diff --git a/android-plugin/app/src/main/java/top/mobilegl/plugin/NavBar.java b/android-plugin/app/src/main/java/top/mobilegl/plugin/NavBar.java
new file mode 100644
index 00000000..cd65f3d6
--- /dev/null
+++ b/android-plugin/app/src/main/java/top/mobilegl/plugin/NavBar.java
@@ -0,0 +1,79 @@
+package top.mobilegl.plugin;
+
+import android.app.Activity;
+import android.content.Intent;
+import android.graphics.Typeface;
+import android.util.TypedValue;
+import android.view.Gravity;
+import android.view.View;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+
+/**
+ * Bottom navigation bar switching between the dev screens (POST and the render
+ * server control). The bar only appears in flavors that ship both screens: the
+ * plugin flavor has no ServerControlActivity, so wrap() returns the content
+ * unchanged there. Tabs switch by reordering the other activity to the front,
+ * so each screen keeps its state while the other is open.
+ */
+public final class NavBar {
+    public static final int TAB_POST = 0;
+    public static final int TAB_SERVER = 1;
+
+    private static final int COLOR_BAR = 0xFF1E1E1E;
+    private static final int COLOR_TAB_ACTIVE = 0xFFEEEEEE;
+    private static final int COLOR_TAB_INACTIVE = 0xFF9E9E9E;
+    private static final int BAR_HEIGHT_DP = 56;
+
+    private static final String SERVER_ACTIVITY = "top.mobilegl.plugin.ServerControlActivity";
+
+    private NavBar() {}
+
+    /** Returns content wrapped with the bottom bar, or content unchanged in plugin builds. */
+    public static View wrap(Activity activity, View content, int currentTab) {
+        final Class<?> serverClass;
+        try {
+            serverClass = Class.forName(SERVER_ACTIVITY);
+        } catch (ClassNotFoundException notInThisFlavor) {
+            return content;
+        }
+
+        LinearLayout root = new LinearLayout(activity);
+        root.setOrientation(LinearLayout.VERTICAL);
+        root.addView(content, new LinearLayout.LayoutParams(
+                LinearLayout.LayoutParams.MATCH_PARENT, 0, 1f));
+
+        LinearLayout bar = new LinearLayout(activity);
+        bar.setOrientation(LinearLayout.HORIZONTAL);
+        bar.setBackgroundColor(COLOR_BAR);
+        addTab(activity, bar, "POST", PostActivity.class, currentTab == TAB_POST);
+        addTab(activity, bar, "Render Server", serverClass, currentTab == TAB_SERVER);
+        root.addView(bar, new LinearLayout.LayoutParams(
+                LinearLayout.LayoutParams.MATCH_PARENT, dp(activity, BAR_HEIGHT_DP)));
+        return root;
+    }
+
+    private static void addTab(final Activity activity, LinearLayout bar, String label,
+                               final Class<?> target, boolean active) {
+        TextView tab = new TextView(activity);
+        tab.setText(label);
+        tab.setGravity(Gravity.CENTER);
+        tab.setTextSize(TypedValue.COMPLEX_UNIT_SP, 13);
+        tab.setTypeface(Typeface.MONOSPACE, active ? Typeface.BOLD : Typeface.NORMAL);
+        tab.setTextColor(active ? COLOR_TAB_ACTIVE : COLOR_TAB_INACTIVE);
+        if (!active) {
+            tab.setOnClickListener(v -> {
+                activity.startActivity(
+                        new Intent(activity, target).addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT));
+                // Tab switch, not navigation: suppress the slide-in activity transition.
+                activity.overridePendingTransition(0, 0);
+            });
+        }
+        bar.addView(tab, new LinearLayout.LayoutParams(
+                0, LinearLayout.LayoutParams.MATCH_PARENT, 1f));
+    }
+
+    private static int dp(Activity activity, int value) {
+        return Math.round(value * activity.getResources().getDisplayMetrics().density);
+    }
+}
diff --git a/android-plugin/app/src/main/java/top/mobilegl/plugin/PostActivity.java b/android-plugin/app/src/main/java/top/mobilegl/plugin/PostActivity.java
index c6910500..55a13898 100644
--- a/android-plugin/app/src/main/java/top/mobilegl/plugin/PostActivity.java
+++ b/android-plugin/app/src/main/java/top/mobilegl/plugin/PostActivity.java
@@ -15,6 +15,7 @@ import android.view.View;
 import android.widget.Button;
 import android.widget.HorizontalScrollView;
 import android.widget.LinearLayout;
+import android.widget.ProgressBar;
 import android.widget.ScrollView;
 import android.widget.TextView;
 
@@ -69,6 +70,7 @@ public final class PostActivity extends Activity {
 
     private LinearLayout contentLayout;
     private TextView statusView;
+    private ProgressBar progressBar;
 
     /**
      * Per-backend bench UI state. Unlike the POST itself (single-flight, latched),
@@ -93,11 +95,20 @@ public final class PostActivity extends Activity {
         scrollView.setBackgroundColor(COLOR_BACKGROUND);
         scrollView.setFillViewport(true);
         scrollView.addView(contentLayout);
-        setContentView(scrollView);
+        setContentView(NavBar.wrap(this, scrollView, NavBar.TAB_POST));
 
         addText("MobileGL Driver POST", 20, COLOR_TEXT, true, 0);
         statusView = addText("Running self-test...", 14, COLOR_INFO, false, dp(8));
 
+        progressBar = new ProgressBar(this, null, android.R.attr.progressBarStyleHorizontal);
+        progressBar.setIndeterminate(true);
+        LinearLayout.LayoutParams progressParams = new LinearLayout.LayoutParams(
+                LinearLayout.LayoutParams.MATCH_PARENT,
+                LinearLayout.LayoutParams.WRAP_CONTENT
+        );
+        progressParams.topMargin = dp(8);
+        contentLayout.addView(progressBar, progressParams);
+
         boolean startWorker = false;
         boolean renderNow = false;
         synchronized (POST_LOCK) {
@@ -298,6 +309,7 @@ public final class PostActivity extends Activity {
     }
 
     private void renderCachedResult() {
+        progressBar.setVisibility(View.GONE);
         String json;
         Throwable failure;
         synchronized (POST_LOCK) {
diff --git a/android-plugin/app/src/trace/AndroidManifest.xml b/android-plugin/app/src/trace/AndroidManifest.xml
index 6719a6cf..ccfe5cb3 100644
--- a/android-plugin/app/src/trace/AndroidManifest.xml
+++ b/android-plugin/app/src/trace/AndroidManifest.xml
@@ -8,17 +8,16 @@
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_DATA_SYNC" />
 
     <application>
-        <!-- Launcher entry: start/stop the offscreen TCP supervisor (MobileGLServerService).
-             The trace flavor removes PostActivity, so without this the APK has no icon. -->
+        <!-- Render server control screen: start/stop the offscreen TCP supervisor
+             (MobileGLServerService) or the on-screen display server. Not the launcher:
+             PostActivity is the entry icon and the bottom navigation bar switches between
+             the two screens; exported so adb can drive it by explicit component with
+             listen/token/env/onscreen/start/stop extras. -->
         <activity
             android:name=".ServerControlActivity"
             android:exported="true"
-            android:theme="@style/Theme.MobileGLPlugin">
-            <intent-filter>
-                <action android:name="android.intent.action.MAIN" />
-                <category android:name="android.intent.category.LAUNCHER" />
-            </intent-filter>
-        </activity>
+            android:launchMode="singleTop"
+            android:theme="@style/Theme.MobileGLPlugin" />
         <service
             android:name=".MobileGLServerService"
             android:exported="true"
@@ -42,9 +41,6 @@
         <activity
             android:name=".PluginActivity"
             tools:node="remove" />
-        <activity
-            android:name=".PostActivity"
-            tools:node="remove" />
         <meta-data
             android:name="fclPlugin"
             tools:node="remove" />
diff --git a/android-plugin/app/src/trace/java/top/mobilegl/plugin/ServerControlActivity.java b/android-plugin/app/src/trace/java/top/mobilegl/plugin/ServerControlActivity.java
index 3094a999..bc3fd8cb 100644
--- a/android-plugin/app/src/trace/java/top/mobilegl/plugin/ServerControlActivity.java
+++ b/android-plugin/app/src/trace/java/top/mobilegl/plugin/ServerControlActivity.java
@@ -72,7 +72,7 @@ public final class ServerControlActivity extends Activity {
         scrollView.setBackgroundColor(COLOR_BACKGROUND);
         scrollView.setFillViewport(true);
         scrollView.addView(contentLayout);
-        setContentView(scrollView);
+        setContentView(NavBar.wrap(this, scrollView, NavBar.TAB_SERVER));
 
         contentLayout.addView(makeText("MobileGL Render Server", 20, COLOR_TEXT, true));
 
@@ -142,11 +142,23 @@ public final class ServerControlActivity extends Activity {
             setStatus("Stopped.", COLOR_INFO);
         }
 
-        // Intent extras prefill the form, so adb can drive the screen without the IME:
-        // --es listen @name --es token T --es env "K=V;K" --ez onscreen true --ez start true
-        // (--ez stop true instead stops). This mirrors how every other entry point in this
-        // APK is already driven by extras.
-        Intent intent = getIntent();
+        handleIntent(getIntent());
+    }
+
+    @Override
+    protected void onNewIntent(Intent intent) {
+        super.onNewIntent(intent);
+        setIntent(intent);
+        handleIntent(intent);
+    }
+
+    /**
+     * Intent extras prefill the form, so adb can drive the screen without the IME:
+     * --es listen @name --es token T --es env "K=V;K" --ez onscreen true --ez start true
+     * (--ez stop true instead stops). This mirrors how every other entry point in this
+     * APK is already driven by extras.
+     */
+    private void handleIntent(Intent intent) {
         if (intent != null) {
             String prefillListen = intent.getStringExtra("listen");
             if (prefillListen != null) listenField.setText(prefillListen);