Applying support for CarrierConfig overriding

Gakmots

wizoatk I still have question about it, because it seems not be a problem of Backup Calling support of GrapheneOS, the only thing needed is just an option to enable backup calling for SIM, in carrier settings, just like what we do for VoLTE and VoNR, It can be done with Pixel IMS or other simple tools, why it is broken in native GrapheneOS? Or maybe I can write a simple patch for it?

wizoatk

Gakmots

the only thing needed is just an option to enable backup calling for SIM

I'm fairly sure that isn't true.

Specifically, Backup_Calling options are no longer in AOSP Android 16. I've built images with the same options turned on as Pixel IMS (cross_sim) does. I can occasionally get a few calls through the data on the second SIM, but then subsequent calls just never connect. There's something more needed or broken or that I don't understand yet. It's not clear whether Cross SIM or WFC (Wi-Fi Calling) is the better path to explore.

There are also claims that Cross Sim Calling works on Stock Android 16. I personally have been unable to replicate that either, beyond just a few calls. If that could be replicated, there should be clues about the path that Google has taken.

If you can show me wrong, I'd be happy to test.

Summary: It's harder than you might imagine. The obvious simple things have been tried.

wizoatk

Gakmots the only thing needed is just an option to enable backup calling for SIM

Turns out that that's close.

I've got a better development environment now and have made some progress. A bit of code that is breaking is:
https://cs.android.com/android/platform/superproject/main/+/main:frameworks/opt/net/ims/src/java/com/android/ims/ImsManager.java;l=1217-1247

Specifically both isCrossSimCallingEnabledByUser() and isCrossSimCallingEnabled() are returning false. It's not obvious to me how to make the SubscriptionManager happy, so I hacked isCrossSimCallingEnabledByUser() so that it does nothing except "return true;" and things started working. I now have one local carrier SIM that does backup calling onto both a different local carrier SIM and multiple roaming data only SIMs. My other local carrier SIM additionally needed a carrier-override (e.g. adb shell cmd phone cc set-value enable_cross_sim_calling_on_opportunistic_data_bool true) to enable Backup Calling.

I haven't yet determined why my second carrier SIM won't backup call onto the roaming data only SIMs. I strongly suspect other SIMs/carriers will need other tweaks (carrier overrides) as well.

Gakmots

wizoatk Thanks for your help! Based on my test, the Backup Calling do works when the carrier config was enabled in stock OS, the main problem is that Android does not support manually using Backup Calling, so if there are any weak signal, it will try to use this signal. i use Ultra Mobile and Pixel 8 Pro for test, if force it to use a signal from non-supported carrier, it will use Backup Calling without problem. However, I need more test to do because Google fixed the feature used by Pixel IMS and will automatically restore the carrier settings, So now I have to root my test device to enable the Backup Calling option. Maybe it also lead to the situation you mentioned, it works on several call, but not work on others.

wizoatk

Best of luck.

If you get it working again with root on Stock OS (or GrapheneOS) I'd be interested in the details of what you did and the output of "adb shell dumpsys carrier_config".

Gakmots

wizoatk Also a personal DP: I think android will dealing with local carrier and roaming carrier in different way, in latest GrapheneOS 20260206, when set in CarrierOverride with NSA and SA forced enabled, it will only work in NSA when roaming but SA in local, even if SA roaming is supported (I tested on iPhone and it works). The only method to resolve, I currently know, is using Network Signal Guru, and force it to use SA, and also enable n79, n78 and n41 band. However, Network Signal Guru is totally a private software, so I have no idea on how it works..

Gakmots

Thanks for your work! My Pixel 8 Pro is currently using as my main phone so I am still waiting for free time to backup all data and root it, but you seems did a great job, thank you!

FM-World

wizoatk 5G being blocked by carrier policy, like saudia uae kuwait pakistan these countries where pixel phonee are not officially sold is now working? With this update?

wizoatk

FM-World

The issue you describe is not related to any feature that was added in Release 2025100300.

FM-World

wizoatk this is not feature just they block 5g on software level in google pixel via carrier policy file where pixel not officially sold pixel devices , it can be easily managed by rooting or if gos change carrier policy to all regions,
can possible?

refer this link

https://propakistani.pk/2026/03/19/heres-why-5g-is-not-working-in-iphones-pixels-some-samsung-phones-in-pakistan/

wizoatk

FM-World

Yes, I'm aware. It might be possible.

If someone can point me to a proper description of how/where to change carrier policy that is still valid for android 16, I'd enjoy the challenge. I have the ability to integrate and test. Everything that I've found so far is unhelpful.

FM-World

wizoatk
Edit Carrier Config: Locate data_mirror/data_de/null/0/com.android.phone/files/Carrierconfig-com.google.android.carrier-(ID_sim_card).xml.
Delete Restriction: Find and remove the line: <int-array name="carrier_nr_availabilities_int_array" num="0" />.

update this settings in next OTA then 5g will be work in all locations

wizoatk

FM-World Locate data_mirror/data_de/null/0/com.android.phone/files/Carrierconfig-com.google.android.carrier-(ID_sim_card).xml

I've seen this before. The information is out of date and/or not applicable to GrapheneOS.

Location and format of configuration file names have changed, in the build they are:

CarrierConfig/assets/carrier_config_carrierid_(ID_sim_card).xml

The larger issue is that your suggestion of what to edit/delete, doesn't exist.
The entire content of one of the country/providers in question is:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<carrier_config>
    <boolean name="show_4g_for_lte_data_icon_bool" value="true"/>
    <string name="default_vm_number_string">121</string>
</carrier_config>

FM-World

So isnthese configurations are same as google stock firmware?

wizoatk

FM-World So isnthese configurations are same as google stock firmware?

They are the same as AOSP. I don't know if Pixel stock varies from this.

https://cs.android.com/android/platform/superproject/main/+/main:packages/apps/CarrierConfig/assets/

In any case, I've changed "carrier_nr_availabilities_int_array" directly with adb shell cmd phone cc set-value and that didn't have any affect for the one provider that I can test with. So I don't think that's the problem/solution.

FM-World

wizoatk I DIDNOT FIND ANY FILE FOR PAKISTANI CARRIERS LIKE ZONG, JAZZ AND UFONE , ANY HELP REGARDING THIS?

FM-World

wizoatk I THIS THIS CODE ENABLES 5G IN UNSUPPORTED COUNTRIES CAN U TRY THIS?

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<carrier_config>
<string name="5g_icon_configuration_string">connected_mmwave:5G_Plus,connected:5G,not_restricted_rrc_idle:5G,not_restricted_rrc_con:5G</string>
<string name="5g_icon_display_grace_period_string">connected_mmwave,connected,30;connected_mmwave,not_restricted_rrc_idle,30;connected_mmwave,not_restricted_rrc_con,30</string>
<int-array name="additional_nr_advanced_bands_int_array" num="1">
<item value="78"/>
</int-array>
<int name="nr_advanced_threshold_bandwidth_khz_int" value="60000"/>
<boolean name="enable_nr_advanced_for_roaming_bool" value="true"/>
<boolean name="include_lte_for_nr_advanced_threshold_bandwidth_bool" value="true"/>
</carrier_config>

https://cs.android.com/android/platform/superproject/main/+/main:packages/apps/CarrierConfig/assets/carrier_config_carrierid_2089_Public-Mobile.xml

Freek

@"wizoatk" hi iam new here , iam looking for this back-up calling option from long back and now iam back on this intresting feature.
The back-up calling is working in any custom ROM now ? If some one confirm or is there any work around, i will give a try. And thanks for the info.
Sorry if iam missing something.
By the way is there a way to incorporate or write our own features in GOS , as i see custom ROM's having VPN sharing option , so like that is there any possibility to bypass roaming SIM .

Developer-Dude

FM-World theres a button on your keyboard that let's you disable all caps, btw.

wizoatk

FM-World

Your caps lock key appears stuck ...

OK, I'll bite. Specifically, why do you think this works?

FM-World

wizoatk i dont know but i want a solution please help

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