Cepheus on Xiaomi Mi9: everything you need to know about custom firmware

Xiaomi Mi9 is still one of the most popular flagships of the brand, despite the release of new models. owners of this smartphone often face the question: how to extend the life of the device, improve its performance and get the latest features? Here comes the custom firmware Cepheus, specialized software developed by enthusiasts specifically for the Mi9 (codenamed cepheus).

But what is Cepheus really? It's not just an alternative to standard MIUI, but a deeply optimized firmware based on pure Android (AOSP) or modified versions like LineageOS, Pixel Experience or ArrowOS. Its key advantage is the lack of excess software from Xiaomi, regular security updates and the ability to fine-tune "yourself." However, installing custom firmware requires unlocking the bootloader, which deprives warranties and carries certain risks. In this guide, we will understand whether the game is worth a candle, how to install Cepheus correctly and what underwater stones await you.

What is Cepheus and why it is related to Xiaomi Mi9

The name Cepheus is the internal code name Xiaomi Mi9, which is used by developers to identify the model in firmware and cores. When people talk about "Cepheus firmware", they usually mean custom software adapted for this particular smartphone. It is important to understand that this is not official firmware from Xiaomi, but community products such as:

• 🔹 LineageOS - lightweight and stable firmware based on AOSP.
• 🔹 Pixel Experience – Replays the interface and functions of Google Pixel.
• 🔹 ArrowOS – Balance between productivity and customization.
• 🔹 HaventOS or Project Elixir – firmware with unique chips (for example, dynamic design).

What all of these firmware has in common is that they are designed specifically for the Mi9 hardware platform (Snapdragon 855 processor, 6/8 GB of RAM, AMOLED display), which ensures that the hardware works properly. Unlike MIUI, where updates for the Mi9 have long been discontinued, custom firmware continues to come out regularly, including security patches from Google.

But why not just stay on MIUI? The reasons for switching to Cepheus are usually:

• 🚀 Productivity: lack of background processes MIUI Saves charge and speeds up work.
• 🔄 Relevance: Support for new versions of Android (e.g. Android) 13/14 on Mi9).
• 🎨 Customization: the ability to change themes, icons, animations without restrictions.
• 🔒 Privacy: No Xiaomi data collectors and Chinese services.

⚠️ Attention: Installing custom firmware voids warranty and can result in a device blink if the process is disrupted, such as an incorrectly selected kernel or firmware for another model (Mi9 SE or Mi9 Pro) will make the smartphone a “brick".

Advantages and Disadvantages of Cepheus Firmware

Before you switch to custom software, weigh the pros and cons. Below is a comparative table of key aspects:

One of the main disadvantages of custom firmware is that it doesn't have official support if something goes wrong (for example, it doesn't work). NFC or VoLTE, you will have to fix the problem yourself or contact forums like XDA Developers or 4PDA. In addition, some functions Mi9 They may not work properly:

• 📸 Camera: Without manually configuring GCam, photo quality will deteriorate.
• 🔋 Charging: Quick Charge 4 Quick Charge+ may not be supported.
• 🎧 Sound: possible problems with Dolby Atmos or Hi-Res Audio.

Preparation for installation: unlocking the loader

Before installing Cepheus, you need to unlock the bootloader (bootloader) Xiaomi Mi9. This is a mandatory step, without which it is impossible to flash custom software.

1. Mi Account Link: You need to link the device to your Xiaomi account in settings (Settings → Mi Account → Link the device).
2. Unlock request: apply through the official Mi Unlock app (you can download it on the Xiaomi website).
3. Waiting: It usually takes 72–168 hours (up to 7 days) to unlock.
4. Connect to a PC: After approval, connect the smartphone in Fastboot mode and start unlocking.

Important: Once the bootloader is unlocked, all data on the phone will be erased. Backup photos, contacts and apps in advance.

• 🔓 Unlocking will void the warranty (even if the bootloader is later blocked back).
• 🛡️ Some banking applications (such as Sberbank Online or Tinkoff) may stop working due to the lack of SafetyNet.
• 🔄 After unlocking. Mi9 It will be reset to factory settings with each flashing.

Make a backup of data | Charge your phone at least 60% | Install Xiaomi drivers on PC | Download Mi Unlock Tool | Link your Mi Account to your device-->

⚠️ Note: If you have purchased Xiaomi Mi9 b/w, make sure the previous owner untie his Mi Account from the device. Otherwise, you will not be able to unlock the bootloader - you will need to contact Xiaomi with proof of purchase.

Step-by-step instructions for installing Cepheus

When the bootloader is unlocked, you can start installing custom firmware.

• 📱 Xiaomi Mi9 loader-free.
• 💻 Computer with drivers installed ADB and Fastboot.
• 🔗 Cepheus firmware (e.g. Pixel Experience or LineageOS in.zip format).
• 🔧 Castom Recovery TWRP for Mi9 (The version should support Android 10+).
• 🔋 Battery charge of at least 80%.

We follow the instructions:

1. Installation TWRP: Download the current version TWRP For cepheus (e.g., from here). Put the phone in Fastboot mode (turn off, then press Volume down). + Power. Connect to your PC and execute the command: fastboot flash recovery. twrp-3.7.0_9-0-cepheus.img Reboot to Recovery: Fastboot Reboot Recovery.
2. Cleaning of sections: B TWRP run the Wipe → Advanced Wipe and mark: 📁 Dalvik / ART Cache 📁 System 📁 Data 📁 Cache ❗ Do not touch the Internal Storage section if you do not want to lose files on internal memory.
3. Install firmware: Copy the firmware file (.zip) to your phone or flash drive. In TWRP, select Install, specify the file, and install it. Once complete, press Reboot System.

The first run can take 5-10 minutes - don't interrupt the process! If after the reboot the phone is stuck on startup the logo, try re-installing or checking the firmware compatibility with your Mi9 version (e.g. global MI9 vs. Chinese MI9 SE).

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If the sensor doesn't work after the firmware is running or the screen flashes, chances are you've installed firmware for another model.

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cepheus

Firmware settings after installation

After successful installation of Cepheus, you need to follow several steps to properly work the smartphone:

1. Install Gapps: If you have chosen firmware without Google services (for example, LineageOS without Gapps), download the appropriate Open Gapps package (nano or pico option is recommended) and install it via TWRP immediately after you have firmware.
2. Magisk configuration: To get root rights and pass SafetyNet (needed for banking applications), install Magisk: Download the latest version of Magisk (.zip). Install via TWRP (similar to firmware). After restart, install Magisk Manager from.apk.
3. Battery Optimization: In Developer Settings (Settings) → The phone. → Build number - tap 7 times) activate: 🔋 Limitation of background processes (maximum 2–3). 🔄 Window animation and Transitions - install 0.5x speed up. 📶 Switch to 2G (if the cover is weak).

To improve the camera performance, it is recommended to install Google Camera (GCam) with settings for the Snapdragon 855.

• 📷 BSG GCam (Stable version for the Mi9).
• 📷 Nikita GCam (with support) HDR+ Night Sight).

Solving common problems

Even after a successful Cepheus installation, bugs can occur, and here are the most common ones and ways to fix them:

If the Mi9 has stopped turning on (brick) after the firmware, try the following steps:

1. Connect your phone to your PC in Fastboot mode.
2. Check if the device is determined by the command: fastboot devices
3. If yes, run the official firmware through the Mi Flash Tool (select the clean all option).
4. If not, it may have been damaged. EDL-Mode (programmer required).

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If the phone doesn't turn on after Cepheus firmware, DO NOT PANIC. 90% of the time, it helps to re-install the firmware via Fastboot or EDL. The main thing is not to interrupt the process and use the verified files.

Cepheus alternatives: other ways to upgrade Xiaomi Mi9

If installing custom firmware seems too risky, consider alternative options for extending the life of the Mi9:

• 🔄 Official global firmware: Xiaomi has stopped supporting Mi9, You can manually install the latest stable version. MIUI It's not going to give you new features, but it's going to fix bugs.
• 📱 Ported firmware: Some developers migrate firmware from other devices (e.g, Mi9T or Redmi K20 Pros, which have similar iron, are less risky than full custom firmware.
• ⚡ Optimization of the current MIUI: Remove unnecessary applications through ADB, Turn off auto-start services and use Greenify to save battery. It won't replace custom firmware, but it will improve performance.
• 🔧 Cores and Mods: You can install a custom core (for example, FrancoKernel) or a fashion like ViPER4Android for sound without a complete firmware change.

If your goal is simply to get the latest version of Android, look for projects like MIUI Mix or MIUI Pro. These are modified versions of MIUI, where developers add features from new versions of Android without drastically reflashing.

FAQ: Frequent questions about Cepheus on Xiaomi Mi9