diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index 3569209..b8c1e5a 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -15,6 +15,9 @@ android {
     buildTypes { release { isMinifyEnabled = false } }
     compileOptions { sourceCompatibility = JavaVersion.VERSION_17; targetCompatibility = JavaVersion.VERSION_17 }
     kotlinOptions { jvmTarget = "17" }
+    // 本地单元测试中 android.* 桩方法返回默认值（避免 Log.d 抛 "not mocked"）
+    // android.* stub methods return default values in local unit tests (avoid Log.d "not mocked")
+    testOptions { unitTests { isReturnDefaultValues = true } }
 }
 dependencies {
     implementation("androidx.core:core-ktx:1.13.1")
diff --git a/app/src/main/java/top/yeij/hearth/MainActivity.kt b/app/src/main/java/top/yeij/hearth/MainActivity.kt
index bab453f..f1b2e41 100644
--- a/app/src/main/java/top/yeij/hearth/MainActivity.kt
+++ b/app/src/main/java/top/yeij/hearth/MainActivity.kt
@@ -1,10 +1,13 @@
 package top.yeij.hearth
 
 import android.app.Activity
+import android.content.res.Configuration
 import android.os.Bundle
 import android.util.Log
 import android.view.WindowInsets
 import android.view.WindowInsetsController
+import top.yeij.hearth.webview.JsBridge
+import top.yeij.hearth.webview.WebViewManager
 
 // HOME 桌面 activity，后续 Task 挂载 WebView 与 JsBridge
 // HOME launcher activity; later tasks mount WebView and JsBridge
@@ -18,6 +21,28 @@ class MainActivity : Activity() {
         super.onCreate(savedInstanceState)
         Log.d(TAG, "onCreate: enter immersive mode")
         enterImmersive()
+        setupWebView()
+    }
+
+    // 创建 JsBridge 并挂载 WebView 桌面层
+    // Create JsBridge and mount the WebView launcher layer
+    private fun setupWebView() {
+        val dm = resources.displayMetrics
+        val darkMode =
+            (resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK) ==
+                Configuration.UI_MODE_NIGHT_YES
+        val bridge = JsBridge(
+            deviceWidthPx = dm.widthPixels,
+            deviceHeightPx = dm.heightPixels,
+            density = dm.density,
+            darkMode = darkMode,
+        )
+        WebViewManager(this).attach(bridge)
+        Log.d(
+            TAG,
+            "setupWebView: attached WebView ${dm.widthPixels}x${dm.heightPixels}" +
+                " density=${dm.density} darkMode=$darkMode"
+        )
     }
 
     // 进入沉浸式全屏：隐藏状态栏与导航栏，滑动可临时唤出
diff --git a/app/src/main/java/top/yeij/hearth/webview/JsBridge.kt b/app/src/main/java/top/yeij/hearth/webview/JsBridge.kt
new file mode 100644
index 0000000..0d5ae33
--- /dev/null
+++ b/app/src/main/java/top/yeij/hearth/webview/JsBridge.kt
@@ -0,0 +1,25 @@
+package top.yeij.hearth.webview
+
+import android.util.Log
+
+class JsBridge(
+    private val deviceWidthPx: Int,
+    private val deviceHeightPx: Int,
+    private val density: Float,
+    private val darkMode: Boolean,
+) {
+    private val gson = com.google.gson.Gson()
+
+    @android.webkit.JavascriptInterface
+    fun getDeviceInfo(): String {
+        Log.d("HearthBridge", "getDeviceInfo called")
+        return gson.toJson(
+            mapOf(
+                "widthPx" to deviceWidthPx,
+                "heightPx" to deviceHeightPx,
+                "density" to density,
+                "darkMode" to darkMode
+            )
+        )
+    }
+}
diff --git a/app/src/main/java/top/yeij/hearth/webview/WebViewManager.kt b/app/src/main/java/top/yeij/hearth/webview/WebViewManager.kt
new file mode 100644
index 0000000..ebcc73d
--- /dev/null
+++ b/app/src/main/java/top/yeij/hearth/webview/WebViewManager.kt
@@ -0,0 +1,26 @@
+package top.yeij.hearth.webview
+
+import android.annotation.SuppressLint
+import android.app.Activity
+import android.webkit.WebView
+import android.webkit.WebSettings
+import android.webkit.WebViewClient
+
+class WebViewManager(private val activity: Activity) {
+    @SuppressLint("SetJavaScriptEnabled")
+    fun attach(bridge: JsBridge): WebView {
+        val webView = WebView(activity)
+        webView.settings.apply {
+            javaScriptEnabled = true
+            useWideViewPort = true
+            loadWithOverviewMode = true
+            setSupportZoom(false)
+            domStorageEnabled = true
+        }
+        webView.addJavascriptInterface(bridge, "HearthBridge")
+        webView.webViewClient = WebViewClient()
+        webView.loadUrl("file:///android_asset/h5/index.html")
+        activity.setContentView(webView)
+        return webView
+    }
+}
diff --git a/app/src/test/java/top/yeij/hearth/webview/JsBridgeTest.kt b/app/src/test/java/top/yeij/hearth/webview/JsBridgeTest.kt
new file mode 100644
index 0000000..6d95cc1
--- /dev/null
+++ b/app/src/test/java/top/yeij/hearth/webview/JsBridgeTest.kt
@@ -0,0 +1,14 @@
+package top.yeij.hearth.webview
+
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class JsBridgeTest {
+    @Test
+    fun getDeviceInfo_returnsJsonWithDarkMode() {
+        val bridge = JsBridge(deviceWidthPx = 800, deviceHeightPx = 480, density = 2.0f, darkMode = true)
+        val json = bridge.getDeviceInfo()
+        assertTrue(json.contains("\"widthPx\":800"))
+        assertTrue(json.contains("\"darkMode\":true"))
+    }
+}