dograh/docs/integrations/telephony/custom.mdx

---
title: "Custom Telephony Provider"
description: "Build your own telephony provider integration for Dograh AI"
---

## Prerequisites

This guide assumes familiarity with two libraries the provider interface is built on:

- **[Pipecat](https://docs.pipecat.ai)** — the open-source real-time voice/multimodal pipeline framework Dograh's call pipeline is built on. Its [`FastAPIWebsocketTransport`](https://docs.pipecat.ai/server/services/transport/fastapi-websocket) is what streams audio between the telephony provider and Dograh's pipeline — you'll be constructing one of these in your transport factory. If you haven't built a Pipecat transport or frame serializer before, skim their [transports guide](https://docs.pipecat.ai/server/base-classes/transport) first.
- **[Pydantic](https://docs.pydantic.dev)** — used for the request/response schemas that define a provider's stored credentials (`config.py` below). If you're new to Pydantic, its [models documentation](https://docs.pydantic.dev/latest/concepts/models/) covers everything used here (`BaseModel`, `Field`, `Literal` discriminators).

You don't need deep expertise in either — enough to read a `BaseModel` and a Pipecat transport class is sufficient to follow this guide.

## Overview

A telephony provider is implemented as a **self-registering package** under `api/services/telephony/providers/<name>/`. The package contributes everything Dograh needs to wire the provider in — the provider class, transport factory, audio config, request/response schemas, optional HTTP routes, and the form metadata used to render its configuration UI — through a single `ProviderSpec` registered at import time.

Adding a new provider should not require touching the factory, the audio config, the API routes module, the run-pipeline module, or the frontend. The only edits outside the provider folder are:

1. One import line in `api/services/telephony/providers/__init__.py`
2. One import line in `api/schemas/telephony_config.py` to add the request/response classes to the `TelephonyConfigRequest` discriminated union

## Provider Package Layout

```
api/services/telephony/providers/your_provider/
├── __init__.py        # Builds and registers ProviderSpec
├── config.py          # Pydantic Request/Response schemas
├── provider.py        # TelephonyProvider subclass
├── transport.py       # Pipecat WebSocket transport factory
├── serializers.py     # Frame serializer (usually re-exports from pipecat)
├── routes.py          # (optional) HTTP webhook/callback handlers
└── strategies.py      # (optional) Transfer/hangup strategies
```

Three files are required (`__init__.py`, `config.py`, `provider.py`, `transport.py`). The rest are optional and are discovered automatically when present:

- **`routes.py`** — if the module exists and exports `router: APIRouter`, the routes module is imported lazily and mounted under `/api/v1/telephony` by `api.routes.telephony` via `importlib`. Providers that only stream over WebSocket (e.g. ARI) can omit it.
- **`strategies.py`** — used by transports that need provider-specific call transfer/hangup logic in the frame serializer (e.g. Twilio Conference transfers).
- **`serializers.py`** — typically a re-export from pipecat. Keep the file even when it's a one-line re-export so transport code imports from `.serializers`, giving you an obvious place to drop a custom subclass later.

## The `TelephonyProvider` Interface

Subclass `TelephonyProvider` in `provider.py`:

```python
from api.services.telephony.base import (
    CallInitiationResult,
    NormalizedInboundData,
    ProviderSyncResult,
    TelephonyProvider,
)


class YourProvider(TelephonyProvider):
    PROVIDER_NAME = "your_provider"
    WEBHOOK_ENDPOINT = "your-provider-xml"  # path under /api/v1/telephony

    def __init__(self, config: dict):
        self.api_key = config.get("api_key")
        self.from_numbers = config.get("from_numbers", [])

    # ---------- outbound ----------
    async def initiate_call(self, to_number, webhook_url, workflow_run_id=None,
                            from_number=None, **kwargs) -> CallInitiationResult: ...
    async def get_call_status(self, call_id) -> dict: ...
    async def get_call_cost(self, call_id) -> dict: ...
    async def get_available_phone_numbers(self) -> list[str]: ...
    def validate_config(self) -> bool: ...

    # ---------- webhooks ----------
    async def verify_webhook_signature(self, url, params, signature) -> bool: ...
    async def get_webhook_response(self, workflow_id, user_id, workflow_run_id) -> str: ...
    def parse_status_callback(self, data: dict) -> dict: ...

    # ---------- websocket ----------
    async def handle_websocket(self, websocket, workflow_id, user_id, workflow_run_id): ...

    # ---------- inbound ----------
    @classmethod
    def can_handle_webhook(cls, webhook_data, headers) -> bool: ...

    @staticmethod
    def parse_inbound_webhook(webhook_data) -> NormalizedInboundData: ...

    @staticmethod
    def validate_account_id(config_data, webhook_account_id) -> bool: ...

    def normalize_phone_number(self, phone_number: str) -> str: ...

    async def verify_inbound_signature(self, url, webhook_data, headers, body="") -> bool: ...

    async def start_inbound_stream(self, *, websocket_url, workflow_run_id,
                                   normalized_data, backend_endpoint): ...

    @staticmethod
    def generate_error_response(error_type, message) -> tuple: ...

    # ---------- transfers ----------
    async def transfer_call(self, destination, transfer_id, conference_name,
                            timeout=30, **kwargs) -> dict: ...
    def supports_transfers(self) -> bool: ...

    # ---------- optional ----------
    async def configure_inbound(self, address, webhook_url) -> ProviderSyncResult:
        # Default returns ok=True — implement only if your provider supports
        # programmatic webhook configuration (e.g. binding a number to a URL
        # via API). Used to point inbound numbers at /api/v1/telephony/inbound/run.
        return ProviderSyncResult(ok=True)
```

See `api/services/telephony/base.py` for the full docstrings on each method.

## Implementation Guide

### 1. Configuration schemas

Define Pydantic models for the credential payload. The `provider` `Literal` discriminator is what makes the schemas dispatch correctly through the registry's discriminated union.

```python
# providers/your_provider/config.py
from typing import List, Literal
from pydantic import BaseModel, Field


class YourProviderConfigurationRequest(BaseModel):
    provider: Literal["your_provider"] = Field(default="your_provider")
    api_key: str = Field(..., description="Your Provider API key")
    api_secret: str = Field(..., description="Your Provider API secret")
    from_numbers: List[str] = Field(default_factory=list)


class YourProviderConfigurationResponse(BaseModel):
    provider: Literal["your_provider"] = Field(default="your_provider")
    api_key: str        # masked when returned
    api_secret: str     # masked when returned
    from_numbers: List[str]
```

### 2. Transport factory

Build the Pipecat `FastAPIWebsocketTransport` for accepted WebSockets. Always load credentials through `load_credentials_for_transport` so the right config row is picked when the workflow run carries a `telephony_configuration_id` (multi-config orgs).

```python
# providers/your_provider/transport.py
from fastapi import WebSocket
from api.services.pipecat.audio_config import AudioConfig
from api.services.pipecat.audio_mixer import build_audio_out_mixer
from api.services.telephony.factory import load_credentials_for_transport
from pipecat.transports.websocket.fastapi import (
    FastAPIWebsocketParams,
    FastAPIWebsocketTransport,
)
from .serializers import YourProviderFrameSerializer


async def create_transport(
    websocket: WebSocket,
    workflow_run_id: int,
    audio_config: AudioConfig,
    organization_id: int,
    *,
    vad_config: dict | None = None,
    ambient_noise_config: dict | None = None,
    telephony_configuration_id: int | None = None,
    # provider-specific kwargs (forwarded by run_pipeline_telephony as **transport_kwargs)
    stream_id: str,
    call_id: str,
):
    config = await load_credentials_for_transport(
        organization_id, telephony_configuration_id,
        expected_provider="your_provider",
    )

    serializer = YourProviderFrameSerializer(
        stream_id=stream_id,
        call_id=call_id,
        api_key=config["api_key"],
    )
    mixer = await build_audio_out_mixer(
        audio_config.transport_out_sample_rate, ambient_noise_config
    )

    return FastAPIWebsocketTransport(
        websocket=websocket,
        params=FastAPIWebsocketParams(
            audio_in_enabled=True,
            audio_out_enabled=True,
            audio_in_sample_rate=audio_config.transport_in_sample_rate,
            audio_out_sample_rate=audio_config.transport_out_sample_rate,
            audio_out_mixer=mixer,
            serializer=serializer,
        ),
    )
```

### 3. Routes (optional)

If your provider POSTs webhooks to Dograh (answer URL, status callbacks, hangup callbacks), expose them through a module-level `router`. The routes are auto-mounted under `/api/v1/telephony`.

```python
# providers/your_provider/routes.py
from fastapi import APIRouter, Request
from api.services.telephony.status_processor import (
    StatusCallbackRequest,
    _process_status_update,
)

router = APIRouter()


@router.post("/your-provider/status-callback/{workflow_run_id}")
async def status_callback(workflow_run_id: int, request: Request):
    ...
```

Routes are loaded lazily via `importlib` from `api.routes.telephony._mount_provider_routers`, so your route module can freely import other backend services without creating import cycles at provider-class load time.

### 4. Register the `ProviderSpec`

The package's `__init__.py` is where everything comes together:

```python
# providers/your_provider/__init__.py
from typing import Any, Dict

from api.services.pipecat.audio_config import AudioConfig
from api.services.telephony.registry import (
    ProviderSpec,
    ProviderUIField,
    ProviderUIMetadata,
    register,
)

from .config import YourProviderConfigurationRequest, YourProviderConfigurationResponse
from .provider import YourProvider
from .transport import create_transport


def _config_loader(value: Dict[str, Any]) -> Dict[str, Any]:
    """Normalize the stored credentials dict into the constructor shape."""
    return {
        "provider": "your_provider",
        "api_key": value.get("api_key"),
        "api_secret": value.get("api_secret"),
        "from_numbers": value.get("from_numbers", []),
    }


_AUDIO_CONFIG = AudioConfig(
    transport_in_sample_rate=8000,
    transport_out_sample_rate=8000,
    vad_sample_rate=8000,
    pipeline_sample_rate=8000,
    buffer_size_seconds=5.0,
)


_UI_METADATA = ProviderUIMetadata(
    display_name="Your Provider",
    docs_url="https://docs.your-provider.com",
    fields=[
        ProviderUIField(name="api_key",    label="API Key",    type="text",     sensitive=True),
        ProviderUIField(name="api_secret", label="API Secret", type="password", sensitive=True),
        ProviderUIField(
            name="from_numbers", label="Phone Numbers", type="string-array",
            description="E.164-formatted phone numbers used for outbound calls",
        ),
    ],
)


SPEC = ProviderSpec(
    name="your_provider",
    provider_cls=YourProvider,
    config_loader=_config_loader,
    transport_factory=create_transport,
    audio_config=_AUDIO_CONFIG,
    config_request_cls=YourProviderConfigurationRequest,
    config_response_cls=YourProviderConfigurationResponse,
    ui_metadata=_UI_METADATA,
    # Credential field that uniquely identifies the provider account.
    # Used to disambiguate inbound webhooks across multiple configs of the
    # same provider. Empty string for providers without an account-id concept.
    account_id_credential_field="api_key",
)

register(SPEC)
```

`ProviderSpec` covers everything downstream code needs:

| Field | Used by |
| --- | --- |
| `name` | Stored as the discriminator on every `TelephonyConfiguration` row and as the `WorkflowRunMode` value |
| `provider_cls` | `factory.get_default_telephony_provider`, `get_telephony_provider_by_id`, `get_telephony_provider_for_run` |
| `config_loader` | `factory._normalize_with_phone_numbers` (replaces the old if/elif chain) |
| `transport_factory` | `run_pipeline_telephony` |
| `audio_config` | `create_audio_config()` and `run_pipeline_telephony` |
| `config_request_cls` / `config_response_cls` | `TelephonyConfigRequest` discriminated union |
| `ui_metadata` | `GET /api/v1/organizations/telephony-providers/metadata` (drives the form UI) and the `_sensitive_fields` masking helper |
| `account_id_credential_field` | Inbound webhook routing across multiple configs of the same provider |

### 5. Wire the package into the registry import chain

Add one import line to `api/services/telephony/providers/__init__.py`:

```python
from api.services.telephony.providers import (  # noqa: F401  -- side effects
    ari,
    cloudonix,
    plivo,
    telnyx,
    twilio,
    vobiz,
    vonage,
    your_provider,        # ← add this
)
```

### 6. Add to the discriminated union

Add one import block to `api/schemas/telephony_config.py` so the request/response classes participate in the `TelephonyConfigRequest` union and the `TelephonyConfigurationResponse` shape:

```python
from api.services.telephony.providers.your_provider.config import (
    YourProviderConfigurationRequest,
    YourProviderConfigurationResponse,
)

TelephonyConfigRequest = Annotated[
    Union[
        # ...existing entries...
        YourProviderConfigurationRequest,
    ],
    Field(discriminator="provider"),
]


class TelephonyConfigurationResponse(BaseModel):
    # ...existing entries...
    your_provider: Optional[YourProviderConfigurationResponse] = None
```

That's it for backend wiring.

## Frontend

The configuration form is **metadata-driven**. The UI calls `GET /api/v1/organizations/telephony-providers/metadata`, gets back the list of providers and their `ProviderUIField` definitions, and renders each form generically. **No per-provider frontend code is needed** — your `ProviderUIMetadata` declaration is what drives the form.

If you add a new field type that the existing renderer doesn't support (e.g. a file upload), extend the renderer in `ui/src/app/(authenticated)/telephony-configurations/`. The supported `ProviderUIField.type` values today are `text`, `password`, `textarea`, `string-array`, and `number`.

## Audio Format Considerations

Each provider declares its wire format through its `AudioConfig`. Common shapes:

- **Twilio / Plivo**: 8 kHz μ-law, base64-encoded JSON frames
- **Vonage**: 16 kHz Linear PCM as binary frames
- **Asterisk ARI**: 8 kHz Linear PCM via externalMedia

The pipeline sample rate is capped at 16 kHz to satisfy [VAD](/configurations/interruption#what-is-vad), which only accepts 8000 Hz or 16000 Hz; transports handle resampling between the wire format and the pipeline's internal rate.

## Testing

```python
# api/tests/telephony/test_your_provider.py
import pytest
from api.services.telephony.providers.your_provider import YourProvider


@pytest.mark.asyncio
async def test_validate_config():
    provider = YourProvider({
        "api_key": "test_key",
        "api_secret": "test_secret",
        "from_numbers": ["+1234567890"],
    })
    assert provider.validate_config() is True
```

For end-to-end testing, save your provider through the telephony-configurations UI and trigger a test call from a workflow.

## Best Practices

1. **Trust the registry** — never import another provider's class directly; resolve through the factory helpers (`get_default_telephony_provider`, `get_telephony_provider_by_id`, etc.).
2. **Sensitive fields** — mark every credential field `sensitive=True` in `ProviderUIMetadata`. The save endpoint masks these on read and preserves the original when the client re-submits a masked value.
3. **Inbound signature verification** — always validate inbound webhook signatures in `verify_inbound_signature`. Returning `True` when no signature header is present is acceptable; return `False` when a signature *is* present but invalid.
4. **Transports load credentials lazily** — call `load_credentials_for_transport` with the `telephony_configuration_id` from the workflow run. Don't read the org's default config from `transport.py`.
5. **Logging** — use `loguru.logger`.

## Reference Implementations

| Provider | Notable for |
| --- | --- |
| `providers/twilio/` | Full-featured: outbound, inbound, conference transfers, status callbacks, custom strategies |
| `providers/plivo/` | Recently-added reference; mirrors Twilio's shape with multi-callback signatures |
| `providers/vonage/` | JWT auth, 16 kHz Linear PCM, NCCO responses |
| `providers/cloudonix/` | SIP-based, custom call strategies |
| `providers/telnyx/` | Call-control style: REST-driven inbound answer flow rather than markup response |
| `providers/ari/` | Minimal example — no `routes.py`, no inbound webhook verification, WebSocket-only |

<Note>
  Use ARI as the smallest viable example when your provider doesn't expose HTTP
  webhooks, and Twilio as the reference when it does.
</Note>