImageBase64Only;
     private AgentHttpVersionPolicy httpVersionPolicy = AgentHttpVersionPolicy.AUTO;
+    private AgentSystemContentFormat systemContentFormat = AgentSystemContentFormat.STRING;
     private Map<String, Object> metadata = new LinkedHashMap<>();
 
     /**
@@ -162,6 +163,26 @@ public class AgentModelSpec {
         this.httpVersionPolicy = httpVersionPolicy == null ? AgentHttpVersionPolicy.AUTO : httpVersionPolicy;
     }
 
+    /**
+     * 获取 OpenAI-compatible 请求中的 system content 格式。
+     *
+     * @return system content 格式
+     */
+    public AgentSystemContentFormat getSystemContentFormat() {
+        return systemContentFormat;
+    }
+
+    /**
+     * 设置 OpenAI-compatible 请求中的 system content 格式。
+     *
+     * @param systemContentFormat system content 格式
+     */
+    public void setSystemContentFormat(AgentSystemContentFormat systemContentFormat) {
+        this.systemContentFormat = systemContentFormat == null
+                ? AgentSystemContentFormat.STRING
+                : systemContentFormat;
+    }
+
     /**
      * 获取元数据。
      *

easy-agents-agent-runtime/src/main/java/com/easyagents/agent/runtime/model/AgentSystemContentFormat.java

@@ -0,0 +1,13 @@
+package com.easyagents.agent.runtime.model;
+
+/**
+ * OpenAI-compatible 请求中 system 消息的 content 格式。
+ */
+public enum AgentSystemContentFormat {
+
+    /** 使用字符串 content，保持 OpenAI Chat Completions 的常规格式。 */
+    STRING,
+
+    /** 使用仅包含 text 内容块的数组 content。 */
+    TEXT_PARTS
+}

easy-agents-agent-runtime/src/test/java/com/easyagents/agent/runtime/agentscope/AgentOpenAIChatFormatterTest.java

@@ -0,0 +1,62 @@
+package com.easyagents.agent.runtime.agentscope;
+
+import com.easyagents.agent.runtime.model.AgentGenerationOptions;
+import com.easyagents.agent.runtime.model.AgentModelProviderType;
+import com.easyagents.agent.runtime.model.AgentModelSpec;
+import com.easyagents.agent.runtime.model.AgentSystemContentFormat;
+import io.agentscope.core.formatter.openai.dto.OpenAIContentPart;
+import io.agentscope.core.formatter.openai.dto.OpenAIMessage;
+import io.agentscope.core.message.Msg;
+import io.agentscope.core.message.MsgRole;
+import io.agentscope.core.model.OpenAIChatModel;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.util.List;
+
+/**
+ * Agent OpenAI Chat 消息格式兼容测试。
+ */
+public class AgentOpenAIChatFormatterTest {
+
+    /**
+     * 验证 system 文本转换为 text 内容块数组，普通 user 文本保持字符串。
+     */
+    @Test
+    public void shouldConvertOnlySystemTextToContentParts() {
+        AgentOpenAIChatFormatter formatter = new AgentOpenAIChatFormatter();
+        List<OpenAIMessage> messages = formatter.format(List.of(
+                Msg.builder().role(MsgRole.SYSTEM).textContent("system prompt").build(),
+                Msg.builder().role(MsgRole.USER).textContent("hello").build()));
+
+        Assert.assertTrue(messages.get(0).getContent() instanceof List<?>);
+        List<OpenAIContentPart> contentParts = messages.get(0).getContentAsList();
+        Assert.assertEquals(1, contentParts.size());
+        Assert.assertEquals("text", contentParts.get(0).getType());
+        Assert.assertEquals("system prompt", contentParts.get(0).getText());
+        Assert.assertEquals("hello", messages.get(1).getContent());
+    }
+
+    /**
+     * 验证内容块数组策略会安装 EasyAgents 的 OpenAI Formatter。
+     *
+     * @throws Exception 反射读取 Formatter 失败时抛出
+     */
+    @Test
+    public void textPartsPolicyShouldInstallAgentOpenAIFormatter() throws Exception {
+        AgentModelSpec spec = new AgentModelSpec();
+        spec.setProviderType(AgentModelProviderType.OPENAI_COMPATIBLE);
+        spec.setModelName("vlm-test");
+        spec.setBaseUrl("http://model.example.com/v1");
+        spec.setApiKey("test-key");
+        spec.setSystemContentFormat(AgentSystemContentFormat.TEXT_PARTS);
+
+        OpenAIChatModel model = (OpenAIChatModel) new AgentScopeModelFactory()
+                .create(spec, new AgentGenerationOptions());
+        Field formatterField = OpenAIChatModel.class.getDeclaredField("formatter");
+        formatterField.setAccessible(true);
+
+        Assert.assertTrue(formatterField.get(model) instanceof AgentOpenAIChatFormatter);
+    }
+}