Does Zendesk Talk offer SIP trunking? Can I register an SIP softphone to Zendesk Talk?
Zendesk Talk does not offer Session Initiation Protocol (SIP) trunking because the product manages the trunking for you. While you cannot register an SIP softphone with Zendesk Talk, agents can take calls on SIP phones by forwarding calls to a phone number on a SIP phone (see How do I forward calls from Talk to a personal phone). Agents can only answer SIP forwarded calls in their browser or by hard phone when the call is forwarded via the public switched telephone network (PSTN).
Additionally, Zendesk offers a robust Partner Edition API that allows developers to build out deeper integrations, which act exactly like the Zendesk Talk console in that they can create tickets, pop tickets for agents, etc. See our Talk API documentation.