diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/InstalledImage.kt b/android/TerminalApp/java/com/android/virtualization/terminal/InstalledImage.kt
index 086ff3d..59be4ae 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/InstalledImage.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/InstalledImage.kt
@@ -83,7 +83,7 @@
     }
 
     @Throws(IOException::class)
-    fun getSize(): Long {
+    fun getApparentSize(): Long {
         return Files.size(rootPartition)
     }
 
@@ -118,7 +118,7 @@
     @Throws(IOException::class)
     fun resize(desiredSize: Long): Long {
         val roundedUpDesiredSize = roundUp(desiredSize)
-        val curSize = getSize()
+        val curSize = getApparentSize()
 
         runE2fsck(rootPartition)
 
@@ -130,7 +130,21 @@
             allocateSpace(rootPartition, roundedUpDesiredSize)
         }
         resizeFilesystem(rootPartition, roundedUpDesiredSize)
-        return getSize()
+        return getApparentSize()
+    }
+
+    @Throws(IOException::class)
+    fun shrinkToMinimumSize(): Long {
+        // Fix filesystem before resizing.
+        runE2fsck(rootPartition)
+
+        val p: String = rootPartition.toAbsolutePath().toString()
+        runCommand("/system/bin/resize2fs", "-M", p)
+        Log.d(TAG, "resize2fs -M completed: $rootPartition")
+
+        // resize2fs may result in an inconsistent filesystem state. Fix with e2fsck.
+        runE2fsck(rootPartition)
+        return getApparentSize()
     }
 
     @Throws(IOException::class)
@@ -213,7 +227,7 @@
             }
         }
 
-        private fun roundUp(bytes: Long): Long {
+        internal fun roundUp(bytes: Long): Long {
             // Round up every diskSizeStep MB
             return ceil((bytes.toDouble()) / RESIZE_STEP_BYTES).toLong() * RESIZE_STEP_BYTES
         }
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/MainActivity.kt b/android/TerminalApp/java/com/android/virtualization/terminal/MainActivity.kt
index d85242b..52afef4 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/MainActivity.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/MainActivity.kt
@@ -50,6 +50,7 @@
 import com.android.internal.annotations.VisibleForTesting
 import com.android.microdroid.test.common.DeviceProperties
 import com.android.system.virtualmachine.flags.Flags
+import com.android.virtualization.terminal.ErrorActivity.Companion.start
 import com.android.virtualization.terminal.VmLauncherService.VmLauncherServiceCallback
 import com.google.android.material.tabs.TabLayout
 import com.google.android.material.tabs.TabLayoutMediator
@@ -368,7 +369,7 @@
                 )
                 .build()
 
-        val diskSize = intent.getLongExtra(EXTRA_DISK_SIZE, image.getSize())
+        val diskSize = intent.getLongExtra(EXTRA_DISK_SIZE, image.getApparentSize())
 
         val intent =
             VmLauncherService.getIntentForStart(
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/SettingsActivity.kt b/android/TerminalApp/java/com/android/virtualization/terminal/SettingsActivity.kt
index a4a0a84..1183b46 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/SettingsActivity.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/SettingsActivity.kt
@@ -19,6 +19,7 @@
 import androidx.appcompat.app.AppCompatActivity
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import com.android.system.virtualmachine.flags.Flags
 import com.google.android.material.appbar.MaterialToolbar
 
 class SettingsActivity : AppCompatActivity() {
@@ -29,27 +30,34 @@
 
         val toolbar: MaterialToolbar = findViewById(R.id.settings_toolbar)
         setSupportActionBar(toolbar)
-        val settingsItems =
-            arrayOf(
+        var settingsItems = mutableListOf<SettingsItem>()
+        if (!Flags.terminalStorageBalloon()) {
+            settingsItems.add(
                 SettingsItem(
                     resources.getString(R.string.settings_disk_resize_title),
                     resources.getString(R.string.settings_disk_resize_sub_title),
                     R.drawable.baseline_storage_24,
                     SettingsItemEnum.DiskResize,
-                ),
-                SettingsItem(
-                    resources.getString(R.string.settings_port_forwarding_title),
-                    resources.getString(R.string.settings_port_forwarding_sub_title),
-                    R.drawable.baseline_call_missed_outgoing_24,
-                    SettingsItemEnum.PortForwarding,
-                ),
-                SettingsItem(
-                    resources.getString(R.string.settings_recovery_title),
-                    resources.getString(R.string.settings_recovery_sub_title),
-                    R.drawable.baseline_settings_backup_restore_24,
-                    SettingsItemEnum.Recovery,
-                ),
+                )
             )
+        }
+        settingsItems.add(
+            SettingsItem(
+                resources.getString(R.string.settings_port_forwarding_title),
+                resources.getString(R.string.settings_port_forwarding_sub_title),
+                R.drawable.baseline_call_missed_outgoing_24,
+                SettingsItemEnum.PortForwarding,
+            )
+        )
+        settingsItems.add(
+            SettingsItem(
+                resources.getString(R.string.settings_recovery_title),
+                resources.getString(R.string.settings_recovery_sub_title),
+                R.drawable.baseline_settings_backup_restore_24,
+                SettingsItemEnum.Recovery,
+            )
+        )
+
         val settingsListItemAdapter = SettingsItemAdapter(settingsItems)
 
         val recyclerView: RecyclerView = findViewById(R.id.settings_list_recycler_view)
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/SettingsDiskResizeActivity.kt b/android/TerminalApp/java/com/android/virtualization/terminal/SettingsDiskResizeActivity.kt
index af1ae95..144db40 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/SettingsDiskResizeActivity.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/SettingsDiskResizeActivity.kt
@@ -71,7 +71,7 @@
         diskSizeStepMb = 1L shl resources.getInteger(R.integer.disk_size_round_up_step_size_in_mb)
 
         val image = InstalledImage.getDefault(this)
-        diskSizeMb = bytesToMb(image.getSize())
+        diskSizeMb = bytesToMb(image.getApparentSize())
         val minDiskSizeMb = bytesToMb(image.getSmallestSizePossible()).coerceAtMost(diskSizeMb)
         val usableSpaceMb =
             bytesToMb(Environment.getDataDirectory().getUsableSpace()) and
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/SettingsItemAdapter.kt b/android/TerminalApp/java/com/android/virtualization/terminal/SettingsItemAdapter.kt
index 132d749..aa0c3f5 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/SettingsItemAdapter.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/SettingsItemAdapter.kt
@@ -24,7 +24,7 @@
 import androidx.recyclerview.widget.RecyclerView
 import com.google.android.material.card.MaterialCardView
 
-class SettingsItemAdapter(private val dataSet: Array<SettingsItem>) :
+class SettingsItemAdapter(private val dataSet: List<SettingsItem>) :
     RecyclerView.Adapter<SettingsItemAdapter.ViewHolder>() {
 
     class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/SplitInitializer.kt b/android/TerminalApp/java/com/android/virtualization/terminal/SplitInitializer.kt
index 7562779..2653ba9 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/SplitInitializer.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/SplitInitializer.kt
@@ -15,16 +15,96 @@
  */
 package com.android.virtualization.terminal
 
+import android.content.ComponentName
 import android.content.Context
+import android.content.Intent
 import androidx.startup.Initializer
+import androidx.window.embedding.ActivityFilter
+import androidx.window.embedding.EmbeddingAspectRatio
 import androidx.window.embedding.RuleController
+import androidx.window.embedding.SplitAttributes
+import androidx.window.embedding.SplitPairFilter
+import androidx.window.embedding.SplitPairRule
+import androidx.window.embedding.SplitPlaceholderRule
+import androidx.window.embedding.SplitRule
+import com.android.system.virtualmachine.flags.Flags
 
 class SplitInitializer : Initializer<RuleController> {
 
     override fun create(context: Context): RuleController {
-        return RuleController.getInstance(context).apply {
-            setRules(RuleController.parseRules(context, R.xml.main_split_config))
+        val filters =
+            mutableSetOf(
+                SplitPairFilter(
+                    ComponentName(context, SettingsActivity::class.java),
+                    ComponentName(context, SettingsPortForwardingActivity::class.java),
+                    null,
+                )
+            )
+
+        if (Flags.terminalStorageBalloon()) {
+            filters.add(
+                SplitPairFilter(
+                    ComponentName(context, SettingsActivity::class.java),
+                    ComponentName(context, SettingsDiskResizeActivity::class.java),
+                    null,
+                )
+            )
         }
+
+        filters.add(
+            SplitPairFilter(
+                ComponentName(context, SettingsActivity::class.java),
+                ComponentName(context, SettingsRecoveryActivity::class.java),
+                null,
+            )
+        )
+        val splitPairRules =
+            SplitPairRule.Builder(filters)
+                .setClearTop(true)
+                .setFinishPrimaryWithSecondary(SplitRule.FinishBehavior.ADJACENT)
+                .setFinishSecondaryWithPrimary(SplitRule.FinishBehavior.ALWAYS)
+                .setDefaultSplitAttributes(
+                    SplitAttributes.Builder()
+                        .setLayoutDirection(SplitAttributes.LayoutDirection.LOCALE)
+                        .setSplitType(
+                            SplitAttributes.SplitType.ratio(
+                                context.resources.getFloat(R.dimen.activity_split_ratio)
+                            )
+                        )
+                        .build()
+                )
+                .setMaxAspectRatioInPortrait(EmbeddingAspectRatio.ALWAYS_ALLOW)
+                .setMinWidthDp(context.resources.getInteger(R.integer.split_min_width))
+                .build()
+
+        val placeholderRule =
+            SplitPlaceholderRule.Builder(
+                    setOf(
+                        ActivityFilter(ComponentName(context, SettingsActivity::class.java), null)
+                    ),
+                    Intent(context, SettingsDiskResizeActivity::class.java),
+                )
+                .setFinishPrimaryWithPlaceholder(SplitRule.FinishBehavior.ADJACENT)
+                .setDefaultSplitAttributes(
+                    SplitAttributes.Builder()
+                        .setLayoutDirection(SplitAttributes.LayoutDirection.LOCALE)
+                        .setSplitType(
+                            SplitAttributes.SplitType.ratio(
+                                context.resources.getFloat(R.dimen.activity_split_ratio)
+                            )
+                        )
+                        .build()
+                )
+                .setMaxAspectRatioInPortrait(EmbeddingAspectRatio.ALWAYS_ALLOW)
+                .setMinWidthDp(context.resources.getInteger(R.integer.split_min_width))
+                .setSticky(false)
+                .build()
+
+        val ruleController = RuleController.getInstance(context)
+        ruleController.addRule(splitPairRules)
+        ruleController.addRule(placeholderRule)
+
+        return ruleController
     }
 
     override fun dependencies(): List<Class<out Initializer<*>>> {
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/VmLauncherService.kt b/android/TerminalApp/java/com/android/virtualization/terminal/VmLauncherService.kt
index f426ce6..d43a8d1 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/VmLauncherService.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/VmLauncherService.kt
@@ -41,6 +41,7 @@
 import android.widget.Toast
 import androidx.annotation.WorkerThread
 import com.android.system.virtualmachine.flags.Flags
+import com.android.virtualization.terminal.InstalledImage.Companion.roundUp
 import com.android.virtualization.terminal.MainActivity.Companion.PREFIX
 import com.android.virtualization.terminal.MainActivity.Companion.TAG
 import io.grpc.Grpc
@@ -120,7 +121,7 @@
                 // Note: this doesn't always do the resizing. If the current image size is the same
                 // as the requested size which is rounded up to the page alignment, resizing is not
                 // done.
-                val diskSize = intent.getLongExtra(EXTRA_DISK_SIZE, image.getSize())
+                val diskSize = intent.getLongExtra(EXTRA_DISK_SIZE, image.getApparentSize())
 
                 mainWorkerThread.submit({
                     doStart(notification, displayInfo, diskSize, resultReceiver)
@@ -140,16 +141,18 @@
         return START_NOT_STICKY
     }
 
-    private fun truncateDiskIfNecessary(image: InstalledImage) {
-        val curSize = image.getSize()
-        val physicalSize = image.getPhysicalSize()
-
-        // Change the rootfs disk's apparent size to GUEST_SPARSE_DISK_SIZE_PERCENTAGE of the total
-        // disk size.
-        // Note that the physical size is not changed.
+    private fun calculateSparseDiskSize(): Long {
+        // With storage ballooning enabled, we create a sparse file with 95% of the total size.
         val statFs = StatFs(filesDir.absolutePath)
         val hostSize = statFs.totalBytes
-        val expectedSize = hostSize * GUEST_SPARSE_DISK_SIZE_PERCENTAGE / 100
+        return roundUp(hostSize * GUEST_SPARSE_DISK_SIZE_PERCENTAGE / 100)
+    }
+
+    private fun truncateDiskIfNecessary(image: InstalledImage) {
+        val curSize = image.getApparentSize()
+        val physicalSize = image.getPhysicalSize()
+
+        val expectedSize = calculateSparseDiskSize()
         Log.d(
             TAG,
             "rootfs apparent size=$curSize, physical size=$physicalSize, expectedSize=$expectedSize",
@@ -164,6 +167,38 @@
         }
     }
 
+    // Convert the rootfs disk to a non-sparse file.
+    private fun convertToNonSparseDiskIfNecessary(image: InstalledImage) {
+        try {
+            val curApparentSize = image.getApparentSize()
+            val curPhysicalSize = image.getPhysicalSize()
+            Log.d(TAG, "Current disk size: apparent=$curApparentSize, physical=$curPhysicalSize")
+
+            // If storage ballooning was enabled via Flags.terminalStorageBalloon() before but it's
+            // now disabled, the disk is still a sparse file whose apparent size is too large.
+            // We need to shrink it to the minimum size.
+            //
+            // The disk file is considered sparse if its apparent disk size matches the expected
+            // sparse disk size.
+            // In addition, we consider it sparse if the physical size is clearly smaller than its
+            // apparent size. This additional condition is a fallback for cases
+            // where the logic of calculating the expected sparse disk size since the disk is
+            // created.
+            if (
+                curApparentSize == calculateSparseDiskSize() ||
+                    curPhysicalSize <
+                        curApparentSize * EXPECTED_PHYSICAL_SIZE_PERCENTAGE_FOR_NON_SPARSE / 100
+            ) {
+                Log.d(TAG, "A sparse disk is detected. Shrink it to the minimum size.")
+                val newSize = image.shrinkToMinimumSize()
+                Log.d(TAG, "Shrink the disk image: $curApparentSize -> $newSize")
+            }
+        } catch (e: IOException) {
+            throw RuntimeException("Failed to shrink rootfs disk", e)
+            return
+        }
+    }
+
     @WorkerThread
     private fun doStart(
         notification: Notification,
@@ -180,6 +215,10 @@
             // When storage ballooning flag is enabled, convert rootfs disk into a sparse file.
             truncateDiskIfNecessary(image)
         } else {
+            // Convert rootfs disk into a sparse file if storage ballooning flag had been enabled
+            // and then disabled.
+            convertToNonSparseDiskIfNecessary(image)
+
             // Note: this doesn't always do the resizing. If the current image size is the same as
             // the requested size which is rounded up to the page alignment, resizing is not done.
             image.resize(diskSize)
@@ -479,6 +518,7 @@
         private const val KEY_TERMINAL_PORT = "port"
 
         private const val GUEST_SPARSE_DISK_SIZE_PERCENTAGE = 95
+        private const val EXPECTED_PHYSICAL_SIZE_PERCENTAGE_FOR_NON_SPARSE = 90
 
         private val VM_BOOT_TIMEOUT_SECONDS: Int =
             {
diff --git a/android/TerminalApp/res/values/config.xml b/android/TerminalApp/res/values/config.xml
index 7f0b5e6..a2c9183 100644
--- a/android/TerminalApp/res/values/config.xml
+++ b/android/TerminalApp/res/values/config.xml
@@ -16,4 +16,5 @@
 
 <resources xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2">
     <bool name="terminal_portrait_only">true</bool>
+    <item name="activity_split_ratio" format="float" type="dimen">0.3</item>
 </resources>
diff --git a/android/TerminalApp/res/values/dimens.xml b/android/TerminalApp/res/values/dimens.xml
deleted file mode 100644
index e00ef7c..0000000
--- a/android/TerminalApp/res/values/dimens.xml
+++ /dev/null
@@ -1,19 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--  Copyright 2024 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
- -->
-
-<resources>
-    <dimen name="activity_split_ratio">0.3</dimen>
-</resources>
\ No newline at end of file
diff --git a/android/TerminalApp/res/xml/main_split_config.xml b/android/TerminalApp/res/xml/main_split_config.xml
deleted file mode 100644
index bd0271b..0000000
--- a/android/TerminalApp/res/xml/main_split_config.xml
+++ /dev/null
@@ -1,50 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--  Copyright 2024 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
- -->
-
-<resources xmlns:window="http://schemas.android.com/apk/res-auto">
-
-    <!-- Define a split for the named activities. -->
-    <SplitPairRule
-        window:clearTop="true"
-        window:finishPrimaryWithSecondary="adjacent"
-        window:finishSecondaryWithPrimary="always"
-        window:splitLayoutDirection="locale"
-        window:splitMaxAspectRatioInPortrait="alwaysAllow"
-        window:splitMinWidthDp="@integer/split_min_width"
-        window:splitRatio="@dimen/activity_split_ratio">
-        <SplitPairFilter
-            window:primaryActivityName="com.android.virtualization.terminal.SettingsActivity"
-            window:secondaryActivityName="com.android.virtualization.terminal.SettingsDiskResizeActivity" />
-        <SplitPairFilter
-            window:primaryActivityName="com.android.virtualization.terminal.SettingsActivity"
-            window:secondaryActivityName="com.android.virtualization.terminal.SettingsPortForwardingActivity" />
-        <SplitPairFilter
-            window:primaryActivityName="com.android.virtualization.terminal.SettingsActivity"
-            window:secondaryActivityName="com.android.virtualization.terminal.SettingsRecoveryActivity" />
-    </SplitPairRule>
-
-    <SplitPlaceholderRule
-        window:placeholderActivityName="com.android.virtualization.terminal.SettingsDiskResizeActivity"
-        window:finishPrimaryWithPlaceholder="adjacent"
-        window:splitLayoutDirection="locale"
-        window:splitMaxAspectRatioInPortrait="alwaysAllow"
-        window:splitMinWidthDp="@integer/split_min_width"
-        window:splitRatio="@dimen/activity_split_ratio"
-        window:stickyPlaceholder="false">
-        <ActivityFilter
-            window:activityName="com.android.virtualization.terminal.SettingsActivity"/>
-    </SplitPlaceholderRule>
-</resources>
\ No newline at end of file
diff --git a/android/virtmgr/src/aidl.rs b/android/virtmgr/src/aidl.rs
index d7f68b8..190acc7 100644
--- a/android/virtmgr/src/aidl.rs
+++ b/android/virtmgr/src/aidl.rs
@@ -641,6 +641,24 @@
 
         let calling_partition = find_partition(CALLING_EXE_PATH.as_deref())?;
 
+        let instance_id = extract_instance_id(config);
+        // Require vendor instance IDs to start with a specific prefix so that they don't conflict
+        // with system instance IDs.
+        //
+        // We should also make sure that non-vendor VMs do not use the vendor prefix, but there are
+        // already system VMs in the wild that may have randomly generated IDs with the prefix, so,
+        // for now, we only check in one direction.
+        const INSTANCE_ID_VENDOR_PREFIX: &[u8] = &[0xFF, 0xFF, 0xFF, 0xFF];
+        if matches!(calling_partition, CallingPartition::Vendor | CallingPartition::Odm)
+            && !instance_id.starts_with(INSTANCE_ID_VENDOR_PREFIX)
+        {
+            return Err(anyhow!(
+                "vendor initiated VMs must have instance IDs starting with 0xFFFFFFFF, got {}",
+                hex::encode(instance_id)
+            ))
+            .or_service_specific_exception(-1);
+        }
+
         check_config_features(config)?;
 
         if cfg!(early) {
@@ -668,7 +686,6 @@
             check_gdb_allowed(config)?;
         }
 
-        let instance_id = extract_instance_id(config);
         let mut device_tree_overlays = vec![];
         if let Some(dt_overlay) =
             maybe_create_reference_dt_overlay(config, &instance_id, &temporary_directory)?
diff --git a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl
index 5193e21..7db5135 100644
--- a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl
+++ b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl
@@ -23,7 +23,11 @@
     /** Name of VM */
     String name;
 
-    /** Id of the VM instance */
+    /**
+     * Id of the VM instance
+     *
+     * See AVirtualMachineRawConfig_setInstanceId for details.
+     */
     byte[64] instanceId;
 
     /** Main APK */
diff --git a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl
index c5fe982..1e4fe03 100644
--- a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl
+++ b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl
@@ -31,7 +31,11 @@
     /** Name of VM */
     String name;
 
-    /** Id of the VM instance */
+    /**
+     * Id of the VM instance
+     *
+     * See AVirtualMachineRawConfig_setInstanceId for details.
+     */
     byte[64] instanceId;
 
     /** The kernel image, if any. */
diff --git a/android/virtualizationservice/src/aidl.rs b/android/virtualizationservice/src/aidl.rs
index 1646117..e26cd4f 100644
--- a/android/virtualizationservice/src/aidl.rs
+++ b/android/virtualizationservice/src/aidl.rs
@@ -489,6 +489,9 @@
         id.try_fill(&mut rand::thread_rng())
             .context("Failed to allocate instance_id")
             .or_service_specific_exception(-1)?;
+        // Randomly allocated IDs always start with all 7s to avoid colliding with statically
+        // assigned IDs.
+        id[..4].fill(0x77);
         let uid = get_calling_uid();
         info!("Allocated a VM's instance_id: {:?}..., for uid: {:?}", &hex::encode(id)[..8], uid);
         self.try_updating_sk_state(&id);
diff --git a/libs/libavf/include/android/virtualization.h b/libs/libavf/include/android/virtualization.h
index 4bfe47a..e907ac4 100644
--- a/libs/libavf/include/android/virtualization.h
+++ b/libs/libavf/include/android/virtualization.h
@@ -78,6 +78,9 @@
  * The `instanceId` is expected to be re-used for the VM instance with an associated state (secret,
  * encrypted storage) - i.e., rebooting the VM must not change the instanceId.
  *
+ * `instanceId` MUST start with 0xFFFFFFFF if and only if this library is being
+ * called from code in a vendor or odm partition,
+ *
  * \param config a virtual machine config object.
  * \param instanceId a pointer to a 64-byte buffer for the instance ID.
  * \param instanceIdSize the number of bytes in `instanceId`.