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A lightweight, no-root watchdog for HyperOS 3 China ROM that keeps Google Play services in Xiaomi's no-restrict background list so FCM push stays reliable.

Designed for: China-market Xiaomi / Redmi / POCO phones with Google Play services already installed and working.

Download latest APK · Latest release

• No root or Shizuku — uses the user-grantable Modify system settings permission instead of root, persistent ADB, Accessibility, VPN, overlay, or device-admin privileges.
• Finance-app friendly — keeps the implementation deliberately low-privilege for better compatibility with security-sensitive apps.
• Low background power — exact event-driven monitoring is the main path; the 30-minute fallback is in-process and does not deliberately wake a sleeping phone.
• Reconnects only when needed — FCM/MCS reconnect broadcasts are sent only after a real whitelist repair or a manual request.
• Optional persistent notification — foreground mode uses a visible-but-silent notification channel for stronger process survival; quiet background mode remains available.
• FCM app assistant — scans likely Firebase/GCM clients and, when HyperOS exposes the vendor AppOps state, shows read-only Autostart status with automatic re-check after returning from system settings.
• Native dark mode — System / Light / Dark, with System as the default.
• 10-language UI — English, Simplified Chinese, Traditional Chinese, French, Japanese, Korean, Spanish, Portuguese, German, and Russian through Android's native per-app language mechanism.
• Compact-phone ready — responsive layout checks cover 320–480dp widths, including a Xiaomi 17-class 393dp profile.

1. Install the latest APK from GitHub Releases.
2. Open FCM Guard and grant Modify system settings.
3. Tap Repair now once.
4. Enable Automatic protection.
5. In HyperOS, enable Autostart for FCM Guard and set battery policy to No restrictions.
6. Keep Persistent notification enabled for maximum survival reliability. If Android/HyperOS blocks notifications for FCM Guard, the app opens the system notification settings so the foreground notification can be enabled.
7. Optional: scan FCM apps. If HyperOS exposes readable Autostart state, the list marks apps as Enabled / Partial / Disabled / Unknown and refreshes after you return from Configure all in HyperOS. If the ROM blocks the query, FCM Guard shows a clear Unknown/unavailable fallback instead of guessing.
8. Optional: tap Open FCM diagnostics to open Google Play services diagnostics and inspect the mtalk.google.com:5228 connection.
9. If one app still receives notifications late while other FCM apps are normal, configure that app separately. For apps such as WhatsApp, set Battery saver / Battery optimization → No restrictions in HyperOS; enabling Autostart is also recommended when available.

FCM Guard is mainly for China-ROM HyperOS 3 devices where Google services work normally but PowerKeeper / Greezer can still interrupt the background FCM connection.

Affected HyperOS builds can rebuild the private setting:

Settings.System.MILLET_NO_RESTRICT_APP

If com.google.android.gms is removed, Google Play services can be treated like a normal background process and its long-lived FCM/MCS connection may be interrupted.

FCM Guard reads the current comma-separated value, preserves all existing packages, and appends com.google.android.gms only when it is missing.

%%{init: {'theme':'base','themeVariables': {'background':'#ffffff','primaryColor':'#ffffff','primaryTextColor':'#000000','primaryBorderColor':'#000000','lineColor':'#000000'}}}%%
flowchart TD
    A[Watch MILLET_NO_RESTRICT_APP] --> B[Read current value]
    B --> C{GMS present?}
    C -- Yes --> D[Do nothing]
    C -- No --> E[Preserve current packages]
    E --> F[Append com.google.android.gms]
    F --> G[Write once]
    G --> H[Best-effort FCM reconnect]
    classDef bw fill:#ffffff,stroke:#000000,color:#000000,stroke-width:1.5px;
    class A,B,C,D,E,F,G,H bw;

FCM Guard intentionally uses compileSdk 35 with targetSdk 22. The modern compile SDK keeps current tooling, while the legacy target preserves the compatibility path needed to write Xiaomi's vendor-private Settings.System key with the user-grantable Modify system settings permission and without root/Shizuku.

• Exact ContentObserver only for MILLET_NO_RESTRICT_APP.
• ~400 ms debounce after an observed change.
• 30-minute in-process fallback instead of rapid polling.
• No AlarmManager, repeating exact alarm, or WakeLock for the fallback.
• No write when GMS is already present.
• No reconnect broadcast unless a repair actually happened or the user requests one.

Persistent mode runs GuardService as a foreground service. The current implementation uses a dedicated IMPORTANCE_LOW, silent notification channel so the notification remains visible without sound or vibration. Because FCM Guard deliberately targets SDK 22, Android 13+ controls the notification-permission prompt timing; if notifications are already blocked, FCM Guard links directly to the app's system notification settings.

Open FCM diagnostics now launches the current Google Play services activity first:

com.google.android.gms/com.google.android.gms.gcm.GcmDiagnostics

Older GTalkServiceDiagnostics is retained as a compatibility fallback, with a final best-effort lookup for a diagnostics activity inside Google Play services.

The scanner looks for standard manifest signals such as:

com.google.firebase.MESSAGING_EVENT
com.google.android.c2dm.intent.RECEIVE

A match means the app is a likely FCM/GCM client, not proof that every notification from that app uses FCM.

For detected apps, FCM Guard performs a read-only, best-effort check of Xiaomi's vendor Autostart AppOps (10008 and 10053). When both are readable, the UI reports:

• Enabled — both Autostart AppOps are allowed.
• Partial — one is allowed and the other is explicitly ignored.
• Disabled — both are explicitly ignored.
• Unknown — HyperOS blocked the query, returned a vendor/default state that cannot be interpreted safely, or otherwise did not expose a reliable result.

FCM Guard never treats Unknown as Disabled. If every detected app is Unknown, the per-app list is hidden and the assistant falls back to the detected count plus the single Configure all in HyperOS action. After returning from HyperOS settings, an expanded result is checked again automatically.

No Autostart state is modified programmatically, and no Shizuku/root/ADB privilege is introduced.

FCM Guard protects the Google Play services / FCM transport layer, but it does not override HyperOS battery rules for every receiving app. Some apps — including messaging apps such as WhatsApp — may use FCM as a wake-up/tickle path and still need their own process to run, open a background network connection, synchronize data, and generate the local notification.

Therefore, if FCM diagnostics are healthy and other apps receive pushes normally but one app is still delayed, configure that app separately. For WhatsApp, the recommended HyperOS setting is:

WhatsApp → Battery saver / Battery optimization → No restrictions

Also enable Autostart for the affected app when the ROM exposes that option. This should be applied only to apps that actually show delayed delivery rather than globally disabling battery optimization for every app.

• System / Light / Dark appearance modes.
• 10 native app languages: English, Simplified Chinese, Traditional Chinese, French, Japanese, Korean, Spanish, Portuguese, German, and Russian.
• Compact and large-width resource profiles.
• CI geometry checks for 320, 360, 393, 411, 430, and 480dp widths.

FCM Guard uses WRITE_SETTINGS, RECEIVE_BOOT_COMPLETED, foreground-service/notification support, and narrow package visibility for FCM/GCM handlers, Google Play services, and Xiaomi Security Center.

It does not require root, Shizuku, persistent ADB, Accessibility, VPN, overlay, device-admin, account access, or traffic inspection.

This project depends on Xiaomi's current HyperOS implementation. Xiaomi can change PowerKeeper / Greezer behavior, the private setting, app-management pages, or vendor AppOps behavior in future releases. FCM reconnect, FCM-client detection, and Autostart-status reading are all best-effort because Android does not expose public APIs that guarantee these vendor-specific operations.

FCM Guard protects the shared GMS/FCM connection; it cannot guarantee that HyperOS will allow every individual app enough background execution or network time to process a delivered FCM wake-up. Per-app battery settings may still be required for apps such as WhatsApp.

The PowerKeeper / Greezer investigation and the MILLET_NO_RESTRICT_APP repair strategy were originally documented by HyperOS FCM Fix:

• HyperOS FCM Fix by dingwen07: https://github.com/dingwen07/hyperos-fcm-fix
• Technical investigation: https://github.com/dingwen07/hyperos-fcm-fix/blob/main/docs/xiaomi-hyperos-gms-fcm-greezer-investigation.md

FCM Guard is an independent implementation focused on no Shizuku/root dependency, minimal privileges, event-driven monitoring, and low idle background activity. No source code from HyperOS FCM Fix is copied into this repository.

GitHub Actions checks responsive layout profiles and builds a signed debug APK. Pushes to main publish/update the versioned GitHub Release; feature branches can be validated before release.

For normal phone installation, use:

https://github.com/ReedGAOOO/FCMGuard-HyperOS/releases/latest/download/FCMGuard-HyperOS.apk

MIT License — see LICENSE.