can't call nested route

const appRouter = router({
    hello: procedure.query(() => 'hello world'),
    chess: chessRouter,
});

const appRouter = router({
    hello: procedure.query(() => 'hello world'),
    chess: chessRouter,
});

export const chessRouter = router({
    login: procedure.mutation(async (opts) => {
      //...
    }),
});

export const chessRouter = router({
    login: procedure.mutation(async (opts) => {
      //...
    }),
});