feat(arena): add info message for forwarded chat history

- Add info message when chatHistory is passed to spawned agents
- Add tests for info message presence and absence

This provides visibility to users when chat history context is included
in spawned agent sessions.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/core/src/agents/runtime/agent-interactive.test.ts

@@ -554,6 +554,37 @@ describe('AgentInteractive', () => {
     await agent.shutdown();
   });
 
+  it('should add info message when chatHistory is present', async () => {
+    const { core } = createMockCore();
+    const chatHistory = [
+      { role: 'user' as const, parts: [{ text: 'earlier question' }] },
+      { role: 'model' as const, parts: [{ text: 'earlier answer' }] },
+    ];
+    const agent = new AgentInteractive(createConfig({ chatHistory }), core);
+
+    await agent.start(context);
+
+    const messages = agent.getMessages();
+    expect(messages).toHaveLength(1);
+    expect(messages[0]).toMatchObject({
+      role: 'info',
+      content: 'History context from parent session included (2 messages)',
+    });
+
+    await agent.shutdown();
+  });
+
+  it('should not add info message when chatHistory is absent', async () => {
+    const { core } = createMockCore();
+    const agent = new AgentInteractive(createConfig(), core);
+
+    await agent.start(context);
+
+    expect(agent.getMessages()).toHaveLength(0);
+
+    await agent.shutdown();
+  });
+
   it('should pass undefined extraHistory when chatHistory is not set', async () => {
     const { core } = createMockCore();
     const config = createConfig();

packages/core/src/agents/runtime/agent-interactive.ts

@@ -111,6 +111,13 @@ export class AgentInteractive {
     this.toolsList = this.core.prepareTools();
     this.core.stats.start(Date.now());
 
+    if (this.config.chatHistory?.length) {
+      this.addMessage(
+        'info',
+        `History context from parent session included (${this.config.chatHistory.length} messages)`,
+      );
+    }
+
     if (this.config.initialTask) {
       this.queue.enqueue(this.config.initialTask);
       this.executionPromise = this.runLoop();