Signal Calls Interrupted by Incoming Phone Calls on iOS

[plia7]

Platform/Device/OS/Version
Device: iPhone SE
Operating System: iOS 15
App Version: 7.42
Description of the Issue
When participating in an active Signal call, receiving a regular (cellular) phone call causes the Signal call to be immediately interrupted and disconnected. This differs from how incoming calls are handled during standard phone calls, where the current call continues and the new call is indicated with a notification.

Expected Behavior
If an incoming cellular call arrives while on a Signal call, the ongoing Signal call should remain active.
Users should receive a simple notification about the incoming call or have the caller notified that the user is currently busy.
The Signal call should not be disconnected unless explicitly ended by the user.
Steps to Reproduce
Start a Signal voice or video call.
While the Signal call is ongoing, receive a regular phone call on your device.
Observe that the Signal call is interrupted and ends immediately.
Actual Result
The active Signal call is interrupted but remains on the screen, appearing as if it is still ongoing. However, both parties cannot hear each other, and the other side often sees a “reconnecting” message. This is particularly confusing for the other party on the Signal call, as the call ends abruptly without any proper notice or explanation.

Expected Result
The Signal call should remain uninterrupted, and the incoming cellular call should:

Trigger a notification for the user to decide whether to answer or ignore.
Optionally, notify the incoming caller that the recipient is busy.
Additional Information
This issue significantly impacts the reliability of Signal for calls, especially in professional or critical settings.
Implementing a seamless call waiting feature would greatly enhance the user experience, aligning Signal’s functionality with standard telephony behavior.

Additional Notes

• Previously, in iOS 14, version 7.19.1, it wasn’t doing that.

• Someone reported this issue happening in the latest iOS/version as well: https://community.signalusers.org/t/signal-calls-interrupted-by-incoming-phone-calls-on-ios