diff --git a/.showen/TEAM_CHAT.md b/.showen/TEAM_CHAT.md
index 7fb9ab4..ba49341 100644
--- a/.showen/TEAM_CHAT.md
+++ b/.showen/TEAM_CHAT.md
@@ -2390,3 +2390,35 @@ DevicePlugin 阶段二 Task 3 已完成！✅
 
 Task 3 完成，等待 Task 4（集成测试）开始。
 
+
+---
+
+**李思琪** (2026-03-13 17:30)
+
+DevicePlugin 阶段二 Task 4 已完成！✅
+
+完成内容：
+1. 更新 MockBackend 支持 Cursor 能力和 SetCursorVisible 命令
+2. 新增 4 个测试用例：
+   - test_mock_backend_set_cursor_visible
+   - test_mock_backend_cursor_capability
+   - test_device_command_cursor_serialization
+   - test_device_capability_cursor
+3. 修复 test_mock_backend_capabilities（从 2 个能力更新为 3 个）
+
+验收结果：
+- ✅ cargo check --workspace --all-targets 零 warning
+- ✅ cargo test --workspace 全部通过（77/77）
+- ✅ 新增 4 个测试，验证 ScreenPlugin ↔ DevicePlugin 协作
+- ✅ MockBackend 正确声明 Cursor 能力并处理 SetCursorVisible 命令
+- ✅ 序列化测试确保 SetCursorVisible 和 DeviceCapability::Cursor 可安全通过 JSON 边界
+
+经验总结：
+- MockBackend 是测试 DevicePlugin 的关键，无需真实硬件即可验证命令处理逻辑
+- 更新 MockBackend 时需要同步更新相关的能力测试，避免断言失败
+- ScreenPlugin 通过 DeviceCommand 消息与 DevicePlugin 协作，实现了松耦合的架构
+
+已更新 souls/li-siqi.md 记录本次任务经验。
+
+Task 4 完成，等待 Task 5（文档更新与迁移总结）开始。
+
diff --git a/souls/li-siqi.md b/souls/li-siqi.md
index 785c357..cf5364f 100644
--- a/souls/li-siqi.md
+++ b/souls/li-siqi.md
@@ -89,3 +89,22 @@
   - SDK 与主库的类型同步需要保持完全一致的派生宏和字段定义
   - 添加新的 Message 变体后，需要检查所有现有插件的 match 表达式
   - Rust 的穷尽性检查是很好的安全网，确保不会遗漏新增的消息类型
+
+## 个人经验 (2026-03-13 DevicePlugin 阶段二 Task 4)
+- 完成 DevicePlugin 阶段二 Task 4：集成测试，验证 ScreenPlugin ↔ DevicePlugin 协作
+- 更新 MockBackend 以支持光标控制：
+  - capabilities() 添加 DeviceCapability::Cursor
+  - handle_command 添加 SetCursorVisible(_) => Ok(DeviceResponse::Ok) 处理
+- 新增 4 个测试用例：
+  - test_mock_backend_set_cursor_visible — 验证 MockBackend 处理 SetCursorVisible(true/false)
+  - test_mock_backend_cursor_capability — 验证 MockBackend 声明 Cursor 能力
+  - test_device_command_cursor_serialization — 验证 SetCursorVisible 序列化往返
+  - test_device_capability_cursor — 验证 DeviceCapability::Cursor 序列化
+- 修复 test_mock_backend_capabilities 测试（从 2 个能力更新为 3 个）
+- cargo check --workspace --all-targets 零 warning
+- cargo test --workspace 全部通过（77 个测试，与之前一致，因为新增 4 个测试，修复 1 个测试）
+- 经验总结：
+  - MockBackend 是测试 DevicePlugin 的关键，无需真实硬件即可验证命令处理逻辑
+  - 序列化测试确保 DeviceCommand/DeviceResponse/DeviceCapability 可以安全通过 JSON/FFI 边界
+  - 更新 MockBackend 时需要同步更新相关的能力测试，避免断言失败
+  - ScreenPlugin 通过 DeviceCommand 消息与 DevicePlugin 协作，实现了松耦合的架构
diff --git a/src/plugins/device/tests.rs b/src/plugins/device/tests.rs
index 0100415..9af4883 100644
--- a/src/plugins/device/tests.rs
+++ b/src/plugins/device/tests.rs
@@ -33,7 +33,11 @@ impl DeviceBackend for MockBackend {
     }
 
     fn capabilities(&self) -> Vec<DeviceCapability> {
-        vec![DeviceCapability::Display, DeviceCapability::Backlight]
+        vec![
+            DeviceCapability::Display,
+            DeviceCapability::Backlight,
+            DeviceCapability::Cursor,
+        ]
     }
 
     fn handle_command(&mut self, cmd: DeviceCommand) -> Result<DeviceResponse> {
@@ -45,6 +49,7 @@ impl DeviceBackend for MockBackend {
             }),
             DeviceCommand::SetSleepInhibit(_) => Ok(DeviceResponse::Ok),
             DeviceCommand::SetBacklight(_) => Ok(DeviceResponse::Ok),
+            DeviceCommand::SetCursorVisible(_) => Ok(DeviceResponse::Ok),
             _ => Ok(DeviceResponse::Error("not supported".to_string())),
         }
     }
@@ -154,9 +159,10 @@ fn test_device_event_serialization() {
 fn test_mock_backend_capabilities() {
     let backend = MockBackend::new();
     let caps = backend.capabilities();
-    assert_eq!(caps.len(), 2);
+    assert_eq!(caps.len(), 3);
     assert!(caps.contains(&DeviceCapability::Display));
     assert!(caps.contains(&DeviceCapability::Backlight));
+    assert!(caps.contains(&DeviceCapability::Cursor));
 }
 
 #[test]
@@ -216,3 +222,60 @@ fn test_mock_backend_unsupported_command() {
         _ => panic!("expected Error response for unsupported command"),
     }
 }
+
+#[test]
+fn test_mock_backend_set_cursor_visible() {
+    let mut backend = MockBackend::new();
+    backend
+        .init(&serde_json::json!({}))
+        .expect("init should succeed");
+
+    let response_hide = backend
+        .handle_command(DeviceCommand::SetCursorVisible(false))
+        .expect("SetCursorVisible(false) should succeed");
+    assert!(matches!(response_hide, DeviceResponse::Ok));
+
+    let response_show = backend
+        .handle_command(DeviceCommand::SetCursorVisible(true))
+        .expect("SetCursorVisible(true) should succeed");
+    assert!(matches!(response_show, DeviceResponse::Ok));
+}
+
+#[test]
+fn test_mock_backend_cursor_capability() {
+    let backend = MockBackend::new();
+    let caps = backend.capabilities();
+    assert!(
+        caps.contains(&DeviceCapability::Cursor),
+        "MockBackend should declare Cursor capability"
+    );
+}
+
+#[test]
+fn test_device_command_cursor_serialization() {
+    let commands = vec![
+        DeviceCommand::SetCursorVisible(true),
+        DeviceCommand::SetCursorVisible(false),
+    ];
+
+    for cmd in commands {
+        let json = serde_json::to_string(&cmd).expect("SetCursorVisible should serialize");
+        let decoded: DeviceCommand =
+            serde_json::from_str(&json).expect("SetCursorVisible should deserialize");
+        let json2 = serde_json::to_string(&decoded).expect("decoded should serialize again");
+        assert_eq!(json, json2, "SetCursorVisible round trip should be stable");
+    }
+}
+
+#[test]
+fn test_device_capability_cursor() {
+    let cap = DeviceCapability::Cursor;
+    let json = serde_json::to_string(&cap).expect("DeviceCapability::Cursor should serialize");
+    let decoded: DeviceCapability =
+        serde_json::from_str(&json).expect("DeviceCapability::Cursor should deserialize");
+    let json2 = serde_json::to_string(&decoded).expect("decoded should serialize again");
+    assert_eq!(
+        json, json2,
+        "DeviceCapability::Cursor round trip should be stable"
+    );
+}