# Your v11 links

> fromV11Link runs a v11 TRPCLink in a v12 chain, so you can move links one at a time, and what a rewritten link looks like.

Your own v11 links (`TRPCLink`s) run in a v12 chain through `fromV11Link`, so you can move them over one at a time:

```ts
import { fromV11Link } from '@trpc12/trpc/interop';

createTrpcClient({
  router: routerType<AppRouter>(),
  links: [fromV11Link(authLink), httpLink({ url })],
});
```

The v11 link gets v11 operations and observables, so `observable()`, `tap()` and `share()` from `@trpc/server/observable` work as before. What it gets from `next` differs in two ways:

- Errors are v12 `TrpcError`s, with the code on `error.code`. Errors the link fails with keep their `data.code`.
- Subscription results are `{ type: 'started' }`, then `{ type: 'data', data }` for each event; there is no `stopped` result.

A v11 terminating link (one that sends the request itself, such as v11's `httpBatchLink`) works too.

Rewritten for v12, a link returns an Effect `Stream`:

```ts
const authLink = link((opts) =>
  opts.next({
    ...opts.op,
    context: { ...opts.op.context, headers: { authorization: token() } },
  }),
);
```