Clojurians Log v2

I'm trying to create a tempid on client, and use it to make relations between queries and mutations

(let [id (om/tempid)]
  `[(create-user {:db/id ~id :user/username "me"})
    {(:app/user {:db/id ~id}) '[:user/username]}])

I'm parsing on the server with (edn/read-string {:readers {'om/id first}} s), so #om/id["foo"] turns into "foo", which are valid datomic tempids. From transact I can get :tempids {"foo" 123213231}, but I cant find how to access the result from transaction on the read multi-method