Viewable screen based call leg transition

A system for causing a call leg transition based on determining that a screen of a device is not viewable to a user, comprising:

• one or more processors;
• and
• a memory storing computer-executable instructions that, when executed, cause the one or more processors to control the system to perform operations comprising:
• receiving, using a default first telephony application, an incoming call event having a first call leg over a first connection to a telecommunication network addressed to the device;
• accepting the incoming call event using a second telephony application, creating a second connection having a second call leg to the telecommunication network corresponding to the incoming call event;
• associating a call event continuity identifier unique to the incoming call event with each of the first and second call legs so that the first and second call legs are connectable at a common port in the telecommunication network;
• determining if the screen of the device is viewable to the user;
• and
• causing a transition from the second call leg to the first call leg based on determining that the screen of the device is not viewable to the user.