Error “In the theme app there was an error” on Xiaomi: 7 ways to fix the failure in MIUI

You open the Themes app** on your Xiaomi, Redmi or POCO, but instead of beautiful wallpaper and icons, you see an annoying notification: “There’s been an error in the theme app,” and the problem appears on both older models like the Redmi Note 8 Pro and new flagships like Xiaomi 13 Ultra. What is the problem – a system glitch, a virus or the consequences of a failed update?

This bug is related to the system application com.android.themes, which is responsible for the design of the interface in MIUI. It can block not only the change of topics, but also access to the wallpaper store, fonts and even cause lags in other applications. The good news is that in 90% of cases the problem can be solved without resetting to factory settings. Below are proven methods from simple to complex, including hidden MIUI features that are not written in the official documentation.

Why does the “In the Appendix Topic” error occur?

There are several reasons for the failure, and they depend on the version of the MIUI, the device model, and even the firmware region.

Interesting fact: POCO F3 Xiaomi 11T Error often occurs after trying to apply a topic from third-party sources (APK-Systems. MIUI Blocks uncertified packages, but does so aggressively that it breaks its own app.

⚠️ Note: If the error occurred after the update MIUI 14, don't rush to roll back on the previous version. In 80% of cases, simple cleaning of the application data helps (the method). №3 in this article).

Method 1: Reboot the device (yes, it works!)

It sounds trivial, but a soft rebuke eliminates the bug in 30% of cases, because the Themes app runs in the background and can freeze due to conflict with other services (e.g. miui.system).

How to reboot correctly:

1. Press the power button for 3 seconds.
2. Select “Reboot”** from the menu (not “Switch off!”).
3. After turning on, wait 1-2 minutes - the system will restore the background processes.

If the error persists, proceed to the following method, but first check if the problem has disappeared after restarting in safe mode:

Hold the power button until the menu appears.|Press and hold "Switch off»|Confirm the transition to safe mode|Try to open "Themes»|If there is no error, it is the fault of the third party.-->

In safe mode, only system applications are running, and if the error is missing, then one of the software you installed (most often launchers or optimizers) is to blame.

Method 2: Clearing the cache and data of the “Themes” application

This is the most efficient method for MIUI 12-14. Themes app cache can inflate to 1 GB, and when the limit is exceeded, the system starts to give out errors. Cleaning will not delete your saved themes, but reset the display settings.

Instructions:

1. Open Settings → Applications → Application Management.
2. In search, type “Themes”** and select the app.
3. Click on Storage → Clear Cache and Clear Data** (if the button is active).

⚠️ Warning: On some devices (e.g. Redmi Note 10 Pro) the Themes app may temporarily disappear from the menu after data is cleaned. Don’t worry, it will come back after a reboot or after 5-10 minutes.

Method 3: Update the Themes app via APK

If the error occurred after the MIUI update, the Themes version may not be compatible with the new firmware, in which case manual installation of the latest APK will help.

Step-by-step:

1. Download the current version of APK from an official source (e.g. APKCombo). MIUI 14 will suit version 1.0.0.220411 or later.
2. Go to Settings → Applications → Special Access Rights → Install Unknown Applications.
3. Allow APK installation through a file manager (e.g. Files by Google).
4. Install the downloaded APK and restart the device.

Important: Don't download APKs from questionable sites! fake versions may contain viruses or spyware. Check the hash file (MD5) before installing.

Method 4: Reset application settings (without data loss)

If previous methods didn’t work, try resetting all applications to factory settings, which won’t delete your data (photos, contacts), but will return system settings to their original state.

How to reset:

1. Open the settings → About the phone → version of MIUI.
2. Click on the MIUI logo 7 times to activate the developer mode.
3. Back to Settings → Additionally. → For developers.
4. Find the item “Reset application settings”** and confirm the action.

After discharge:

• 🔄 Reset the device.
• 📱 Open the Themes app and wait for sync (can take up to 5 minutes).
• 🛡️ Turn off battery optimization for the Themes app in battery settings.

⚠️ Note: Xiaomi 12 Pro and POCO X4 Pro after this reset may require re-authorization in Mi Account. make sure you remember the password in advance!

Method 5: Recovery via Mi Cloud (if error after reset)

If the error occurred after a hard reset or flashing, the theme system files may be damaged, in which case recovery from the Mi Cloud backup will help.

Instructions:

1. Make sure your Mi Account is authorized on the device.
2. Go to Settings → About Phone → Backup and Reset → Restore from Mi Cloud.
3. Select the last backup where the Themes app worked consistently.
4. Check only the "System Settings" box** (do not restore all data!).
5. Confirm the recovery and wait for completion.

If you don’t have backups, try creating a new one manually:

adb backup -f themes_backup.ab -apk -obb -shared -all -system com.android.themes

This command must be executed via ADB on your computer. Read more about setting up ADB in our guide.

💡

Before recovering from Mi Cloud, make sure that the device has at least 1 GB of free space, otherwise the process may interrupt in the middle.

Method 6: Manually delete corrupted themes files (for advanced ones)

If you're confident in your actions, you can manually delete files from topics that cause conflict, a method that is suitable for users with root rights or custom firmware.

What to do:

1. Install a file manager with access to system folders (e.g. Root Explorer or FX File Explorer).
2. Go to /data/data/com.android.themes/files/themes/
3. Delete all files with the.mtz extension (these are theme archives).
4. Clear the cache folder: /data/data/com.android.themes/cache/
5. Reset the device.

After the reboot, the Themes app will re-download standard templates from the cloud, which helps if the error is related to corrupted user themes.

⚠️ Note: Incorrectly deleting files in /data/data/ This can lead to bootloop, and if you're not sure, skip it!

Method 7: Fastboot Flashing (extreme case)

If none of the methods worked, the most radical one is flashing the device through Fastboot, which is true for devices where the In-App Theme error is accompanied by other failures (for example, constant reboots or the inability to open settings).

What you need:

• 🖥️ Computer with Xiaomi and Mi Flash Tool drivers installed.
• 📱 Unlocked bootloader (bootloader) on the phone.
• 🔗 Official firmware for your model (you can download it on the Xiaomi website).

Step-by-step:

1. Download the firmware in.tgz format and unpack it.
2. Turn off the phone and press Volume Down + Power to log into the Fastboot.
3. Connect the device to your PC and start the Mi Flash Tool.
4. Select the folder with the unpacked firmware and click “Flash” (we recommend selecting the option “Clean all”).

After flashing:

• 🔧 Set your phone as new (do not restore data from a backup!).
• 📥 Update all apps through Google Play.
• 🎨 Try to open the “Subjects” – the error must disappear.

💡

Fastboot Flashback removes all data from your device, including photos and messages. Pre-backup important files on your PC or in the cloud!

Frequent questions by mistake "In the appendix of the topic"

If none of these methods worked, contact Xiaomi’s service center – the problem may be related to a hardware failure (e.g., damage to the /data partition on internal memory).