diff --git a/.idea/compiler.xml b/.idea/compiler.xml
index b589d56..b86273d 100644
--- a/.idea/compiler.xml
+++ b/.idea/compiler.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="CompilerConfiguration">
-    <bytecodeTargetLevel target="17" />
+    <bytecodeTargetLevel target="21" />
   </component>
 </project>
\ No newline at end of file
diff --git a/.idea/deploymentTargetSelector.xml b/.idea/deploymentTargetSelector.xml
index b268ef3..c4a0da7 100644
--- a/.idea/deploymentTargetSelector.xml
+++ b/.idea/deploymentTargetSelector.xml
@@ -4,6 +4,14 @@
     <selectionStates>
       <SelectionState runConfigName="app">
         <option name="selectionMode" value="DROPDOWN" />
+        <DropdownSelection timestamp="2025-12-29T05:27:36.573544400Z">
+          <Target type="DEFAULT_BOOT">
+            <handle>
+              <DeviceId pluginId="LocalEmulator" identifier="path=C:\Users\natsu\.android\avd\Pixel_7_2.avd" />
+            </handle>
+          </Target>
+        </DropdownSelection>
+        <DialogSelection />
       </SelectionState>
     </selectionStates>
   </component>
diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 0897082..639c779 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -4,6 +4,7 @@
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
+        <option name="testRunner" value="CHOOSE_PER_TEST" />
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
         <option name="gradleJvm" value="#GRADLE_LOCAL_JAVA_HOME" />
         <option name="modules">
@@ -12,7 +13,6 @@
             <option value="$PROJECT_DIR$/app" />
           </set>
         </option>
-        <option name="resolveExternalAnnotations" value="false" />
       </GradleProjectSettings>
     </option>
   </component>
diff --git a/.idea/misc.xml b/.idea/misc.xml
index 8978d23..74dd639 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,6 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" default="true" project-jdk-name="jbr-17" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="jbr-21" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
   <component name="ProjectType">
diff --git a/app/src/main/java/com/example/tampopo_client/views/FriendIconView.java b/app/src/main/java/com/example/tampopo_client/views/FriendIconView.java
index e4c197e..4f52187 100644
--- a/app/src/main/java/com/example/tampopo_client/views/FriendIconView.java
+++ b/app/src/main/java/com/example/tampopo_client/views/FriendIconView.java
@@ -132,7 +132,9 @@
             chatNotification = false;
 
             // 通話を開始する
-            Tampopo tampopo = (Tampopo) ((MainActivity) getContext()).getApplication();
+            // FriendIconView がどの Activity 上に配置されていても安全に動作するよう、
+            // Activity ではなく Application から Tampopo を取得する
+            Tampopo tampopo = (Tampopo) context.getApplicationContext();
 //            String chatroomId = chatViewModel.enterChatroom(tampopo.getUserId(), friendUserId, tampopo.getToken());
             tampopo.setChatFriendId(friendUserId);
 
@@ -167,7 +169,8 @@
             toDialog.dismiss();
 
             // 通話を開始する
-            Tampopo tampopo = (Tampopo) ((MainActivity) getContext()).getApplication();
+            // こちらも Application から直接 Tampopo を取得して Activity への依存をなくす
+            Tampopo tampopo = (Tampopo) context.getApplicationContext();
             new Thread(new Runnable() {
                 @Override
                 public void run() {
@@ -199,6 +202,8 @@
 
     //アクティビティの背景（吹き出し）
     public void setImageResource(int resId) {
+        // 既存の挙動との後方互換性を保つため、ここではフレンドアイコン側の画像を更新する。
+        // 吹き出し背景を変更したい場合は、別メソッド追加などで明示的に扱う方が安全。
         if (mFriendIcon != null) {
             mFriendIcon.setImageResource(resId);
         }
diff --git a/app/src/main/java/com/example/tampopo_client/views/MainActivity.java b/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
index 9911876..f29ce64 100644
--- a/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
+++ b/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
@@ -358,7 +358,9 @@
                 public void onChanged(List<Activity> activities) {
                     if (activities == null || activities.isEmpty()) return;
 
-                    Activity latest = activities.get(activities.size() - 1);
+                    // ActivityViewModel 側では最新のアクティビティが先頭(index 0)に入る想定のため、
+                    // 常に先頭要素を参照して吹き出しや並び順を更新する
+                    Activity latest = activities.get(0);
                     Log.d("ActivityUpdate", friendId + " 最新: " + latest.getText());
 
                     // FriendIconView の更新