[Bug] GATT 133/147 errors on Android 17 with Libre 2 Plus (3MH0) sensors due to OS-level BLE throttling

[bbfsdev]

FYI, I'm a developer and will fork and work on this issue, I just want to sync and align the work with maintainers to make sure I'm doing the right thing.

On Android 17 (Pixel 10), Juggluco is consistently failing to maintain a stable Bluetooth connection to Libre 2 Plus (3MH0) sensors. The logs show a cyclical failure pattern: GATT Error 133 followed by 147 (SEC_CHAR_CHALLENGE_DATA).

The issue persists even after setting battery usage to "Unrestricted" and locking the app in the recent-app switcher. It appears that Android 17's background GATT client throttling prevents the app from completing the sensor’s mandatory cryptographic challenge-response handshake when the device is in a low-power state or stationary.

Environment:

Device: Google Pixel 10

OS: Android 17 (API 37)

Sensor: FreeStyle Libre 2 Plus (Prefix: 3MH0)

Juggluco Version: 10.8.1

Configuration: Juggluco -> xDrip+ -> AAPS (Virtual Bridge)

Steps to Reproduce:

Initialize Libre 2 Plus (3MH0) sensor via NFC.

Allow the Bluetooth connection to establish while the app is in the foreground.

Place the phone in a stationary position and allow the screen to turn off.

Observe the logs: 133 (GATT_ERROR) occurs followed by 147 (Security Challenge failure).

Expected Behavior:
The app should maintain the GATT connection or reliably re-initialize the handshake upon screen wake/device movement without triggering a permanent 133 error state.

Actual Behavior:
The Bluetooth stack becomes unresponsive, requiring a manual Bluetooth toggle or phone restart to clear the 133 error.

FYI, seldom a reading is going through:

[j-kaltes]

I don't think that a disconnection with status=147 has any relation with SEC_CHAR_CHALLENGE_DATA, which I only know as a characteristic of Libre 3 (

Juggluco/Common/src/libre3/java/tk/glucodata/Libre3GattCallback.java

Line 1013 in d49a71b

this.gattCharChallengeData = bluetoothGattService.getCharacteristic(LIBRE3_SEC_CHAR_CHALLENGE_DATA);

).
If it is really a connection error, you will gain little from modifying Juggluco because that is totally in the control of Android.
You should look at the following:

• Are there other battery optimisations and activity in the background allowances in Android settings;
• Is another app or device connecting with the sensor;
• Try switching Bluetooth off and on;
• Reboot the phone;
• Keep Juggluco in the foreground, don't hide the notification of Juggluco.

[bbfsdev]

Unfortunately Gemini was able to provide all 5 points you mentioned and I tried them all putting into this many hours.
Another thing to note is that the official libre application or xDrip+ with OOP2 is also not working with similar symptoms.

When I had my Pixel 9 with Android 15 it was working well.

Can it be that Android 16/17 introduces new types of bluetooth enforcement, for example in Android 16 and 17, the legacy Bluetooth Health Device Profile (HDP) is officially deprecated and no longer used by the Android system. Instead, Android relies entirely on Bluetooth Low Energy (BLE) to connect with health and fitness monitors: https://developer.android.com/reference/android/bluetooth/BluetoothHealth

Or any other OS change, as this was the event for me for things to start breaking for the second sensor now.
I wonder if other devices (not Pixel) with Android 16/17 had similar issues.

[bbfsdev]

What about the Tubo or Android modes in the application, they did not work for me, but can this be some kind of direction?
3MH01... is Libre 2+?

[bbfsdev]

Example for 133 error:

[j-kaltes]

Setting Android in left menu->Sensor makes that it takes longer to get a connection, but that will not the cause of your difficulties.
From what you write here, I think that you are here at the wrong place, you need to contact the manufacturer of your phone.

[bbfsdev]

You mean a specific device? Or all Pixel 10 devices?
FYI, moving to a different phone with an older android (15) solved the problem.

[keynator]

Maybe it is the wrong place for this question but does anyone has run Juggluco run successfully on Android 17 (what currently may only be possible for Pixel devices)?

I really hesitate so to the upgrade with my Pixel 8 since I do not want to miss a working Juggluco since the app is so great.

Now I did a upgrade and it worked flawless.