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# router

> Build the APIRouter serving the handoff, escalate, and say routes.

[ref-handoffrouter]: /docs/server-sdks/reference/python/agents/handoff-router

[mount]: /docs/server-sdks/reference/python/agents/agent-base/mount

[gateway-router]: /docs/server-sdks/reference/python/agents/chat-gateway/router

Return an `APIRouter` serving `POST /handoff`, `POST /escalate`, and `POST /say`. Mount it at the
same prefix as the [gateway's router][gateway-router]: the browser derives all three paths from the
one URL it was configured with, so they must be siblings of the gateway's endpoint.

Each route checks the `Origin` header against the gateway's allowlist and answers `403` when it
isn't allowed. A malformed or unknown nonce answers `404`; a missing handle on `/escalate` answers
`400`.

## Parameters

None.

## Returns

`fastapi.APIRouter`

## Example

```python {4-5}
gateway = ChatGateway(config_url="https://bayview-taxi.example.com/dispatch")
handoff = HandoffRouter(gateway=gateway, capture_leg=save_leg, end_call=hang_up)

agent.mount(gateway.router(), prefix="/chat")
agent.mount(handoff.router(), prefix="/chat")
```

Use [`mount()`][mount] rather than `get_app().include_router()`, so the new routes aren't shadowed
by the agent's catch-all. See [`HandoffRouter`][ref-handoffrouter] for the full flow.

> Build the APIRouter serving the handoff, escalate, and say routes.