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# registerGlobalRoutingCallback

> Register a routing callback across all agents for custom request routing.

[setup-sip-routing]: /docs/server-sdks/reference/typescript/agents/agent-server/sip-routing

Register a custom routing callback on every registered agent at the specified path.
When a request arrives at that path on any agent, the callback is invoked to determine
whether to redirect the request to a different agent route.

Use this alongside or instead of [`setupSipRouting()`][setup-sip-routing] when you
need custom routing logic — for example, routing based on request body content,
tenant IDs, or feature flags.

> **Note**
>
> The callback is also applied to agents registered **after** this method is called.
> The server stores each callback internally so new agents automatically receive it.

## **Parameters**

**`callbackFn`** `RoutingCallback` — required

A function that receives the parsed request body and returns a route string
(e.g., `"/sales"`) to redirect the request, or `null` / `undefined` to let the
current agent handle it. May return a `Promise` for asynchronous routing decisions.
Signature: `(body: Record<string, unknown>) => string | null | undefined | Promise<string | null | undefined>`.

---

**`path`** `string` — required

The URL path where the callback is triggered (e.g., `"/route"`). Leading slashes are
added and trailing slashes are stripped automatically.

---

## **Returns**

`void`

## **Example**

```typescript {21}
import { AgentBase, AgentServer } from '@signalwire/sdk';

function routeByLanguage(body: Record<string, unknown>): string | undefined {
  const lang = (body['lang'] as string | undefined) ?? 'en';
  if (lang.startsWith('es')) return '/spanish-agent';
  if (lang.startsWith('fr')) return '/french-agent';
  return undefined;
}

const english = new AgentBase({ name: 'english', route: '/english-agent' });
english.setPromptText('You are a helpful assistant. Respond in English.');
const spanish = new AgentBase({ name: 'spanish', route: '/spanish-agent' });
spanish.setPromptText('You are a helpful assistant. Respond in Spanish.');
const french = new AgentBase({ name: 'french', route: '/french-agent' });
french.setPromptText('You are a helpful assistant. Respond in French.');

const server = new AgentServer({ port: 3000 });
server.register(english);
server.register(spanish);
server.register(french);
server.registerGlobalRoutingCallback(routeByLanguage, '/route');
await server.run();
```

> Register a routing callback across all agents for custom request routing.