Carrier

The carrier delivers the phone call to Patter. Patter supports Twilio, Telnyx, and Plivo. All three share inbound DTMF, call transfer, AMD, status callbacks, recording, voicemail drop, and cost tracking. Plivo additionally supports native DTMF send over the media WebSocket — a capability Twilio Media Streams lacks. You configure one carrier per Patter instance by passing an instance to the carrier= keyword argument. Each carrier class falls back to environment variables when constructor arguments are omitted. Each carrier ships as both a flat alias (from getpatter import Twilio, Telnyx, Plivo) and a namespaced class (from getpatter.carriers import twilio → twilio.Carrier()). They are equivalent.

Twilio

from getpatter import Patter, Twilio

phone = Patter(carrier=Twilio(), phone_number="+15550001234")   # reads env
# Or explicitly:
phone = Patter(
    carrier=Twilio(account_sid="AC...", auth_token="..."),
    phone_number="+15550001234",
)

Parameter	Type	Default	Description
`account_sid`	`str`	`""`	Twilio Account SID (starts with `AC`). Reads from `TWILIO_ACCOUNT_SID` when empty.
`auth_token`	`str`	`""`	Twilio Auth Token. Reads from `TWILIO_AUTH_TOKEN` when empty.

Namespaced form:

from getpatter.carriers import twilio

carrier = twilio.Carrier()                            # reads env
carrier = twilio.Carrier(account_sid="AC...", auth_token="...")

On serve(), Patter automatically sets the voice_url on the Twilio number to https://<webhook_url>/webhooks/twilio/voice via the Twilio REST API — no manual Console configuration needed.

Twilio trial account limitations

Twilio trial accounts apply a few platform-level restrictions that affect first-time testing. None of these are Patter limitations — they’re Twilio platform rules:

Verified Caller IDs required for outbound — trial accounts can only call numbers you’ve added under Phone Numbers › Verified Caller IDs in the Twilio Console. Verifying via the CLI is also restricted; do it from the Console.
Trial announcement prepended on outbound calls — Twilio plays an English trial-account message before connecting the call to your agent; the callee has to press a key to continue.
Trial caller-ID restrictions — the caller-ID shown to the recipient may be masked or labelled differently than your purchased number until the account is upgraded.

Upgrading the account in the Twilio Console clears all three. Refer to the Twilio docs (search: “trial account”) for the current exact behaviour — Twilio may change these over time.

Signature verification

The Auth Token is also used to verify every Twilio webhook with HMAC-SHA1 against the X-Twilio-Signature header. Requests with invalid signatures are rejected with HTTP 403.

Telnyx

from getpatter import Patter, Telnyx

phone = Patter(carrier=Telnyx(), phone_number="+15550001234")    # reads env
# Or explicitly:
phone = Patter(
    carrier=Telnyx(
        api_key="KEY...",
        connection_id="2000000000000000000",
        public_key="...",  # optional — enables Ed25519 signature verification
    ),
    phone_number="+15550001234",
)

Parameter	Type	Default	Description
`api_key`	`str`	`""`	Telnyx API v2 key. Reads from `TELNYX_API_KEY` when empty.
`connection_id`	`str`	`""`	Call Control Application ID. Reads from `TELNYX_CONNECTION_ID` when empty.
`public_key`	`str`	`""`	Optional. Ed25519 public key for webhook signature verification. Reads from `TELNYX_PUBLIC_KEY` when empty.

Namespaced form:

from getpatter.carriers import telnyx

carrier = telnyx.Carrier()                            # reads env

Signature verification

When public_key is set (or TELNYX_PUBLIC_KEY is present), every Telnyx webhook is verified with Ed25519. Requests older than 5 minutes are rejected (replay protection).

Plivo

from getpatter import Patter, Plivo

phone = Patter(carrier=Plivo(), phone_number="+15550001234")    # reads env
# Or explicitly:
phone = Patter(
    carrier=Plivo(auth_id="MA...", auth_token="..."),
    phone_number="+15550001234",
)

Parameter	Type	Default	Description
`auth_id`	`str`	`""`	Plivo Auth ID (starts with `MA` or `SA`). Reads from `PLIVO_AUTH_ID` when empty.
`auth_token`	`str`	`""`	Plivo Auth Token. Used for HTTP Basic auth on the Plivo REST API and as the V3 webhook signature key. Reads from `PLIVO_AUTH_TOKEN` when empty.

Namespaced form:

from getpatter.carriers import plivo

carrier = plivo.Carrier()                              # reads env
carrier = plivo.Carrier(auth_id="MA...", auth_token="...")

On serve(), Patter best-effort creates a Plivo Application bound to https://<webhook_url>/webhooks/plivo/voice and links it to your phone number via the Plivo REST API. Most production deployments pre-configure the Plivo Application in the console — pass manage_webhook=False on serve() to opt out.

Wire format and parity gains

Audio: mulaw 8 kHz, pinned via the <Stream contentType="audio/x-mulaw;rate=8000"> answer XML. Plivo’s <Stream> element places the WSS URL as its text content (not a url= attribute, as Twilio does).
Native DTMF send over the media WebSocket via sendDTMF — a parity gain over Twilio Media Streams.
Voicemail drop uses Plivo’s live-call Speak API + DELETE /Call/{uuid}/ hangup.
AMD is async: Patter sets machine_detection="true" + machine_detection_url=/webhooks/plivo/amd so human pickups don’t incur the detection-window latency.
Status callback: Patter wires hangup_url=/webhooks/plivo/status on outbound calls so no-answer / busy / failed transitions reach the dashboard before any media webhook fires.

Signature verification

The Auth Token doubles as the V3 webhook signature key. The V3 scheme is:

POST: signed = url + sorted_post_params + "." + nonce — POST params sorted alphabetically by key (case-sensitive) and concatenated as key1value1key2value2… with no delimiters.
GET: signed = url + "." + nonce — query parameters live in the URL already.

Both are HMAC-SHA256 keyed on the Auth Token and base64-encoded, delivered as the X-Plivo-Signature-V3 header alongside X-Plivo-Signature-V3-Nonce. The signature header may carry comma-separated values during key rotation; any matching value accepts. Requests with invalid signatures are rejected with HTTP 403.

Webhook Endpoints

The embedded server exposes these endpoints regardless of carrier choice:

Endpoint	Purpose
`POST /webhooks/twilio/voice`	Incoming Twilio call → returns TwiML to start streaming.
`POST /webhooks/twilio/status`	Call lifecycle status callbacks (initiated, ringing, answered, completed).
`POST /webhooks/twilio/recording`	Recording completion callbacks.
`POST /webhooks/twilio/amd`	Async AMD (answering machine detection) results.
`POST /webhooks/telnyx/voice`	Incoming Telnyx call → returns Call Control commands.
`POST /webhooks/plivo/voice`	Incoming Plivo call → returns Plivo XML to start streaming. Also serves outbound `answer_url`.
`POST /webhooks/plivo/status`	Plivo `hangup_url` callback — call lifecycle (completed, busy, no-answer, failed, timeout, cancel).
`POST /webhooks/plivo/amd`	Async AMD result (`machine_detection_url`).
`GET	POST /webhooks/plivo/transfer`	`<Dial>` XML for blind transfer (Plivo `aleg_url`).

Outbound calls

Use phone.call(...) to place an outbound call on either carrier. Every keyword argument is snake_case:

import asyncio
from getpatter import Patter, Twilio, OpenAIRealtime

phone = Patter(carrier=Twilio(), phone_number="+15550001234")
agent = phone.agent(engine=OpenAIRealtime(), system_prompt="You are a friendly receptionist.")

async def main():
    server = asyncio.create_task(phone.serve(agent, tunnel=True))
    await phone.ready                                   # wait until tunnel + listener are up

    await phone.call(
        to="+15550009876",
        agent=agent,
        first_message="Hi! This is a courtesy call from Acme.",
        machine_detection=True,                          # default since 0.6.2
        ring_timeout=25,                                 # default since 0.6.2
        voicemail_message="Please call us back at +15550001234.",
    )

asyncio.run(main())

Key defaults changed in 0.6.2:

machine_detection defaults to True. On Twilio Patter sends MachineDetection=DetectMessageEnd + Async AMD so there is no answer-latency penalty on human pickups. Pass False to skip per-call AMD billing.
ring_timeout defaults to 25 seconds. Pass 60 for legacy carrier-default parity, or None to omit the parameter entirely.
The AMD callback was renamed on_machine → on_machine_detection and now receives a MachineDetectionResult (not a raw dict).

See Local Mode › call() Parameters for the full parameter table.

What’s Next

STT

Speech-to-text providers.

LLM

Language model providers.

TTS

Text-to-speech providers.

Tunneling

Expose your local server publicly.

Get Started

Setting up Patter

Observability

Integrations

Development

Carrier

Carrier

Twilio

Twilio trial account limitations

Signature verification

Telnyx

Signature verification

Plivo

Wire format and parity gains

Signature verification

Webhook Endpoints

Outbound calls

What’s Next

STT

LLM

TTS

Tunneling

​Carrier

​Twilio

​Twilio trial account limitations

​Signature verification

​Telnyx

​Signature verification

​Plivo

​Wire format and parity gains

​Signature verification

​Webhook Endpoints

​Outbound calls

​What’s Next

STT

LLM

TTS

Tunneling

Carrier

Twilio

Twilio trial account limitations

Signature verification

Telnyx

Signature verification

Plivo

Wire format and parity gains

Signature verification

Webhook Endpoints

Outbound calls

What’s Next