LiveKit phone numbers cover one country, inbound only. No outbound, no transfers, no international. That is a preview, not telephony.
Sigmond is a voice AI agent running on the SignalWire infrastructure this page is about. Ask him about anything you just read.

Twilio shows a call ringing while LiveKit reports it ended. Production calls drop at one-second durations because neither system owns the truth.
SIP REFER returns 603 errors through the Twilio-to-LiveKit bridge. Voice-triggered transfers fail without error logs. Developers wait months for fixes.
Twilio charges for SIP trunking. LiveKit charges for audio orchestration. At 22,000 monthly calls, connectivity alone costs $860/month before any AI processing.
Debugging a dropped call means correlating LiveKit logs with Twilio logs across two platforms, two credential sets, and two support channels.
from signalwire_agents import AgentBase
from signalwire_agents.core.function_result import SwaigFunctionResult
class SupportAgent(AgentBase):
def __init__(self):
super().__init__(name="Support Agent", route="/support")
self.prompt_add_section("Instructions",
body="You are a customer support agent. "
"Greet the caller and resolve their issue.")
self.add_language("English", "en-US", "rime.spore:mistv2")
@AgentBase.tool(name="check_order")
def check_order(self, order_id: str):
"""Check the status of a customer order.
Args:
order_id: The order ID to look up
"""
return SwaigFunctionResult(f"Order {order_id}: shipped, ETA April 2nd")
agent = SupportAgent()
agent.run()
| Capability | LiveKit Phone Numbers | LiveKit + Twilio/Telnyx | SignalWire |
|---|---|---|---|
| Countries available | US only | Depends on CPaaS provider | Global |
| Inbound calling | Yes | Yes | Yes |
| Outbound calling | No | Yes (via CPaaS) | Yes (native) |
| Cold transfers | No | SIP REFER fails (603 errors) | Native |
| Warm transfers | No | Fragile through bridge | Native |
| Number porting | Not documented | Via CPaaS provider | Yes |
| Call recording | Not included | Separate config per provider | Built in |
| Call state ownership | LiveKit only | Split across two systems | Single source of truth |
| Billing | LiveKit only | Two vendors, two invoices | One vendor, one invoice |
| Setup complexity | Low (US inbound only) | High (multi-provider config) | Low (native platform) |
We didn't add SIP support as an afterthought. We wrote the SIP stack the industry runs on. FreeSWITCH has processed trillions of carrier minutes across nearly 20 years of production deployment.
Run `pip install signalwire-agents` to get telephony, AI, and agent framework in one package.
Same AI logic, new SDK surface. AgentBase replaces VoicePipelineAgent with built-in transfers and state management.
Bring your existing phone numbers to SignalWire. Global coverage, inbound and outbound, all transfer types.
No more Twilio bill, no more bridge latency, no more split call state. One platform handles everything.
Yes. SignalWire supports number porting for US and international numbers. Your existing numbers move to the platform with no downtime for your callers.
Yes. Outbound calling is native to the platform. Appointment reminders, lead follow-ups, and campaign calls work with the same agent framework and phone numbers.
All of them: cold, warm, blind, and attended. Transfers are built into the platform and work with agent-to-agent, agent-to-queue, and agent-to-external-number scenarios.
LiveKit is an agent framework built on WebRTC. Phone calls require SIP and PSTN connectivity, which LiveKit does not include. A bridge to Twilio or Telnyx adds latency, cost, and failure modes.
Trusted by 2,000+ companies
Stop bridging two providers for what should be one phone call.
SignalWire is a communications infrastructure platform. Voice, video, messaging, conferencing, queuing, recording, and AI all run on the same real-time voice and video substrate.
AI is one capability among many, not the whole business. Customers compose multiple services on a single carrier-billed call; margin expands as the service mix shifts toward higher-margin capabilities stacked on top of the transport layer.
The platform was built by the team that created FreeSWITCH. It processes 2.7 billion minutes and messages annually and is in production at 2,000+ companies, including Salesforce, Sprinklr, and Apple.